Natural Mercury Isotope Variation in Coal Deposits and Organic Soils

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• 作者：Abir Biswas ; Joel D. Blum ; Bridget A. Bergquist ; Gerald J. Keeler ; Zhouqing Xie
• 刊名：Environmental Science & Technology
• 出版年：2008
• 出版时间：November 15, 2008
• 年：2008
• 卷：42
• 期：22
• 页码：8303-8309
• 全文大小：213K
• 年卷期：v.42,no.22(November 15, 2008)
• ISSN：1520-5851

文摘

There is a need to distinguish among sources of Hg to the atmosphere in order to more fully understand global Hg pollution. In this study we investigate whether coal deposits within the United States, China, and Russia-Kazakhstan, which are three of the five greatest coal-producing regions, have diagnostic Hg isotopic fingerprints that can be used to discriminate among Hg sources. We also investigate the Hg isotopic composition of modern organic soil horizons developed in areas distant from point sources of Hg in North America. Mercury stored in coal deposits displays a wide range of both mass dependent fractionation (MDF, δ²⁰²Hg) and mass independent fractionation (MIF, Δ²⁰¹Hg). δ²⁰²Hg varies in coals by 3‰ and Δ²⁰¹Hg varies by 0.9‰. Combining these two Hg isotope signals results in what may be a unique isotopic “fingerprint” for many coal deposits. Mass independent fractionation of mercury has been demonstrated to occur during photochemical reactions of mercury. This suggests that Hg found in most coal deposits was subjected to photochemical reduction near the Earth’s surface prior to deposition. The similarity in MDF and MIF of modern organic soils and coals from North America suggests that Hg deposition from coal may have imprinted an isotopic signature on soils. This research offers a new tool for characterizing mercury inputs from natural and anthropogenic sources to the atmosphere and provides new insights into the geochemistry of mercury in coal and soils.