Distribution And Inhibition Of AChE Of Phoxim To Crucian Carp (Carassius Auratus)

Phoxim was an organophosphorus pesticide widely used in agriculture and fishery in China. Phoxim sprayed in the farmland would transferred to river and lake and accumulated in the body of aquatic organisms.The safety of aquatic products would also affected by phoxim used in fishery. When the concentration of phoxim was high in water body, toxic symptoms appeared in fish since the activity of acetylcholinesterase of fish was inhibited by the pesticide. When the concentration was low, phoxim would accumulated in fish and was a potential hazard to the health of human. As a consequence, the determination and supervision of phoxim in fish was of great importance. The research and results were as following:1 Determination of phoxim in tissue of crucian carpA method based on matrix solid-phase dispersion and high performance liquid chromatography for quantification of an organophosphorus pesticide phoxim in four tissues (liver, muscle, brain and gill) of crucian carp(Carassius auratus) is described. The results suggested that the operational conditions were 0.1 g of sample mixed with 0.5 g of anhydrous sodium sulfate and 1.5 g of Florisil as dispersant and subsequent extraction with 8 mL of dichloromethane. The eluent was evaporated to dryness and dissolved in 1 mL of methanol for HPLC analysis. At two spiking levels, the average recoveries were in the range of 86.2% to 103.6% with relative standard deviations<15% for all tissues. The response was linear in the concentration range of 0.0105 mg/kg and 5.25 mg/kg with correlation coefficients of 0.9996. The limits of detection were 0.02 mg/kg for all tissues when using 0.1 g of sample. The proposed method was reliable for the routine analysis of phoxim residue in the body of fish.2 Acute toxicity of phoxim to crucian carpThe acute toxicity of phoxim to crucian carp was conducted for 96 h. Test solutions and control water were renewed at 24 h intervals. The lowest concentration of phoxim was 6.6 mg/L when the mortality of carp was 100%. Toxic symptoms were observed at carps exposed to high and moderate concentration of phoxim. LC50 were obtained by using PAS W software to process the toxic data and 96 h LC50 of phoxim to crucian carp was 3.110 mg/L. The safe concentration was 0.311mg/L and the toxicity of phoxim to crucian carp was moderate.3 Acetylcholinesterase activity affected by phoximAcetylcholinesterase activity of brain and muscle of carp were obviously inhibited by phoxim. The enzyme activity was inhibited to the lowest values at 24 h or 48 h when the concentration of phoxim were 0.1 mg/L and 0.5 mg/L. Acetylcholinesterase activity was increased slowly as the exposure duration extended, but the values were significantly different lower compared with control(P<0.01).4 Distribution of phoximPhoxim was absorbed and accumulated by crucian carp after the exposure. The amount of phoxim residue arrived at highest level afer 144 h duration for all tissues.The accumulation of phoxim were conspicuous in liver, brain and gill while the accumulation was low in muscle. The result indicated that the muscle of crucian carp was not prone to accumulate phoxim and this was advantageous to the safety of carp.