Water Quality of the Ozark Plateaus, Arkansas, Kansas, Missouri, and Oklahoma, 1992-95

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Major issues and findings
Pesticides and other organic compounds in water, bed sediment, and tissue

More than 1,000 organic compounds are contained in various products used to control pests in urban, agricultural, and forested areas and along rights of way. Most pesticides introduced in recent years are more water soluble and more degradable in the environment than many pesticides used extensively in the past. Most presently used compounds tend to be found more often in water, whereas many formerly used compounds are found more in sediment and biological tissue. In addition, numerous other organic compounds (such as phenols, polyaromatic hydrocarbons, and phthalate esters) are used for various industrial and manufacturing processes. Many of these compounds tend to associate with sediment particles rather than water.

In streams and ground water, pesticides were more prevalent in agricultural areas than in forested areas. Concentrations generally were low and seldom exceeded U.S. Environmental Protection Agency drinking-water criteria or standards, or criteria for the protection of aquatic life.

Concentrations of pesticides in streams and ground water were usually below method detection limits and when detected were usually relatively low compared to detection limits and concentrations in samples from other NAWQA Study Units (p. 24-25). Concentrations seldom exceeded U.S. Environmental Protection Agency (EPA) maximum contaminant levels or lifetime health-advisory levels for drinking water, EPA or National Academy of Sciences/National Academy of Engineering (NAS/NAE) ambient water-quality criteria for the protection of aquatic life, or related State criteria. However, no standards or criteria exist for about one-third of the detected pesticides. Dieldrin concentrations in two ground-water samples exceeded levels estimated by EPA to increase the risk of cancer (Nowell and Resek, 1994).

In water samples collected in 1994-95, pesticides were detected more commonly and in higher concentrations in streams in agricultural basins than in streams in forested basins (Bell and others, 1997). Data for a limited number of sites downstream from nearby urban areas indicate that pesticide detection frequencies and concentrations in urban basins are similar to those in agricultural basins. For most individual pesticides, the highest percentages of detections and the highest concentrations were in samples from streams in larger, more agricultural basins. Atrazine (one of the more commonly used herbicides in the Study Unit) and its metabolites (breakdown products) were the most commonly detected organic pesticide compounds in both forested and agricultural basins. Pesticides were detected at 39 of the 43 sites.

The presence of pesticides in ground water in the Springfield and Salem Plateaus also is related to land use. Springs and domestic wells were sampled for pesticides in 1993-95 (Adamski, 1997b). Pesticides were detected more frequently at sites associated with greater percentages of agricultural land use. Pesticides were more likely to be detected in samples from springs than in samples from domestic wells.

In bed sediment, the greatest numbers of pesticides and other organic compounds generally were detected at sites downstream from urban areas. No concentrations exceeded U.S. Environmental Protection Agency criteria for the protection of aquatic life.

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In bed sediment, the greatest number of pesticides and other organic compounds was found near urban areas. Concentrations were usually relatively low. Samples collected in 1992-95.

No organic compounds detected in the bed-sediment samples exceeded either the preliminary sediment-quality criteria developed by the EPA or concentrations expected to have a high probability of adverse effects on aquatic life (U.S. Environmental Protection Agency, 1996). Criteria or adverse effects levels have not been established for most of the detected compounds. Most of the compounds detected had maximum concentrations of less than 100 micrograms per kilogram (parts per billion).

Pesticides and semivolatile organic compounds (SVOCs) in 27 bed-sediment samples collected in 1992-95 were more frequently detected at sites downstream from urban areas (Bell and others, 1997). Samples were analyzed for 95 organic compounds. Two pesticides (chlordane compounds) and 44 SVOCs were detected. Samples from three sites contained detectable concentrations of more than 16 compounds. Two of these sites (one from the James River downstream from Springfield, Mo., one from Center Creek downstream from Joplin, Mo.) were in urban basins. In the sample from the James River, 39 compounds were detected; in the sample from Center Creek, 17 compounds were detected. The third sample contained 23 compounds and was from Richland Creek near Witts Spring, Ark., in a forested basin.

Sites with detected compounds are distributed throughout the Study Unit, with respect to both physiography and land use. Sites with 12 or more organic compounds detected are located in each physiographic area and major land-use category.

In biological tissue, pesticides were detected at 5 of 26 stream sites. Chlordane was detected downstream from Springfield, Mo. DDT, DDE, or dieldrin was detected at four sites in agricultural basins.

Tissue samples from fish and freshwater clams at 26 sites were analyzed for 26 organic compounds. Six compounds were detected at five sites (Bell and others, 1996). Three chlordane compounds were detected in Asiatic clam tissue at a site on the James River downstream from Springfield, Mo. These compounds frequently are present downstream from urban areas. DDT, DDE, or dieldrin was detected in tissue at four widely separated sites.

The concentrations in the tissues were below guidelines recommended as maximum concentrations to protect fish-eating wildlife (National Academy of Sciences and National Academy of Engineering, 1973). The sum of the three chlordane compound concentrations (0.0223 milligram per kilogram [mg/kg]) was below the recommended chlordane concentration of 0.1 mg/kg. The DDT, DDE, and dieldrin concentrations were well below the recommended maximum concentrations.

U.S. Geological Survey Circular 1158

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