Study On Accumulation And Spatial Distribution Of Organochlorine Pesticides And Heavy Metals In Mussels In Chaohu Lake

Organochlorine pesticides and heavy metals are both highly toxic pollutants,stable in nature,not easily degraded,and have bioaccumulation,especially in aquatic organisms,which can be transmitted and amplified through the food chain and food web.After being continuously enriched,these pollutants will also increase through the secondary release after being deposited in the sediments.Human beings will also cause health risks partly due to the ingestion of aquatic products.Chaohu Lake is one of five major freshwater lakes in China and an important link for the Diversion from the Yangtze River to the Huaihe River project.Chaohu Lake is an indispensable water source.Since the 1970 s,with the continuous development of industry and agriculture in the surrounding cities of Chaohu Lake basin,a large amount of pesticides and heavy metal pollutants have entered Chaohu Lake through surface runoff and atmospheric deposition,causing the water of Chaohu Lake continue to deteriorate,and the sediments and aquatic organisms in Chaohu Lake continue to deposition and accumulate.In order to explore the current status of organochlorine pesticide(OCPs)residues and heavy metal pollution in Chaohu Lake,this study collected 18 sampling points of surface sediments(0?20cm)and 8 kind of mussels(Lanceolaria lanceolata,Sinohyriopsis cumingii,Cristaria plicata,Nodularia douglasiae,Lamprotula leaii,Sinanodonta woodiana,Cuneopsis capitata,Gibbosula rochechouarti)in Chaohu Lake area under the premise of comprehensively considering the distribution of Chaohu and the desirability.Used accelerated solvent extraction(mussels dissected into visceral mass,mantle film and axefoot)and Soxhlet extraction(sediment samples),and GC-MS detection to analyze the content and distribution of 20 kinds of organochlorine pesticide residues.Used microwave digestion(mussels)and wet digestion(Surface sediment samples),and ICP-MS detection to analyze the content and distribution of 5 heavy metals(Cu,Zn,As,Cd,and Pb),and evaluated their ecological risks.The results are expected to provide basic data for Chaohu pollution control,and provide scientific basis and theoretical support for the selection of tolerant species in ecological restoration biological monitoring of degraded water.The main findings are as follows:(1)Organochlorine pesticides in surface sediments and mussels of Chaohu had been detected.14 kinds of Organochlorine pesticides were detected in sediments,the total content was 5.64?29.74 ng/g,average content was 15.39 ng/g,mainly polluted by HCHs and DDTs,the contents were 1.04?9.07 ng/g and ND?14.26 ng/g,and the average content were 5.46 ng/g and 6.42 ng/g,respectively.The pollution in sediments of Chaohu Lake was at a medium level among freshwater lakes in China.The results of the isomer ratio method showed that there was no new HCHs and DDTs input in Chaohu recently,and 15 organochlorine pesticides were detected in mussels.The content of organochlorine pesticides in different mussels ranged from 2.564?16.835 ng/g,where the content of DDTs and HCHs accounted for 81%?96% of the total organochlorine pesticides.The content of ?OCPs in descending order was Sinohyriopsis cumingii > Lanceolaria lanceolata > Nodularia douglasiae > Cristaria plicata > Lamprotula leaii > Sinanodonta woodiana > Cuneopsis capitata > Gibbosula rochechouarti,organochlorine pesticides had tissue specificity among the tissues of the eight species of mussels,and the order was visceral mass> mantle film> axefoot.From a spatial point of view,the content of organochlorine pesticides in the sediments and mussels showed a high degree of consistency.The content of organochlorine pesticides in the vicinity of Nanfei River,Hangbu River and Shiwuli River in the west,and the Yuxi River in the east were relatively high,indicating that the pollution of OCPs in these estuaries was serious.(2)Five heavy metals were detected in the surface sediments and mussels of Chaohu Lake.The samples which Cd exceeded the background value in the sediment accounted for77.78%,and As content exceeding the background value accounted for 66.67%.The difference in the content of heavy metals in mussel tissues was roughly as follows: visceral mass> mantle film> axefoot.The difference in the content of heavy metals between different species was greater than the spatial difference,and the content of heavy metals in mussels was also different.The heavy metal pollution in the sediments and mussels in the west lake was higher than that in the east lake.The heavy metal content of the mussels between the samples was significantly correlated with the heavy metal content in the sediments(P<0.05),indicated that using mussels to monitor the heavy metals in the water was feasible.(3)Used the Ingersoll risk assessment to evaluate the pollution of organochlorine pesticides in the surface sediments of Chaohu Lake,the results showed that the biological toxicity of OCPs in the sediments exceeded 25%.It was necessary to strengthen prevention and control.OCPs had a low ecological risk and low probability of causing health risks to the human beings.The ecological risk index showed that As and Cd pollution were at level?and Cd in the sediments of Chaohu Lake was at a moderate-severe risk level,77.78% of the samples were at a moderate risk level,and As,Cd and Pb in mussels were all not exceed the limit values of standard(GB 2762-2017).While heavy metals are not easily metabolized and will accumulate,consuming mussels in large quantities was not recommended.