Bollen A, Wenke A, Biester H
Institute of Environmental Geochemistry, University of Heidelberg, Im Neuenheimer Feld 236, 69120 Heidelberg, Germany.
Water Res. 2008 Jan;42(1-2):91-100. doi: 10.1016/j.watres.2007.07.011. Epub 2007 Jul 18.
Since the 19th century, mercury(II)chloride (HgCl(2)) has been used on wood impregnation sites to prevent wooden poles from decay, leaving behind a legacy of highly contaminated soil/aquifer systems. Little is known about species transformation and mobility of HgCl(2) in contaminated soils and groundwater. At such a site the behaviour of HgCl(2) in soils and groundwater was investigated to assist in risk assessment and remediation. The soil is low in organic carbon and contains up to 11,000 mg Hg/kg. Mercury (Hg) concentrations in groundwater decrease from 230 to 0.5 microg/l within a distance of 1.3 km. Hg species transformations in soil and aqueous samples were analysed by means of solid-phase Hg pyrolysis and CV-AAS. In aqueous samples, Hg species were distinguished between ionic/reactive Hg and complex-bound Hg. Potential mobility of Hg in soils was studied through batch experiments. Most Hg in the soil is matrix-bound HgCl(2), whereas in the aquifer secondary formation to Hg(0) could be observed. Aqueous Hg speciation in groundwater and soil solutions shows that an average of 84% of soluble Hg exists as easily reducible, inorganic Hg species (mostly HgCl(2)). The proportion of complex-bound Hg increases with distance due to the transformation of inorganic HgCl(2). The frequent occurrence of Hg(0) in the aquifer suggests the formation and degassing of Hg(0), which is, in addition to dilution, an important process, lowering Hg concentrations in the groundwater. High percentage of mobile Hg (3-26%) and low seepage fluxes will result in continuous Hg release over centuries requiring long-term groundwater remediation. Results of soluble Hg speciation suggest that filtering materials should be adapted to ionic Hg species, e.g. specific resins or amalgamating metal alloys.
自19世纪以来，氯化汞（HgCl₂）一直被用于木材浸渍场地，以防止木杆腐烂，从而留下了大量土壤/含水层系统受到高度污染的遗留问题。关于HgCl₂在受污染土壤和地下水中的物种转化和迁移情况，人们了解甚少。在这样一个场地，对土壤和地下水中HgCl₂的行为进行了研究，以协助进行风险评估和修复。该土壤有机碳含量低，汞含量高达11000毫克/千克。在1.3千米的距离内，地下水中汞（Hg）的浓度从230微克/升降至0.5微克/升。通过固相汞热解和冷原子吸收光谱法（CV-AAS）分析了土壤和水样中的汞物种转化情况。在水样中，汞物种分为离子态/反应性汞和络合态汞。通过批量实验研究了汞在土壤中的潜在迁移性。土壤中的大部分汞是与基质结合的HgCl₂，而在含水层中可以观察到汞向Hg(0)的二次生成。地下水和土壤溶液中的汞形态分析表明，平均84%的可溶性汞以易于还原的无机汞物种（主要是HgCl₂）形式存在。由于无机HgCl₂的转化，络合态汞的比例随距离增加。含水层中频繁出现Hg(0)表明Hg(0)的形成和脱气，这除了稀释作用外，还是一个降低地下水中汞浓度的重要过程。高比例的可移动汞（3%-26%）和低渗流通量将导致汞在数百年内持续释放，需要长期进行地下水修复。可溶性汞形态分析结果表明，过滤材料应适用于离子态汞物种，例如特定的树脂或汞齐化金属合金。
