Tracing sources of pollution in soils from the Jinding Pb–Zn mining district in China using cadmium and lead isotopes

Abstract

Systematic variations in the Cd and Pb isotope ratios in polluted topsoils surrounding the Jinding Pb–Zn mine in China were measured so that the sources of the metals could be traced. The average δ114/110Cd value and 206Pb/207Pb isotope ratio in background soils from the region were +0.41‰ and 1.1902, respectively, whereas the contaminated soil samples had different values, with the δ114/110Cd values varying between −0.59‰ and +0.33‰ and the 206Pb/207Pb isotope ratios varying between 1.1764 and 1.1896. We also measured the Cd and Pb isotopic compositions in oxide ores, sulfide ores, and slags, and found that binary mixing between ores and background soils could explain almost all of the variations in the Cd and Pb isotope ratios in the contaminated soils. This suggests that Cd and Pb pollution in the soils was mainly caused by the deposition of dust emitted during anthropogenic activities (mining and refining). The Pb and Cd isotope ratios clearly showed that contamination in soils in the northeastern part of the area was caused by surface mines and zinc smelters and their slagheaps, while contamination in soils in the southwestern part of the area also came from tailing ponds and underground mines. The main area of soil polluted by dust from Pb–Zn mining processes roughly extended for up to 5km from the mine itself.