Estimate of sulfur, arsenic, mercury, fluorine emissions due to spontaneous combustion of coal gangue: An important part of Chinese emission inventories Shaobin Wang a, b , Kunli Luo a, * , Xing Wang c , Yuzhuang Sun d a Institute of Geographic Sciences and Natural Resources Research, Chinese Academy of Sciences, Beijing 100101, China b University of Chinese Academy of Sciences, Beijing 100049, China c Key Laboratory of Coal Resources Exploration and Comprehensive Utilization, Ministry of Land and Resources of P. R. China, Xi'an 710021, China d Key Laboratory of Hebei Province for Resource Exploration Research, Hebei University of Engineering, Handan 056038, China article info Article history: Received 29 July 2015 Received in revised form 19 November 2015 Accepted 19 November 2015 Available online 7 December 2015 Keywords: China Coal gangue spontaneous combustion As, Hg and F emissions Sulfur and harmful trace elements abstract A rough estimate of the annual amount of sulfur, arsenic, mercury and fluoride emission from sponta- neous combustion of coal gangue in China was determined. The weighted mean concentrations of S, As, Hg, and F in coal gangue are 1.01%, 7.98, 0.18, and 365.54 mg/kg, respectively. Amounts of S, As, Hg, and F emissions from coal gangue spontaneous combustion show approximately 1.13 Mt, and 246, 45, and 63,298 tons in 2013, respectively. The atmospheric release amount of sulfur from coal gangue is more than one tenth of this from coal combustion, and the amounts of As, Hg, and F are close to or even exceed those from coal combustion. China's coal gangue production growth from 1992 to 2013 show an obvious growth since 2002. It may indicate that Chinese coal gangue has become a potential source of air pollution, which should be included in emission inventories. © 2015 Elsevier Ltd. All rights reserved. 1. Introduction Coal gangue is one of the largest industrial residues in China that is discharged during the processing and utilization of coal (Gu, 1997; Liu and Liu, 2010). With continuous growth of coal mining and coal cleaning, a large amount of coal gangue are produced, which contain sulfide minerals, alumino-silicates minerals, other inorganic minerals, and organic matter (Querol et al., 2008; Zhao et al., 2008; Zhou et al., 2014). The current disposal of such a large quantity of coal gangue occupies a lot of land and has caused many serious environmental problems (e.g. Querol et al., 2008; Bian et al., 2009; Zhou et al., 2014). Among them, spontaneous combustion of coal gangue stockpiles is a serious environmental concern in China, and hazardous trace elements are released into the atmosphere (Zhao et al., 2008). Extensive studies focused on toxic trace elements released from coal combustion and its air pollution in China (e.g. Wang et al., 2000; Zhang and Zhao, 2007; Tian et al., 2010; You and Xu, 2010; Chen et al., 2013; Liu et al., 2013). Some studies involved the trace elements abundance properties, toxicity and partitioning characterization of coal gangue, and the control of its spontaneous combustion (e.g. Querol et al., 2008; Zhao et al., 2008; Fu et al., 2012; Zhou et al., 2012, 2014). However, few quantitative esti- mates have been conducted on total emissions of sulfur and toxic trace elements (e.g. As, Hg, and F) during spontaneous combustion of coal gangue in China. Consequently, their environmental impacts and proportion in total atmospheric release in China are still obscure. Since the takeoff of China's economy, environmental issues, including air pollution, have become a matter of concern by the public. The heavy air pollution has become frequent in recent years in China, and has had serious influence on the urban and rural at- mospheric environment, traffic safety, industrial, agricultural development, etc. (e.g. He et al., 2002; Tie et al., 2006; Ma et al., 2010; Leung et al., 2014). Chinese official data and other studies manifest that industrial sulfur dioxide emissions peaked in 2006, and then it exhibited a downward trend (MEPC, 1996e2011, 2012e2013; Zhang et al., 2012; Klimont et al., 2013). However, it is still unclear whether there exist some undetermined emission sources such as coal gangue. * Corresponding author. Institute of Geographical Sciences & Natural Resource Research, Chinese Academy of Sciences, A11 Datun Road, Anwai, Beijing 100101, China. E-mail address: luokl@igsnrr.ac.cn (K. Luo). Contents lists available at ScienceDirect Environmental Pollution journal homepage: www.elsevier.com/locate/envpol http://dx.doi.org/10.1016/j.envpol.2015.11.026 0269-7491/© 2015 Elsevier Ltd. All rights reserved. Environmental Pollution 209 (2016) 107e113