Leaching Behavior of Metallic Elements from Abandoned Mine Sites in Varying Environmental Factors

Abstract

Improper management of abandoned mine sites can cause heavy metal contamination of down-gradient agricultural soil, groundwater, and surface water. In this study, we investigated the effects of changes in environmental factors on the leaching behavior of the heavy metals and suggested future research direction for better risk management of the abandoned mine sites under climate change. Numerous studies showed that the concentration of heavy metals in the leachate frequently exceed the environmental criteria even though the leachable heavy metal was negligible (< 1 % of the total concentration), which indicates that mine soils can be long-term resources of contamination. From the result of batch and column experiments, it has been found that soil properties (e.g., soil pH, redox potential, etc.) affect the leaching behavior by solubility change, complex formation, precipitation, etc. Two-site kinetic leaching models were mainly applied for understanding nonequilibrium leaching behavior of the metals due to heterogeneous physical structure and various binding sites of the soil. Meanwhile, it was also reported that the change in hydrodynamic properties due to rainfall pattern can influence leaching behavior by changing the interfacial interaction between soil and water. Several researchers recognized that extreme weather condition (high temperature and increased drought period) due to climate change can elevate initial leaching concentration of the heavy metal. In reality, climate change can cause the nonequilibrium leaching of the metals by influencing hydrodynamic condition and chemical stability of the soil system. Therefore, future works to precisely predict the heavy metal leaching behavior across abandoned mine sites are necessary and risk management of these sites in response to climate change should be designed.