Effects of water hardness on the toxicity of several organic and inorganic herbicides to fish

Effects of water hardness on the acute toxicity of organic and inorganic herbicides were determined in static bioassays. Bluegills were the principal test species; rainbow trout, blue spotted sunfish, goldfish, readear sunfish, and black bullheads were also tested. Organic herbicides tested included three formulations of 2,4-D, three formulations of endothall, and one formulation of silvex, pentachlorophenol, dichlobenil; inorganic herbicides included technical grades of sodium arsenite and copper sulfate. Hardness had no significant effect on toxicity of the organic herbicides or that of sodium arsenite; the toxicity of copper sulfate decreased in harder waters. Technical papers.