| As an important economic developing area of Guangxi,the pollution of heavy metals at Beibu Gulf has been paid much attention.In order to evaluate the pollution,risk and sources of heavy metals at Beibu Gulf,surface sediment was sampled in 2018 and 2019,respectively,heavy metal content of Pb,Cr,Cu,Cd,Zn,and Hg were measured.Several methods including Hakanson potential ecological risk assessment,ratio of secondary and primary phase?RSP?and stochastic geo-accumulation model?SGM?were utilized to evaluate the pollution situation and risk of heavy metals.Principal component analysis?PCA?,positive matrix factorization?PMF?source analysis model and mercury isotope technique were applied to identify the sources of heavy metals.The following conclusions could be drawn from the proposed studies:The concentrations of Cr,Hg,Pb,As,Cu,Zn and Cd in the surface sediment of Beibu Gulf were 21.90±12.83 mg·kg-1?0.04±0.03 mg·kg-1?19.97±12.58mg·kg-1?9.11±4.86 mg·kg-1?11.30±11.13 mg·kg-1?45.73±28.83 mg·kg-1?0.07±0.08 mg·kg-1?mean±SD?,which was lowered than that of Pearl River Estuary and Daya Bay,comparable with that of Yangtze Estuary.The distribution of heavy metals was mainly affected by human activities,which could be divided into two types according to its distribution characters:The areas at high concentration of Cr,Hg and As was mainly distributed in the nearshore and the estuary of rivers locating the coal-burning,chemical industry and other industries.High level of Cu,Zn and Cd were mainly found in the harbors where petroleum chemical industry,metallurgy and other industries located.The pollution level of heavy metal at most sites?82.3%?of Beibu Gulf was slight,and that at some sites in Qinzhou Bay was moderate.The average ecological risk of seven heavy metals was slight,while Hg and Cd had distinct higher risk than that of other heavy metals.The morphology analysis of Hg indicated that Hg was mainly in the residual state,at low ecological risk.The pollution assessment from SGM model at surface sediment in Beibu Gulf remaindered that Cd,Cu,Pb,Zn,Hg was belonged to“none-moderate pollution”,As and Cr to“none pollution”,Cd,Cu,Pb,Zn and Hg had 48%,46%,4%,17%,15%probability to get worsen to“moderate pollution”,and As and Cr had 33%and 39%probability to deteriorate to“none-moderate pollution”.In general,seven kinds of heavy metal pollution level was“none-moderate pollution”,and percentage of 13.5%was found to further deterioration to“moderate pollution”,hinting the pollution was slight.Combine the results from PCA,PMF model and mercury isotope analysis,it was revealed that three dominating sources of heavy metals in the surface sediment of Beibu Gulf.They were industrial sources including petrochemical,coal burning,paper making,phosphorous chemical and other industries;human activities containing nearshore sewage discharging,ships sailing;environmental background which caused by atmospheric dry and wet deposition.Their contributions to heavy metals were 36.2%,36.6%and 27.2%,meaning that the metal level was heavily impacted by anthropogenic sources.The proposed results could provide technological means for assessing the heavy metal pollution,data basic for making relevant prevention and control measures,and certain directive meaning for the sustainable development of regional economy. |
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