Heavy Metal Pollution And Risk Assessment And Uncertainty Analysis In Sediments And Marine Organisms From Three Typical Estuary/Gulfs Of The South China Sea

The South China Sea is the largest marginal sea in China with abundant marine and fishery resources.In recent years,with the rapid development of urbanization and modernization in coastal areas and the vigorous development of marine resources,environmental problems have become increasingly serious.The pollution of the coastal marine environment mainly includes organic pollutants and inorganic pollutants,and the problem of heavy metal pollution of inorganic pollutants has attracted considerable attention.Heavy metal pollution not only threatens the habitat of aquatic organisms,but also destroys the structure and function of the ecosystem through the transmission of the food chain,and ultimately threatens human health.This study systematically analyzed the contents of heavy metals(Cu,Zn,Pb,Cd,Cr,As and Hg)in the water,sediments and marine organisms of the three typical estuaries and bays of the South China Sea(Changhua River Estuary,Daya Bay and Shangchuan Island),and a variety of index evaluation and multivariate statistical analysis methods are used to analyze its heavy metal pollution and distribution,bioaccumulation characteristics,and ecological and health risks.At the same time,the Monte-Carlo simulation is used for uncertainty analysis and sensitivity analysis.The contents of heavy metals in sediments is in the order of Shangchuan Island >Daya Bay>Changhua River Estuary,and the heavy metal contents are ranked from high to low as Zn>Cr>Pb>Cu>As>Cd>Hg(Cr not analyzed in Changhua River Estuary).All three sea areas are between unpolluted and moderately polluted.The main pollutant in the Changhua River Estuary is As,Cd has the strongest spatial variability,and the ecological risk is between low and high risks;the main pollutant in Daya Bay is Pb,followed by Hg,and the ecological risk is at low to medium risk;The As pollution coverage rate on Shangchuan Island is 100%(69% moderate pollution and 31% slight pollution),and the pollution of Hg,Pb,Cd and Zn cannot be ignored,and the ecological risk is at a low to medium risk.The contribution of the heavy metal elements in the sediments of the three sea areas to the potential ecological risk is basically the same.Hg and Cd are the main contributors to the marine ecological risk.The contents of heavy metals in the sediments has the highest possible toxic hazard to the biological community,Pb is the highest,and As is the second.There are significant differences in the content of heavy metals in organisms.In terms of average content,the content of heavy metals in organisms in the three sea areas basically meets the safety standards of the Maximum Levels of Contaminations in Foods(GB 2762-2017).Marine organisms are easy to accumulate heavy metals from seawater,and the accumulation capacity of fish is lower than that of crustaceans and mollusks.Cu and Zn are the two elements with the highest content in all organisms,and species have different sensitivities to the enrichment of each metal.The same species lives in different marine environments,and their bioaccumulation of heavy metals also has significant differences.The health risk assessment results indicated that the risk of mollusks(mainly bivalve)is relatively high,and the risk of children is higher than that of adults.The probability of Changhua River Estuary seafood exceeding the acceptable noncarcinogenic health risk is 0.51%(adults,the same below)and 1.84%(children,the same below),and the probability of exceeding the acceptable carcinogenic health risk is 31.73%and 46.56%;There is no obvious non-carcinogenic risk in Daya Bay and Shangchuan Island.The cumulative probability of carcinogenic risk is 11.19% and 22.27%(Daya Bay)and 83.87% and 89.57%(Shangchuan Island),respectively.Hg is the main contributor to the non-carcinogenic risk.The main contributor to the carcinogenic risk of Changhua River Estuary and Daya Bay is As,and the main contributor to the carcinogenic risk of Shangchuan Island is Cr,followed by As.Sensitivity analysis results showed that the impact of daily intake(IR)on health risks is generally higher than the risk contribution of the total contents of heavy metals.