[Environmental characteristics of heavy metals in surface sediments from the Huanghe estuary]

The contents of Cu, Pb, Zn, Cr, As and Hg in surface sediment from 14 sampling sites in the Huanghe estuary during July-August, 2011 were measured to investigate environmental geochemical characteristics of heavy metals related to multiple factors. The distribution, relationship with fine fraction and TOC, and sediment quality assessment concerning heavy metals were analyzed. The results showed that average concentrations of Cu, Pb, Zn, Cr, As and Hg in the Huanghe estuary were (16.5 +/- 2.7), (16.0 +/- 3.4), (21.0 +/- 3.3), (17.4 +/- 3.1), (6.5 +/- 1.2), (0.0444 +/- 0.0307) mg x kg(-1), respectively, which were lower than those in other typical areas along the coast of China. The distribution of metals displayed higher profiles in south than that in north of the Huanghe estuary, with a trend of increase seaward, especially for stations in southwest of the Laizhou bay. The insignificant correlation among metals indicated the complex sources of heavy metals in flood season. Pearson correlation was also conducted between metal contents and percentage of fine particulates and TOC, which was also insignificant, suggesting heavy metal concentration and distribution in the study region were also controlled by other factors except grain size and TOC. There was a good correlation between clay fraction and TOC (r = 0.724, P < 0.05), indicating TOC tends to accumulate in clay. Compared with variety of background values and an internationally used consensus-based sediment quality guidelines (CBSQGs) for saltwater ecosystem, heavy metals in surface sediments from the Huanghe estuary implied a low probability of toxic effect, despite a sharp contamination trend pertaining to Hg and Pb since 1980s.