The precipitation, growth and stability of mercury sulfide nanoparticles formed in the presence of marine dissolved organic matter
The precipitation, growth and stability of mercury sulfide nanoparticles formed in the presence of marine dissolved organic matter
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海洋溶解有机物存在下形成的硫化汞纳米粒子的沉淀、生长和稳定性
DOI：
10.1039/c7em00593h
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发表时间：
2018
期刊：
影响因子：
--
通讯作者：
Mason, Robert P.
中科院分区：
文献类型：
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作者：
Mazrui, Nashaat M.;Seelen, Emily;King'ondu, Cecil K.;Thota, Sravan;Awino, Joseph;Rouge, Jessica;Zhao, Jing;Mason, Robert P.
已知汞的甲基化取决于环境中汞的化学形式和甲基化细菌的活性。在硫化物沉积物中，在相对于变辰砂过饱和的条件下，最近的研究表明汞以β-HgS（s）纳米颗粒（β-HgS（s）nano）的形式沉淀。海洋溶解有机物（DOM）存在下β-HgS（s）纳米粒子的沉淀研究较少。在这项工作中，我们使用动态光散射（DLS）结合紫外-可见光谱和透射电子显微镜（TEM）来研究β-HgS（s）纳米的形成和归宿，这些纳米是与从长岛海峡东部和西部提取的海洋DOM以及与低分子量硫醇一起形成的。我们发现，虽然在海洋DOM存在下形成的β-HgS（s）纳米颗粒在5周后尺寸翻了一番，但在沿海DOM溶液中形成的纳米颗粒并没有随着时间的推移而增长。此外，当HgII：DOM比率变化时，β-HgS（s）纳米仅在高比率（>41 μmol HgII/mg C）下快速聚集，其中硫醇基团的浓度被确定为相对于HgII基本上较低。 这表明除了硫醇之外的官能团可能参与β-HgS（s）纳米的稳定化。此外，我们发现，在缺氧条件下形成的β-HgS（s）纳米保持稳定，因此可以在环境中持续存在，足以影响甲基化潜力。然而，暴露于阳光和氧化环境中，β-HgS（s）纳米颗粒会发生快速聚集和沉降，这表明吸附在β-HgS（s）纳米颗粒表面的有机物的光诱导变化或氧化影响了其在表面沃茨中的稳定性。
The methylation of mercury is known to depend on the chemical forms of mercury (Hg) present in the environment and the methylating bacterial activity. In sulfidic sediments, under conditions of supersaturation with respect to metacinnabar, recent research has shown that mercury precipitates as β-HgS(s) nanoparticles (β-HgS(s)nano). Few studies have examined the precipitation of β-HgS(s)nano in the presence of marine dissolved organic matter (DOM). In this work, we used dynamic light scattering (DLS) coupled with UV-Vis spectroscopy and transmission electron microscopy (TEM) to investigate the formation and fate of β-HgS(s)nano formed in association with marine DOM extracted from the east and west of Long Island Sound, and at the shelf break of the North Atlantic Ocean, as well as with low molecular weight thiols. We found that while the β-HgS(s)nano formed in the presence of oceanic DOM doubled in size after 5 weeks, those forming in solutions with coastal DOM did not grow over time. In addition, when the HgII : DOM ratio was varied, β-HgS(s)nano only rapidly aggregated at high ratios (>41 μmol HgII per mg C) where the concentration of thiol groups was determined to be substantially low relative to HgII. This suggests that functional groups other than thiols could be involved in the stabilization of β-HgS(s)nano. Furthermore, we showed that β-HgS(s)nano forming under anoxic conditions remained stable and could therefore persist in the environment sufficiently to impact the methylation potential. Exposure of β-HgS(s)nano to sunlit and oxic environments, however, caused rapid aggregation and sedimentation of the nanoparticles, suggesting that photo-induced changes or oxidation of organic matter adsorbed on the surface of β-HgS(s)nano affected their stability in surface waters.