Pollution Assessment and Source Identification of Heavy Metals in Farmland Soils around a Coal Mine Area in Yunnan Province
- ZHAO Jia-yin, YANG Di, YANG Xiang-zhi, ZHANG Ning, LIU Yu, WANG Meng-meng, WU Yun-cheng, CHEN Qiu-hui, TIAN Wei
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The research area was located in one of the 100 priority coal mine counties in China. The area is an epitome of China's coal development, and thus is typical and representative. Samples from the soil, dust-fall, agrochemical and coal residue were collected, so as to analyse the soil contamination and the inventory and contribution of main pollutants around the coal mining site. The pollution factor, spatial distribution, and environmental medium of the heavy metals were comprehensively analysed, and statistical methods including homology analysis, profile analysis, principal component analysis, and positive matrix factorization, were combined to investigate the soil contamination and the inventory and contribution of main pollutants. Results show that:(1) 91.00% of samples were contaminated by heavy metals. The rate of soil Cd, Cu, Cr, Ni, Zn, Pb, and As exceeded risk screening values for soil contamination of agricultural land were 86.0%, 15.00%, 14.00%, 19.00%, 12.00%, 6.00%, and 19.00%, respectively. The rate of soil Cd, Zn, Pb and As exceeded risk intervention values for soil contamination of agricultural land were 23.00%, 2.00%, 2.00%, and 3.00%, respectively. (2) Based on the results of pollution source analysis, the heavy metal contamination in the area mainly came from three sources, i. e., soil background, coal mining production, and fertilizer application, which account for 64.20%, 23.10%, and 12.60% of the contamination, respectively. Specifically, the soil background has the highest contribution to Cu, Cr, and Ni, and the corresponding contribution rate was 83.00%, 90.80% and 89.40%, respectively. Coal mining production and fertilizer application have the highest contribution to Cd and As separately, and the corresponding contribution rate were 93.70% and 93.90%. The results could be a reference for heavy metal evaluation and pollution resources quantitative analysis of similar areas. Meanwhile, the study may provide data support for investigating the heavy metal pollution status around coal mine, cutting off the pollution sources, and taking effective measures for farmland safe utilization.