The distribution and speciation of dissolved Cd and Pb in the Bohai Sea and Yellow Sea, China.

The speciation of dissolved trace metals is important due to its closely linkage with toxicity and bioavailability in seawater. We investigate the speciation of dissolved Pb (DPb) and Cd (DCd), and their spatial distributions in the Yellow Sea and Bohai Sea, China. The results showed that the organic complexation of DPb and DCd accounted for 35 ± 14 % and 75 ± 10 % of their dissolved concentrations, respectively. The measured free ion activity of Cd ({Cd2 +}) and organic ligand concentration of Cd ([LCd]) were highest near the Yellow River mouth, where the free ion activity of Pb ({Pb2+}) were also found to be the highest. In this study, both {Pb2+} and {Cd2+} did not exceed the toxicity threshold, and they were identified not toxic in the waters of the Yellow Sea and Bohai Seas, but biological accumulation effects potentially exist.

Distribution and assessment of heavy metal in sediments of Malacca Strait.

In this study, we explored the heavy metal elements in 42 surface sediments from the Malacca Strait in terms of distribution, controlling factors, environmental quality, and primary sources. An analysis of grain size revealed finer sediments near the coast of Malaysia, which gradually thickened toward offshore. In addition, heavy metal elements were abundantly distributed near the coastal area of Malaysia, with a gradual decrease toward the sea; their content increased within waters close to the Perak estuary. Source analysis of heavy metals showed that Cr, Hg, Zn, Cd, and Cu were mostly derived from natural weathering, and their distribution was significantly influenced by sediment grain size. As and Pb were affected by human activities. The environmental quality assessment results showed that Cu, Cr, Cd, and Zn in our study regions were pollution-free. Pb elements showed low-to-moderate pollution, and Hg showed a certain degree of ecological risk due to its high toxicity coefficient. The content of As elements in surface sediments increased significantly when compared to the background value, with several evaluation methods indicating a high-risk index. According to these findings, the area near the mouth of the Perak River is the most polluted, followed by the surrounding coastal areas.

Impact of extreme metal contamination at the supra-individual level in a contaminated bay ecosystem.

Anthropogenic stressors impact the global environment and adversely affect the health of organisms and humans. This study was designed as an attempt to evaluate the ecological consequences of severe metal contamination at the supra-individual level based on a field investigation in Jinzhou Bay (JZB), North China in 2010. The chemical results showed high concentrations of metals in the sediment of JZB that were ~129 times greater than the local geochemical background. Furthermore, the measured metals exhibited considerably high toxicity potential indicated by sediment quality guidelines (SQGs). The mean SQGs quotients suggested the overall toxicity incidence was >70% in locations neighboring the Wulihe River mouth. Biomonitoring revealed 116 individuals distributed among a mere 6 species, 4 of which were polychaetes, at 33% of the sampling sites. Thus, few benthic organisms were present in the damaged community structures across the region, which was consistent with the extreme metal contamination. Moreover, the sediment quality assessment, in a weight of evidence framework, demonstrated that the sediment throughout the entire JZB was moderately to severely impaired, especially in the vicinity of the Wulihe River mouth. By synthesizing the present and previous chemical-biological monitoring campaigns, a possible cause-effect relationship between chemical stressors and benthic receptors was established. We also found that the hydrodynamics, sediment sources, and geochemical characteristics of the metals (in addition to the sources of the metals) were responsible for the geochemical distribution of metals in JZB. The significance of the overall finding is that the deleterious responses observed at the community level may possibly be linked to the extreme chemical stress in the sediment of JZB.