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In this study, the sources of nine heavy metals (Cd, As, Hg, Cu, Pb, Ni, Cr, Zn, and Co) in the sediments of the Bohai Sea were quantitatively identified through a positive factor matrix to provide better advice for marine and coastal management. In Bohai Sea sediments, most metals fell below detectable contamination levels, including As, Cu, Pb, Ni, Cr, Zn, and Co. Unfortunately, Bohai Sea sediments were moderately to significantly enrich with Cd and Hg, posing potentially adverse ecological risks to aquatic ecosystems. Our modeled results showed three factors representing natural, anthropogenic, and atmospheric deposition sources. Enriched Cd and Hg were likely derived from anthropogenic activities through river runoff and atmospheric deposition due to adjacent Zn smelting and chlor-alkali production, respectively. The other metals were mainly derived from natural sources. • Nine heavy metals were analyzed in 404 surficial sediments from the Bohai Sea. • A positive factor matrix method was used to trace heavy metal sources of sediments. • Enriched Cd may be derived from anthropogenic activities via riverine discharge. • Hg is mostly likely enriched by atmospheric deposition. [ABSTRACT FROM AUTHOR]

Background metal concentrations are important in assessing pollution level of marine sediments; however, they can be significantly altered by local depositional environments, resulting in significant errors in regional pollution assessment. This study was based on the investigation of the background levels of heavy metals in the Bohai Sea sediments using sediment core, 2-sigma outlier, and regression methods. We also estimate the ecological risks of heavy metals for surface sediments collected from the Bohai Sea using the three methods mentioned above. Ecological risks of heavy metals calculated using the regression method show wide disparities and significant differences from those calculated using the sediment core and 2-sigma methods, indicating that the regression method is not suitable for the Bohai Sea, likely as a result of its complex sources. Conversely, the estimated ecological risks using the sediment core method are moderate, and most heavy metals, except for Hg and Cd, have negligible contamination. • Regional metal (Fig. 1) backgrounds in the semi-closed Bohai Sea sediments are determined. • Three methods are used to determine metal backgrounds. • Regression is not suitable to determine metal backgrounds of Bohai Sea sediments. • Pollution levels of Bohai Sea sediments may be overestimated in previous studies. [ABSTRACT FROM AUTHOR]

In this study, we analyzed heavy metals in 404 surface sediment samples from the Bohai Sea to measure contamination status and distribution. We found Zn levels to be the highest, whereas Hg concentrations were the lowest of measured heavy metals. We found that the samples containing the most heavy metals were those collected from Fuzhou Bay, Jinzhou Bay, central Bohai Sea mud area, and the Yellow River Delta. Further analyses suggest that these heavy metals in surface sediments in the Jinzhou Bay and Fuzhou Bay pose a serious ecological risk, with substantial Cd and Hg accumulation in the Jinzhou Bay and Yellow River Delta regions being indicative of intense human activities. • Eight heavy metals of 404 surface sediments from the Bohai Sea were analyzed. • The mean heavy metal concentrations detected were, in descending order: Zn > Cr > Ni > Pb > Cu > As > Cd > Hg. • Samples containing the most heavy metals were those collected from Fuzhou Bay, Jinzhou Bay, central Bohai Sea mud area, and the Yellow River Delta. • Heavy metals in surface sediments in the Jinzhou Bay and Fuzhou Bay pose a serious ecological risk. [ABSTRACT FROM AUTHOR]