Geological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa 403004, India.
Geological Oceanography Division, CSIR-National Institute of Oceanography, Dona Paula, Goa 403004, India; Centre for Oceans, Rivers, Atmosphere and Land Sciences, Indian Institute of Technology Kharagpur, Kharagpur, West Bengal 721302, India.
Sci Total Environ. 2019 Jun 10;668:592-601. doi: 10.1016/j.scitotenv.2019.02.353. Epub 2019 Feb 23.
Sedimentary organic matter (SOM) plays an important role in hosting and reducing Hg in marine/estuarine sediment. This study provides a better understanding on the influence of nature of SOM, in regulating sedimentary mercury (Hg) and elemental mercury (Hg) distribution, and speciation in the Zuari and Mandovi Estuaries that are representative of monsoon fed tropical estuaries, located in the central west coast of India. Salinity of the overlying water column controlled the physical and chemical characteristics of SOM in the estuarine systems. The high molecular weight (MW) SOM dominated at the mid and upstream (low salinity region) of the estuaries, whereas, the low MW SOM prevailed at the downstream (high salinity region). Sediment Hg showed more affinity towards the SOM of high MW. Increasing MW of SOM increased total sedimentary Hg in both the estuaries. SOM with low MW in the estuarine sediment displayed a negative relationship with the sediment Hg concentration. Distribution of Hg concentration in the estuarine sediment suggests that reduction of Hg in presence low MW SOM was a dominant process. It was also found that distribution and speciation of Hg in the estuarine sediment depends on the quantity, quality of the SOM, and the total sediment Hg loading. This study demonstrated that the competition between Hg-SOM complexation and Hg reduction by SOM controls Hg/Hg distribution in tropical estuarine sediment systems.
沉积物中的有机物质（SOM）在容纳和减少海洋/河口沉积物中的汞方面起着重要作用。本研究更好地了解了 SOM 的性质对调节沉积汞（Hg）和元素汞（Hg）在代表季风驱动的热带河口的 Zuari 和 Mandovi 河口的分布和形态的影响，这些河口位于印度中西部海岸。上层水柱的盐度控制了河口系统中 SOM 的物理和化学特性。高分子量（MW）的 SOM 在河口的中部和上游（低盐度区域）占主导地位，而低分子量（MW）的 SOM 在下游（高盐度区域）占主导地位。沉积物 Hg 更倾向于与 MW 较高的 SOM 结合。MW 较高的 SOM 增加了两个河口的总沉积 Hg。河口沉积物中低 MW 的 SOM 与沉积物 Hg 浓度呈负相关。河口沉积物中 Hg 浓度的分布表明，在低 MW SOM 存在下还原 Hg 是一个主要过程。研究还发现，Hg 在河口沉积物中的分布和形态取决于 SOM 的数量、质量和总沉积物 Hg 负荷。本研究表明，Hg-SOM 络合与 SOM 还原之间的竞争控制了热带河口沉积物系统中的 Hg/Hg 分布。
