Distribution and transformation of potentially toxic elements in crack under coal mining disturbance

Abstract

In China, coal provides about 56.8% of the energy. Most of China's coal mines are shaft mines, which cause the surface to collapse and crack during the mining process. The soil near the cracks changes its physicochemical properties due to the altered stress conditions. This will affect the distribution of PTEs in the soil. We collected 18 samples from a selected crack in the abandoned land. The pH, Eh, and PTE and their fractions of the samples were determined. With the test results, we understand the distribution characteristics of pH, Eh, PTEs, and their fractions at the cracks. Meanwhile, we explored the key factors that contribute to this distribution. It was determined that crack decreases surface soil pH while increasing Eh. The total amount of 7 PTEs is higher in the bottom soil of the main crack and 2 m away from the main crack. The content of reducible fractions of PTEs increases with the increase of soil Eh. The oxidizable and residual fractions of PTEs adsorbed to the clay particles migrate to and enrich the deeper layers of the main crack. This study emphasizes the effect of crack generation on the distribution of PTEs in soil. It provides insights to describe the distribution of PTE throughout the full life cycle of crack.

Keywords: Chemical speciation; Crack; Distribution characteristics; Mining area; PTEs; Physicochemical property.