Geochemical Evolution and Risk Assessment of Soil and Groundwater Influenced by a Decade-Old Coal Gangue Dump in North China

This study conducts an environmental risk assessment of coal gangue dump that have been stored for decades in North China, focusing on their long-term impacts on soil and groundwater. Coal gangue, a byproduct of coal mining, contains toxic heavy metals, including As, Cd, Pb, and Hg, which leach into surrounding soil and water, posing serious ecological and human health risks. Soil samples from areas in direct contact with the gangue reveal significant contamination, particularly with Pb and Cd, which exceed natural background levels. Groundwater samples from wells near the gangue piles show elevated fluoride and sulfate concentrations, indicating leachate contamination. The study employs pollution assessment indices such as the Pollution Index (PI) and Risk Index (RI) to quantify the extent of contamination, with results showing high pollution and risk in areas directly affected by the coal gangue. The seasonal variation of water quality is also examined, revealing fluctuating pollution levels, especially in ammonia nitrogen, nitrate concentrations. These findings highlight the need for targeted remediation strategies to prevent further contamination and safeguard human health and local ecosystems.