Preliminary investigation of soil organic carbon distribution and turnover patterns, and potential pollution sources in and around a typical coking plant in North China

The variation characteristics of soil organic carbon (SOC) in and around the coking plant area are still unclear. In this work, the concentration and stable carbon isotope composition of SOC in coke plant soils were investigated to preliminarily identify the sources of SOC in and around the plant area, and to characterize soil carbon turnover. Meanwhile, the carbon isotopic technique was used to initially identify the soil pollution processes and sources in and around the coking plant area. The results demonstrate that the SOC content (12.76 mg g-1) of the surface soil in the coking plant is about 6 times higher than that outside the coking plant (2.05 mg g-1), and the variation range of 813C value of the surface soil in the plant (-24.63--18.55%o) is larger than that of the soil outside the plant (-24.92--20.22%o). The SOC concentration decreases gradually from the center of the plant outward with increasing distance, and the 813C in the middle and north of the plant tends to be positive compared with the 813C in the west and southeast of the plant. As the increase of soil depth, the SOC content and 813C value in the plant increases. On the contrary, 813C value and SOC content outside the plant decreases, with a minor variation. Based on the carbon isotope method, the SOC in and around the coking plant area is mainly from industrial activities (e.g., coal burning and coking), and partly from C3 plants. Notably, organic waste gases containing heavy hydrocarbons, light oils, and organic compounds accumulated in the northern and northeastern areas outside the plant due to south and southwest winds, which may pose an environmental health risk.