"The effects of suspended solids, dissolved organic matter, pH, temperature, and major inorganic cations (Cap2s, Mgp+2s, Nap+s, Kp+s) and anions (HCOb3p-s, Clp-s, SOb4p-2s) on the lethality of copper sulfate to larval fathead minnows were investigated. Increases in all these parameters, except potassium salts, were found to increase LC50s (decrease toxicity) on the basis of total copper. Empirical models were developed for the dependence of LC50s on seven 'toxicity factors' - dissolved organic matter, suspended solids, temperature, pH, and three factors involving variation of major inorganic cations and anions. These models were combined to predict the toxicity of copper to larval fathead minnows as a function of water chemistry. This work demonstrated the importance of these factors to copper toxicity and the feasibility of developing mathematical models for predicting toxicity as a function of water chemistry. Validation and further refinement of these models would provide improved methods for establishing and applying water quality criteria."--Abstract.