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This study aimed to determine sediment contamination in the Beidagang Wetland Nature Reserve to describe atmospheric deposition of trace metals. We analyzed Hg, Cd, Pb, TOC, TN, TP, δ13C, and δ15N, and studied their variations in surface sediments and in the vertical profiles of sediment cores collected from the reserve. Evaluation of environmental trace metal contamination using sediment quality guidelines and geochemical background values indicated that the risk of metal pollution in the reserve sediments was relatively low. Concentrations of Hg, Cd, and Pb in the sediments were much lower than concentrations in sediment samples from Bohai Bay and polluted rivers in Tianjin. Enrichment factors indicate that samples are moderately contaminated with Hg, Cd, and Pb; whereas the geo-accumulation index results classify the sediments as uncontaminated to moderately contaminated with Hg, Cd, and Pb. The distribution patterns of trace metal concentrations in the three core samples were uniform. δ13C and δ15N were used to track the sources of TOC and TN in sediments. Results show that TOC mainly originated from the residue and decaying matter of aquatic plants (e.g., algae, reeds, and Typha), while TN was derived from soil N and elevated atmospheric N deposition. Because domestic and industrial waste is not discharged into the Beidagang Wetland Nature Reserve, trace metals found in sediments mainly originate from atmospheric deposition. The results provide baseline data for analysis of trace metal accumulation in Beijing-Tianjin-Hebei, a region subject to atmospheric deposition in northern China. [ABSTRACT FROM AUTHOR]

A tide gate was built in 2010 to prevent seawater from moving upstream into the Yongdingxin River estuary in Bohai Bay, Northern China. We analysed the concentrations of Hg, Cd, Pb, TOC, TN, δ 13 C and δ 15 N and studied their variations in the surface layer and vertical profiles of sediment cores collected from the Yongdingxin River estuary. Contamination factors and geo-accumulation indices were calculated for each metal, which revealed high levels of contamination for Hg and Cd in the sediments, likely from anthropogenic sources. δ 13 C and δ 15 N were used as natural tracers to determine the sources of TOC and TN. The results revealed that sewage was the main source of TOC, while TN may have more than one source in the Yongdingxin River estuary. Sewage dominated trace metal pollution in the Yongdingxin River estuary. Our results provide a baseline for trace metal contamination in an estuary facing a large water project. [ABSTRACT FROM AUTHOR]

The impact of tide gate on heavy metal mobility in Haihe River sediments was studied in a laboratory leaching simulation experiment. The results indicated that seawater promoted a higher release of Cd and Cu than deionized water and river water, and river water extracts high amounts of Zn. This release may be a result of both the formation of chloride complexes and ion exchange. However, the salinity induced by seawater did not significantly enhance the mobility of Pb. This implied that the mobility of Cd and Cu can be reduced by the insufficiency of the salinity when constructing tide gates in the brackish zones of an estuary. In the acidification processes, Cd and Zn were not, but Cu and Pb were, affected by an increase of salinity and ionic strength. [ABSTRACT FROM AUTHOR]

Highlights: [•] Heavy metals were analysed in nine estuaries along the coast of Bohai Bay. [•] Strong correlations were found between higher Hg and organic matter and nutrients. [•] Cd exposure was rather low in all of the nine selected estuaries. [•] High mobility of Cd explained its spatial variations in sediments between rivers and estuaries. [ABSTRACT FROM AUTHOR]