Flux and source-sink relationship of heavy metals and arsenic in the Bohai Sea, China

Abstract

This study conducted a field campaign to collect atmospheric deposition samples of heavy metals and arsenic, a metalloid element with typical chemical-physical characteristics (HMA), from 12 sampling sites and water samples from 37 rivers across the Bohai Sea (BS) and North Yellow Sea (NYS) in China. The HMA budgets in the BS and NYS were quantified by a budget model, which was developed based on the HMA inputs from atmospheric deposition and riverine discharge, sequestration to sediment, and interexchange among the BS's four subareas and the NYS. Statistical analyses of 76 deposition samples and 109 water concentration samples showed that atmospheric deposition was a main pathway of Pb entering the BS and NYS, whereas riverine discharge dominated the input of Cr, Cu, Zn, Cd, and As into the marine environment. Modeled results showed that the fractions of HMA in the water bodies compared with their total burdens were 86.6 ± 4.55% in the Liaodong Bay, 60.5 ± 10.5% in the Bohai Bay, 20.9 ± 9.05% in the Laizhou Bay, 95.1 ± 2.06% in the Central BS, and 94.3 ± 1.93% in the NYS. The lowest fraction of HMA in the Laizhou Bay was attributed to high sedimentation rates and higher suspended particulate matter concentrations due to inputs from the Yellow River. The modeled 1-, 10- and 100- year mass budgets indicated that the Liaodong Bay in the north of the BS was a sink of HMA, the Bohai Bay and Laizhou Bay in the west and south of the BS acted as sources, and the Central BS and NYS were a transition area for most HMA.