Etique Marjorie, Bouchet Sylvain, Byrne James M, ThomasArrigo Laurel K, Kaegi Ralf, Kretzschmar Ruben
Soil Chemistry Group, Institute of Biogeochemistry and Pollutant Dynamics, Department of Environmental Systems Science, ETH Zürich, Universitätstrasse 16, CHN, 8092 Zürich, Switzerland.
School of Earth Sciences, University of Bristol, Wills Memorial Building, Queens Road, BS8 1RJ Bristol, U.K.
Environ Sci Technol. 2021 Mar 2;55(5):3399-3407. doi: 10.1021/acs.est.0c05203. Epub 2021 Feb 8.
Mercury (Hg) is a toxic trace element of global environmental concern which has been increasingly dispersed into the environment since the industrial revolution. In aquatic and terrestrial systems, Hg can be reduced to elemental Hg (Hg) and escape to the atmosphere or converted to methylmercury (MeHg), a potent neurotoxin that accumulates in food webs. Fe-bearing minerals such as magnetite, green rusts, siderite, and mackinawite are recognized Hg reducers. Another potentially Hg-reducing mineral, which commonly occurs in Fe- and organic/P-rich sediments and soils, is the ferrous iron phosphate mineral vivianite (Fe(PO)·8HO), but its reaction with Hg has not been studied to date. Here, nanoparticulate vivianite (particle size ∼ 50 nm; Fe content > 98%) was chemically synthesized and characterized by a combination of chemical, spectroscopic, and microscopic analyses. Its ability to reduce Hg was investigated at circumneutral pH under anoxic conditions over a range of Fe/Hg ratios (0.1-1000). For Fe/Hg ratios ≥1, which are representative of natural environments, Hg was very quickly and efficiently reduced to Hg. The ability of vivianite to reduce Hg was found to be similar to those of carbonate green rust and siderite, two of the most effective Hg-reducing minerals. Our results suggest that vivianite may be involved in abiotic Hg reduction in Fe and organic/P-rich soils and sediments, potentially contributing to Hg evasion while also limiting MeHg formation in these ecosystems.
汞（Hg）是一种全球环境关注的有毒微量元素，自工业革命以来，它在环境中的扩散日益增加。在水生和陆地系统中，汞可以还原为元素汞（Hg）并逃逸到大气中，或者转化为甲基汞（MeHg），一种在食物网中积累的强效神经毒素。含铁矿矿物，如磁铁矿、绿锈、菱铁矿和马基诺矿，被认为是汞的还原剂。另一种潜在的汞还原矿物，通常存在于富含铁和有机/磷的沉积物和土壤中，是磷酸亚铁矿物蓝铁矿（Fe₃(PO₄)₂·8H₂O），但其与汞的反应至今尚未得到研究。在这里，通过化学、光谱和显微镜分析相结合的方法，化学合成并表征了纳米级蓝铁矿（粒径约50纳米；铁含量>98%）。在缺氧条件下，在一系列铁/汞比（0.1 - 1000）的中性pH值下，研究了其还原汞的能力。对于代表自然环境的铁/汞比≥1的情况，汞被非常迅速且有效地还原为Hg。发现蓝铁矿还原汞的能力与碳酸盐绿锈和菱铁矿这两种最有效的汞还原矿物相似。我们的结果表明，蓝铁矿可能参与了富含铁和有机/磷的土壤和沉积物中的非生物汞还原过程，这可能导致汞的逸出，同时也限制了这些生态系统中甲基汞的形成。
