Archives of Environmental Contamination and Toxicology

, Volume 45, Issue 2, pp 258-263

First online:

Toxicity of Chlorpyrifos Adsorbed on Humic Colloids to Larval Walleye (Stizostedion vitreum)

  • T. A. PhillipsAffiliated withDepartment of Animal Ecology, Iowa State University, 124 Science II, Ames, Iowa 50011-3221
  • , R. C. SummerfeltAffiliated withDepartment of Animal Ecology, Iowa State University, 124 Science II, Ames, Iowa 50011-3221
  • , J. WuAffiliated withDepartment of Agronomy, Iowa State University, 2101 Agronomy, Ames, Iowa 50011-1010
  • , D. A. LairdAffiliated withNational Soil Tilth Laboratory, Agricultural Research Service, United States Department of Agriculture, Ames, Iowa 50011-3120

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After application, organophosphorus insecticides (OPs) are often strongly adsorbed to soil constituents. Because of their relatively low water solubility, OPs may be transferred from field to stream adsorbed on suspended solids. However, we are not aware of research done to evaluate the bioavailability (i.e., toxicity) of OPs transported on suspended solids to fish. We conducted 48-h static toxicity tests to determine the toxicity of chlorpyrifos in aqueous solution and adsorbed on calcium-saturated humic acid (HA) to three larval stages of walleye (Stizostedion vitreum). Three concentrations of chlorpyrifos adsorbed on HA, a HA control, and a chlorpyrifos-only treatment were tested. Fish that survived the 48-h static toxicity tests were analyzed to determine total cholinesterase (ChE) activity. In general, survival of all larval stages of walleye exposed to chlorpyrifos–HA complexes was less than that of walleye exposed to HA controls and the chlorpyrifos-only treatment, which were not toxic to walleye. Cholinesterase inhibition of larval walleye exposed to chlorpyrifos–HA complexes was similar to the ChE inhibition observed in larval walleye exposed to chlorpyrifos in the aqueous phase. These laboratory experiments indicate potential toxicity of chlorpyrifos–soil complexes to larval fish.