Canonical Correspondence Analysis for Soil Properties and Heavy Metal Pollution from Pb-Zn Mine Tailings in Different Land Use Types

The collapse of the lead-zinc mine tailing dam in Sidi village (Yangshuo, Guangxi Zhuang Autonomous Region, and SW China) led to the spread of mining waste spills on the farmland along the river. Past reports concentrated on environmental pollution caused by metal mining process, and were less focused on the special pattern of heavy metal pollution caused by the dam collapse. Canonical correspondence analysis (CCA)was employed to reveal the relationship between heavy metal contamination and soil properties in different land use types around the polluted area. 12 soil samples from rice paddy fields, 12 from corn fields and 9 from citrus orchards were collected from the surface layer (0-20 cm) to analyze SOC, AN, AP, AK, CEC, C/N, pH, total and DTPA-extractable Pb, Zn, Cu, Cd. The results show that Pb-Zn mine tailing sand is a multi-mineral orebody of which Pb, Zn and Cd are the main pollutants and Cd is the environmental risk key factor controlling the soil quality. The spatial distribution pattern of Pb and Zn affected by land use type is more obvious. Moreover, from the arrow distribution of heavy metals, it can be seen that the heavy metal pollution was relatively more serious in the rice paddy fields than in the corn fields and citrus orchards. From the distance between the heavy metals arrow and the soil properties point, the combined pollution of Pb, Zn, Cu and Cd decreased CEC content and increased SOC concentration, but had only small effects on soil pH value and available nutrients (AN, AP, AK). There existed positive significant correlations between heavy metals and SOC.The SOC content in rice paddy fields was 18.14 g/kg, and had the significant statistical differences with other land use types. In summary, Pb-Zn tailing sands as the sustained release source of heavy metals have the consecutive inputting mechanism into the soil, which inhibited microbial communities' metabolism, resulting in carbon accumulation, and then influenced the carbon cycle in the area.