Natural Mercury Isotope Variation in Coal Deposits and Organic Soils

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 dia...

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Bibliographic Details
Published in:Environmental science & technology 2008-11, Vol.42 (22), p.8303-8309
Main Authors: Biswas, Abir, Blum, Joel D, Bergquist, Bridget A, Keeler, Gerald J, Xie, Zhouqing
Format: Article
Language:English
Subjects:
01 COAL, LIGNITE, AND PEAT
AIR POLLUTION
Applied sciences
Chemical reactions
CHINA
COAL
COAL DEPOSITS
COAL PRODUCING DISTRICTS
DEPOSITION
Environmental monitoring
Environmental Processes
ENVIRONMENTAL SCIENCES
Exact sciences and technology
Fossil fuels
GEOCHEMISTRY
Humans
Incineration
ISOTOPE RATIO
Isotopes
KAZAKHSTAN
MERCURY
MERCURY 201
MERCURY 202
Mercury Isotopes - analysis
NORTH AMERICA
Pollution
Power Plants
RUSSIAN FEDERATION
Soil
Soil Pollutants - analysis
SOILS
Studies
USA
VARIATIONS
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Summary: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.
ISSN:0013-936X
1520-5851
DOI:10.1021/es801444b