Tentative Exploration Of Sensitivity Distribution (SSDs) On Freshwater Fish To3Kinds Of Pesticides

As it is commonly used, chlorpyrifos, butachlor, and triadimefon are widespread in the paddy field, ditch, pond and river. The research ecological toxicology of these three kinds of pesticides to freshwater fish is of great significance. This paper discussed the toxicology effect and Species Sensitivity Distribution (SSDs) of above three kinds of pesticides to12species of freshwater fish and one species of frog, influence of chlorpyrifos on AchE activity in the brains of12species of fish and one species of frog, the acute toxicity of the3kinds of pesticides to fish in water-sediment system, and the bioaccumulation and distribution of the pesticides in fish.Freshwater fish that belong to9families and12species were tested in this research. SSDs for the3kinds of pesticides on the freshwater fish was built for sensitive species selection and calculation of the safe concentration of the pesticides to the fish. The result showed that sunfish, Pseudorasbora parva, and Gobiocypris rarus were the most sensitive species for chlorpyrifos, butachlor and triadimefon separately. Compared with the standard test system, the acute toxicity of pesticides to fish was significantly reduced in the pond water-sediment system, and the pesticides in the water significantly shifted to the sediment.Study of chlorpyrifos on AchE activity in the brain of12species of freshwater fish and the frog indicated that the AchE activity were all inhibited. The results showed that the most obviously affected was trout and the least was mosquitofish. Used96h enzyme activity of fish brain to draw the SSD curve, it was found that the curve be not completely consistent with LC50SSD. It indicated that enzyme activity level and mortality of fish were lack of corresponding relation.The representative fish species was used to conduct bioaccumulation test of three kinds of pesticides. The results showed that bio-enrichment coefficient (BCF) of chlorpyrifos was the highest, butachlor took the second place, and triadimefon had almost no enrichment in fish body. The experiment showed that the pesticides were mainly distributed in the intestine, liver, gill.This paper preliminary builded up sensitivity distribution curve of12kinds of freshwater fish and one species of frog to representative insecticide (chlorpyrifos), herbicide (butachlor) and fungicide (triadimefon) which were commonly used in paddy field. It used population mortality and the level of enzyme inhibition rate to compare sensitivity distribution and difference of the12representative fish and one frog to chlorpyrifos. And further more the paper analysed the difference of acute toxicity of pesticides to fish in simulated ponds (water-sediment syetems) and environmental effect. It defined the enrichment and the main distribution of the three representative pesticides in fish bodies. The research provided scientific basis for risk assessment of commonly used pesticides to fish in ecological environment of paddy field and enriched the connotation of aquatic toxicology.