Risk Assessment Of Heavy Metal Pollution In Liangzi Lake Water Environment And Representative Fish

Since the industrial revolution in the 18 th century,the demand for minerals,fossil fuels,and steel has greatly increased,resulting in a series of human activities,a lot of pollutants such as heavy metals are discharged into the global aquatic ecosystem.Heavy metals not only have a serious impact on aquatic organisms,but also pass along the food chain and further threaten human health.The Liangzi Lake is the second largest lake in Hubei province.It is not only the reserve water source of Hubei province,but also has ecological protection and other functions.Therefore,it is of great significance to ensure the ecological security of the Liangzi Lake.However,from the 1970 s to the beginning of the 21 th century,as human exploitation of the lake increased,the Liangzi Lake area gradually shrank and pollution became more serious.During the previous survey,it was found that there were significant biological effects caused by pollutants in the Liangzi Lake.To explore the pollution level and potential ecological risks of heavy metals in the Liangzi Lake,we investigated a variety of pollutants in the Liangzi Lake environment.To investigate the status of heavy metal pollution in the Liangzi Lake,we collected water samples,sediment samples,Aristichthys nobilis,Carassius auratus,Culter mongolicus and Megalobrama amblycephala from the Liangzi Lake in March and July2021.Afterward,we determined the age of these fish using fish scales.The concentrations of seven heavy metals(Cr,Cu,Zn,As,Cd,Pb,and Hg)in the sample were measured by microwave resolution ICP–MS and AFS.Use the Potential Ecological Risk Index,Comprehensive Potential Ecological Risk Index.The potential health risks to humans by eating muscle tissue of Aristichthys nobilis,Carassius auratus,Culter mongolicus and Megalobrama amblycephala were evaluated by carcinogenic risk coefficient and target risk coefficient.The final results show that:(1)The concentration of heavy metals in the water environment of the Liangzi Lake generally conforms to the national Class I water standard,but the sediments are polluted by heavy metals to a certain extent.Cd in sediments has the highest risk level.By comparing with previous studies,it is found that the As in the sediments of the Liangzi Lake is significantly higher than that of the Dongting Lake,the Poyang Lake and the middle reaches of the Yangtze River;(2)Aristichthys nobilis,Carassius auratus,Culter mongolicus and Megalobrama amblycephala in the Liangzi Lake have relatively low pollution levels,and the noncarcinogenic risk to the human body caused by eating the four kinds of fish can be ignored.However,the consumption of muscle parts of Aristichthys nobilis,Carassius auratus may pose a carcinogenic risk to humans due to As,indicating that even in clean waters,the carcinogenic risk may be caused by the accumulation of contaminants by fish;(3)The accumulation level of heavy metals in fish of the same age with different feeding habits was related to the size of fish body and living water layer.The concentrations of heavy metals in different tissues of fish are mainly related to the species of heavy metals.Relatively high concentrations of heavy metals are found in liver tissue.The concentrations of heavy metals in gonads of Megalobrama amblycephala increased after spawning,which suggested that there might be some protective mechanism of progeny.In view of the current situation of heavy metal pollution in the Liangzi Lake environment,corresponding measures should be taken to strictly implement the "One Lake,One Policy Implementation Plan for the Liangzi Lake in Hubei Province",focusing on the potential ecological risks that may be caused by Cd and As in the sediments of the Liangzi Lake.Given the declining population of Megalobrama amblycephala in the Liangzi Lake,the law enforcement against poaching should be intensified,the reemployment of fishermen after landing should be implemented,and the proliferation and release of Megalobrama amblycephala should be properly carried out.At the same time,during the actual sampling,we found that there is an extremely serious problem of multiple management in the Liangzi Lake,and there is even a phenomenon of individuals carrying out law enforcement.In this regard,it is recommended that the provincial departments take the lead in clarifying the management rights and responsibilities of the Liangzi Lake,and rectify the management chaos in the Liangzi Lake.