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Final Report: Application of Sediment Quality Criteria for Metals to a Montane Lotic Ecosystem: Field Validation During Reclamation of a Copper Mine Causing Acid Mine Drainage
EPA Grant Number: R826199Title: Application of Sediment Quality Criteria for Metals to a Montane Lotic Ecosystem: Field Validation During Reclamation of a Copper Mine Causing Acid Mine Drainage
Investigators: Meyer, Joseph S. , Lockwood, Jeffrey A. , Rockwell, Richard W.
Institution: University of Wyoming
EPA Project Officer: Stelz, Bill
Project Period: April 1, 1998 through March 31, 2001 (Extended to September 30, 2002)
Project Amount: $449,558
RFA: Contaminated Sediments (1997)
Research Category: Hazardous Waste/Remediation
Description:
Objective:We used a typical Rocky Mountain stream receiving acid mine drainage to test if a method proposed by the U.S. Environmental Protection Agency for deriving sediment quality guidelines (SQGs) for metals (Ankley et al. 1996), developed in lowland estuarine, lacustrine, and riverine habitats, can be applied to the dynamic and heterogeneous hydrological and biogeochemical conditions found in high-elevation, lotic waters.
Summary/Accomplishments (Outputs/Outcomes):Our study stream was Haggarty Creek, flowing west from the Continental Divide in Carbon County, Wyoming. Over a 3-year period (1998–2001), we used this site as a model system that represents a typical mine-impacted, montane stream in the Rocky Mountains. We established three sampling sites on Haggarty Creek at increasing distances downstream from a Cu-contaminated effluent flowing out of the Rudefeha Mine. We also established a reference site in Bachelor Creek, an uncontaminated tributary of Haggarty Creek. The locations of the sampling sites were based on preliminary findings of Rockwell (2001) concerning metal bioaccumulation in the creek’s food web. Field bouts in July, August, and September of each of the three project years included collection of (1) sediment samples for determination of acid volatile sulfides (AVS), simultaneously extracted metals (SEM), and organic carbon (OC); and (2) water samples from the water column, sediment-water interface, and interstitial pores in the sediment for measurement of dissolved metals, OC, and routine water chemistry parameters (pH, alkalinity, and major cations and anions). In situ sediment and water toxicity tests using laboratory-reared (Chironomus tentans and Hyalella azteca) and field-collected (Hesperoperla pacifica and Polycelis coronata) macroinvertebrates were conducted at each station during each sampling bout, and metal accumulation was analyzed in the organisms that survived those tests as well as in simultaneously collected native benthos. Water-only reference toxicity tests were conducted in the laboratory to determine LC50s for the test species. Although we tested five metals (Cd, Cu, Ni, Pb, and Zn) individually in the Year 1 laboratory toxicity tests, we only tested Cu toxicity in Years 2 and 3 because Cu was the only metal measured at toxicologically relevant concentrations in Haggarty Creek.
Year 1 (Summer 1998 Sampling)
AVS was not detected in sediments collected from any station in spring (July), was only detected in sediments from the reference station in August (summer; 0.01 µmol/g dry weight [dw]), and was measured at slightly higher concentrations in sediments from the reference and the most effluent-distal stations in September (fall; 0.5 and 1.8 µmol/g dw, respectively), consistent with the anticipated paucity of AVS in the montane, lotic ecosystem. Concentrations of sediment OC (10–90 mg/g dw) generally were consistent with an expected trend of seasonal increase related to deposition of allochthonous detritus. Dissolved OC (DOC) concentrations in interstitial water (0.2–6.5 mg/L), at the sediment-water interface (0.2–2.8 mg/L), and in the water column (0.1–2.0 mg/L) suggested seasonal decreases in DOC from spring to fall and general increases of DOC with distance downstream from the mine.
Sediment Cu concentrations (0.2–2.1 mg Cu/g dw) decreased with distance from the mine, but no significant seasonal trends were observed within stations. On the other hand, dissolved Cu concentrations (10–380 µg Cu/L) from all three water compartments demonstrated spatial and seasonal trends in which aqueous Cu decreased with distance from the mine and decreased within stations throughout the year. Simultaneously extracted Cu was always present in excess of the AVS at all stations, with the excess usually > 1 µmol/g dw at the contaminated stations but always < 0.5 µmol/g dw at the reference station. However, considerable in situ toxicity was only observed at the station closest to the mine effluent, where high aqueous concentrations of Cu appeared to also contribute to the observed toxicity. Copper accumulation in survivors of the in situ toxicity tests also decreased with distance from the mine, as did Cu accumulation in native benthos. Thus, toxicity of sediment Cu at the more downstream sites might have been ameliorated by the presence of OC in the sediments or determined primarily by aqueous Cu.
Year 2 (Summer 1999 Sampling)
AVS was not detected in sediments collected from any station during any of the 3 months, consistent with 1998 results and with the anticipated lack of AVS in this highly oxygenated stream. Spatial trends in sediment OC distribution (1.0–71 mg/g dw) were similar to 1998, increasing with distance downstream of the mine. Seasonal trends in sediment OC suggested an increase from July to August but a decrease between August and September, possibly indicative of a sediment-flushing event such as rain. This differed from 1998 observations that were consistent with seasonal increases in sediment OC associated with fall deposition of allochthonous detritus. Spatial distributions of DOC in all three aqueous compartments were similar to those observed in 1998, generally increasing with distance downstream from the mine. Seasonal trends of DOC in the water column (0.2–2.5 mg/L) and at the sediment-water interface (0.5–1.5 mg/L) were consistent with seasonal increases in detritus deposition, as in 1998. However, interstitial-water DOC (0.6–2.4 mg/L) decreased from July to August, with little change between August and September, unlike seasonally linked increases in 1998.
Sediment Cu (5.0–102 mg/g dw) decreased with distance downstream from the mine, as in 1998. However, distinct seasonal distributions in sediment Cu in 1999 differed from unremarkable seasonal trends in 1998. Sediment Cu in the two mine-proximal, upstream stations decreased from July through September. In contrast, sediment Cu in the two mine-distal, downstream stations increased from July to August and decreased from August to September. This appears to correspond to seasonal trends observed for sediment OC, again suggesting a flushing event. As in 1998, SEM Cu consistently exceeded AVS by > 1 µmol/g dw at Haggarty Creek stations but by < 0.5 µmol/g dw in the reference stream. Thus, mortalities observed in sediment and water-only in situ toxicity tests for all three test species correlated directly with spatial and temporal distributions of interstitial-water and water-column concentrations of dissolved Cu, being highest at the most mine-proximal station in July. Similar to 1998, dissolved concentrations of Cu from all three water compartments—the water column (4.4–166 µg/L Cu), the sediment-water interface (3.8–170 µg/L Cu), and the interstitial water (7.1–111 µg/L Cu)—demonstrated spatial and seasonal trends in which aqueous Cu decreased with distance downstream from the mine and with time (July–September). Accumulation of Cu in in situ survivors and native benthos decreased with distance from the mine, as in 1998. Our 1999 results again suggested that toxicity of sediment Cu to benthos was either regulated by OC or by aqueous Cu concentrations, rather than by AVS.
Year 3 (Summer 2000 Sampling)
AVS was detected in sediments from all sampling sites in all three months. However, the range of AVS concentrations (0.010–0.013 µmol/g dw) was near the detection limit, and no patterns corresponding to spatial or seasonal influences were apparent. As in 1998 and 1999, spatial trends in sediment OC (1.4–45 mg C/g dw) in 2000 were consistent with increased detritus deposition as a function of distance downstream from the mine. Increases in sediment OC at all stations in September of 2000 reflected seasonal addition of allochthonous detritus that was consistent with results from prior years. But unlike prior years, concentrations of DOC in all three aqueous compartments in 2000 were generally similar among sampling sites within each season. Concentrations of DOC in the water column (0.5–3.5 mg C/L), at the sediment-water interface (0.5–4.6 mg C/L), and in interstitial water (0.3–4.1 mg C/L) decreased consistently from July through September at the mine-proximal sampling site; however, DOC concentrations increased slightly at downstream and reference sites in August before decreasing in September. This differs from seasonally associated increases in DOC concentrations in the water column and interstitial water in 1999 and in all three aqueous compartments in 1998.
Although, as in prior years, sediment Cu concentrations (0.0–0.7 mg Cu/g dw) decreased with distance downstream from the mine, seasonal distributions of sediment Cu in 2000 differed from 1998 and 1999. Sediment Cu concentrations increased from July to August at the most upstream and downstream sites on Haggarty Creek before they decreased in September, whereas sediment Cu concentration steadily decreased at the central sampling site on Haggarty Creek. This was generally consistent with the seasonal trends for DOC in 2000, as opposed to the similarity between trends in sediment Cu and sediment OC in 1999. As in prior years, SEM Cu was consistently in excess of AVS by > 1 µmol/g dw at the Haggarty Creek sites. Mortalities for all three species in the in situ sediment and water-only toxicity tests correlated with spatial and temporal distributions of dissolved Cu in the water column, at the sediment-water interface, and in the interstitial water, being highest across seasons at the most mine-proximal sampling site. Spatial trends in dissolved Cu concentrations in the water column (0.0–207 µg/L), at the sediment-water interface (0.0–179 µg/L), and in the interstitial (0.0–87 µg/L) waters were similar to prior years, decreasing with distance downstream. However, temporal trends in dissolved Cu differed in 2000, with concentrations increasing at all stations in September after a decrease from July to August. Trends in tissue concentrations of Cu in survivors of the in situ toxicity tests and in native benthos were erratic but generally suggested decreases in Cu accumulation with distance from the mine.
As in prior project years, sediment AVS did not appear to control the toxicity of Cu to benthos in this high-elevation lotic system. Instead, OC (dissolved and/or particulate) was probably the only major modifier of Cu toxicity.
Conclusions:Unlike the situation in lower-gradient lotic ecosystems that have slower water velocities and higher concentrations of OC and AVS in their sediments, the chemical characteristics of the Cu-contaminated sediments in Haggarty Creek did not appear to be a strong predictor of acute toxicity to aquatic invertebrates. Instead, the aqueous exposure to Cu (the dominant metal in this system) in the water column of Haggarty Creek was as good or better of a predictor of acute toxicity. Water-column and interstitial-water Cu concentrations were approximately equally good predictors of mean whole-body Cu concentration in aquatic insects in Haggarty Creek, but Σ[SEM] – [AVS] appeared to be a slightly better predictor of mean whole-body Cu concentration. Therefore, sediment characteristics might be a better index of long-term bioaccumulation of Cu in this system, whereas instantaneous dissolved Cu concentrations in the water column are a better index of short-term lethality of Cu.
The proposed SQGs were relatively good predictors of acute toxicity and community composition of aquatic invertebrates in Haggarty Creek because the number of SQG exceedances generally decreased as the acute toxicity decreased and as the taxonomic richness and number of individuals increased among the sampling stations. However, those toxicity and community-structure metrics also correlated well with the water-column Cu concentrations. Therefore, we cannot conclusively isolate the causative factor(s) in this study. But if anything, a comparison of the results of the water-only and the sediment + water in situ toxicity tests suggests that the presence of the sediments tended to slightly decrease the toxicity of the water-column Cu (i.e., mortality usually was lower in the in situ sediment + water chambers than in the paired in situ water-only chambers).
References:
Ankley GT, Di Toro DM, Hansen DJ, Berry WJ. Technical basis and proposal for deriving sediment quality criteria for metals. Environmental Toxicology and Chemistry 1996;15:2056-2066.
Rockwell RW. Bioaccumulation of metals in the benthic food web of a Rocky Mountain stream ecosystem contaminated by acid mine drainage. Ph.D. Dissertation. Department of Renewable Resources, University of Wyoming, Laramie, WY, 2001.
Journal Articles:No journal articles submitted with this report: View all 2 publications for this project
Supplemental Keywords:Ecosystem Protection/Environmental Exposure & Risk, Water, Geographic Area, Scientific Discipline, Waste, RFA, Ecosystem/Assessment/Indicators, Biology, Ecology, Bioavailability, Ecological Risk Assessment, Ecological Indicators, EPA Region, Environmental Chemistry, Ecological Effects - Environmental Exposure & Risk, Ecosystem Protection, Contaminated Sediments, State, copper, heavy metal contamination, heavy metals, nickel, water quality, chironomus tentans, Wyoming, WY, aquatic ecosystem, sediment quality criteria, bioaccumulation, lead, mesocosm, acid mine drainage, cadmium, metal release, LC50s, contaminated sediment, dose-response, field validation, hyalella azteca, Haggarty Creek, ecological exposure, benthic biota, metals, Zinc, hesperoperla pacifica, Bachelor Creek, ecosystem, Montane Lotic ecosystem, Region 7, copper mine, montane stream system
Progress and Final Reports:
1999 Progress Report
2000 Progress Report
2001 Progress Report
Original Abstract