Source identification of arsenic contamination in agricultural soils surrounding a closed Cu smelter, South Korea

Arsenic sources were identified in As-contaminated soils 4 km–7 km from a closed Cu smelter. Host rocks, heavy minerals in contaminated soils, ore minerals in quartz veins (geogenic sources) and bottom ash from the Cu smelter (an anthropogenic source) were investigated as potential sources. As a result, heavy minerals and bottom ash were found to contain higher As concentrations than the contaminated soils. Some of the host rock samples also showed higher As levels than the contaminated soils. Arsenopyrite was one of the frequently detected ore minerals in quartz veins. The As concentrations in soils did not decrease with soil depth or distance from the smelter. These results imply that the atmospheric emission from the smelter was not a major arsenic source. Based on the geochemical investigation and Pb isotopic analysis, the As contamination was affected by both regional ore mineralization and the host rock, and the influence of the smelter was limited. The spatial analysis of As concentrations and Pb isotopic ratios suggested that As contamination was mainly due to regional ore mineralization. The 206Pb/207Pb and 206Pb/204Pb ratios of the contaminated soils were plotted on the mixing line between background soils and ore minerals. The source apportionment results indicated a significant contribution of regional ore mineralization (average 52.9 ± 30.3%) to the As contamination. The contribution of this study is that we identified that the major source of soil contamination was of geologic origin despite an anthropogenic source nearby using geochemical and Pb isotopic investigation. •Arsenic sources with distinct Pb isotopic signatures were found.•Geogenic sources were more influential to As levels than an anthropogenic source.•Ore-bearing particles from unmined regional mineralization were a major As source.•Geochemical and Pb isotope maps helped to identify hotspots and assess As sources.