Institute of Surface-Earth System Science, School of Earth System Science, Tianjin University, Tianjin 300072, China.
College of Geoscience and Survey Engineering, China University of Mining and Technology (Beijing), Beijing 100083, China.
Environ Sci Technol. 2023 Jun 13;57(23):8638-8649. doi: 10.1021/acs.est.2c08637. Epub 2023 May 11.
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.
燃煤排放的污染物已在主要产煤国家引起了严重关注。中国在抑制这些污染物排放方面做出了巨大努力，特别是在内蒙古臭名昭著的乌达煤田。最近的调查显示，尽管该煤田地表的火灾已基本扑灭，但地下仍有火灾存在。然而，地下煤火释放的汞的影响尚不清楚。在这里，我们在乌达煤田附近的一个城市点测量了大气中气态和颗粒态汞的浓度和同位素组成。大气汞的浓度（秋季比冬季高 5-7 倍）和同位素组成均具有很强的季节性。结合潜在汞源的特征同位素组成和大气轨迹，我们得出结论，地下煤火仍在向大气中排放大量汞，这些汞已顺风输送到相邻的城区。当地其他人为汞排放仅在到达的气团没有直接穿过煤田时才会在城市大气中显现。我们的研究表明，大气汞同位素测量是检测隐蔽地下煤火的有用工具。
