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

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 delta Cd-114/110 value and Pb-206/Pb-207 isotope ratio in background soils from the region were +0.41 parts per thousand and 1.1902, respectively, whereas the contaminated soil samples had different values, with the delta Cd-114/110 values varying between -0.59 parts per thousand and +0.33 parts per thousand and the Pb-206/Pb-207 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 5 km from the mine itself. (C) 2014 Elsevier Ltd. All rights reserved.