Long-term variations of the riverine input of potentially toxic dissolved elements and the impacts on their distribution in Jiaozhou Bay, China

Abstract

The concentrations of the potentially toxic dissolved elements (PTEs) As, Hg, Cr, Pb, Cd, and Cu in the main rivers into Jiaozhou Bay (JZB) during 1981–2006 were measured, and the impact of the fluvial PTE fluxes on their distributions in the bay was investigated. The overall average concentration in the rivers into JZB ranged from 8.8 to 39.6 μg L⁻¹ for As, 10.1 to 632.6 ng L⁻¹ for Hg, 4.1 to 3003.6 μg L⁻¹ for Cr, 8.5 to 141.9 μg L⁻¹ for Pb, 1.1 to 34.2 μg L⁻¹ for Cd, and 13.2 to 1042.8 μg L⁻¹ for Cu. The interannual average concentration variations of the PTEs in these rivers were enormous, with maximum differences of 41–21,680 times, while their relative seasonal changes were far smaller with maximum differences of 3–12 times. The total annual fluvial fluxes for As, Hg, and Cr into JZB exhibited the inverse "U" pattern, while those for Pb and Cd showed the "N" pattern. As a whole, the total annual Cu flux presented a growing tendency from 1998 to 2006. In general, the changing trends of the PTE concentrations in JZB were similar to those of their annual fluxes from the rivers, indicating a great impact of their fluvial fluxes on their distributions in JZB. The annual concentration of Cd in the bay almost remained constant and differed from the fluvial flux of Cd. The diversified pattern of the environmental Kuznets curve (EKC) represented China's approach to industrialization as "improving while developing."