Characteristics of tailings from the closed metal mines as potential contamination source in South Korea

Abstract

There are about 1,500 closed metal mines in South Korea. Most of the tailings have been left without any management in these mines and have become the main source of heavy metal contamination of agricultural soils and crops in the mining areas. In this study, to predict the potential impact of tailings on nearby environments, the characteristics such as PH, particle size distribution, loss on ignition, cation exchange capacity, and the concentration and speciation of heavy metals in the tailings collected from ten closed metal mines in South Korea were investigated. Based on these characteristics, the relative metal-binding capacity, pollution index, and danger index were calculated so as to enumerate the priorities for remediation. The relative metal-binding capacities based on PH, clay, and organic content were very weak (<1) in the tailings from the Daduck, Duckum, and Imchun mines. The concentrations of Cd, Cu, Pb, and Zn exceeded the tolerable levels to the degree of being phytotoxically excessive in all the tailings, and the pollution indices ranged from 5.45 to 58.58. The results of the sequential extraction analysis showed that a large proportion of heavy metals existed in the form of a residual fraction in most tailings. The concentrations of the mobile phase of these heavy metals, however, were relatively high in the tailings from the Daduck, Dalsung, Imchun, and Duckum mines. Considering the results of the relative metal-binding capacity, pollution index, and danger index, the priority of remediation for these mines from most urgent to less urgent were Daduck, Imchun, Dalsung and Sujum, and then Goobong.