Risk assessment and binding mechanisms of potentially toxic metals in sediments from different water levels in a coastal wetland

The excessive accumulation of potentially toxic metals (Pb and Cd) in coastal wetlands is among the main factors threatening wetland ecosystems. However, the effects of water table depth (WTD) on the risk and binding mechanisms of potentially toxic metals in sediments remain unclear. Here, sediments from different WTD obtained from a typical coastal wet-land were evaluated using a newly developed strategy based on chemical extraction meth-ods coupled with high-resolution spectroscopy. Our findings indicated that the WTD of the coastal wetland fluctuates frequently and the average enrichment factor for Pb was catego-rized as minor, whereas Cd enrichment was categorized as moderate. High-resolution spec-troscopy techniques also demonstrated that organic functional groups and partly inorganic compounds (e.g., Fe-O/Si-O) played a vital role in the binding of Pb and Cd to surface sedi-ments. Additionally, mineral components rather than organic groups were mainly bound to these metals in the bottom sediments. Collectively, our findings provide key insights into the potential health effects and binding characteristics of potentially toxic metals in sediments, as well as their dynamic behavior under varying sediment depths at a microscale.(c) 2022 The Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences. Published by Elsevier B.V.

Automated summary

This study assessed the risk and binding mechanisms of potentially toxic metals in sediments from a coastal wetland under different water table depths using chemical extraction methods and high-resolution spectroscopy. The results showed that the water table depth fluctuated frequently in the coastal wetland, with minor enrichment of Pb and moderate enrichment of Cd. High-resolution spectroscopy revealed the importance of organic functional groups and partly inorganic compounds in the binding of Pb and Cd to surface sediments, while mineral components were the main binding agents in the bottom sediments.