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USGS South Dakota Water Science Center Publication |
By Michael J. Moran
U.S. GEOLOGICAL SURVEY
Scientific Investigations Report 2005–5268
National Water-Quality Assessment Program
National Synthesis on Volatile Organic Compounds
The U.S. Geological Survey has collected or compiled data on select chlorinated solvents in samples of ground water, source water, and drinking water. The water samples were collected during 1993–2002. Data on solvents in ground water and source water were available for the conterminous United States, Alaska, and Hawaii. Data on solvents in drinking water only were available for 12 Northeast and Mid-Atlantic States. The occurrence and distribution of four solvents were examined in these data sources—methlyene chloride, 1,1,1-trichloroethane, tetrachloroethene, and trichloroethene.
Out of 51 to 55 volatile organic compounds (VOCs) analyzed in samples, solvents were among the most frequently detected VOCs in all data sets. When data from ground water and source water were confined to 12 Northeast and Mid-Atlantic States, the detection frequencies of solvents were similar among all three data sets. Although low concentrations of solvents commonly were detected in ground water, some solvents had higher median quantified concentrations than other VOCs. Relative to other VOCs, solvents were ranked high in all data sets in terms of the frequency of concentrations higher than U.S. Environmental Protection Agency Maximum Contaminant Levels. Mixtures were a common mode of occurrence of solvents.
The probability of occurrence of solvents was most strongly related to the dissolved-oxygen content in ground water, with solvents having a higher probability of occurrence in conditions of relatively high dissolved oxygen compared to conditions of relatively low dissolved oxygen. The probability of occurrence of solvents in ground water also was strongly associated with urban land use and population density and with variables that represented the transport of solvents through the soil zone to ground water.
It is important for ground-water resource managers to understand the contamination potential posed by solvents, especially in resources that are critical as drinking-water supplies. Low-level analytical methods are most useful for determining the complete environmental distribution of solvents in ground water. To protect ground-water resources, it is important for ground-water managers to (1) delineate the redox conditions of ground water in the aquifer in order to predict the potential fate of solvents, (2) determine and control the sources, or potential sources, of solvents to ground water, and (3) establish the susceptibility of aquifers by fully ascertaining the hydraulic properties of the saturated and vadose zones.
Abstract
Introduction
Background
Physical and Chemical Properties and Environmental Behavior of Solvents
Transformation of Solvents
Production and Usage of Solvents
Methylene Chloride
Perchloroethene
1,1,1-Trichloroethane
Trichloroethene
Health Effects of Solvents
Methylene Chloride
Perchloroethene
1,1,1-Trichloroethane
Trichloroethene
Potential Sources of Solvents to Ground Wate
Anthropogenic Sources
Natural Sources
Data and Methods
Solvent Data Sets
Ground-Water Data
Source-Water Data
Drinking-Water Data
Computational Procedures
Statistical Tests
Occurrence of Solvents
Occurrence and Distribution of Solvents in Ground Water
Occurrence and Distribution of Solvents in Source Water
Occurrence and Distribution of Solvents in Drinking Water
Concentrations of Solvents in Ground Water
Concentrations of Solvents in Source Water
Concentrations of Solvents in Drinking Water
Comparisons of Solvent Occurrence and Concentrations Between Ground Water, Source Water, and Drinking Water
Associations of Solvents with Hydrogeologic and Anthropogenic Variables
Variables Associated With One or More Solvents
Variables Associated With Individual Solvents
Summary of Significantly Associated Explanatory Variables
Implications
Summary
References
Appendixes
Suggested Citation:
Moran, M.J., 2006, Occurrence and implications of selected chlorinated solvents in ground water and source water in the United States and in drinking water in 12 Northeast and Mid-Atlantic States, 1993–2002: U.S. Geological Survey Scientific Investigations Report 2005–5268, 70 p.
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Send questions or comments about this report to the author, M.J. Moran (605) 394-3244.
For more information about USGS activities in South Dakota, visit the USGS South Dakota Water Science Center home page.
For more information about USGS National Water-Quality Assessment Program, visit the NAWQA Program home page or more information about the USGS National Water-Quality Assessment Program Volatile Organic Compound National Syntheses, visit the VOC National Synthesis home page.
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