Distribution Pattern of Selected Macro- and Trace Elements in Paddy Soil Profiles Impacted by Coal Mine Drainage

<p indent="0mm"> Sulfur‒rich coal mines are widespread in southwestern China, and the oxidation of sulfides generates large amounts of sulfur– and iron–rich acid coal mine drainage, which is a potential source of water and soil pollution. However, the impact of coal mine drainage on the distribution characteristics of sulfur, iron, and harmful elements in regional paddy soils, and its potential environmental risks, remain poorly studied. This study collected three paddy soil profiles from central Guizhou Province, which are influenced by coal mine wastewater to varying degrees. The contents and speciation of sulfur, iron, and uranium were analyzed. The potential environmental risks of uranium were assessed using the Risk Assessment Code (RAC) and Geo-accumulation Index (<italic>I</italic>_geo). The results indicate that the sulfur, iron, and uranium contents in the studied soils are significantly higher than the regional soil background values. The sulfate concentration increased with the degree of contamination. Iron in the soil mainly occurs in the form of free ferric oxides. Uranium is primarily found in residual and oxidizable fractions, whereas the weak acid-soluble fraction accounted for &lt;1% of total uranium. The correlation analysis and speciation results showed that organic matter is an important factor affecting uranium accumulation. The <italic>I</italic>_geo of soil uranium shows that the highest affected soil profile belongs to the unpolluted-to-moderately polluted level (0&lt;<italic>I</italic>_geo​&lt;1); meanwhile, the RAC values, calculated based on speciation, were all less than 1%, indicating no risk at any of the three profiles. This study clarifies the distribution characteristics and potential risks of selected elements in the paddy field soils influenced by coal mine wastewater. The results provide valuable references for the risk prevention and control of coal mine drainage influenced soil in southwestern China.