Distribution And Assessment Of Heavy Metals In Water And Sediments Of The Pearl River Estuary

The rapid economic development in the Pearl River Delta (PRD) region in SouthChina has had a significant impact on the local environment. We choose Zn、Pb、Cu、Cr、Ni、Cd、Co and Tl in water and sediments of Jiaomen, Hongqimen, Humen,Maodaomen, Jitimen, Yamen of the Pearl River Estuary (PRE) as research object. Theconcentrations of heavy metals in water and sediments have been determined byInductively Coupled Plasma Atomic Emission Spectrometry (ICP-AES) andInductively Coupled Plasma Mass Spectrometry (ICP-MS) in this study, what’s more,the spatial distribution and seasonal distribution of heavy metals in water have beenanalyzed, and the heavy metals spatial distribution, seasonal distribution, temporaldistribution and size distribution in sediments also have been analyzed.Simultaneously, Correlation analysis and Principal Component Analysis (PCA) havebeen used to analysis the source of heavy metals, and Ecological risk assessment andhuman health risk assessment of heavy metals have been evaluated.The distribution of heavy metals in water from PRE showed that theconcentration of Zn is the highest one, the lowest is Tl, and the order of the heavymetals concentration is Zn>Pb>Cu>Cr>Ni>Cd>Co>Tl. The seasonal distribution ofCr, Cd and Pb is obvious, and the concentration of Cr, Cd and Pb in Autumn andWinter is higher than Spring and Summer, which was effected by precipitation andhuman activities.The size distribution of heavy metals in sediments showed that the peliticfraction was more enriched in heavy metals. The spatial distribution of heavy metalsin sediments showed the pollution of heavy metals were more serious in Modaomen,Jitimen and Yamen. Because of the stability and persistence of heavy metals insediments, the seasonal distribution of heavy metals in sediments was not obvious.The vertical profiles of heavy metal concentrations in sediments can mirror changesover time, the vertical profiles showed that the change trends of heavy metals indifferent estuary were different, which means that the history pollution of heavy metals in different estuary were different.Pearson Correlation Analysis and PCA were used to analysis the source of Zn, Pb,Cu, Cr, Ni, Cd, Co and Tl in water, the result showed that there were four componentswhich can reflect all the information of heavy metal contaminations in water, the totalvariance is94.92％. And the result of analyzing the source of Zn, Pb, Cu, Cr, Ni, Cd,Co, Tl, Fe and Al in sediments showed that there are three components of heavymetals in sediments, and the total variance is85.46%. The variance of the firstcomponent is53.96%, which dominate the source of most heavy metals in sediments.According to the study of heavy metal pollution in sediments, the source of heavymetals comes mainly from industrial wastewater, domestic sewage, iron mine andaluminum mine.According to the water quality assessment of heavy metals in PRE, theconcentration of Cu、Cr、Ni and Cd in water were belong to the first kind of sea waterquality standard. The United States Environmental Protection Agency risk assessmentmodel was used in determining the potential health risk by means of drinking water ofthe pollution to heavy metal contents in water. The result showed that the health riskvalues of the carcinogens was3000to4000times higher than the non-carcinogens.The highest cancer risk value is3.9×10-3a-1for Cr, and the order of the non-cancer riskvalues is Pb>Tl>Co>Ni>Cu>Zn. An order of relative risk significance of heavymetals in sediments from the PRE was Zn>Cu>Co>Cr>Pb>Ni>Cd>Tl based on thecalculation of the geo-accumulation index (Igeo), and the results of Enrichment Factor(EF) was similar to Igeo. The heavy metal ecotoxicity risks were assessed with theapplication of Sediment Quality Guideline (SQG) and toxic units approach, the resultindicated that the order of the heavy metal ecotoxicity risks wereZn>Cu=Ni>Pb>Cr>Cd, the total toxic units value of the heavy metals in sedimentsfrom Modaomen, Jitimen and Yamen is greater than4and less than6, which meansthat Modaomen, Jitimen and Yamen have higher ecotoxicity risk.