Heavy Metal Contamination in a Typical Mining Town of a Minority and Mountain Area, South China

This study was conducted in Dachang, a small mining town in Gaungxi Zhuang Autonomous Region in southern China. A total of 23 farmland soil samples and two atmospheric samples of particulate matter less than 10 microns (PM10) were collected in this town. ICP-MS was used to analyze for 20 elements in each of the samples. All of the samples contained some level of heavy metals. The most commonly detected heavy metals detected in the soil samples were: Cd (up to 29.0 mg kg−1), As (up to 776 mg kg−1), Sb (up to 36.8 mg kg−1), Pb (up to 582 mg kg−1), Zn (up to 1379 mg kg−1) and Cu (up to 156 mg kg−1), Mn (up to 1476 mg kg−1). The PM10 content in air samples exceeded the Chinese standard by nearly ten-fold. The most commonly detected heavy metals detected in the PM10 atmospheric samples were Cd (up to 210 mg kg−1), As (up to 15239 mg.kg−1), Sb (up to 445 mg kg−1), Pb (up to 8053 mg kg−1), Zn (up to 13151 mg kg−1) and Cu (up to 673 mg kg−1), Mn (up to 2826 mg kg−1), Mo (up to 120 mg kg−1). All of these heavy metals are associated with significant human health effects ranging from reduced intelligent quotients (IQs) in children (cf. Pb) to cancer (e.g., Cd and As). Muller Geo-accumulation Index (Igeo) and enrichment factor (EF) were used to assess the findings. The results to the two assessments showed the same ranking: Cd > As > Sb > Pb > Zn > Cu > Mn, which would imply that the particulate matter in ambient air was the source of the contamination in the soil. The correlation analysis supported this inference. Upon further examination, ore transportation through the town was identified as the most likely source of contamination. Therefore, steps should be taken to improve the management of the ore transportation in order to protect the farmland and the health of the residents.