Investigation of the potential risk of coal fire to local environment: A case study of Daquanhu coal fire, Xinjiang region, China.

Underground coal fires are disasters associated with coal mining activities. This study, attempts to investigate the impact of coal fires on the soil and atmosphere by measuring heavy metal concentration and borehole gas emissions for the Daquanhu coal fire zone. Different methods and equipment were used in this study, such as remote sensing, determination of the surface temperature and vegetation, field meteorological surveys, air/smoke analysis, flame photometry, atomic absorption spectrophotometry, atomic fluorescence spectrophotometry, and alkali diffusion. The results show that the surface temperature of the Daquanhu coal fire zone was reduced with a progress in coal fire extinction since 2015. Surface vegetation grew better in 2016 than in other years. The mercury (Hg) content in the western part of the fire zone is much higher than that in other parts of the fire zone. The arsenic (As) content in the eastern part is much higher than that of other parts. Data show that the estimated total amount of gas emissions during fire extinction is ~31,500 kg for CO, 489 kg for SO2, 12,885 kg for NO, 576 kg for NO2, and 20,295 kg for NOx. The intensity of the gas emissions during extinction is notably higher than that before extinction. The results also indicate coal fire's potential risk to adjacent communities, especially the risks associated with borehole injection of large amounts of possible harmful slurry, which needs to be taken seriously.