Luo Hong-Wei, Yin Xiangping, Jubb Aaron M, Chen Hongmei, Lu Xia, Zhang Weihua, Lin Hui, Yu Han-Qing, Liang Liyuan, Sheng Guo-Ping, Gu Baohua
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA; Department of Chemistry, University of Science and Technology of China, Hefei, 230026, China.
Environmental Sciences Division, Oak Ridge National Laboratory, Oak Ridge, TN 37831, USA.
Environ Pollut. 2017 Jan;220(Pt B):1359-1365. doi: 10.1016/j.envpol.2016.10.099. Epub 2016 Nov 9.
Atmospheric deposition of mercury (Hg) to surface water is one of the dominant sources of Hg in aquatic environments and ultimately drives methylmercury (MeHg) toxin accumulation in fish. It is known that freshly deposited Hg is more readily methylated by microorganisms than aged or preexisting Hg; however the underlying mechanism of this process is unclear. We report that Hg bioavailability is decreased by photochemical reactions between Hg and dissolved organic matter (DOM) in water. Photo-irradiation of Hg-DOM complexes results in loss of Sn(II)-reducible (i.e. reactive) Hg and up to an 80% decrease in MeHg production by the methylating bacterium Geobacter sulfurreducens PCA. Loss of reactive Hg proceeded at a faster rate with a decrease in the Hg to DOM ratio and is attributed to the possible formation of mercury sulfide (HgS). These results suggest a new pathway of abiotic photochemical formation of HgS in surface water and provide a mechanism whereby freshly deposited Hg is readily methylated but, over time, progressively becomes less available for microbial uptake and methylation.
大气汞（Hg）沉降至地表水是水生环境中汞的主要来源之一，并最终导致鱼类体内甲基汞（MeHg）毒素的积累。众所周知，新沉降的汞比老化的或先前存在的汞更容易被微生物甲基化；然而，这一过程的潜在机制尚不清楚。我们报告称，汞与水中溶解有机物（DOM）之间的光化学反应会降低汞的生物有效性。汞-DOM络合物的光照射导致可被Sn（II）还原的（即活性）汞损失，并且使甲基化细菌硫还原地杆菌PCA产生的甲基汞减少了80%。随着汞与DOM比例的降低，活性汞的损失速率加快，这归因于可能形成了硫化汞（HgS）。这些结果表明了地表水非生物光化学形成硫化汞的新途径，并提供了一种机制，据此新沉降的汞易于甲基化，但随着时间的推移，逐渐变得不易被微生物摄取和甲基化。
