Distribution Characteristic and Migration Pathways of Metals in Subsidence Zone in a Coal Mine, China

Subsidence can influence the distribution characteristics and migration pathways of metals in coal mines. In order to understand the two important and related issues of subsidence and pollution in coal mines, ten sample cores were collected in the coal mining subsidence and non-subsidence zones in Anhui province, China, and the concentration and forms of metals were analyzed. The results showed that concentrations for all metals significantly increased at the depth of 0-20 cm in these two zones. Concentrations of Cd, Cu, and Zn in the non-subsidence zone were 1.14, 1.69 and 1.48 times higher, respectively, than those in the subsidence zone, while concentrations of Cr and Pb showed no significant difference. The proportion of exchangeable and acid-extracted fractions of Cd, Cu and Zn in the non-subsidence zone were higher than those in the subsidence zone. This may be due to the different migration pathways for exchangeable and acid-extracted fractions of metals in subsidence and non-subsidence zones.