Mercury Stable Isotopic Compositions in Coals from Major Coal Producing Fields in China and Their Geochemical and Environmental Implications

Abstract

Total mercury (Hg) concentrations (THg) and stable mercury isotopic compositions were measured in coal samples (n = 61) from major coal producing fields in China. The THg concentrations in coals ranged from 0.05 to 0.78 μg g(-1), with a geometric mean of 0.22 μg g(-1). Hg isotopic compositions in coals showed large variations both in mass-dependent fractionation (MDF, δ(202)Hg: -2.36 to -0.14‰) and mass-independent fractionation (MIF, Δ(199)Hg: -0.44 to +0.38‰). The MIF signatures in coals may reveal important information on the coal-forming conditions (e.g., humic and sapropelic). The Δ(199)Hg/Δ(201)Hg of ∼1 determined in coals indicated that a portion of Hg has been subjected to photoreduction process prior to being incorporated to coals. On the basis of THg, Hg isotopic signatures, and other geological factors (e.g., total ash content and total sulfur content), the potential sources of Hg in coals from different coal producing regions were estimated. The main source of Hg in coals from southwestern China and eastern part of northern China is likely geogenic Hg, whereas the source of Hg in coals from other parts of northern China is mainly biogenic Hg. Finally, we estimated that Hg emission from coal combustion in China is characterized by diagnostic Hg isotopic signatures (δ(202)Hg: ∼-0.70‰ and Δ(199)Hg: ∼-0.05‰). The present study demonstrates that Hg isotopes can serve as a tool in understanding the sources and transformation of Hg in coals and may also be used as a tracer to quantify Hg emissions from coal combustion.

Sedimentary records of mercury stable isotopes in Lake Michigan

“…Following the convention recommended by Blum and Bergquist (2007) , n = 9) agreed well with previous studies . Measurements of UM-Almadén with different Hg concentrations showed no statistical differences in isotopic composition (Table S3) Hg 0.02±0.05‰; 2σ, n = 3) also agreed well with previous studies (Biswas et al, 2008;Donovan et al, 2013;Yin et al, 2014b).…”

“…202 Hg and D 199 Hg values have been reported in environmentally relevant matrices such as rocks (Smith et al, 2008), mineral deposits (Hintelmann and Lu, 2003;Smith et al, 2005Smith et al, , 2008Stetson et al, 2009;Sonke et al, 2010), coals (Biswas et al, 2008;Lefticariu et al, 2011;Sun et al, 2014;Yin et al, 2014b), soils (Biswas et al, 2008;Zhang et al, 2013;Feng et al, 2013), sediments (Gehrke et al, 2011;Foucher and Hintelmann, 2009;Feng et al, 2010;Liu et al, 2011;Bartov et al, 2013;Donovan et al, 2013;Ma et al, 2013;Yin et al, 2013aYin et al, , 2015, water (Štrok et al, 2014), air (Demers et al, 2013;Rolison et al, 2013), precipitation (Gratz et al, 2010;Chen et al, 2012;Demers et al, 2013;Sherman et al, 2011Sherman et al, , 2015 and biological samples Blum et al, 2013;Demers et al, 2013;Yin et al, 2013b). With well-defined source signatures, researchers may estimate the relative contribution of sources of Hg through the utilization of binary and/or triple mixing models (Foucher and Hintelmann, 2009;Feng et al, 2010;Liu et al, 2011;Bartov et al, 2013;Donovan et al, 2013;Ma et al, 2013;…”

Historical (1850–2010) mercury stable isotope inventory from anthropogenic sources to the atmosphere

“…During the thermal processing of source materials, Hg in source materials is transformed into GEM, GOM and PBM in generated flue gases by a series of physicochemical reactions (oxidation, reduction, adsorption, diffusion etc.). These phase and redox transformations of Hg in high-temperature facilities are expected to induce significant Hg isotope MDF, but no photochemical MIF (Sherman et al, 2012;Sonke et al, 2010;Sun et al, 2013; (Biswas et al, 2008;Lefticariu et al, 2011;Sherman et al, 2012;Sun et al, 2013Sun et al, , 2014aSun et al, , 2014bYin et al, 2014a). In contrast, only a limited number of oil sand samples from Athabasca, Canada have been reported .…”

“…The data points either greater than the upper quartile + 1.5 IQR or less than the lower quartile-1.5 IQR are considered to be extreme values. Data sources: coal (Biswas et al, 2008;Lefticariu et al, 2011;Sherman et al, 2012;Sun et al, 2013Sun et al, , 2014aSun et al, , 2014bYin et al, 2014a); oil ; cinnabar (Cooke et al, 2013;Foucher et al, 2009;Gehrke et al, 2011;Smith et al, 2005Smith et al, , 2008Stetson et al, 2009;Yin et al, 2013); Commercial liquid Hg 0 Estrade et al, 2009;Foucher et al, 2009;Laffont et al, 2011;Mead et al, 2013;Sonke et al, 2008); Zn ores (Smith, 2010;Sonke et al, 2010); Au ores (Smith, 2010); silicate rocks (Blum and Anbar, 2010;North, 2011;Sun et al, 2014b;Zhang et al, 2013Zhang et al, , 2014; limestone (sampled from Huainan Basin, China, this study); volcanic gases (this study; Zambardi et al, 2009 144 sector/fuel/technology combinations for combustion sources are designated to coal combustion, and all these combinations have their corresponding Hg species emission characteristics. Here, we improve the previous estimates on isotope composition of speciated Hg from coal combustion as follows: 1) APCDs are divided into five types: cyclone, scrubber, fiber filter (FF), electrostatic precipitator (ESP), flue gas desulfurization (FGD).…”

“…Hg stable isotope signatures have the potential to differentiate natural and anthropogenic Hg sources, and identify and quantify Hg transformations (Blum et al, 2014;Sonke, 2011;Sonke and Blum, 2013;Yin et al, 2014b Hg) of odd Hg isotopes have been documented in natural samples such as crustal rocks , cinnabar Gray et al, 2013;Smith et al, 2008;Stetson et al, 2009;, coal (Biswas et al, 2008;Sun et al, 2016;Yin et al, 2014a), and non-ferrous metals (Smith, 2010;Sonke et al, 2010;Yin et al, 2016). Different physical, chemical and biological Hg transformation processes induce characteristic MDF and MIF signs and magnitudes Chandan et al, 2015;Ghosh et al, 2013;Jiskra et al, 2012;Kritee et al, 2013;Perrot et al, 2015;Rodríguez-González et al, 2009;Rose et al, 2015;Smith et al, 2015;Wiederhold et al, 2010;Hintelmann, 2010a, 2010b).…”