Atmospheric Mercury Isotope Shifts in Response to Mercury Emissions from Underground Coal Fires

Abstract

Pollutant emissions from coal fires have caused serious concerns in major coal-producing countries. Great efforts have been devoted to suppressing them in China, notably at the notorious Wuda Coalfield in Inner Mongolia. Recent surveys revealed that while fires in this coalfield have been nearly extinguished near the surface, they persist underground. However, the impacts of Hg volatilized from underground coal fires remain unclear. Here, we measured concentrations and isotope compositions of atmospheric Hg in both gaseous and particulate phases at an urban site near the Wuda Coalfield. The atmospheric Hg displayed strong seasonality in terms of both Hg concentrations (5−7-fold higher in fall than in winter) and isotope compositions. Combining characteristic isotope compositions of potential Hg sources and air mass trajectories, we conclude that underground coal fires were still emitting large amounts of Hg into the atmosphere that have been transported to the adjacent urban area in the prevailing downwind direction. The other local anthropogenic Hg emissions were only evident in the urban atmosphere when the arriving air masses did not pass directly through the coalfield. Our study demonstrates that atmospheric Hg isotope measurement is a useful tool for detecting concealed underground coal fires.

Detection and management of coal seam outcrop fire in China: a case study

“…The test results revealed that the radon content is positively correlated with the potential temperature 29 . Sun measured concentrations and isotope compositions of atmospheric Hg in both gaseous and particulate phases on an urban site near the Wuda coalfield 30 . The measurement results demonstrated that atmospheric Hg isotope measurement functions as a useful tool for detecting concealed underground coal fires.…”

Distribution and 13C Signature of Dicarboxylic Acids and Related Compounds in Fine Aerosols Near Underground Coal Fires in North China: Implications for Fossil Origin of Azelaic Acid

“…However, studies on characterization of atmospheric fine aerosols at underground coal fire areas are very limited, which focused only on bulk components (organic carbon (OC) and elemental carbon (EC)), PAHs, toxic metals (e.g., Hg, As) and trace elements (e.g., Li, F) (Cheng et al., 2015; Dai et al., 2012; Liang, 2018; S. Q. Liu et al., 2012; P. Liu et al., 2022; Shan et al., 2019; Sun et al., 2023; van Dijk et al., 2011; Wang et al., 2003; W. Y. Zhao et al., 2008). To the best of our knowledge, diacids and related compounds have not been studied at coalfield areas, where the emission of VOCs from underground spontaneous combustion could significantly influence their loadings and molecular distributions in aerosols, and thus significantly impact the Earth's climate system at local to regional scales.…”

“…However, studies on characterization of atmospheric fine aerosols at underground coal fire areas are very limited, which focused only on bulk components (organic carbon (OC) and elemental carbon (EC)), PAHs, toxic metals (e.g., Hg, As) and trace elements (e.g., Li, F) (Cheng et al, 2015;Dai et al, 2012;Liang, 2018;S. Q. Liu et al, 2012;Shan et al, 2019;Sun et al, 2023;van Dijk et al, 2011;Wang et al, 2003; W. Y. Zhao et al, 2008).…”