Hydrogeochemical evolution induced by long-term mining activities in a multi-aquifer system in the mining area

Area of Science:

• Hydrogeology
• Environmental Science
• Geochemistry

Background:

• Long-term mining activities significantly impact groundwater quality.
• The Fengfeng mine exhibits complex geological conditions and a 30-year mining history.
• Understanding hydrogeochemical evolution is crucial for groundwater management in mining regions.

Purpose of the Study:

• Investigate the hydrogeochemical evolution mechanism of groundwater in a multi-aquifer system.
• Assess the impact of mining activities on groundwater chemistry.
• Provide insights for groundwater resource management in mining areas.

Main Methods:

• Employed machine learning techniques, specifically self-organizing maps combined with K-means clustering.
• Utilized stable isotopes of sulfur and oxygen (δ³⁴S_SO4 and δ¹⁸O_SO4) to trace hydrogeochemical processes.
• Analyzed spatiotemporal variations in groundwater components across different aquifers.

Main Results:

• Mining activities altered groundwater hydrogeochemical characteristics in various aquifers.
• Pyrite oxidation, gypsum dissolution, and carbonate dissolution were identified as key controlling factors.
• Pyrite oxidation was prominent in the Carboniferous thin-layer limestone aquifer (CLA) and Permian sandstone aquifer (PSA).
• Leakage recharge from CLA and PSA influenced the Ordovician limestone aquifer (OLA), the primary aquifer.

Conclusions:

• Altered groundwater flow systems due to mining affect groundwater component evolution, especially sulfate levels.
• Hydrogeochemical evolution is distinctly influenced by mining activities in the studied area.
• Findings offer a scientific basis for managing groundwater resources in mined regions.