Shenzhen Key Laboratory of Marine Microbiome Engineering, Institute for Advanced Study, Shenzhen University, Shenzhen, 518060, China; State Key Laboratory of Organic Geochemistry, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China.
State Key Laboratory of Pollution Control and Resources Reuse, School of the Environment, Nanjing University, Nanjing 210046, China.
Sci Total Environ. 2021 Apr 15;765:142763. doi: 10.1016/j.scitotenv.2020.142763. Epub 2020 Oct 6.
Mercury (Hg) contamination in mangrove ecosystems has received increasing attention in recent years. Although many studies have investigated methylmercury (MeHg) contamination and its relationship to a number of environmental factors in mangrove sediments, the production of MeHg in this carbon-rich ecosystem has not been fully evaluated. In this study, we measured the total mercury (THg) and MeHg concentrations in the sediments collected from seven mangrove forests in China. In addition, we examined the origin and quality of sedimentary organic matter (OM), trying to evaluate their influence on the MeHg accumulation in mangrove sediments. We found that litterfall played an important role in regulating THg and MeHg contents in mangrove sediments. THg and MeHg concentrations in the mangrove sediments were positively correlated to OM content and the labile fraction of the OM. Multiple evidence (stable carbon isotopes, monosaccharide compositions, and biogenic silica) suggested that OM in mangrove sediments was dominated by input from litterfall. THg and MeHg concentrations were elevated at the sediments with higher input of mangrove OM. We observed that addition of mangrove litter stimulated the production of MeHg under anaerobic conditions. Overall, our results suggested that litterfall acted as a source of inorganic Hg, labile carbon, and low-molecular-weight OM which greatly favor the Hg methylation. Our study provides new insights into the MeHg production in mangrove sediments.
近年来，红树林生态系统中的汞（Hg）污染受到了越来越多的关注。尽管许多研究已经调查了甲基汞（MeHg）污染及其与红树林沉积物中许多环境因素的关系，但在这个富含碳的生态系统中，MeHg 的产生尚未得到充分评估。在这项研究中，我们测量了中国七个红树林森林中沉积物的总汞（THg）和 MeHg 浓度。此外，我们还检查了沉积物中有机物质（OM）的来源和质量，试图评估它们对红树林沉积物中 MeHg 积累的影响。我们发现，凋落物在调节红树林沉积物中的 THg 和 MeHg 含量方面起着重要作用。红树林沉积物中的 THg 和 MeHg 浓度与 OM 含量和 OM 的易变部分呈正相关。多种证据（稳定的碳同位素、单糖组成和生物硅）表明，红树林沉积物中的 OM 主要来自凋落物的输入。在具有较高红树林 OM 输入的沉积物中，THg 和 MeHg 浓度升高。我们观察到，添加红树林凋落物会在厌氧条件下刺激 MeHg 的产生。总的来说，我们的结果表明，凋落物充当了无机 Hg、易变碳和低分子量 OM 的来源，这极大地有利于 Hg 的甲基化。我们的研究为红树林沉积物中 MeHg 的产生提供了新的见解。
