| Heavy metals are a class of metal elements with density over 5 g/cm~3 and their metal properties are stable.Now a large number of harmful heavy metals inevitably enter the water environment due to the rapid development of industry and agriculture and human activities,which has caused a series of adverse effects on the stability and health of aquatic ecosystem,and even serious pollution of water environment.At present,the pollution of water quality and soil caused by heavy metals is becoming worsen worldwidely.The Taihu lake is the biggest fishery and drinking water source for the surrounding cities ncluding Wuxi,China and it is polluted by heavy metals.Therefore,it is necessary to study the seasonal enrichment of heavy metals in lake water,sediment,fish and shellfish.In this study,we determined the contents of 4 heavy metals Pb,Cr,Cd and Cu in water samples,sediments,fish Carassius auratus and oysters Crassostrea gigas from 7 sampling sites of Meiliang Bay area of Taihu Lake for one year by using the method of atomic absorption spectrometry(AAS).Meanwhile,we also analyzed the pollution and distribution of heavy metals in Meiliang Bay sediments of Taihu Lake by means of the pollution load index method and the ground accumulation index method.The results reveal the accumulation and seasonal pollution level and distribution of Pb,Cr,Cd and Cu in water samples,sediments,fish and oysters from 7 sampling sites of Meiliang Bay area of Taihu Lake.This result will be helpful to understand the seasonal variation and enrichment behavior of heavy metals in shallow lake ecosystem and also valuable for protecting Taihu Lake and the health of its surrounding residents.The main results obtained in the present study are as follows:(1)Through the detection and analysis of 4 The pollution levels of 4 harmful heavy metals were found not high,and the average concentration trend was in decreasing order of Pb>Cu>Cr>Cd according to the determination results of harmful heavy metals in water samples from 7 sampling sites in Meiliang Bay of Taihu Lake.The average concentration of Pb in water(6.0?g/L)is the highest among the four heavy metals,which is higher than the toxicity reference values(TRV)proposed by American EPA(1999).This result indicates that Pb pollution in Taihu lake may pose a potential threat to the health of surrounding residents.(2)The detection results of heavy metal content in the sediments of Taihu Lake indicated that the amount of Cr is the largest among the four harmful heavy metals.The average concentration of Cr was observed to be 13.99?g/g in winter,suggesting that Cr pollution in the lake sediments is more serious.However,the average contents of Cu and Pb were 7.19 and 8.53?g/g,respectively,which were lower than the average shale value(20?g/g).(3)The detection results of heavy metal contents in different tissues of the fish C.carassius showed that the enrichment order of four heavy metals was Liver>Kidney>Gill>Intestinal>Muscle.The contents of Pb and Cu were the highest among the four harmful heavy metals.In the winter,Pb,Cu and Cr contents in muscle tissue were as high as 0.873?g/g,1.376?g/g and 0.326?g/g,respectively,indicating that heavy metals are enriched and contaminated in fish tissue,and consumption may have an harmful impact on human health.(4)The order of enrichment of the four heavy metals in oysters was Pb>Cu>Cr>Cd.All four heavy metals reached the highest levels in winter,with the highest lead content(4.03?g/g)and the second copper content(2.73?g/g).This result indicates that Taihu Lake oysters have suffered from different levels of heavy metal pollution.(5)The results of the pollution load index evaluation and analysis showed that the PLI values of the four seasons are all higher than 1 in winter,spring,summer and autumn,in which the winter PLI value was the highest(6.96 to 11.25).The highest CF values for chromium,lead,and copper were between 1 and 3,all of which were moderately polluted.The value of chromium was greater than 6,which reached a very high level of pollution.(6)The evaluation results of the geoaccumulation index method showed that the pollution of chromium was the most serious,with an average value is above 5,and the pollution level reached extremely strong pollution;followed by lead and copper;the average pollution level of cadmium was the lowest,which belongs to moderate pollution.In summary,the results of this study indicate that the Taihu lake not only suffers from the pollution of four heavy metals such as lead,chromium,cadmium,and copper,but also bioaccumulation of these harmful heavy metals in lake sediment,fish,and oysters.This may be a certain threat to the health of the residents around the Taihu Lake and suggests the necessity of heavy metal pollution control. |
PDF Full Text Request