Pesticides and Pesticide Degradates in Groundwater Used for Public Supply across the United States: Occurrence and Human-Health Context
- Laura M. Bexfield*Laura M. Bexfield*Email: [email protected], Tel: 505-830-7972. Fax: 505-830-7998.New Mexico Water Science Center, U.S. Geological Survey, 6700 Edith Boulevard NE, Albuquerque, New Mexico 87113, United StatesMore by Laura M. Bexfield,
- Kenneth BelitzKenneth BelitzU.S. Geological Survey, 10 Bearfoot Road, Northborough, Massachusetts 01532, United StatesMore by Kenneth Belitz,
- Bruce D. LindseyBruce D. LindseyU.S. Geological Survey, 215 Limekiln Road, New Cumberland, Pennsylvania 17070, United StatesMore by Bruce D. Lindsey,
- Patricia L. ToccalinoPatricia L. ToccalinoU.S. Geological Survey, 911 Northeast 11th Avenue, Portland, Oregon 97232, United StatesMore by Patricia L. Toccalino, and
- Lisa H. NowellLisa H. NowellU.S. Geological Survey, 6000 J Street, Placer Hall, Sacramento, California 95819, United StatesMore by Lisa H. Nowell
Abstract
This is the first assessment of groundwater from public-supply wells across the United States to analyze for >100 pesticide degradates and to provide human-health context for degradates without benchmarks. Samples from 1204 wells in aquifers representing 70% of the volume pumped for drinking supply were analyzed for 109 pesticides (active ingredients) and 116 degradates. Among the 41% of wells where pesticide compounds were detected, nearly two-thirds contained compound mixtures and three-quarters contained degradates. Atrazine, hexazinone, prometon, tebuthiuron, four atrazine degradates, and one metolachlor degradate were each detected in >5% of wells. Detection frequencies were largest for aquifers with more shallow, unconfined wells producing modern-age groundwater. To screen for potential human-health concerns, benchmark quotients (BQs) were calculated by dividing concentrations by the human-health benchmark, when available. For degradates without benchmarks, estimated values (estimated benchmark quotients (BQE)) were first calculated by assuming equimolar toxicity to the most toxic parent; final analysis excluded degradates with likely overestimated toxicity. Six pesticide compounds and 1.6% of wells had concentrations approaching levels of potential concern (individual or summed BQ or BQE values >0.1), and none exceeded these levels (values >1). Therefore, although pesticide compounds occurred frequently, concentrations were low, even accounting for mixtures and degradates without benchmarks.
Introduction
Methods
Study Design
Sample Collection
Laboratory Analysis
Quality Assurance and Quality Control
Data Preparation Steps
Screening Approach for Potential Relevance to Human Health
Ancillary Datasets
Results and Discussion
Occurrence of Pesticide Compounds and Mixtures
Screening of Concentrations for Potential Human-Health Concerns
Individual Compounds
TIER 1: cmpds (no. wells) with | FINAL/TIER 2: cmpds (no. wells) with | |||
---|---|---|---|---|
BQ or BQE > 1 | BQ or BQE > 0.1 | BQ or BQE > 1 | BQ or BQE > 0.1 | |
compounds with a benchmark | alachlor (1) | alachlor (1) | ||
atrazine (1) | atrazine (1) | |||
diuron (1) | diuron (1) | |||
didealkylatrazine/CAAT (2) | didealkylatrazine/CAAT (2) | |||
degradates without a benchmark | alachlor SA (1 well)b | 4-hydroxychlorothalonil (1)a | 4-hydroxychlorothalonil (1)a | |
deethylatrazine/DEA (3)a | deethylatrazine/DEA (3)a | |||
fipronil amide (1)b | ||||
alachlor OA (2)b | ||||
alachlor SA (18)b | ||||
hydroxyalachlor (1)b | ||||
pyrimidinol (1)b | ||||
totals | 1 cmpd (1 well) | 11 cmpds (27 wells)c | 0 cmpds (0 wells) | 6 cmpds (8 wells)c |
Compound likely has similar toxicity to the parent and so was retained in tier 2 analysis and included in final totals.
Compound likely has substantially lower toxicity than the parent and so was dropped in tier 2 analysis and not included in final totals.
Some wells had multiple compounds with BQ or BQE > 0.1.
Individual Wells With Mixtures
Implications
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acs.est.0c05793.
Additional information on particular topics as noted in the text, with figures (PDF)
Data tables as noted in the text (XLSX)
Terms & Conditions
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Acknowledgments
This work was funded by the U.S. Geological Survey (USGS) National Water-Quality Assessment Project. The study would not have been possible without the dedication of numerous USGS field crews and the generous assistance of participating well owners and operators. We also appreciate the contributions of Mark Sandstrom and other USGS National Water Quality Laboratory personnel, who analyzed samples and assisted in quality-control evaluations; Delicia Beaty, who compiled and examined Quality Systems Branch performance data; Tyler Johnson, who processed ancillary data; and reviewers of this article. Any use of trade, firm, or product names is for descriptive purposes only and does not imply endorsement by the U.S. Government.
Abbreviations | |
BQ | benchmark quotient |
BQE | estimated benchmark quotient |
CAAT | didealkylatrazine |
DEA | deethylatrazine |
DIA | deisopropylatrazine |
DL | detection limit |
EPA | U.S. Environmental Protection Agency |
LB | laboratory set blank |
NAWQA | National Water-Quality Assessment |
NWQL | National Water-Quality Laboratory |
OA | oxanilic acid |
OEAT | 2-hyroxy-6-ethylamino-4-amino-s-triazine |
OIAT | desethylhydroxyatrazine |
OIET | hydroxyatrazine |
PAS | principal aquifer survey |
RL | reporting limit |
SA | sulfonic acid |
μg/L | micrograms per liter |
USGS | U.S. Geological Survey |
VRPBR | Valley and Ridge and Piedmont and Blue Ridge |
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- 25Price, P. S.; Han, X. Maximum cumulative ratio (MCR) as a tool for assessing the value of performing a cumulative risk assessment. Int. J. Environ. Res. Public Health 2011, 8, 2212– 2225, DOI: 10.3390/ijerph8062212[Crossref], [PubMed], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC3MnpvVGhtA%253D%253D&md5=653198aaad284dc02ff6483adae8e9d6Maximum cumulative ratio (MCR) as a tool for assessing the value of performing a cumulative risk assessmentPrice Paul S; Han XiangluInternational journal of environmental research and public health (2011), 8 (6), 2212-25 ISSN:.Due to the vast number of possible combinations of chemicals to which individuals are exposed and the resource-intensive nature of cumulative risk assessments, there is a need to determine when cumulative assessments are most required. This paper proposes the use of the maximum cumulative ratio (MCR) as a tool for this evaluation. MCR is the ratio of the cumulative toxicity received by an individual from exposure to multiple chemical stressors to the largest toxicity from a single chemical stressor. The MCR is a quantitative measure of the difference in an individual's toxicity estimated using a chemical-by-chemical approach and using an additive model of toxicity. As such, it provides a conservative estimate of the degree to which individuals' toxicities could be underestimated by not performing a cumulative risk assessment. In an example application, MCR is shown to be applicable to the evaluation of cumulative exposures involving up to 81 compounds and to provide key insights into the cumulative effects posed by exposures to multiple chemicals. In this example, MCR values suggest that individuals exposed to combinations of chemicals with the largest Hazard Indices were dominated by the contributions of one or two compounds.
- 26Toccalino, P. L.; Norman, J. E.; Scott, J. C. Chemical mixtures in untreated water from public-supply wells in the U.S.—Occurrence, composition, and potential toxicity. Sci. Total Environ. 2012, 431, 262– 270, DOI: 10.1016/j.scitotenv.2012.05.044[Crossref], [PubMed], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XpsVOisb8%253D&md5=ce3d6de61f6d6fe7f2c430e98c3a286dChemical mixtures in untreated water from public-supply wells in the U.S. - Occurrence, composition, and potential toxicityToccalino, Patricia L.; Norman, Julia E.; Scott, Jonathon C.Science of the Total Environment (2012), 431 (), 262-270CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)Chem. mixts. are prevalent in groundwater used for public water supply, but little is known about their potential health effects. As part of a large-scale ambient groundwater study, the authors evaluated chem. mixts. across multiple chem. classes, and included more chem. contaminants than in previous studies of mixts. in public-supply wells. They (1) assessed the occurrence of chem. mixts. in untreated source-water samples from public-supply wells, (2) detd. the compn. of the most frequently occurring mixts., and (3) characterized the potential toxicity of mixts. using a new screening approach. The U.S. Geol. Survey collected one untreated water sample from each of 383 public wells distributed across 35 states, and analyzed the samples for as many as 91 chem. contaminants. Concns. of mixt. components were compared to individual human-health benchmarks; the potential toxicity of mixts. was characterized by addn. of benchmark-normalized component concns. Most samples (84%) contained mixts. of two or more contaminants, each at concns. greater than one-tenth of individual benchmarks. The chem. mixts. that most frequently occurred and had the greatest potential toxicity primarily were composed of trace elements (including arsenic, strontium, or uranium), radon, or nitrate. Herbicides, disinfection byproducts, and solvents were the most common org. contaminants in mixts. The sum of benchmark-normalized concns. was greater than 1 for 58% of samples, suggesting that there could be potential for mixts. toxicity in more than half of the public-well samples. The findings can be used to help set priorities for groundwater monitoring and suggest future research directions for drinking-water treatment studies and for toxicity assessments of chem. mixts. in water resources.
- 27Framework for Assessing Health Impacts of Multiple Chemicals and Other Stressors (Update); U.S. Department of Health and Human Services: Washington, D.C., 2018. https://www.atsdr.cdc.gov/interactionprofiles/ip-ga/ipga.pdf (accessed April 23, 2020).
- 28Cumulative Assessment of Risk from Pesticides; U.S. Environmental Protection Agency: Washington, D.C., 2020. https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/cumulative-assessment-risk-pesticides (accessed March 20, 2020).
- 29Manamsa, K.; Crane, E.; Stuart, M.; Talbot, J.; Lapworth, D.; Hart, A. A national-scale assessment of micro-organic contaminants in groundwater of England and Wales. Sci. Total Environ. 2016, 568, 712– 726, DOI: 10.1016/j.scitotenv.2016.03.017[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlslCisL8%253D&md5=15bebbb4d8937e4aec667e0cbd0e748eA national-scale assessment of micro-organic contaminants in groundwater of England and WalesManamsa, Katya; Crane, Emily; Stuart, Marianne; Talbot, John; Lapworth, Dan; Hart, AlwynScience of the Total Environment (2016), 568 (), 712-726CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)A large variety of micro-org. (MO) compds. is used in huge quantities for a range of purposes (e.g., manufg., food prodn., healthcare) and is now being frequently detected in the aquatic environment. Interest in the occurrence of MO contaminants in the terrestrial and aquatic environments continues to grow, as well as in their environmental fate and potential toxicity. However, the contamination of groundwater resources by MOs has a limited evidence base compared to other freshwater resources. Of particular concern are newly 'emerging contaminants' such as pharmaceuticals and lifestyle compds., particularly those with potential endocrine disrupting properties. While groundwater often has a high degree of protection from pollution due to phys., chem. and biol. attenuation processes in the subsurface compared to surface aquatic environments, trace concns. of a large range of compds. are still detected in groundwater and in some cases may persist for decades due to the long residence times of groundwater systems. This study provides the first national-scale assessment of micro-org. compds. in groundwater in England and Wales. A large set of monitoring data was analyzed to det. the relative occurrence and detected concns. of different groups of compds. and to det. relationships with land-use, aquifer type and groundwater vulnerability. MOs detected including emerging compds. such as caffeine, DEET, bisphenol A, anti-microbial agents and pharmaceuticals as well as a range of legacy contaminants including chlorinated solvents and THMs, petroleum hydrocarbons, pesticides and other industrial compds. There are clear differences in MOs between land-use types, particularly for urban-industrial and natural land-use. Temporal trends of MO occurrence are assessed but establishing long-term trends is not yet possible.
- 30Kiefer, K.; Muller, A.; Singer, H.; Hollender, J. New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS. Water Res. 2019, 165, 114972 DOI: 10.1016/j.watres.2019.114972[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1emsLnN&md5=9bb29e6932b0cf9b8337199a3649db48New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMSKiefer, Karin; Muller, Adrian; Singer, Heinz; Hollender, JulianeWater Research (2019), 165 (), 114972CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)Groundwater is a major drinking water resource, but its quality is threatened by a broad variety of anthropogenic micropollutants (MPs), originating from agriculture, industry, or households, and undergoing various transformation processes during subsurface passage. To det. a worst-case impact of pesticide application in agriculture on groundwater quality, a target and suspect screening for more than 300 pesticides and more than 1100 pesticide transformation products (TPs) was performed in 31 Swiss groundwater samples which predominantly originated from areas with intensive agriculture. To assess addnl. urban contamination sources, more than 250 common urban MPs were quantified. Most of the screened pesticide TPs were exptl. obsd. by the pesticide producers within the European pesticide registration. To cover very polar pesticide TPs, vacuum-assisted evaporative concn. was used for enrichment, followed by liq. chromatog. high-resoln. tandem mass spectrometry (LC-HRMS/MS). Based on intensity, isotope pattern, retention time, and in silico fragmentation, the suspect hits were prioritised and verified. We identified 22 suspects unequivocally and five tentatively; 13 TPs are reported here for the first time to be detected in groundwater. In 13 out of 31 groundwater samples, the total concn. of the 20 identified and quantified suspects (1 pesticide and 19 pesticide TPs) exceeded the total concn. of the 519 targets (236 pesticides and TPs; 283 urban MPs) for which we screened. Pesticide TPs had higher concns. than the parent pesticides, illustrating their importance for groundwater quality. The newly identified very polar chlorothalonil TP R471811 was the only compd. detected in all samples with concns. ranging from 3 to 2700 ng/L. Agricultural MP concn. and detection frequency correlated with agricultural land use in the catchment, except for aquifers, where protective top layers reduced MP transport from the surface. In contrast to agricultural MPs, urban MPs displayed almost no correlation with land use. The dominating entry pathway of urban MPs was river bank filtration.
- 31Close, M. E.; Humphries, B.; Northcott, G. Outcomes of the first combined national survey of pesticides and emerging organic contaminants (EOCs) in groundwater in New Zealand 2018. Sci. Total Environ. 2020, 754, 142005 DOI: 10.1016/j.scitotenv.2020.142005
- 32Kolpin, D. W.; Goolsby, D. A.; Thurman, M. E. Pesticides in near-surface aquifers: an assessment using highly sensitive analytical methods and tritium. J. Environ. Qual. 1995, 24, 1125– 1132, DOI: 10.2134/jeq1995.00472425002400060011x[Crossref], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXps1Klsrs%253D&md5=43050239537b15d67623b17b80dfca9bPesticides in near-surface aquifers: an assessment using highly sensitive analytical methods and tritiumKolpin, Dana W.; Goolsby, Donald A.; Thurman, E. MichaelJournal of Environmental Quality (1995), 24 (6), 1125-32CODEN: JEVQAA; ISSN:0047-2425. (American Society of Agronomy)In 1992, the U.S. Geol. Survey (USGS) detd. the distribution of pesticides in near-surface aquifers of the midwestern USA to be much more widespread than originally detd. during a 1991 USGS study. The frequency of pesticide detection increased from 28.4% during the 1991 study to 59.0% during the 1992 study. This increase in pesticide detection was primarily the result of a more sensitive anal. method that used reporting limits as much as 20 times lower than previously available and a threefold increase in the no. of pesticide metabolites analyzed. No pesticide concns. exceeded the U.S. Environmental Protection Agency's (USEPAs) max. contaminated levels or health advisory levels for drinking water. However, five of the six most frequently detected compds. during 1992 were pesticide metabolites that currently do not have drinking water stds. detd. The frequent presence of pesticide metabolites for this study documents the importance of obtaining information on these compds. to understand the fate and transport of pesticides in the hydrol. system. It appears that the 56 parent compds. analyzed follow similar pathways through the hydrol. system as atrazine. When atrazine was detected by routine or sensitive anal. methods, there was an increased likelihood of detecting addnl. parent compds. As expected, the frequency of pesticide detection was highly dependent on the anal. reporting limit. The no. of atrazine detections more than doubled as the reporting limit decreased from 0.10 to 0.01 μg/L. The 1992 data provided no indication that the frequency of pesticide detection would level off as improved anal. methods provide concns. below 0.003 μg/L. A relation was detd. between groundwater age and the frequency of pesticide detection, with 15.8% of the samples composed of pre-1953 water and 70.3% of the samples of post-1953 water having a detection of at least one pesticide or metabolite. Pre-1953 water is less likely to contain pesticides because it tends to predate the use of pesticides to increase crop prodn. in the Midwest. Pre-1953 water was more likely to occur in the near-surface bedrock aquifers (50.0%) than in the near-surface unconsolidated (9.1%) sampled.
- 33Kolpin, D. W.; Thurman, M. E.; Goolsby, D. A. Occurrence of selected pesticides and their metabolites in near-surface aquifers of the midwestern United States. Environ. Sci. Technol. 1996, 30, 335– 340, DOI: 10.1021/es950462q[ACS Full Text ], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXpsFyrtLo%253D&md5=f98656d7cf25ee213b709cde2a473c58Occurrence of Selected Pesticides and Their Metabolites in Near-Surface Aquifers of the Midwestern United StatesKolpin, Dana W.; Thurman, E. Michael; Goolsby, Donald A.Environmental Science and Technology (1996), 30 (1), 335-40CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)The occurrence and distribution of selected pesticides and their metabolites were investigated through the collection of 837 water-quality samples from 303 wells across the Midwest. Results of this study showed that 5 of the 6 most frequently detected compds. were pesticide metabolites. Thus, it was common for a metabolite to be found more frequently in groundwater than its parent compd. The metabolite alachlor ethanesulfonic acid (alachlor-ESA; 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoethanesulfonic acid) was detected almost 10 times as frequently and at much higher concns. than its parent compd. alachlor (2-chloro-2',6'-diethyl-N-(methoxymethyl)acetamide). The median detectable atrazine (2-chloro-4-ethylamino-6- isopropylamino-s-triazine) concn. was almost half that of atrazine residue (atrazine plus the 2 atrazine metabolites analyzed). Cyanazine amide [2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-ethylamino-s-triazine] was detected almost twice as frequently as cyanazine (2-chloro-4-ethylamino-6-methylpropionitrileamino-s-triazine). Results show that information on pesticide metabolites is necessary to understand the environmental fate of pesticides. Consequently, if pesticide metabolites are not quantified, the effects of chem. use on groundwater quality would be substantially underestimated. Thus, continued research is needed to identify major degrdn. pathways for all pesticides and to develop anal. methods to det. their concns. in water and other environmental data.
- 34Kolpin, D. W.; Barbash, J. E.; Gilliom, R. J. Occurrence of pesticides in shallow groundwater of the United States: Initial results from the National Water-Quality Assessment Program. Environ. Sci. Technol. 1998, 32, 558– 566, DOI: 10.1021/es970412g[ACS Full Text ], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXmt1Ogsg%253D%253D&md5=6b6d0101bb356573d60001b344d36fb0Occurrence of Pesticides in Shallow Groundwater of the United States: Initial Results from the National Water-Quality Assessment ProgramKolpin, Dana W.; Barbash, Jack E.; Gilliom, Robert J.Environmental Science and Technology (1998), 32 (5), 558-566CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)The first phase of intensive data collection for the National Water Quality Assessment (NAWQA) program was completed during 1993-1995 in 20 major hydrol. basins of the USA. Groundwater land use studies, designed to sample recently recharged groundwater (generally within 10 yr) beneath specific land use and hydrogeol. settings, are a major component of the groundwater quality assessment for NAWQA. Pesticide results from 41 land use studies conducted during 1993-1995 indicated that pesticides were commonly detected in shallow groundwater, being obsd. at 54.4% of the 1034 sites sampled in agricultural and urban settings across the USA. Pesticide concns. were generally low, with >95% of the detections at concns. <1 mg/L; of 46 pesticide compds. examd., 39 were detected. Compds. detected most frequently were atrazine (38.2%), deethylatrazine (34.2%), simazine (18.0%), metolachlor (14.6%), and prometon (13.9%). Statistically significant relations were obsd. between frequencies of detection and the use, mobility, and persistence of these compds. Pesticides were commonly detected in agricultural (56.4%; 813 sites) and urban (46.6%; 221 sites) settings. Frequent pesticide detection in urban areas indicated that, as with agricultural pesticide use in agricultural areas, urban and suburban pesticide use significantly contributed to pesticide occurrence in shallow groundwater. Although pesticides were detected in groundwater sampled in urban areas and all 9 agricultural land-use categories examd., significant variations in occurrence were obsd. among these categories. Max. contaminant levels (MCL) established by USEPA for drinking water were exceeded for only 1 pesticide (atrazine, 3 mg/L) at a single location; however, MCL have been established for only 25 of 46 pesticide compds. examd., do not cover pesticide degradates, and, currently, do not account for additive or synergistic effects of combinations of pesticide compds. or potential effects on nearby aquatic ecosystems.
- 35Kolpin, D. W.; Barbash, J. E.; Gilliom, R. J. Pesticides in groundwater of the United States, 1992-96. Ground Water 2000, 38, 858– 863, DOI: 10.1111/j.1745-6584.2000.tb00684.x[Crossref], [CAS], Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXnvFyktbc%253D&md5=9be13ebf210aaee41fd6657a856767b9Pesticides in ground water of the United States, 1992-1996Kolpin, Dana W.; Barbash, Jack E.; Gilliom, Robert J.Ground Water (2000), 38 (6), 858-863CODEN: GRWAAP; ISSN:0017-467X. (National Ground Water Association)During the 1st cycle of the National Water Quality Assessment (1992-1996), groundwater in 20 of the nation's major hydrol. basins was analyzed for 90 pesticide compds. (pesticides and degradates). One or more of the pesticide compds. examd. were detected at 48.4% of the 2485 groundwater sites sampled. However, ∼70% of the sites where pesticides were detected, ≥2 pesticide compds. analyzed were present-documenting the prevalence of pesticide mixts. in groundwater. The pesticide concns. encountered were generally low, with the median total concn. (summation of concns. for the 90 pesticide compds.) being 0.046 μg/L. Pesticides were commonly detected in shallow groundwater beneath both agricultural (60.4%) and urban (48.5%) areas. This is an important finding because, although agricultural activities have long been assocd. with pesticide contamination, urban areas have only recently been recognized as a potential source of these types of compds. Pesticides with higher frequencies of detection were generally those with more extensive use, greater environmental persistence, and greater mobility in groundwater (lower soil-water partition coeffs.).
- 36Bexfield, L. M. Decadal-scale changes of pesticides in ground water of the United States, 1993-2003. J. Environ. Qual. 2008, 37, S-226– S-239, DOI: 10.2134/jeq2007.0054[Crossref], [CAS], Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFagurnN&md5=fbfd578357bd283f3d5a9239b881a2c7Decadal-scale changes of pesticides in ground water of the United States, 1993-2003Bexfield, Laura M.Journal of Environmental Quality (2008), 37 (5, Suppl.), S/226-S/239CODEN: JEVQAA; ISSN:0047-2425. (American Society of Agronomy)Pesticide data for groundwater sampled across the US between 1993-1995 and 2001-2003 by the US Geol. Survey National Water-Quality Assessment Program were evaluated for trends in detection frequency and concn. The data anal. evaluated samples collected from a total of 362 wells located in 12 local well networks characterizing shallow groundwater in agricultural areas and 6 local well networks characterizing the drinking water resource in areas of variable land use. Each well network was sampled once during 1993-1995 and once during 2001-2003. The networks provide an overview of conditions across a wide range of hydrogeol. settings and in major agricultural areas that vary in dominant crop type and pesticide use. Of ∼80 pesticide compds. analyzed, only 6 compds. were detected in groundwater from ≥10 wells during both sampling events. These compds. were the triazine herbicides atrazine, simazine, and prometon; the acetanilide herbicide metolachlor; the urea herbicide tebuthiuron; and an atrazine degradate, deethylatrazine (DEA). Obsd. concns. of these compds. generally were <0.12 μg/L. At individual wells, changes in concns. typically were <0.02 μg/L. Data anal. incorporated adjustments for changes in lab. recovery as assessed through lab. spikes. In wells yielding detectable concns. of atrazine, DEA, and prometon, concns. were significantly lower (α =0.1) in 2001-2003 than in 1993-1995, whereas detection frequency of these compds. did not change significantly. Trends in atrazine concns. at shallow wells in agricultural areas were found to be consistent overall with recent atrazine use data.
- 37Toccalino, P. L.; Gilliom, R. J.; Lindsey, B. D.; Rupert, M. G. Pesticides in groundwater of the United States: Decadal-scale changes, 1993-2011. Groundwater 2014, 52, 112– 125, DOI: 10.1111/gwat.12176[Crossref], [PubMed], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFyrs7nJ&md5=f86b694d1e2b0da1fab6ac6fba4161c7Pesticides in Groundwater of the United States: Decadal-Scale Changes, 1993-2011Toccalino, Patricia L.; Gilliom, Robert J.; Lindsey, Bruce D.; Rupert, Michael G.Groundwater (2014), 52 (S1), 112-125CODEN: GRWAAP; ISSN:0017-467X. (Wiley-Blackwell)The national occurrence of 83 pesticide compds. in groundwater of the United States and decadal-scale changes in concns. for 35 compds. were assessed for the 20-yr period from 1993-2011. Samples were collected from 1271 wells in 58 nationally distributed well networks. Networks consisted of shallow (mostly monitoring) wells in agricultural and urban land-use areas and deeper (mostly domestic and public supply) wells in major aquifers in mixed land-use areas. Wells were sampled once during 1993-2001 and once during 2002-2011. Pesticides were frequently detected (53% of all samples), but concns. seldom exceeded human-health benchmarks (1.8% of all samples). The five most frequently detected pesticide compds.-atrazine, deethylatrazine, simazine, metolachlor, and prometon-each had statistically significant (p < 0.1) changes in concns. between decades in one or more categories of well networks nationally aggregated by land use. For agricultural networks, concns. of atrazine, metolachlor, and prometon decreased from the first decade to the second decade. For urban networks, deethylatrazine concns. increased and prometon concns. decreased. For major aquifers, concns. of deethylatrazine and simazine increased. The directions of concn. changes for individual well networks generally were consistent with changes detd. from nationally aggregated data. Altogether, 36 of the 58 individual well networks had statistically significant changes in concns. of one or more pesticides between decades, with the majority of changes attributed to the five most frequently detected pesticide compds. The magnitudes of median decadal-scale concn. changes were small-ranging from -0.09 to 0.03 μg/L-and were 35- to 230,000-fold less than human-health benchmarks.
- 38Kolpin, D. W.; Kalkhoff, S. J.; Goosby, D. A.; Sneck-Fahrer, D. A.; Thurman, M. E. Occurrence of selected herbicides and herbicide degradation products in Iowa’s ground water, 1995. Ground Water 1997, 35, 679– 688, DOI: 10.1111/j.1745-6584.1997.tb00134.x[Crossref], [CAS], Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXktlKmu7w%253D&md5=e0b00710376a49c9bcbc8b1ce840f9a4Occurrence of selected herbicides and herbicide degradation products in Iowa's ground water, 1995Kolpin, Dana W.; Kalkhoff, Stephen J.; Goolsby, Donald A.; Sneck-Fahrer, Debra A.; Thurman, E. MichaelGround Water (1997), 35 (4), 679-688CODEN: GRWAAP; ISSN:0017-467X. (Ground Water Publishing)Herbicide compds. were prevalent in groundwater across Iowa, being detected in 70% of the 106 municipal wells sampled during the summer of 1995. Herbicide degrdn. products were 3 of the 4 most frequently detected compds. for this study. The degrdn. product alachlor ethanesulfonic acid was the most frequently detected compd. (65.1%), followed by atrazine (40.6%), and the degrdn. products deethylatrazine (34.9%), and cyanazine amide (19.8%). The corn herbicide acetochlor, 1st registered for widespread use in the US in Mar. 1994, was detected in a single water sample. No reported herbicide compd. concns. for this study exceeded current US EPA's max. contaminant levels or health advisory levels for drinking water, although the herbicide degrdn. products examd. have yet to have such levels established. The occurrence of herbicide compds. had a significant, inverse relation to well depth and a significant, pos. relation to dissolved O concn. It is felt that both well depth and dissolved O are acting as rough surrogates to groundwater age, with younger groundwater being more likely to contain herbicide compds. The occurrence of herbicide compds. was substantially different among the major aquifer types across Iowa, being detected in 82.5% of the alluvial, 81.8% of the bedrock/karst region, 40.0% of the glacial-drift, and 25.0% of the bedrock/nonkarst region aquifers. The obsd. distribution was partially attributed to variations in general groundwater age among these aquifer types. A significant, inverse relation was detd. between total herbicide compd. concns. in groundwater and the av. soil slope within a 2-km radius of sampled wells. Steeper soil slopes may increase the likelihood of surface runoff occurring rather than groundwater infiltration, decreasing the transport of herbicide compds. to groundwater. As expected, a significant pos. relation was detd. between intensity of herbicide use and herbicide concns. in groundwater.
- 39Kolpin, D. W.; Thurman, M. E.; Linhart, S. M. The environmental occurrence of herbicides: The importance of degradates in ground water. Arch. Environ. Contam. Toxicol. 1998, 35, 385– 390, DOI: 10.1007/s002449900392[Crossref], [PubMed], [CAS], Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXlvFGnsb0%253D&md5=c1030306f771cbae1382382758737745The environmental occurrence of herbicides: the importance of degradates in ground waterKolpin, D. W.; Thurman, E. M.; Linhart, S. M.Archives of Environmental Contamination and Toxicology (1998), 35 (3), 385-390CODEN: AECTCV; ISSN:0090-4341. (Springer-Verlag New York Inc.)Numerous studies are being conducted to investigate the occurrence, fate, and effects on human health and the environment from the extensive worldwide use of herbicides to control weeds. Few studies, however, are considering the degradates of these herbicides in their investigations. Our study of herbicides in aquifers across Iowa found herbicide degradates to be prevalent in ground water, being detected in about 75% of the wells sampled. With the exception of atrazine, the frequencies of detection in ground water for a given herbicide increased multifold when its degradates were considered. Furthermore, a majority of the measured concn. for a given herbicide was in the form of its degradates--even for a relatively persistent compd. such as atrazine. For this study, degradates comprised from 60 to over 99% of a herbicide's measured concn. Because herbicide degradates can have similar acute and chronic toxicity as their parent compds., these compds. have environmental significance as well as providing a more complete understanding of the fate and transport of a given herbicide. Thus, it is essential that degradates are included in any type of herbicide investigation.
- 40Kolpin, D. W.; Thurman, M. E.; Linhart, S. M. Finding minimal herbicide concentrations in ground water? Try looking for their degradates. Sci. Total Environ. 2000, 248, 115– 122, DOI: 10.1016/S0048-9697(99)00535-5[Crossref], [PubMed], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXitlGrsrk%253D&md5=abb772735ce6feebf0cc74af53361338Finding minimal herbicide concentrations in ground water? Try looking for their degradatesKolpin, D. W.; Thurman, E. M.; Linhart, S. M.Science of the Total Environment (2000), 248 (2-3), 115-122CODEN: STENDL; ISSN:0048-9697. (Elsevier Science Ireland Ltd.)In Iowa groundwater, herbicide degradates were frequently detected. Herbicide degradates were 8 of the 10 most frequently detected compds. A majority of a herbicide's measured concn. was in the form of its degradates, 55 to >99%. The herbicide detection frequencies and concns. varied significantly among the major aquifer types sampled. These differences, however, were much more pronounced when herbicide degradates were included. Aquifer types presumed to have the most rapid recharge rates (alluvial and bedrock/karst region aquifers) were those most likely to contain detectable concns. of herbicide compds. Two indirect ests. of groundwater age (depth of well completion and dissolved O concn.) were used to sep. the sampled wells into general vulnerability classes (low, intermediate, and high). The results show that the herbicide detection frequencies and concns. varied significantly among the vulnerability classes regardless of whether or not herbicide degradates were considered. Nevertheless, when herbicide degradates were included, the frequency of herbicide compd. detection within the highest vulnerability class approached 90%, and the median total herbicide residue concn. increased over an order of magnitude, relative to the parent compds. alone, to 2 μg/L. The results from this study demonstrate that obtaining data on herbicide degradates is crit. for understanding the fate of herbicides in the hydrol. system. The prevalence of herbicide degradates documented in this study suggests that to accurately det. the overall effect on human health and the environment of a specific herbicide its degradates should also be considered.
- 41Kolpin, D. W.; Thurman, M. E.; Linhart, S. M. Occurrence of cyanazine compounds in groundwater: Degradates more prevalent than the parent compound. Environ. Sci. Technol. 2001, 35, 1217– 1222, DOI: 10.1021/es001520x[ACS Full Text ], [CAS], Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXhtVWlsLo%253D&md5=38d0d54cf6ed0f97ba058919f22f7e17Occurrence of Cyanazine Compounds in Groundwater: Degradates More Prevalent Than the Parent CompoundKolpin, Dana W.; Thurman, E. Michael; Linhart, S. MichaelEnvironmental Science and Technology (2001), 35 (6), 1217-1222CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)A recently developed anal. method using liq. chromatog./mass spectrometry was used to study the occurrence of cyanazine and its degradates cyanazine acid (CAC), cyanazine amide (CAM), deethylcyanazine (DEC), and deethylcyanazine acid (DCAC) in groundwater. This research represents some of the earliest data on the occurrence of cyanazine degradates in groundwater. Although cyanazine was infrequently detected in the 64 wells across Iowa sampled in 1999, cyanazine degradates were commonly found during this study. The most frequently detected cyanazine compd. was DCAC (32.8%) followed by CAC (29.7%), CAM (17.2%), DEC (3.1%), and cyanazine (3.1%). The frequency of detection for cyanazine or ≥1 of its degradates (CYTOT) was >12-fold over that of cyanazine alone (39.1% for CYTOT vs. 3.1% for cyanazine). Of the total measured concn. of cyanazine, only 0.2% was derived from its parent compd.-with DCAC (74.1%) and CAC (18.4%) comprising 92.5% of this total. Thus, although DCAC and CAC had similar frequencies of detection, DCAC was generally present in higher concns. No concns. of cyanazine compds. for this study exceeded water-quality criteria for the protection of human health. Only cyanazine, however, has such a criteria established. Nevertheless, because these cyanazine degradates are still chlorinated, they may have similar toxicity as their parent compd.-similar to what has been found with the chlorinated degradates of atrazine. Thus, the results of this study documented that data on the degradates for cyanazine are crit. for understanding its fate and transport in the hydrol. system. The prevalence of the chlorinated degradates of cyanazine found in groundwater suggests that to accurately det. the overall effect on human health and the environment from cyanazine its degradates should also be considered. In addn., because CYTOT was found in 57.6% of the samples collected from alluvial aquifers, about 2-5 times more frequently than the other major aquifer types (glacial drift, bedrock/karst, bedrock/nonkarst) under study, this finding has long-term implications for the occurrence of CYTOT in streams. It is anticipated that low-level concns. of CYTOT will continue to be detected in streams for years after the use of cyanazine has terminated (scheduled for the year 2000 in the US), primarily through its movement from groundwater into streams during base-flow conditions.
- 42Kolpin, D. W.; Schnoebelen, D. J.; Thurman, E. M. Degradates provide insight to spatial and temporal trends of herbicides in ground water. Ground Water 2004, 42, 601– 608, DOI: 10.1111/j.1745-6584.2004.tb02628.x[Crossref], [PubMed], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXlslajsrc%253D&md5=07e5cb7637c004e6d59d2e7c827d6b77Degradates provide insight to spatial and temporal trends of herbicides in ground waterKolpin, Dana W.; Schnoebelen, Douglas J.; Thurman, E. MichaelGround Water (2004), 42 (4), 601-608CODEN: GRWAAP; ISSN:0017-467X. (National Ground Water Association)Since 1995, a network of municipal wells in Iowa, representing all major aquifer types (alluvial, bedrock/karst region, glacial drift, bedrock/nonkarst region), has been repeatedly sampled for a broad suite of herbicide compds. yielding one of the most comprehensive statewide databases of such compds. currently available in the US. This dataset is ideal for documenting the insight that herbicide degradates provide to the spatial and temporal distribution of herbicides in groundwater. During 2001, 86 municipal wells in Iowa were sampled and analyzed for 21 herbicide parent compds. and 24 herbicide degradates. The frequency of detection increased from 17% when only herbicide parent compds. were considered to 53% when both herbicide parents and degradates were considered. The transport of herbicide compds. to groundwater is substantially underestimated when herbicide degradates are not considered. A significant difference in the results among the major aquifer types was apparent only when both herbicide parent compds. and their degradates were considered. Including herbicide degradates greatly improved the statistical relation to the age of the water being sampled. When herbicide parent compds. are considered, only 40% of the wells lacking a herbicide detection could be explained by the age of the water predating herbicide use. However, when herbicide degradates were also considered, 80% of the ground water samples lacking a detection could be explained by the age of the water predating herbicide use. A temporal pattern in alachlor concns. in groundwater could only be identified when Alachlor degradates were considered.
- 43Hladik, M. L.; Bouwer, E. J.; Roberts, A. L. Neutral chloroacetamide herbicide degradates and related compounds in Midwestern United States drinking water sources. Sci. Total Environ. 2008, 390, 155– 165, DOI: 10.1016/j.scitotenv.2007.09.042[Crossref], [PubMed], [CAS], Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVSgtLrN&md5=abdf989777329b14e54399dbdcfc5ecaNeutral chloroacetamide herbicide degradates and related compounds in Midwestern United States drinking water sourcesHladik, Michelle L.; Bouwer, Edward J.; Roberts, A. LynnScience of the Total Environment (2008), 390 (1), 155-165CODEN: STENDL; ISSN:0048-9697. (Elsevier Ltd.)Recent studies have revealed the presence of neutral degradates of chloroacetamide herbicides in the Chesapeake Bay at concns. greatly in excess of the parent compds. As some degradates are being considered for regulation in drinking water, exposure of human populations to such micropollutants is of interest. We report the results of a survey of source waters used by 12 drinking water utilities in the Midwestern US. Analytes included 20 neutral and 6 ionic chloroacetamide degradates, 4 parent chloroacetamide herbicides, 3 triazine herbicides, and 2 triazine degradates. Samples were collected during Fall 2003 and Spring 2004. In the fall samples, 16 of 20 neutral chloroacetamide degradates were detected, while 18 of 20 neutral chloroacetamide degradates were detected in the spring samples. Concns. of most parent chloroacetamides and neutral degradates were somewhat to substantially higher in the spring than in the fall, with median concns. of ∼10-100 ng/L. Groundwater sources tended to have lower concns. of parents and neutral degradates than surface water sources in the fall, although concns. of parents and degradates in groundwater were similar to those in surface water in the spring.
- 44Rosecrans, C. Z.; Musgrove, M. Water Quality of Groundwater Used for Public Supply in Principal Aquifers of the United States; Scientific Investigations Report 2020–5078; U.S. Geological Survey, 2020.
- 45U.S. Geological Survey, variously dated. Map of the Principal Aquifers of the United States; U.S. Geological Survey. https://water.usgs.gov/ogw/aquifer/map.html (accessed May 7, 2020).
- 46Lovelace, J. K.; Nielsen, M. G.; Read, A. L.; Murphy, C. J.; Maupin, M. A. Estimated Groundwater Withdrawals from Principal Aquifers in the United States, 2015; Circular 1464; U.S. Geological Survey, 2020.
- 47Burow, K. R.; Belitz, K. Groundwater Studies: Principal Aquifer Surveys; Fact Sheet 2014-3024; U.S. Geological Survey, 2014.
- 48Belitz, K.; Jurgens, B.; Landon, M. K.; Fram, M. S.; Johnson, T. Estimation of aquifer scale proportion using equal area grids: Assessment of regional scale groundwater quality. Water Resour. Res. 2010, 46, W11550 DOI: 10.1029/2010WR009321[Crossref], [CAS], Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVKltLk%253D&md5=b66fba63bf17b0246090ca8b227436d8Estimation of aquifer scale proportion using equal area grids: Assessment of regional scale groundwater qualityBelitz, Kenneth; Jurgens, Bryant; Landon, Matthew K.; Fram, Miranda S.; Johnson, TylerWater Resources Research (2010), 46 (11), W11550/1-W11550/14CODEN: WRERAQ; ISSN:0043-1397. (American Geophysical Union)The proportion of an aquifer with constituent concns. above a specified threshold (high concns.) is taken as a nondimensional measure of regional scale water quality. If computed on the basis of area, it can be referred to as the aquifer scale proportion. A spatially unbiased est. of aquifer scale proportion and a confidence interval for that est. are obtained through the use of equal area grids and the binomial distribution. Traditionally, the confidence interval for a binomial proportion is computed using either the std. interval or the exact interval. Research from the statistics literature has shown that the std. interval should not be used and that the exact interval is overly conservative. On the basis of coverage probability and interval width, the Jeffreys interval is preferred. If more than one sample per cell is available, cell declustering is used to est. the aquifer scale proportion, and Kish's design effect may be useful for estg. an effective no. of samples. The binomial distribution is also used to quantify the adequacy of a grid with a given no. of cells for identifying a small target, defined as a constituent that is present at high concns. in a small proportion of the aquifer. Case studies illustrate a consistency between approaches that use one well per grid cell and many wells per cell. The methods presented in this paper provide a quant. basis for designing a sampling program and for utilizing existing data.
- 49Koterba, M. T.; Wilde, F. D.; Lapham, W. W. Ground-Water Data-Collection Protocols and Procedures for the National Water-Quality Assessment Program—Collection and Documentation of Water-Quality Samples and Related Data; Open-File Report 95-399; U.S. Geological Survey, 1995.
- 50U.S. Geological Survey, variously dated. National Field Manual for the Collection of Water-Quality Data; Techniques of Water-Resources Investigations; Book 9, Chapters A1–A9. http://water.usgs.gov/owq/FieldManual/ (accessed Dec 21, 2018).
- 51Arnold, T. L.; DeSimone, L. A.; Bexfield, L. M.; Lindsey, B. D.; Barlow, J. R.; Kulongoski, J. T.; Musgrove, M.; Kingsbury, J. A.; Belitz, K. Groundwater Quality Data from the National Water-Quality Assessment Project, May 2012 through December 2013; data release; U.S. Geological Survey, 2016.
- 52Arnold, T. L.; Bexfield, L. M.; Musgrove, M.; Lindsey, B. D.; Stackelberg, P. E.; Barlow, J. R.; DeSimone, L. A.; Kulongoski, J. T.; Kingsbury, J. A.; Ayotte, J. D.; Fleming, B. J.; Belitz, K. Datasets from Groundwater-Quality Data from the National Water-Quality Assessment Project, January through December 2014 and Select Quality-Control Data from May 2012 through December 2014; data release; U.S. Geological Survey, 2017.
- 53Arnold, T. L.; Bexfield, L. M.; Musgrove, M.; Stackelberg, P. E.; Lindsey, B. D.; Kingsbury, J. A.; Kulongoski, J. T.; Belitz, K. Datasets from Groundwater-Quality and Select Quality-Control Data from the National Water-Quality Assessment Project, January through December 2015, and Previously Unpublished Data from 2013–2014; data release; U.S. Geological Survey, 2018.
- 54Arnold, T. L.; Sharpe, J. B.; Bexfield, L. M.; Musgrove, M.; Erickson, M. L.; Kingsbury, J. A.; Degnan, J. R.; Tesoriero, A. J.; Kulongoski, J. T.; Belitz, K. Datasets from Groundwater-Quality and Select Quality-Control Data from the National Water-Quality Assessment Project, January through December 2016, and Previously Unpublished Data from 2013 to 2015; data release; U.S. Geological Survey, 2020.
- 55Bexfield, L. M.; Toccalino, P. L.; Belitz, K.; Foreman, W. T.; Furlong, E. T. Environmental and Quality-Control Data Collected by the USGS National Water-Quality Assessment Project for Hormones and Pharmaceuticals in Groundwater Used as a Source of Drinking Water across the United States, 2013–15; data release; U.S. Geological Survey, 2019.
- 56Sandstrom, M. W.; Kanagy, L. K.; Anderson, C. A.; Kanagy, C. J. Determination of Pesticides and Pesticide Degradates in Filtered Water by Direct Aqueous-Injection Liquid Chromatography-Tandem Mass Spectrometry; Techniques and Methods; U.S. Geological Survey: 2015; Book 5, Chapter B11.
- 57Norman, J. E.; Kuivila, K. M.; Nowell, L. H. Prioritizing Pesticide Compounds for Analytical Methods Development; Scientific Investigations Report 2012–5045; U.S. Geological Survey, 2012. https://pubs.usgs.gov/sir/2012/5045/pdf/sir20125045.pdf (accessed Oct 19, 2020).
- 58Reregistration Eligibility Decision: Glyphosate; EPA 738-R-93-014; U.S. Environmental Protection Agency: Washington, D.C., 1993. https://www3.epa.gov/pesticides/chem_search/reg_actions/reregistration/red_PC-417300_1-Sep-93.pdf (accessed Aug 20, 2020).
- 59Shoda, M. E.; Nowell, L. H.; Stone, W. W.; Sandstrom, M. W.; Bexfield, L. M. Data Analysis Considerations for Pesticides Determined by National Water Quality Laboratory Schedule 2437; Scientific Investigations Report 2018-5007; U.S. Geological Survey, 2018.
- 60Bexfield, L. M.; Sandstrom, M. W.; Beaty, D. Field, Laboratory, and Third-Party Data for Assessment of the Quality of Pesticide Results Reported by the National Water Quality Laboratory for Groundwater Samples Collected by the National Water-Quality Assessment Project, 2013-18; data release; U.S. Geological Survey, 2020.
- 61Bexfield, L. M.; Belitz, K.; Sandstrom, M. W.; Beaty, D.; Medalie, L.; Lindsey, B. D.; Nowell, L. H. Quality of Pesticide Data for Groundwater Analyzed for the National Water-Quality Assessment Project, 2013–18; Scientific Investigations Report 2020–5072; U.S. Geological Survey, 2020.
- 62Atrazine Human Health Risk Assessment; EPA-HQ-OPP-2013-0266-1159; U.S. Environmental Protection Agency: Washington, D.C., 2013. https://www.regulations.gov/document?D=EPA-HQ-OPP-2013-0266-1159 (accessed May 8, 2020).
- 63Sinclair, C. J.; Boxall, A. B. Assessing the ecotoxicity of pesticide transformation products. Environ. Sci. Technol. 2003, 37, 4617– 4625, DOI: 10.1021/es030038m[ACS Full Text ], [CAS], Google Scholar63https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXms12kt7c%253D&md5=a8aee69647a67621b9a8e06b6a5b7954Assessing the Ecotoxicity of Pesticide Transformation ProductsSinclair, Chris J.; Boxall, Alistair B. A.Environmental Science and Technology (2003), 37 (20), 4617-4625CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Once released to the environment, pesticides may be degraded by abiotic and biotic processes. While parent compds. are assessed in detail in many regulatory schemes, the requirements for the assessment of transformation products are less well developed. This study was therefore performed to explore the relationships between the toxicity of transformation products and their parent compds. and to develop a pragmatic approach for use in the risk assessment of transformation products. Data were obtained on the properties and ecotoxicity of transformation products arising from a wide range of pesticides. Generally, transformation products were less toxic to fish, daphnids, and algae than their parent compd. In instances where a product was more toxic, the increase in toxicity could be explained by either (1) the presence of a pesticide toxicophore; (2) the fact that the product is the active part of a propesticide; (3) the product is accumulated to a greater extent than the parent compd.; or (4) the product has a more potent mode of action than the parent. On the basis of the findings, an approach has been proposed to est. the ecotoxicity of transformation products based on chem. structure and data on the toxicity of the parent compd. The assessments can be performed at an early stage in the risk assessment process to identify those substances that require further testing.
- 64Boxall, A. B.; Sinclair, C. J.; Fenner, K.; Kolpin, D.; Maund, S. J. When synthetic chemicals degrade in the environment. Environ. Sci. Technol. 2004, 38, 369A– 375A, DOI: 10.1021/es040624v
- 65Lindsey, B. D.; Jurgens, B. C.; Belitz, K. Tritium as an Indicator of Modern, Mixed, and Premodern Groundwater Age; Scientific Investigations Report 2019–5090; U.S. Geological Survey, 2019.
- 66Jin, S.; Homer, C. G.; Yang, L.; Danielson, P.; Dewitz, J.; Li, C.; Zhu, Z.; Xian, G.; Howard, D. Overall methodology design for the United States National Land Cover Database 2016 products. Remote Sens. 2019, 11, 2971 DOI: 10.3390/rs11242971
- 67Belitz, K.; Fram, M. S.; Johnson, T. D. Metrics for assessing the quality of groundwater used for public supply, CA, USA: Equivalent-population and area. Environ. Sci. Technol. 2015, 49, 8330– 8338, DOI: 10.1021/acs.est.5b00265[ACS Full Text ], [CAS], Google Scholar67https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVOktr7I&md5=0d5fd5b69da88b84709e3685d9a9de09Metrics for Assessing the Quality of Groundwater Used for Public Supply, CA, USA: Equivalent-Population and AreaBelitz, Kenneth; Fram, Miranda S.; Johnson, Tyler D.Environmental Science & Technology (2015), 49 (14), 8330-8338CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Data from 11000 public supply wells in 87 study areas were used to assess the quality of nearly all of the groundwater used for public supply in California. Two metrics were developed for quantifying groundwater quality: area with high concns. (km2 or proportion) and equiv.-population relying upon groundwater with high concns. (no. of people or proportion). Concns. are considered high if they are above a human-health benchmark. When expressed as proportions, the metrics are area-weighted and population-weighted detection frequencies. On a statewide-scale, ∼20% of the groundwater used for public supply has high concns. for one or more constituents (23% by area and 18% by equiv.-population). On the basis of both area and equiv.-population, trace elements are more prevalent at high concns. than either nitrate or org. compds. at the statewide-scale, in eight of nine hydrogeol. provinces, and in about three-quarters of the study areas. At a statewide-scale, nitrate is more prevalent than org. compds. based on area, but not on the basis of equiv.-population. The approach developed for this paper, unlike many studies, recognizes the importance of appropriately weighting information when changing scales, and is broadly applicable to other areas.
- 68Lindsey, B. D.; Katz, B. G.; Berndt, M. P.; Ardis, A. F.; Skach, K. A. Relations between sinkhole density and anthropogenic contaminants in selected carbonate aquifers in the eastern United States. Environ. Earth Sci. 2010, 60, 1073– 1090, DOI: 10.1007/s12665-009-0252-9[Crossref], [CAS], Google Scholar68https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptFKgtLY%253D&md5=04fe5b092b4e5000edba523117045918Relations between sinkhole density and anthropogenic contaminants in selected carbonate aquifers in the eastern United StatesLindsey, Bruce D.; Katz, Brian G.; Berndt, Marian P.; Ardis, Ann F.; Skach, Kenneth A.Environmental Earth Sciences (2010), 60 (5), 1073-1090CODEN: EESNCZ; ISSN:1866-6280. (Springer)The relation between sinkhole d. and water quality was investigated in seven selected carbonate aquifers in the eastern United States. Sinkhole d. for these aquifers was grouped into high (>25 sinkholes/100 km2), medium (1-25 sinkholes/100 km2), or low (<1 sinkhole/100 km2) categories using a geog. information system that included four independent databases covering parts of Alabama, Florida, Missouri, Pennsylvania, and Tennessee. Field measurements and concns. of major ions, nitrate, and selected pesticides in samples from 451 wells and 70 springs were included in the water-quality database. Data were collected as a part of the US Geol. Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Areas with high and medium sinkhole d. had the greatest well depths and depths to water, the lowest concns. of total dissolved solids and bicarbonate, the highest concns. of dissolved oxygen, and the lowest partial pressure of CO2 compared to areas with low sinkhole d. These chem. indicators are consistent conceptually with a conduit-flow-dominated system in areas with a high d. of sinkholes and a diffuse-flow-dominated system in areas with a low d. of sinkholes. Higher cave d. and spring discharge in Pennsylvania also support the concept that the high sinkhole d. areas are dominated by conduit-flow systems. Concns. of nitrate-N were significantly higher (p < 0.05) in areas with high and medium sinkhole d. than in low sinkhole-d. areas; when accounting for the variations in land use near the sampling sites, the high sinkhole-d. area still had higher concns. of nitrate-N than the low sinkhole-d. area. Detection frequencies of atrazine, simazine, metolachlor, prometon, and the atrazine degradate deethylatrazine indicated a pattern similar to nitrate; highest pesticide detections were assocd. with high sinkhole-d. areas. These patterns generally persisted when analyzing the detection frequency by land-use groups, particularly for agricultural land-use areas where pesticide use would be expected to be higher and more uniform areally compared to urban and forested areas. Although areas with agricultural land use and a high sinkhole d. were most vulnerable (median nitrate-N concn. was 3.7 mg/L, 11% of samples exceeded 10 mg/L, and had the highest frequencies of pesticide detection), areas with agricultural land use and low sinkhole d. still were vulnerable to contamination (median nitrate-N concn. was 1.5 mg/L, 8% of samples exceeded 10 mg/L, and had some of the highest frequencies of detections of pesticides). This may be due in part to incomplete or missing data regarding karst features (such as buried sinkholes, low-permeability <<dol<<dolword<<dol<<dol.
- 69Rupert, M. G.; Hunt, C. D.; Skinner, K. D.; Frans, L. M.; Maher, B. J. Groundwater Quality in the Columbia Plateau and Snake River Plain Basin-Fill and Basaltic-Rock Aquifers and the Hawaiian Volcanic-Rock Aquifers, Washington, Idaho, and Hawaii, 1993–2005; Circular 1359; U.S. Geological Survey, 2014. https://pubs.usgs.gov/circ/1359/ (accessed Oct 6, 2017).
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- 75Reregistration Eligibility Decision: Alachlor; EPA 738-R-98-020; U.S. Environmental Protection Agency: Washington, D.C., 1998. https://archive.epa.gov/pesticides/reregistration/web/pdf/0063.pdf (accessed May 11, 2020).
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- 77Fipronil: Environmental Fate and Ecological Effects Assessment and Characterization for Section 18 Registration of in-Furrow Applications to Rutabaga and Turnips; U.S. Environmental Protection Agency: Washington, D.C., 2005. https://www3.epa.gov/pesticides/chem_search/cleared_reviews/csr_PC-129121_31-Aug-05_a.pdf (accessed May 11, 2020).
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- 79Biological Evaluation for Diazinon ESA Assessment: Exposure Characterization for Diazinon; U.S. Environmental Protection Agency: Washington, D.C., 2016; Chapter 3. https://www.epa.gov/endangered-species/biological-evaluation-chapters-diazinon-esa-assessment#chapter3 (accessed May 11, 2020).
- 80Reregistration Eligibility Decision: Chlorothalonil; EPA 738-R-99-004; U.S. Environmental Protection Agency: Washington, D.C., 1999. https://archive.epa.gov/pesticides/reregistration/web/pdf/0097red.pdf (accessed May 11, 2020).
- 81Triazine Cumulative Human Health Risk Assessment; EPA-HQ-OPP-2013-0266-1160; U.S. Environmental Protection Agency: Washington, D.C., 2013. https://www.regulations.gov/document?D=EPA-HQ-OPP-2013-0266-1160 (accessed May 12, 2020).
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- 22Ryker, S. J.; Small, M. J. Combining occurrence and toxicity information to identify priorities for drinking-water mixture research. Risk Anal. 2008, 28, 653– 666, DOI: 10.1111/j.1539-6924.2008.00985.x[Crossref], [PubMed], [CAS], Google Scholar22https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BD1cvms1Chtw%253D%253D&md5=0adec0201c972c4a10e06e08e671ada9Combining occurrence and toxicity information to identify priorities for drinking-water mixture researchRyker Sarah J; Small Mitchell JRisk analysis : an official publication of the Society for Risk Analysis (2008), 28 (3), 653-66 ISSN:.Characterizing all possible chemical mixtures in drinking water is a potentially overwhelming project, and the task of assessing each mixture's net toxicity even more daunting. We propose that analyzing occurrence information on mixtures in drinking water may help to narrow the priorities and inform the approaches taken by researchers in mixture toxicology. To illustrate the utility of environmental data for refining the mixtures problem, we use a recent compilation of national ground-water-quality data to examine proposed U.S. Environmental Protection Agency (EPA) and Agency for Toxic Substances and Disease Registry (ATSDR) models of noncancer mixture toxicity. We use data on the occurrence of binary and ternary mixtures of arsenic, cadmium, and manganese to parameterize an additive model and compute hazard index scores for each drinking-water source in the data set. We also use partially parameterized interaction models to perform a bounding analysis estimating the interaction potential of several binary and ternary mixtures for which the toxicological literature is limited. From these results, we estimate a relative value of additional toxicological information for each mixture. For example, we find that according to the U.S. EPA's interaction model, the levels of arsenic and cadmium found in U.S. drinking water are unlikely to have synergistic cardiovascular effects, but the same mixture's potential for synergistic neurological effects merits further study. Similar analysis could in future be used to prioritize toxicological studies based on their potential to reduce scientific and regulatory uncertainty. Environmental data may also provide a means to explore the implications of alternative risk models for the toxicity and interaction of complex mixtures.
- 23Kortenkamp, A.; Faust, M. State of the Art Report on Mixture Toxicity, Final Report: Executive Summary; School of Pharmacy, University of London: London, U.K., 2009.
- 24Meek, M. E.; Boobis, A. R.; Crofton, K. M.; Heinemeyer, G.; Van Raaij, M.; Vickers, C. Risk assessment of combined exposure to multiple chemicals: A WHO/IPCS framework. Regul. Toxicol. Pharmacol. 2011, 60, S1– S14, DOI: 10.1016/j.yrtph.2011.03.010[Crossref], [PubMed], [CAS], Google Scholar24https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXntlGrsLw%253D&md5=c86a6a2b86d9bd368e09890a18367ef8Risk assessment of combined exposure to multiple chemicals: A WHO/IPCS frameworkMeek, M. E.; Boobis, Alan R.; Crofton, Kevin M.; Heinemeyer, Gerhard; Van Raaij, Marcel; Vickers, CarolynRegulatory Toxicology and Pharmacology (2011), 60 (2, Suppl. 1), S1-S14CODEN: RTOPDW; ISSN:0273-2300. (Elsevier B.V.)This paper describes a framework for the risk assessment of combined exposure to multiple chems. based on and developed subsequent to the World Health Organization/International Program on Chem. Safety Workshop on Aggregate/Cumulative Risk Assessment (Combined Exposures to Multiple Chems.) held in 2007. It is designed to aid risk assessors in identifying priorities for risk management for a wide range of applications where co-exposures to multiple chems. are expected. It is based on a hierarchical (phased) approach that involves integrated and iterative consideration of exposure and hazard at all phases, with each tier being more refined than the previous one, but more labor and data intensive. It includes ref. to predictive and probabilistic methodol. in various tiers in addn. to tiered consideration of uncertainty. Two case studies that have been developed to test and refine the framework are shown.
- 25Price, P. S.; Han, X. Maximum cumulative ratio (MCR) as a tool for assessing the value of performing a cumulative risk assessment. Int. J. Environ. Res. Public Health 2011, 8, 2212– 2225, DOI: 10.3390/ijerph8062212[Crossref], [PubMed], [CAS], Google Scholar25https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A280%3ADC%252BC3MnpvVGhtA%253D%253D&md5=653198aaad284dc02ff6483adae8e9d6Maximum cumulative ratio (MCR) as a tool for assessing the value of performing a cumulative risk assessmentPrice Paul S; Han XiangluInternational journal of environmental research and public health (2011), 8 (6), 2212-25 ISSN:.Due to the vast number of possible combinations of chemicals to which individuals are exposed and the resource-intensive nature of cumulative risk assessments, there is a need to determine when cumulative assessments are most required. This paper proposes the use of the maximum cumulative ratio (MCR) as a tool for this evaluation. MCR is the ratio of the cumulative toxicity received by an individual from exposure to multiple chemical stressors to the largest toxicity from a single chemical stressor. The MCR is a quantitative measure of the difference in an individual's toxicity estimated using a chemical-by-chemical approach and using an additive model of toxicity. As such, it provides a conservative estimate of the degree to which individuals' toxicities could be underestimated by not performing a cumulative risk assessment. In an example application, MCR is shown to be applicable to the evaluation of cumulative exposures involving up to 81 compounds and to provide key insights into the cumulative effects posed by exposures to multiple chemicals. In this example, MCR values suggest that individuals exposed to combinations of chemicals with the largest Hazard Indices were dominated by the contributions of one or two compounds.
- 26Toccalino, P. L.; Norman, J. E.; Scott, J. C. Chemical mixtures in untreated water from public-supply wells in the U.S.—Occurrence, composition, and potential toxicity. Sci. Total Environ. 2012, 431, 262– 270, DOI: 10.1016/j.scitotenv.2012.05.044[Crossref], [PubMed], [CAS], Google Scholar26https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC38XpsVOisb8%253D&md5=ce3d6de61f6d6fe7f2c430e98c3a286dChemical mixtures in untreated water from public-supply wells in the U.S. - Occurrence, composition, and potential toxicityToccalino, Patricia L.; Norman, Julia E.; Scott, Jonathon C.Science of the Total Environment (2012), 431 (), 262-270CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)Chem. mixts. are prevalent in groundwater used for public water supply, but little is known about their potential health effects. As part of a large-scale ambient groundwater study, the authors evaluated chem. mixts. across multiple chem. classes, and included more chem. contaminants than in previous studies of mixts. in public-supply wells. They (1) assessed the occurrence of chem. mixts. in untreated source-water samples from public-supply wells, (2) detd. the compn. of the most frequently occurring mixts., and (3) characterized the potential toxicity of mixts. using a new screening approach. The U.S. Geol. Survey collected one untreated water sample from each of 383 public wells distributed across 35 states, and analyzed the samples for as many as 91 chem. contaminants. Concns. of mixt. components were compared to individual human-health benchmarks; the potential toxicity of mixts. was characterized by addn. of benchmark-normalized component concns. Most samples (84%) contained mixts. of two or more contaminants, each at concns. greater than one-tenth of individual benchmarks. The chem. mixts. that most frequently occurred and had the greatest potential toxicity primarily were composed of trace elements (including arsenic, strontium, or uranium), radon, or nitrate. Herbicides, disinfection byproducts, and solvents were the most common org. contaminants in mixts. The sum of benchmark-normalized concns. was greater than 1 for 58% of samples, suggesting that there could be potential for mixts. toxicity in more than half of the public-well samples. The findings can be used to help set priorities for groundwater monitoring and suggest future research directions for drinking-water treatment studies and for toxicity assessments of chem. mixts. in water resources.
- 27Framework for Assessing Health Impacts of Multiple Chemicals and Other Stressors (Update); U.S. Department of Health and Human Services: Washington, D.C., 2018. https://www.atsdr.cdc.gov/interactionprofiles/ip-ga/ipga.pdf (accessed April 23, 2020).
- 28Cumulative Assessment of Risk from Pesticides; U.S. Environmental Protection Agency: Washington, D.C., 2020. https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/cumulative-assessment-risk-pesticides (accessed March 20, 2020).
- 29Manamsa, K.; Crane, E.; Stuart, M.; Talbot, J.; Lapworth, D.; Hart, A. A national-scale assessment of micro-organic contaminants in groundwater of England and Wales. Sci. Total Environ. 2016, 568, 712– 726, DOI: 10.1016/j.scitotenv.2016.03.017[Crossref], [PubMed], [CAS], Google Scholar29https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC28XlslCisL8%253D&md5=15bebbb4d8937e4aec667e0cbd0e748eA national-scale assessment of micro-organic contaminants in groundwater of England and WalesManamsa, Katya; Crane, Emily; Stuart, Marianne; Talbot, John; Lapworth, Dan; Hart, AlwynScience of the Total Environment (2016), 568 (), 712-726CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)A large variety of micro-org. (MO) compds. is used in huge quantities for a range of purposes (e.g., manufg., food prodn., healthcare) and is now being frequently detected in the aquatic environment. Interest in the occurrence of MO contaminants in the terrestrial and aquatic environments continues to grow, as well as in their environmental fate and potential toxicity. However, the contamination of groundwater resources by MOs has a limited evidence base compared to other freshwater resources. Of particular concern are newly 'emerging contaminants' such as pharmaceuticals and lifestyle compds., particularly those with potential endocrine disrupting properties. While groundwater often has a high degree of protection from pollution due to phys., chem. and biol. attenuation processes in the subsurface compared to surface aquatic environments, trace concns. of a large range of compds. are still detected in groundwater and in some cases may persist for decades due to the long residence times of groundwater systems. This study provides the first national-scale assessment of micro-org. compds. in groundwater in England and Wales. A large set of monitoring data was analyzed to det. the relative occurrence and detected concns. of different groups of compds. and to det. relationships with land-use, aquifer type and groundwater vulnerability. MOs detected including emerging compds. such as caffeine, DEET, bisphenol A, anti-microbial agents and pharmaceuticals as well as a range of legacy contaminants including chlorinated solvents and THMs, petroleum hydrocarbons, pesticides and other industrial compds. There are clear differences in MOs between land-use types, particularly for urban-industrial and natural land-use. Temporal trends of MO occurrence are assessed but establishing long-term trends is not yet possible.
- 30Kiefer, K.; Muller, A.; Singer, H.; Hollender, J. New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMS. Water Res. 2019, 165, 114972 DOI: 10.1016/j.watres.2019.114972[Crossref], [PubMed], [CAS], Google Scholar30https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC1MXhs1emsLnN&md5=9bb29e6932b0cf9b8337199a3649db48New relevant pesticide transformation products in groundwater detected using target and suspect screening for agricultural and urban micropollutants with LC-HRMSKiefer, Karin; Muller, Adrian; Singer, Heinz; Hollender, JulianeWater Research (2019), 165 (), 114972CODEN: WATRAG; ISSN:0043-1354. (Elsevier Ltd.)Groundwater is a major drinking water resource, but its quality is threatened by a broad variety of anthropogenic micropollutants (MPs), originating from agriculture, industry, or households, and undergoing various transformation processes during subsurface passage. To det. a worst-case impact of pesticide application in agriculture on groundwater quality, a target and suspect screening for more than 300 pesticides and more than 1100 pesticide transformation products (TPs) was performed in 31 Swiss groundwater samples which predominantly originated from areas with intensive agriculture. To assess addnl. urban contamination sources, more than 250 common urban MPs were quantified. Most of the screened pesticide TPs were exptl. obsd. by the pesticide producers within the European pesticide registration. To cover very polar pesticide TPs, vacuum-assisted evaporative concn. was used for enrichment, followed by liq. chromatog. high-resoln. tandem mass spectrometry (LC-HRMS/MS). Based on intensity, isotope pattern, retention time, and in silico fragmentation, the suspect hits were prioritised and verified. We identified 22 suspects unequivocally and five tentatively; 13 TPs are reported here for the first time to be detected in groundwater. In 13 out of 31 groundwater samples, the total concn. of the 20 identified and quantified suspects (1 pesticide and 19 pesticide TPs) exceeded the total concn. of the 519 targets (236 pesticides and TPs; 283 urban MPs) for which we screened. Pesticide TPs had higher concns. than the parent pesticides, illustrating their importance for groundwater quality. The newly identified very polar chlorothalonil TP R471811 was the only compd. detected in all samples with concns. ranging from 3 to 2700 ng/L. Agricultural MP concn. and detection frequency correlated with agricultural land use in the catchment, except for aquifers, where protective top layers reduced MP transport from the surface. In contrast to agricultural MPs, urban MPs displayed almost no correlation with land use. The dominating entry pathway of urban MPs was river bank filtration.
- 31Close, M. E.; Humphries, B.; Northcott, G. Outcomes of the first combined national survey of pesticides and emerging organic contaminants (EOCs) in groundwater in New Zealand 2018. Sci. Total Environ. 2020, 754, 142005 DOI: 10.1016/j.scitotenv.2020.142005
- 32Kolpin, D. W.; Goolsby, D. A.; Thurman, M. E. Pesticides in near-surface aquifers: an assessment using highly sensitive analytical methods and tritium. J. Environ. Qual. 1995, 24, 1125– 1132, DOI: 10.2134/jeq1995.00472425002400060011x[Crossref], [CAS], Google Scholar32https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXps1Klsrs%253D&md5=43050239537b15d67623b17b80dfca9bPesticides in near-surface aquifers: an assessment using highly sensitive analytical methods and tritiumKolpin, Dana W.; Goolsby, Donald A.; Thurman, E. MichaelJournal of Environmental Quality (1995), 24 (6), 1125-32CODEN: JEVQAA; ISSN:0047-2425. (American Society of Agronomy)In 1992, the U.S. Geol. Survey (USGS) detd. the distribution of pesticides in near-surface aquifers of the midwestern USA to be much more widespread than originally detd. during a 1991 USGS study. The frequency of pesticide detection increased from 28.4% during the 1991 study to 59.0% during the 1992 study. This increase in pesticide detection was primarily the result of a more sensitive anal. method that used reporting limits as much as 20 times lower than previously available and a threefold increase in the no. of pesticide metabolites analyzed. No pesticide concns. exceeded the U.S. Environmental Protection Agency's (USEPAs) max. contaminated levels or health advisory levels for drinking water. However, five of the six most frequently detected compds. during 1992 were pesticide metabolites that currently do not have drinking water stds. detd. The frequent presence of pesticide metabolites for this study documents the importance of obtaining information on these compds. to understand the fate and transport of pesticides in the hydrol. system. It appears that the 56 parent compds. analyzed follow similar pathways through the hydrol. system as atrazine. When atrazine was detected by routine or sensitive anal. methods, there was an increased likelihood of detecting addnl. parent compds. As expected, the frequency of pesticide detection was highly dependent on the anal. reporting limit. The no. of atrazine detections more than doubled as the reporting limit decreased from 0.10 to 0.01 μg/L. The 1992 data provided no indication that the frequency of pesticide detection would level off as improved anal. methods provide concns. below 0.003 μg/L. A relation was detd. between groundwater age and the frequency of pesticide detection, with 15.8% of the samples composed of pre-1953 water and 70.3% of the samples of post-1953 water having a detection of at least one pesticide or metabolite. Pre-1953 water is less likely to contain pesticides because it tends to predate the use of pesticides to increase crop prodn. in the Midwest. Pre-1953 water was more likely to occur in the near-surface bedrock aquifers (50.0%) than in the near-surface unconsolidated (9.1%) sampled.
- 33Kolpin, D. W.; Thurman, M. E.; Goolsby, D. A. Occurrence of selected pesticides and their metabolites in near-surface aquifers of the midwestern United States. Environ. Sci. Technol. 1996, 30, 335– 340, DOI: 10.1021/es950462q[ACS Full Text ], [CAS], Google Scholar33https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2MXpsFyrtLo%253D&md5=f98656d7cf25ee213b709cde2a473c58Occurrence of Selected Pesticides and Their Metabolites in Near-Surface Aquifers of the Midwestern United StatesKolpin, Dana W.; Thurman, E. Michael; Goolsby, Donald A.Environmental Science and Technology (1996), 30 (1), 335-40CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)The occurrence and distribution of selected pesticides and their metabolites were investigated through the collection of 837 water-quality samples from 303 wells across the Midwest. Results of this study showed that 5 of the 6 most frequently detected compds. were pesticide metabolites. Thus, it was common for a metabolite to be found more frequently in groundwater than its parent compd. The metabolite alachlor ethanesulfonic acid (alachlor-ESA; 2-[(2,6-diethylphenyl)(methoxymethyl)amino]-2-oxoethanesulfonic acid) was detected almost 10 times as frequently and at much higher concns. than its parent compd. alachlor (2-chloro-2',6'-diethyl-N-(methoxymethyl)acetamide). The median detectable atrazine (2-chloro-4-ethylamino-6- isopropylamino-s-triazine) concn. was almost half that of atrazine residue (atrazine plus the 2 atrazine metabolites analyzed). Cyanazine amide [2-chloro-4-(1-carbamoyl-1-methylethylamino)-6-ethylamino-s-triazine] was detected almost twice as frequently as cyanazine (2-chloro-4-ethylamino-6-methylpropionitrileamino-s-triazine). Results show that information on pesticide metabolites is necessary to understand the environmental fate of pesticides. Consequently, if pesticide metabolites are not quantified, the effects of chem. use on groundwater quality would be substantially underestimated. Thus, continued research is needed to identify major degrdn. pathways for all pesticides and to develop anal. methods to det. their concns. in water and other environmental data.
- 34Kolpin, D. W.; Barbash, J. E.; Gilliom, R. J. Occurrence of pesticides in shallow groundwater of the United States: Initial results from the National Water-Quality Assessment Program. Environ. Sci. Technol. 1998, 32, 558– 566, DOI: 10.1021/es970412g[ACS Full Text ], [CAS], Google Scholar34https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXmt1Ogsg%253D%253D&md5=6b6d0101bb356573d60001b344d36fb0Occurrence of Pesticides in Shallow Groundwater of the United States: Initial Results from the National Water-Quality Assessment ProgramKolpin, Dana W.; Barbash, Jack E.; Gilliom, Robert J.Environmental Science and Technology (1998), 32 (5), 558-566CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)The first phase of intensive data collection for the National Water Quality Assessment (NAWQA) program was completed during 1993-1995 in 20 major hydrol. basins of the USA. Groundwater land use studies, designed to sample recently recharged groundwater (generally within 10 yr) beneath specific land use and hydrogeol. settings, are a major component of the groundwater quality assessment for NAWQA. Pesticide results from 41 land use studies conducted during 1993-1995 indicated that pesticides were commonly detected in shallow groundwater, being obsd. at 54.4% of the 1034 sites sampled in agricultural and urban settings across the USA. Pesticide concns. were generally low, with >95% of the detections at concns. <1 mg/L; of 46 pesticide compds. examd., 39 were detected. Compds. detected most frequently were atrazine (38.2%), deethylatrazine (34.2%), simazine (18.0%), metolachlor (14.6%), and prometon (13.9%). Statistically significant relations were obsd. between frequencies of detection and the use, mobility, and persistence of these compds. Pesticides were commonly detected in agricultural (56.4%; 813 sites) and urban (46.6%; 221 sites) settings. Frequent pesticide detection in urban areas indicated that, as with agricultural pesticide use in agricultural areas, urban and suburban pesticide use significantly contributed to pesticide occurrence in shallow groundwater. Although pesticides were detected in groundwater sampled in urban areas and all 9 agricultural land-use categories examd., significant variations in occurrence were obsd. among these categories. Max. contaminant levels (MCL) established by USEPA for drinking water were exceeded for only 1 pesticide (atrazine, 3 mg/L) at a single location; however, MCL have been established for only 25 of 46 pesticide compds. examd., do not cover pesticide degradates, and, currently, do not account for additive or synergistic effects of combinations of pesticide compds. or potential effects on nearby aquatic ecosystems.
- 35Kolpin, D. W.; Barbash, J. E.; Gilliom, R. J. Pesticides in groundwater of the United States, 1992-96. Ground Water 2000, 38, 858– 863, DOI: 10.1111/j.1745-6584.2000.tb00684.x[Crossref], [CAS], Google Scholar35https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXnvFyktbc%253D&md5=9be13ebf210aaee41fd6657a856767b9Pesticides in ground water of the United States, 1992-1996Kolpin, Dana W.; Barbash, Jack E.; Gilliom, Robert J.Ground Water (2000), 38 (6), 858-863CODEN: GRWAAP; ISSN:0017-467X. (National Ground Water Association)During the 1st cycle of the National Water Quality Assessment (1992-1996), groundwater in 20 of the nation's major hydrol. basins was analyzed for 90 pesticide compds. (pesticides and degradates). One or more of the pesticide compds. examd. were detected at 48.4% of the 2485 groundwater sites sampled. However, ∼70% of the sites where pesticides were detected, ≥2 pesticide compds. analyzed were present-documenting the prevalence of pesticide mixts. in groundwater. The pesticide concns. encountered were generally low, with the median total concn. (summation of concns. for the 90 pesticide compds.) being 0.046 μg/L. Pesticides were commonly detected in shallow groundwater beneath both agricultural (60.4%) and urban (48.5%) areas. This is an important finding because, although agricultural activities have long been assocd. with pesticide contamination, urban areas have only recently been recognized as a potential source of these types of compds. Pesticides with higher frequencies of detection were generally those with more extensive use, greater environmental persistence, and greater mobility in groundwater (lower soil-water partition coeffs.).
- 36Bexfield, L. M. Decadal-scale changes of pesticides in ground water of the United States, 1993-2003. J. Environ. Qual. 2008, 37, S-226– S-239, DOI: 10.2134/jeq2007.0054[Crossref], [CAS], Google Scholar36https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD1cXhtFagurnN&md5=fbfd578357bd283f3d5a9239b881a2c7Decadal-scale changes of pesticides in ground water of the United States, 1993-2003Bexfield, Laura M.Journal of Environmental Quality (2008), 37 (5, Suppl.), S/226-S/239CODEN: JEVQAA; ISSN:0047-2425. (American Society of Agronomy)Pesticide data for groundwater sampled across the US between 1993-1995 and 2001-2003 by the US Geol. Survey National Water-Quality Assessment Program were evaluated for trends in detection frequency and concn. The data anal. evaluated samples collected from a total of 362 wells located in 12 local well networks characterizing shallow groundwater in agricultural areas and 6 local well networks characterizing the drinking water resource in areas of variable land use. Each well network was sampled once during 1993-1995 and once during 2001-2003. The networks provide an overview of conditions across a wide range of hydrogeol. settings and in major agricultural areas that vary in dominant crop type and pesticide use. Of ∼80 pesticide compds. analyzed, only 6 compds. were detected in groundwater from ≥10 wells during both sampling events. These compds. were the triazine herbicides atrazine, simazine, and prometon; the acetanilide herbicide metolachlor; the urea herbicide tebuthiuron; and an atrazine degradate, deethylatrazine (DEA). Obsd. concns. of these compds. generally were <0.12 μg/L. At individual wells, changes in concns. typically were <0.02 μg/L. Data anal. incorporated adjustments for changes in lab. recovery as assessed through lab. spikes. In wells yielding detectable concns. of atrazine, DEA, and prometon, concns. were significantly lower (α =0.1) in 2001-2003 than in 1993-1995, whereas detection frequency of these compds. did not change significantly. Trends in atrazine concns. at shallow wells in agricultural areas were found to be consistent overall with recent atrazine use data.
- 37Toccalino, P. L.; Gilliom, R. J.; Lindsey, B. D.; Rupert, M. G. Pesticides in groundwater of the United States: Decadal-scale changes, 1993-2011. Groundwater 2014, 52, 112– 125, DOI: 10.1111/gwat.12176[Crossref], [PubMed], [CAS], Google Scholar37https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2cXhsFyrs7nJ&md5=f86b694d1e2b0da1fab6ac6fba4161c7Pesticides in Groundwater of the United States: Decadal-Scale Changes, 1993-2011Toccalino, Patricia L.; Gilliom, Robert J.; Lindsey, Bruce D.; Rupert, Michael G.Groundwater (2014), 52 (S1), 112-125CODEN: GRWAAP; ISSN:0017-467X. (Wiley-Blackwell)The national occurrence of 83 pesticide compds. in groundwater of the United States and decadal-scale changes in concns. for 35 compds. were assessed for the 20-yr period from 1993-2011. Samples were collected from 1271 wells in 58 nationally distributed well networks. Networks consisted of shallow (mostly monitoring) wells in agricultural and urban land-use areas and deeper (mostly domestic and public supply) wells in major aquifers in mixed land-use areas. Wells were sampled once during 1993-2001 and once during 2002-2011. Pesticides were frequently detected (53% of all samples), but concns. seldom exceeded human-health benchmarks (1.8% of all samples). The five most frequently detected pesticide compds.-atrazine, deethylatrazine, simazine, metolachlor, and prometon-each had statistically significant (p < 0.1) changes in concns. between decades in one or more categories of well networks nationally aggregated by land use. For agricultural networks, concns. of atrazine, metolachlor, and prometon decreased from the first decade to the second decade. For urban networks, deethylatrazine concns. increased and prometon concns. decreased. For major aquifers, concns. of deethylatrazine and simazine increased. The directions of concn. changes for individual well networks generally were consistent with changes detd. from nationally aggregated data. Altogether, 36 of the 58 individual well networks had statistically significant changes in concns. of one or more pesticides between decades, with the majority of changes attributed to the five most frequently detected pesticide compds. The magnitudes of median decadal-scale concn. changes were small-ranging from -0.09 to 0.03 μg/L-and were 35- to 230,000-fold less than human-health benchmarks.
- 38Kolpin, D. W.; Kalkhoff, S. J.; Goosby, D. A.; Sneck-Fahrer, D. A.; Thurman, M. E. Occurrence of selected herbicides and herbicide degradation products in Iowa’s ground water, 1995. Ground Water 1997, 35, 679– 688, DOI: 10.1111/j.1745-6584.1997.tb00134.x[Crossref], [CAS], Google Scholar38https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK2sXktlKmu7w%253D&md5=e0b00710376a49c9bcbc8b1ce840f9a4Occurrence of selected herbicides and herbicide degradation products in Iowa's ground water, 1995Kolpin, Dana W.; Kalkhoff, Stephen J.; Goolsby, Donald A.; Sneck-Fahrer, Debra A.; Thurman, E. MichaelGround Water (1997), 35 (4), 679-688CODEN: GRWAAP; ISSN:0017-467X. (Ground Water Publishing)Herbicide compds. were prevalent in groundwater across Iowa, being detected in 70% of the 106 municipal wells sampled during the summer of 1995. Herbicide degrdn. products were 3 of the 4 most frequently detected compds. for this study. The degrdn. product alachlor ethanesulfonic acid was the most frequently detected compd. (65.1%), followed by atrazine (40.6%), and the degrdn. products deethylatrazine (34.9%), and cyanazine amide (19.8%). The corn herbicide acetochlor, 1st registered for widespread use in the US in Mar. 1994, was detected in a single water sample. No reported herbicide compd. concns. for this study exceeded current US EPA's max. contaminant levels or health advisory levels for drinking water, although the herbicide degrdn. products examd. have yet to have such levels established. The occurrence of herbicide compds. had a significant, inverse relation to well depth and a significant, pos. relation to dissolved O concn. It is felt that both well depth and dissolved O are acting as rough surrogates to groundwater age, with younger groundwater being more likely to contain herbicide compds. The occurrence of herbicide compds. was substantially different among the major aquifer types across Iowa, being detected in 82.5% of the alluvial, 81.8% of the bedrock/karst region, 40.0% of the glacial-drift, and 25.0% of the bedrock/nonkarst region aquifers. The obsd. distribution was partially attributed to variations in general groundwater age among these aquifer types. A significant, inverse relation was detd. between total herbicide compd. concns. in groundwater and the av. soil slope within a 2-km radius of sampled wells. Steeper soil slopes may increase the likelihood of surface runoff occurring rather than groundwater infiltration, decreasing the transport of herbicide compds. to groundwater. As expected, a significant pos. relation was detd. between intensity of herbicide use and herbicide concns. in groundwater.
- 39Kolpin, D. W.; Thurman, M. E.; Linhart, S. M. The environmental occurrence of herbicides: The importance of degradates in ground water. Arch. Environ. Contam. Toxicol. 1998, 35, 385– 390, DOI: 10.1007/s002449900392[Crossref], [PubMed], [CAS], Google Scholar39https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADyaK1cXlvFGnsb0%253D&md5=c1030306f771cbae1382382758737745The environmental occurrence of herbicides: the importance of degradates in ground waterKolpin, D. W.; Thurman, E. M.; Linhart, S. M.Archives of Environmental Contamination and Toxicology (1998), 35 (3), 385-390CODEN: AECTCV; ISSN:0090-4341. (Springer-Verlag New York Inc.)Numerous studies are being conducted to investigate the occurrence, fate, and effects on human health and the environment from the extensive worldwide use of herbicides to control weeds. Few studies, however, are considering the degradates of these herbicides in their investigations. Our study of herbicides in aquifers across Iowa found herbicide degradates to be prevalent in ground water, being detected in about 75% of the wells sampled. With the exception of atrazine, the frequencies of detection in ground water for a given herbicide increased multifold when its degradates were considered. Furthermore, a majority of the measured concn. for a given herbicide was in the form of its degradates--even for a relatively persistent compd. such as atrazine. For this study, degradates comprised from 60 to over 99% of a herbicide's measured concn. Because herbicide degradates can have similar acute and chronic toxicity as their parent compds., these compds. have environmental significance as well as providing a more complete understanding of the fate and transport of a given herbicide. Thus, it is essential that degradates are included in any type of herbicide investigation.
- 40Kolpin, D. W.; Thurman, M. E.; Linhart, S. M. Finding minimal herbicide concentrations in ground water? Try looking for their degradates. Sci. Total Environ. 2000, 248, 115– 122, DOI: 10.1016/S0048-9697(99)00535-5[Crossref], [PubMed], [CAS], Google Scholar40https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3cXitlGrsrk%253D&md5=abb772735ce6feebf0cc74af53361338Finding minimal herbicide concentrations in ground water? Try looking for their degradatesKolpin, D. W.; Thurman, E. M.; Linhart, S. M.Science of the Total Environment (2000), 248 (2-3), 115-122CODEN: STENDL; ISSN:0048-9697. (Elsevier Science Ireland Ltd.)In Iowa groundwater, herbicide degradates were frequently detected. Herbicide degradates were 8 of the 10 most frequently detected compds. A majority of a herbicide's measured concn. was in the form of its degradates, 55 to >99%. The herbicide detection frequencies and concns. varied significantly among the major aquifer types sampled. These differences, however, were much more pronounced when herbicide degradates were included. Aquifer types presumed to have the most rapid recharge rates (alluvial and bedrock/karst region aquifers) were those most likely to contain detectable concns. of herbicide compds. Two indirect ests. of groundwater age (depth of well completion and dissolved O concn.) were used to sep. the sampled wells into general vulnerability classes (low, intermediate, and high). The results show that the herbicide detection frequencies and concns. varied significantly among the vulnerability classes regardless of whether or not herbicide degradates were considered. Nevertheless, when herbicide degradates were included, the frequency of herbicide compd. detection within the highest vulnerability class approached 90%, and the median total herbicide residue concn. increased over an order of magnitude, relative to the parent compds. alone, to 2 μg/L. The results from this study demonstrate that obtaining data on herbicide degradates is crit. for understanding the fate of herbicides in the hydrol. system. The prevalence of herbicide degradates documented in this study suggests that to accurately det. the overall effect on human health and the environment of a specific herbicide its degradates should also be considered.
- 41Kolpin, D. W.; Thurman, M. E.; Linhart, S. M. Occurrence of cyanazine compounds in groundwater: Degradates more prevalent than the parent compound. Environ. Sci. Technol. 2001, 35, 1217– 1222, DOI: 10.1021/es001520x[ACS Full Text ], [CAS], Google Scholar41https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3MXhtVWlsLo%253D&md5=38d0d54cf6ed0f97ba058919f22f7e17Occurrence of Cyanazine Compounds in Groundwater: Degradates More Prevalent Than the Parent CompoundKolpin, Dana W.; Thurman, E. Michael; Linhart, S. MichaelEnvironmental Science and Technology (2001), 35 (6), 1217-1222CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)A recently developed anal. method using liq. chromatog./mass spectrometry was used to study the occurrence of cyanazine and its degradates cyanazine acid (CAC), cyanazine amide (CAM), deethylcyanazine (DEC), and deethylcyanazine acid (DCAC) in groundwater. This research represents some of the earliest data on the occurrence of cyanazine degradates in groundwater. Although cyanazine was infrequently detected in the 64 wells across Iowa sampled in 1999, cyanazine degradates were commonly found during this study. The most frequently detected cyanazine compd. was DCAC (32.8%) followed by CAC (29.7%), CAM (17.2%), DEC (3.1%), and cyanazine (3.1%). The frequency of detection for cyanazine or ≥1 of its degradates (CYTOT) was >12-fold over that of cyanazine alone (39.1% for CYTOT vs. 3.1% for cyanazine). Of the total measured concn. of cyanazine, only 0.2% was derived from its parent compd.-with DCAC (74.1%) and CAC (18.4%) comprising 92.5% of this total. Thus, although DCAC and CAC had similar frequencies of detection, DCAC was generally present in higher concns. No concns. of cyanazine compds. for this study exceeded water-quality criteria for the protection of human health. Only cyanazine, however, has such a criteria established. Nevertheless, because these cyanazine degradates are still chlorinated, they may have similar toxicity as their parent compd.-similar to what has been found with the chlorinated degradates of atrazine. Thus, the results of this study documented that data on the degradates for cyanazine are crit. for understanding its fate and transport in the hydrol. system. The prevalence of the chlorinated degradates of cyanazine found in groundwater suggests that to accurately det. the overall effect on human health and the environment from cyanazine its degradates should also be considered. In addn., because CYTOT was found in 57.6% of the samples collected from alluvial aquifers, about 2-5 times more frequently than the other major aquifer types (glacial drift, bedrock/karst, bedrock/nonkarst) under study, this finding has long-term implications for the occurrence of CYTOT in streams. It is anticipated that low-level concns. of CYTOT will continue to be detected in streams for years after the use of cyanazine has terminated (scheduled for the year 2000 in the US), primarily through its movement from groundwater into streams during base-flow conditions.
- 42Kolpin, D. W.; Schnoebelen, D. J.; Thurman, E. M. Degradates provide insight to spatial and temporal trends of herbicides in ground water. Ground Water 2004, 42, 601– 608, DOI: 10.1111/j.1745-6584.2004.tb02628.x[Crossref], [PubMed], [CAS], Google Scholar42https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2cXlslajsrc%253D&md5=07e5cb7637c004e6d59d2e7c827d6b77Degradates provide insight to spatial and temporal trends of herbicides in ground waterKolpin, Dana W.; Schnoebelen, Douglas J.; Thurman, E. MichaelGround Water (2004), 42 (4), 601-608CODEN: GRWAAP; ISSN:0017-467X. (National Ground Water Association)Since 1995, a network of municipal wells in Iowa, representing all major aquifer types (alluvial, bedrock/karst region, glacial drift, bedrock/nonkarst region), has been repeatedly sampled for a broad suite of herbicide compds. yielding one of the most comprehensive statewide databases of such compds. currently available in the US. This dataset is ideal for documenting the insight that herbicide degradates provide to the spatial and temporal distribution of herbicides in groundwater. During 2001, 86 municipal wells in Iowa were sampled and analyzed for 21 herbicide parent compds. and 24 herbicide degradates. The frequency of detection increased from 17% when only herbicide parent compds. were considered to 53% when both herbicide parents and degradates were considered. The transport of herbicide compds. to groundwater is substantially underestimated when herbicide degradates are not considered. A significant difference in the results among the major aquifer types was apparent only when both herbicide parent compds. and their degradates were considered. Including herbicide degradates greatly improved the statistical relation to the age of the water being sampled. When herbicide parent compds. are considered, only 40% of the wells lacking a herbicide detection could be explained by the age of the water predating herbicide use. However, when herbicide degradates were also considered, 80% of the ground water samples lacking a detection could be explained by the age of the water predating herbicide use. A temporal pattern in alachlor concns. in groundwater could only be identified when Alachlor degradates were considered.
- 43Hladik, M. L.; Bouwer, E. J.; Roberts, A. L. Neutral chloroacetamide herbicide degradates and related compounds in Midwestern United States drinking water sources. Sci. Total Environ. 2008, 390, 155– 165, DOI: 10.1016/j.scitotenv.2007.09.042[Crossref], [PubMed], [CAS], Google Scholar43https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD2sXhsVSgtLrN&md5=abdf989777329b14e54399dbdcfc5ecaNeutral chloroacetamide herbicide degradates and related compounds in Midwestern United States drinking water sourcesHladik, Michelle L.; Bouwer, Edward J.; Roberts, A. LynnScience of the Total Environment (2008), 390 (1), 155-165CODEN: STENDL; ISSN:0048-9697. (Elsevier Ltd.)Recent studies have revealed the presence of neutral degradates of chloroacetamide herbicides in the Chesapeake Bay at concns. greatly in excess of the parent compds. As some degradates are being considered for regulation in drinking water, exposure of human populations to such micropollutants is of interest. We report the results of a survey of source waters used by 12 drinking water utilities in the Midwestern US. Analytes included 20 neutral and 6 ionic chloroacetamide degradates, 4 parent chloroacetamide herbicides, 3 triazine herbicides, and 2 triazine degradates. Samples were collected during Fall 2003 and Spring 2004. In the fall samples, 16 of 20 neutral chloroacetamide degradates were detected, while 18 of 20 neutral chloroacetamide degradates were detected in the spring samples. Concns. of most parent chloroacetamides and neutral degradates were somewhat to substantially higher in the spring than in the fall, with median concns. of ∼10-100 ng/L. Groundwater sources tended to have lower concns. of parents and neutral degradates than surface water sources in the fall, although concns. of parents and degradates in groundwater were similar to those in surface water in the spring.
- 44Rosecrans, C. Z.; Musgrove, M. Water Quality of Groundwater Used for Public Supply in Principal Aquifers of the United States; Scientific Investigations Report 2020–5078; U.S. Geological Survey, 2020.
- 45U.S. Geological Survey, variously dated. Map of the Principal Aquifers of the United States; U.S. Geological Survey. https://water.usgs.gov/ogw/aquifer/map.html (accessed May 7, 2020).
- 46Lovelace, J. K.; Nielsen, M. G.; Read, A. L.; Murphy, C. J.; Maupin, M. A. Estimated Groundwater Withdrawals from Principal Aquifers in the United States, 2015; Circular 1464; U.S. Geological Survey, 2020.
- 47Burow, K. R.; Belitz, K. Groundwater Studies: Principal Aquifer Surveys; Fact Sheet 2014-3024; U.S. Geological Survey, 2014.
- 48Belitz, K.; Jurgens, B.; Landon, M. K.; Fram, M. S.; Johnson, T. Estimation of aquifer scale proportion using equal area grids: Assessment of regional scale groundwater quality. Water Resour. Res. 2010, 46, W11550 DOI: 10.1029/2010WR009321[Crossref], [CAS], Google Scholar48https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3MXhsVKltLk%253D&md5=b66fba63bf17b0246090ca8b227436d8Estimation of aquifer scale proportion using equal area grids: Assessment of regional scale groundwater qualityBelitz, Kenneth; Jurgens, Bryant; Landon, Matthew K.; Fram, Miranda S.; Johnson, TylerWater Resources Research (2010), 46 (11), W11550/1-W11550/14CODEN: WRERAQ; ISSN:0043-1397. (American Geophysical Union)The proportion of an aquifer with constituent concns. above a specified threshold (high concns.) is taken as a nondimensional measure of regional scale water quality. If computed on the basis of area, it can be referred to as the aquifer scale proportion. A spatially unbiased est. of aquifer scale proportion and a confidence interval for that est. are obtained through the use of equal area grids and the binomial distribution. Traditionally, the confidence interval for a binomial proportion is computed using either the std. interval or the exact interval. Research from the statistics literature has shown that the std. interval should not be used and that the exact interval is overly conservative. On the basis of coverage probability and interval width, the Jeffreys interval is preferred. If more than one sample per cell is available, cell declustering is used to est. the aquifer scale proportion, and Kish's design effect may be useful for estg. an effective no. of samples. The binomial distribution is also used to quantify the adequacy of a grid with a given no. of cells for identifying a small target, defined as a constituent that is present at high concns. in a small proportion of the aquifer. Case studies illustrate a consistency between approaches that use one well per grid cell and many wells per cell. The methods presented in this paper provide a quant. basis for designing a sampling program and for utilizing existing data.
- 49Koterba, M. T.; Wilde, F. D.; Lapham, W. W. Ground-Water Data-Collection Protocols and Procedures for the National Water-Quality Assessment Program—Collection and Documentation of Water-Quality Samples and Related Data; Open-File Report 95-399; U.S. Geological Survey, 1995.
- 50U.S. Geological Survey, variously dated. National Field Manual for the Collection of Water-Quality Data; Techniques of Water-Resources Investigations; Book 9, Chapters A1–A9. http://water.usgs.gov/owq/FieldManual/ (accessed Dec 21, 2018).
- 51Arnold, T. L.; DeSimone, L. A.; Bexfield, L. M.; Lindsey, B. D.; Barlow, J. R.; Kulongoski, J. T.; Musgrove, M.; Kingsbury, J. A.; Belitz, K. Groundwater Quality Data from the National Water-Quality Assessment Project, May 2012 through December 2013; data release; U.S. Geological Survey, 2016.
- 52Arnold, T. L.; Bexfield, L. M.; Musgrove, M.; Lindsey, B. D.; Stackelberg, P. E.; Barlow, J. R.; DeSimone, L. A.; Kulongoski, J. T.; Kingsbury, J. A.; Ayotte, J. D.; Fleming, B. J.; Belitz, K. Datasets from Groundwater-Quality Data from the National Water-Quality Assessment Project, January through December 2014 and Select Quality-Control Data from May 2012 through December 2014; data release; U.S. Geological Survey, 2017.
- 53Arnold, T. L.; Bexfield, L. M.; Musgrove, M.; Stackelberg, P. E.; Lindsey, B. D.; Kingsbury, J. A.; Kulongoski, J. T.; Belitz, K. Datasets from Groundwater-Quality and Select Quality-Control Data from the National Water-Quality Assessment Project, January through December 2015, and Previously Unpublished Data from 2013–2014; data release; U.S. Geological Survey, 2018.
- 54Arnold, T. L.; Sharpe, J. B.; Bexfield, L. M.; Musgrove, M.; Erickson, M. L.; Kingsbury, J. A.; Degnan, J. R.; Tesoriero, A. J.; Kulongoski, J. T.; Belitz, K. Datasets from Groundwater-Quality and Select Quality-Control Data from the National Water-Quality Assessment Project, January through December 2016, and Previously Unpublished Data from 2013 to 2015; data release; U.S. Geological Survey, 2020.
- 55Bexfield, L. M.; Toccalino, P. L.; Belitz, K.; Foreman, W. T.; Furlong, E. T. Environmental and Quality-Control Data Collected by the USGS National Water-Quality Assessment Project for Hormones and Pharmaceuticals in Groundwater Used as a Source of Drinking Water across the United States, 2013–15; data release; U.S. Geological Survey, 2019.
- 56Sandstrom, M. W.; Kanagy, L. K.; Anderson, C. A.; Kanagy, C. J. Determination of Pesticides and Pesticide Degradates in Filtered Water by Direct Aqueous-Injection Liquid Chromatography-Tandem Mass Spectrometry; Techniques and Methods; U.S. Geological Survey: 2015; Book 5, Chapter B11.
- 57Norman, J. E.; Kuivila, K. M.; Nowell, L. H. Prioritizing Pesticide Compounds for Analytical Methods Development; Scientific Investigations Report 2012–5045; U.S. Geological Survey, 2012. https://pubs.usgs.gov/sir/2012/5045/pdf/sir20125045.pdf (accessed Oct 19, 2020).
- 58Reregistration Eligibility Decision: Glyphosate; EPA 738-R-93-014; U.S. Environmental Protection Agency: Washington, D.C., 1993. https://www3.epa.gov/pesticides/chem_search/reg_actions/reregistration/red_PC-417300_1-Sep-93.pdf (accessed Aug 20, 2020).
- 59Shoda, M. E.; Nowell, L. H.; Stone, W. W.; Sandstrom, M. W.; Bexfield, L. M. Data Analysis Considerations for Pesticides Determined by National Water Quality Laboratory Schedule 2437; Scientific Investigations Report 2018-5007; U.S. Geological Survey, 2018.
- 60Bexfield, L. M.; Sandstrom, M. W.; Beaty, D. Field, Laboratory, and Third-Party Data for Assessment of the Quality of Pesticide Results Reported by the National Water Quality Laboratory for Groundwater Samples Collected by the National Water-Quality Assessment Project, 2013-18; data release; U.S. Geological Survey, 2020.
- 61Bexfield, L. M.; Belitz, K.; Sandstrom, M. W.; Beaty, D.; Medalie, L.; Lindsey, B. D.; Nowell, L. H. Quality of Pesticide Data for Groundwater Analyzed for the National Water-Quality Assessment Project, 2013–18; Scientific Investigations Report 2020–5072; U.S. Geological Survey, 2020.
- 62Atrazine Human Health Risk Assessment; EPA-HQ-OPP-2013-0266-1159; U.S. Environmental Protection Agency: Washington, D.C., 2013. https://www.regulations.gov/document?D=EPA-HQ-OPP-2013-0266-1159 (accessed May 8, 2020).
- 63Sinclair, C. J.; Boxall, A. B. Assessing the ecotoxicity of pesticide transformation products. Environ. Sci. Technol. 2003, 37, 4617– 4625, DOI: 10.1021/es030038m[ACS Full Text ], [CAS], Google Scholar63https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BD3sXms12kt7c%253D&md5=a8aee69647a67621b9a8e06b6a5b7954Assessing the Ecotoxicity of Pesticide Transformation ProductsSinclair, Chris J.; Boxall, Alistair B. A.Environmental Science and Technology (2003), 37 (20), 4617-4625CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Once released to the environment, pesticides may be degraded by abiotic and biotic processes. While parent compds. are assessed in detail in many regulatory schemes, the requirements for the assessment of transformation products are less well developed. This study was therefore performed to explore the relationships between the toxicity of transformation products and their parent compds. and to develop a pragmatic approach for use in the risk assessment of transformation products. Data were obtained on the properties and ecotoxicity of transformation products arising from a wide range of pesticides. Generally, transformation products were less toxic to fish, daphnids, and algae than their parent compd. In instances where a product was more toxic, the increase in toxicity could be explained by either (1) the presence of a pesticide toxicophore; (2) the fact that the product is the active part of a propesticide; (3) the product is accumulated to a greater extent than the parent compd.; or (4) the product has a more potent mode of action than the parent. On the basis of the findings, an approach has been proposed to est. the ecotoxicity of transformation products based on chem. structure and data on the toxicity of the parent compd. The assessments can be performed at an early stage in the risk assessment process to identify those substances that require further testing.
- 64Boxall, A. B.; Sinclair, C. J.; Fenner, K.; Kolpin, D.; Maund, S. J. When synthetic chemicals degrade in the environment. Environ. Sci. Technol. 2004, 38, 369A– 375A, DOI: 10.1021/es040624v
- 65Lindsey, B. D.; Jurgens, B. C.; Belitz, K. Tritium as an Indicator of Modern, Mixed, and Premodern Groundwater Age; Scientific Investigations Report 2019–5090; U.S. Geological Survey, 2019.
- 66Jin, S.; Homer, C. G.; Yang, L.; Danielson, P.; Dewitz, J.; Li, C.; Zhu, Z.; Xian, G.; Howard, D. Overall methodology design for the United States National Land Cover Database 2016 products. Remote Sens. 2019, 11, 2971 DOI: 10.3390/rs11242971
- 67Belitz, K.; Fram, M. S.; Johnson, T. D. Metrics for assessing the quality of groundwater used for public supply, CA, USA: Equivalent-population and area. Environ. Sci. Technol. 2015, 49, 8330– 8338, DOI: 10.1021/acs.est.5b00265[ACS Full Text ], [CAS], Google Scholar67https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2MXhtVOktr7I&md5=0d5fd5b69da88b84709e3685d9a9de09Metrics for Assessing the Quality of Groundwater Used for Public Supply, CA, USA: Equivalent-Population and AreaBelitz, Kenneth; Fram, Miranda S.; Johnson, Tyler D.Environmental Science & Technology (2015), 49 (14), 8330-8338CODEN: ESTHAG; ISSN:0013-936X. (American Chemical Society)Data from 11000 public supply wells in 87 study areas were used to assess the quality of nearly all of the groundwater used for public supply in California. Two metrics were developed for quantifying groundwater quality: area with high concns. (km2 or proportion) and equiv.-population relying upon groundwater with high concns. (no. of people or proportion). Concns. are considered high if they are above a human-health benchmark. When expressed as proportions, the metrics are area-weighted and population-weighted detection frequencies. On a statewide-scale, ∼20% of the groundwater used for public supply has high concns. for one or more constituents (23% by area and 18% by equiv.-population). On the basis of both area and equiv.-population, trace elements are more prevalent at high concns. than either nitrate or org. compds. at the statewide-scale, in eight of nine hydrogeol. provinces, and in about three-quarters of the study areas. At a statewide-scale, nitrate is more prevalent than org. compds. based on area, but not on the basis of equiv.-population. The approach developed for this paper, unlike many studies, recognizes the importance of appropriately weighting information when changing scales, and is broadly applicable to other areas.
- 68Lindsey, B. D.; Katz, B. G.; Berndt, M. P.; Ardis, A. F.; Skach, K. A. Relations between sinkhole density and anthropogenic contaminants in selected carbonate aquifers in the eastern United States. Environ. Earth Sci. 2010, 60, 1073– 1090, DOI: 10.1007/s12665-009-0252-9[Crossref], [CAS], Google Scholar68https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC3cXptFKgtLY%253D&md5=04fe5b092b4e5000edba523117045918Relations between sinkhole density and anthropogenic contaminants in selected carbonate aquifers in the eastern United StatesLindsey, Bruce D.; Katz, Brian G.; Berndt, Marian P.; Ardis, Ann F.; Skach, Kenneth A.Environmental Earth Sciences (2010), 60 (5), 1073-1090CODEN: EESNCZ; ISSN:1866-6280. (Springer)The relation between sinkhole d. and water quality was investigated in seven selected carbonate aquifers in the eastern United States. Sinkhole d. for these aquifers was grouped into high (>25 sinkholes/100 km2), medium (1-25 sinkholes/100 km2), or low (<1 sinkhole/100 km2) categories using a geog. information system that included four independent databases covering parts of Alabama, Florida, Missouri, Pennsylvania, and Tennessee. Field measurements and concns. of major ions, nitrate, and selected pesticides in samples from 451 wells and 70 springs were included in the water-quality database. Data were collected as a part of the US Geol. Survey (USGS) National Water-Quality Assessment (NAWQA) Program. Areas with high and medium sinkhole d. had the greatest well depths and depths to water, the lowest concns. of total dissolved solids and bicarbonate, the highest concns. of dissolved oxygen, and the lowest partial pressure of CO2 compared to areas with low sinkhole d. These chem. indicators are consistent conceptually with a conduit-flow-dominated system in areas with a high d. of sinkholes and a diffuse-flow-dominated system in areas with a low d. of sinkholes. Higher cave d. and spring discharge in Pennsylvania also support the concept that the high sinkhole d. areas are dominated by conduit-flow systems. Concns. of nitrate-N were significantly higher (p < 0.05) in areas with high and medium sinkhole d. than in low sinkhole-d. areas; when accounting for the variations in land use near the sampling sites, the high sinkhole-d. area still had higher concns. of nitrate-N than the low sinkhole-d. area. Detection frequencies of atrazine, simazine, metolachlor, prometon, and the atrazine degradate deethylatrazine indicated a pattern similar to nitrate; highest pesticide detections were assocd. with high sinkhole-d. areas. These patterns generally persisted when analyzing the detection frequency by land-use groups, particularly for agricultural land-use areas where pesticide use would be expected to be higher and more uniform areally compared to urban and forested areas. Although areas with agricultural land use and a high sinkhole d. were most vulnerable (median nitrate-N concn. was 3.7 mg/L, 11% of samples exceeded 10 mg/L, and had the highest frequencies of pesticide detection), areas with agricultural land use and low sinkhole d. still were vulnerable to contamination (median nitrate-N concn. was 1.5 mg/L, 8% of samples exceeded 10 mg/L, and had some of the highest frequencies of detections of pesticides). This may be due in part to incomplete or missing data regarding karst features (such as buried sinkholes, low-permeability <<dol<<dolword<<dol<<dol.
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- 70Nowell, L. H.; Moran, P. W.; Schmidt, T. S.; Norman, J. E.; Nakagaki, N.; Shoda, M. E.; Mahler, B. J.; Van Metre, P. C.; Stone, W. W.; Sandstrom, M. W.; Hladik, M. L. Complex mixtures of dissolves pesticides show potential aquatic toxicity in a synoptic study of Midwestern U.S. streams. Sci. Total Environ. 2018, 613–614, 1469– 1488, DOI: 10.1016/j.scitotenv.2017.06.156[Crossref], [PubMed], [CAS], Google Scholar70https://chemport.cas.org/services/resolver?origin=ACS&resolution=options&coi=1%3ACAS%3A528%3ADC%252BC2sXhtlSrtb3M&md5=4363384d2cfad00489e2e12ac5f06f98Complex mixtures of dissolved pesticides show potential aquatic toxicity in a synoptic study of Midwestern U.S. streamsNowell, Lisa H.; Moran, Patrick W.; Schmidt, Travis S.; Norman, Julia E.; Nakagaki, Naomi; Shoda, Megan E.; Mahler, Barbara J.; Van Metre, Peter C.; Stone, Wesley W.; Sandstrom, Mark W.; Hladik, Michelle L.Science of the Total Environment (2018), 613-614 (), 1469-1488CODEN: STENDL; ISSN:0048-9697. (Elsevier B.V.)Aquatic organisms in streams are exposed to pesticide mixts. that vary in compn. over time in response to changes in flow conditions, pesticide inputs to the stream, and pesticide fate and degrdn. within the stream. To characterize mixts. of dissolved-phase pesticides and degradates in Midwestern streams, a synoptic study was conducted at 100 streams during May-August 2013. In weekly water samples, 94 pesticides and 89 degradates were detected, with a median of 25 compds. detected per sample and 54 detected per site. In a screening-level assessment using aquatic-life benchmarks and the Pesticide Toxicity Index (PTI), potential effects on fish were unlikely in most streams. For invertebrates, potential chronic toxicity was predicted in 53% of streams, punctuated in 12% of streams by acutely toxic exposures. For aquatic plants, acute but likely reversible effects on biomass were predicted in 75% of streams, with potential longer-term effects on plant communities in 9% of streams. Relatively few pesticides in water-atrazine, acetochlor, metolachlor, imidacloprid, fipronil, organophosphate insecticides, and carbendazim-were predicted to be major contributors to potential toxicity. Agricultural streams had the highest potential for effects on plants, esp. in May-June, corresponding to high spring-flush herbicide concns. Urban streams had higher detection frequencies and concns. of insecticides and most fungicides than in agricultural streams, and higher potential for invertebrate toxicity, which peaked during July-August. Toxicity-screening predictions for invertebrates were supported by quantile regressions showing significant assocns. for the Benthic Invertebrate-PTI and imidacloprid concns. with invertebrate community metrics for MSQA streams, and by mesocosm toxicity testing with imidacloprid showing effects on invertebrate communities at environmentally relevant concns. This study documents the most complex pesticide mixts. yet reported in discrete water samples in the U. S. and, using multiple lines of evidence, predicts that pesticides were potentially toxic to nontarget aquatic life in about half of the sampled streams.
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- 77Fipronil: Environmental Fate and Ecological Effects Assessment and Characterization for Section 18 Registration of in-Furrow Applications to Rutabaga and Turnips; U.S. Environmental Protection Agency: Washington, D.C., 2005. https://www3.epa.gov/pesticides/chem_search/cleared_reviews/csr_PC-129121_31-Aug-05_a.pdf (accessed May 11, 2020).
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- 81Triazine Cumulative Human Health Risk Assessment; EPA-HQ-OPP-2013-0266-1160; U.S. Environmental Protection Agency: Washington, D.C., 2013. https://www.regulations.gov/document?D=EPA-HQ-OPP-2013-0266-1160 (accessed May 12, 2020).
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