Investigation of the Impact of Coal Fires on Soil: A Case Study of the Wugong Coal Fire Area, Xinjiang, China

This study focused on the Wugong coal fire area in the Zhunnan coalfield of Xinjiang, analyzing 41 soil samples extending from the fire center outward. The key parameters included pH, soil organic carbon (SOC), total nitrogen (TN), total phosphorus (TP), available potassium (AK), various ions (Ca2+, Na+, Mg2+, SO42−, CO32−, HCO3−, and Cl−), and heavy metal concentrations (As, Cr, Hg, Ni, Cd, Cu, Zn, and Pb). The primary objectives were to evaluate heavy metal pollution levels and potential ecological risks using the single factor pollution index (Pi), the Geo-accumulation index (IGeo), Nemero’s pollution index (Pn), the pollution load index (PLI), and the ecological risk factor (Eri) and risk index (RI). Spatial distribution analysis indicated higher heavy metal concentrations in the southwestern and central regions. The heavy metals Cr, Ni, Cd, Cu, and Zn reached mild pollution levels, while Hg exhibited high pollution, with Pi, IGeo, and Pn values of 3.27, 0.61, and 9.68, respectively. Hg (Eri = 111.07) and Cd (Eri = 45.91) emerged as the primary ecological risk factors. The overall ecological risk index (RI) of 184.98 indicated a moderate ecological risk. The results demonstrate that soils surrounding the coal fire zone are significantly impacted by coal fire, characterized by severe heavy metal contamination and nutrient deficiency.