Study On Toxic Effects Of Acetochlor On Rare Minnow(Gobiocypris Rarus) And Its Adsorption-desorption Characteristics In The Soils

At the process of using, the large consumption of herbicide acetochlor in our country has brought prominent hazard. Thus this paper chooses it as the target pesticide, and studies its acute lethal effect and bioconcentration on Chinese rare minnow. In addition, we study the adsorption and desorption properties of acetochlor in soil, red soil, paddy soil and fluvo- aquic soil are chosen as test material. Our work provides references for other further study and safety evaluation of acetochlor on aquatic fishes. The main results are as follows:1. The results of acute lethal effect of acetochlor on adult rare minnow are that acute poisoning symptom is more obvious with increasing concentrations of acetochlor, low concentration can also lead to depth poisoning symptoms with increasing the exposure time. 96 h-LC50 value is 0.827 mg/L, its 95%confidence interval is from 0.800 to 0.855 mg/L, toxic effect level of acetochlor on rare minnow belongs to high toxicity, the security concentration of acetochlor on rare minnow adult fish is 82.7 μg/L, which should be paid attention to.2. The results of bioconcentration of acetochlor on adult rare minnow are that the test exposure concentrations are divided into two groups with the low concentration group being 8.272 μg/L and the high one being 82.72 μg/L. According to OECD TG305 sampling, the absorption time is 5.371 d, and the elimination time is 14.629 d. BCF5.371-L-O is 82.7 L/kg, BCF5.371-H-O is 14.6 L/kg, BCFk-L-O is 76.03 L/kg,BCFk-H-O is 16.42 L/kg. According to the Draft of the Ministry of Agriculture of the People’s Republic of China(DMA) sampling, BCF8d-L-D is 24.5 L/kg; BCF8d-H-D is 7.8 L/kg; BCFk-L-D is 25.92 L/kg, BCFk-H-D is 10.85 L/kg. The bioconcentration of acetochlor on adult rare minnow belonges to low & moderate rating.The bioconcentration of acetochlor on fish belonges to moderate rating based on model prediction.3. The adsorption properties of acetochlor in three types of soil can be well described by Freundlich equation, and the Kd is from 0.41 to 11.12 mL/g. The adsorption capacity in paddy soil is stronger than it in the red soil and fluvo-aquic soil. r2(between Kd and soil organic matter) is from 0.639 to 1. The standard sorption free energy changes, enthalpy changes and entropy changes are-17.63 to 2.21 kJ/mol, 23.18 to59.16 kJ/mol, and 80.24 to 207.59 kJ/mol. Soil adsorption of acetochlor is mainly determined by its organic matter. Adsorption of acetochlor in red soil is endothermic, chemical adsorption, and increased entropy change process. The adsorption of acetochlor in paddy soil and fluvo-aquic soil are spontaneous,endothermic, physical adsorption, and increased entropy change process.