Background determination, pollution assessment and source analysis of heavy metals in estuarine sediments from Quanzhou Bay, southeast China

The concentrations of ten heavy metals (Cr, Cu, Zn, Cd, Pb, Co, Ni, Fe, Mn, and Hg) and Pb isotope compositions were investigated in two estuarine sediment cores collected in Quanzhou Bay, southeast China. The regional background levels of heavy metals in the estuarine sediments from Quanzhou Bay were established using the fine fractions (< 63 mu m) obtained from the sediment cores. The background values of Cr, Cu, Zn, Cd, Pb, Co, Ni, Mn, Hg, and Fe were 37.14 mg kg(-1), 19.79 mg kg(-1), 130.86 mg kg(-1), 0.24 mg kg(-1), 42.18 mg kg(-1), 10.31 mg kg(-1) 20.89 mg kg(-1), 612.60 mg kg(-1), 0.07 mg kg(-1) and 3.17%, respectively. The background values of most elements (Cr, Cd, Pb, Co, Ni, Mn, Hg, and Fe) detected for the estuarine sediments from Quanzhou Bay in this study were in the middle of the obtained ranges for other locations in China. However, the Pb and Zn background values in Quanzhou Bay were significantly higher than the Chinese average. The enrichment factor (EF), geoaccumulation index (I-geo), and contamination factor (CF) values indicated that sediment contamination associated with Cu, Zn, Pb, Mn, and Cd has occurred since the nineteenth century. Based on principal component analysis (PCA) and cluster analysis (CA), Cu, Zn, and Pb were clustered into a group, and their sources could be related to the mining of metallic ore deposits. The Pb isotope composition data from the dated sediment cores further suggested that the Pb sources transitioned from natural sources during 1715-1788 CE to Pb-Zn ore deposits during 1788-1935 CE and then to multiple anthropogenic sources, including Pb-Zn ore deposits and industrial and domestic emissions, in recent decades (1935-2009 CE).