Study On The Ecological Eenvironmental Toxicity Of Copper Pollution In Le’an River Basin

Le’an River is a river in the northeastern part of Jiangxi Province,a tributary of the Rao River among the five major rivers of Poyang Lake.This river pollution of copper is more serious than other rivers of flow into the Poyang Lake,due to the influence of human activities such as mining and industrial development in the basin.The high content of Cu in the water environment may lead to high exposure risk of aquatic organisms,causing negative biological chain effects,resulting in ecological risks.In this regand,this paper selected the Carassius auratus,widely distributed in the Le’an River Basin,as the aquatic biological model.The toxic effects of copper were analyzed from the perspective of individual,tissue,organ,cell,molecule of the Carassius auratus.Through this study,it is hoped that it will help to promote the study on the ecological environmental toxicity of to aquatic organisms,and provide a scientific basis for the health risk assessment of copper pollution,and thus preventing and reducing the potential risks caused by copper pollution to human beings in the Le’an River Basin.The whole research process and results are as follows:(1)The LC50 was estimated using the probability unit graphical method in accordance with the test method of ISO7346 1-3 《Water Quality-Determination of the Acute Toxicity of Substance to a Freshwater fish(Brachydanio Rerio)》.The results showed:Heavy metal copper is highly toxic to Carassius auratus,and the 48h-LC50,72h-LC50 and 96h-LC50 and corresponding 95% confidence intervals in acute exposure are respectively 0.667 mg/L(0.385～0.968 mg/L),0.513 mg/L(0.256～0.752 mg/L)and 0.412 mg/L(0.224～0.657 mg/L).(2)Taking the copper ion of sublethal concentration as the exposure condition,and the biological toxicity effect and accumulation patterns of copper on Carassius auratus were studied.The results showed: There are obvious differences in the accumulation of copper in different tissues of Carassius auratus.The order of accumulation is: liver>intestine>brain>gill>skin>muscle.After 24 h of copper exposure,the content of copper in liver,intestine,brain,gill,skin and muscle of the Carassius auratus are 67.621 mg/kg,12.723 mg/kg,9.012 mg/kg,7.189 mg/kg,1.198 mg/kg and 1.500 mg/kg,respectively.Within 24～144 h,the accumulation rate of copper in each tissue slowed down,and then the accumulation rate of copper in each tissue basically leveled off.After 168 h exposure,the copper content in liver,intestine,brain,gill,skin and muscle of Carassius auratus are 86.383 mg/kg,31.708 mg/kg,15.686 mg/kg,11.284 mg/kg,3.794 mg/kg and 3.490 mg/kg,respectively.Among them,liver is the main organ of copper enrichment of Carassius auratus.After 168 h of exposure,the content of copper accumulation in liver is 2.72,5.51,7.66,22.76 and 27.75 times of that in intestinal tract,brain,gill,skin and muscle respectively.(3)The effect of copper ion exposure on the antioxidant enzyme system of Carassius auratus was studied.The activities of SOD,CAT,GPx,GST,GR and KNA in gills and liver of Carassius auratus exposed to copper ions were significantly activated,and the contents of MDA and LPO were significantly increased.The activities of SOD,CAT,GPx,GST,GR and KNA were increased-decreased,while the contents of MDA and LPO showed a gradually decreased.Exposed copper ions to Carassius auratus and liver SOD,CAT,GPx,GST,GR and KNA activity and the influence of MDA and LPO content on the whole present similar results,but the liver antioxidant enzymes affect significantly than gill from the trend of the change point of view,the maximum value of liver enzymes activity were higher than gill,and with the extension of exposure experiment,the gill enzyme activity was flat and the liver enzyme activity decreased significantly;In terms of the whole exposure time,with the extension of exposure time,the activity of SOD,CAT,GPx,GST,GR and KNA increased from 24 h to 96 h,and decreased from 196 h to 336 h;The content of MDA and LPO reached the maximum at 24 hours of exposure,and then gradually decreased;From the perspective of different exposure concentrations,copper ion concentrations at different exposure times have different effects on the antioxidant system of the Carassius auratus,but on the whole,the effect of high concentration of copper ion exposure is greater than that of low concentration.(4)Through macroscopic observation of the damage to the tissues and organs of Carassius auratus caused by continuous exposure to copper ions,it was found that the copper ion concentration of 48h-LC50(0.67mg/L)would cause a large amount of congestion in the gill and different degrees of congestion and ascites in the liver.The histopathological analysis showed that the gill tissue injury of Carassius auratus mainly included oedema,hyperplasia and deformation epithelial cells of secondary lamella,proliferation of mucus cells,fusion of secondary lamella,and fusion of the whole primary lamella of the gill,and fusion of secondary lamella and primary lamella.Liver injury of mainly includes vacuole,melanoma,aggregation of blood cell and cells with pyknotic nuclei,and liver tissue cell necrosis and dissolved necrosis.In the exposure group of 0.083 mg /L copper ion concentration,Carassius auratus gill and liver can repair tissue damage through regulating effect.In the exposure group of 0.167 mg/L and 0.334 mg/L copper ion concentration,the physiologic metabolism of the gill and liver was severely disordered,and irreversible lesions occurred in the organ tissues.(5)In this study,the toxic effect of copper ions on Carassius auratus was analyzed by simulating the water environment conditions in the Le’an River Basin,so as to study the ecological environmental toxicity of copper pollution in the Le’an River Basin.The results showed that copper ions in water had a significant toxic effect on Carassius auratus at the level of individual,tissue,organ,cell and molecule.Therefore,it is suggested that in the process of establishing the safe environmental impact concentration threshold of heavy metal copper in the Le’an River Basin,the copper standard conforming to the basin should be established for the purpose of protecting ecological integrity.Starting from the protection of ecological security and human health,the scientific management system of copper polluted water environment is implemented to ensure the ecological system of the Le’an River Basin.