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To investigate the source of Pb within Bohai Bay, Pb concentrations and Pb isotopic compositions (Pb-204, (206)pb, Pb-207, and Pb-208) of surface sediments in this area were determined. The Pb concentration in this bay varied widely from 6.9 to 39.2 mu g/g (average: 21.8 +/- 7.8 mu g/g), and the Pb isotopic compositions ranged from 0.8338 to 0.8864 (average: 2.0997 +/- 0.0180) for Pb-208/Pb-208 and from 2.0797 to 2.1531 (average: 0.8477 +/- 0.0135) for Pb-207/Pb-206, presenting in three distinct clusters. The Pb isotopic ratios of sediments from the northeastern (NE zone) and northwestern (NW zone) coastal areas were significantly influenced by anthropogenic sources such as coal combustion and automobile emission. In sediments from the central and southern Bohai Bay (C-S zone); however, Pb mainly originated from the Yellow River catchment, as a result of lithogenic sediment (from rock weathering) accumulation. The Pb isotopic ratios further indicate that, apart from riverine inputs, the neighboring large-scale ports and aerosols significantly contributed to the anthropogenic Pb contained in these sediments. Pb contamination in the Haihe and Luanhe river mouths as well as in the regions near ports is also suggested from anthropogenic enrichment factors. As cities and ports continue to develop around Bohai Bay, a long-term extensive sewage monitoring program is highly recommended. (C) 2015 Published by Elsevier Ltd.

Geochemical sources, spatio-temporal distribution, and associated environmental risk of Cd in the Bohai Sea were investigated using data from 405 surface sediment samples and two sediment cores. Local point Cd sources, TOC content, and currents are the main controlling factors of Cd distribution. The contribution of Cd from river discharge surpasses that from atmospheric deposition. Sediment-quality guidelines, enrichment factors, and chemical fraction analysis were used to assess metal toxicity in the collected sediments. Results show that Bohai Sea sediments have a moderate Cd enrichment level. This enrichment poses a high risk due to the relatively high mobility and bioavailability of Cd despite measured levels below sediment-quality guidelines at most stations. Vertical profiles of Cd concentrations, Al-normalized enrichment factors, and excess burial fluxes combined with 210Pb dating reveal the history of Cd pollution in the Bohai Sea over the last century. Data show Cd unvaried before the 1800s, a slight increase from the 1800s to the late 1950s, a decrease from the late 1960s to the 1970s, and an increase from the 1980s to 2001, including a relatively high value in 1998. Historic variation in Cd is closely associated with both natural and anthropogenic activities.