Abstract
Metal contamination in soil from tailings induces risks for the ecosystem and for humans. In this study, the concentrations and ecological risks of Cd, Cu, Pb, and Zn in soil contaminated by a tailing from Yangshuo (YS) lead and zinc (Pb–Zn) mine, which collapsed for more than 40 years, were determined in 2015. The mean concentrations of Zn, Pb, Cu, and Cd were 1301.79, 768.41, 82.60, and 4.82 mg/kg, respectively, which, with years of remediation activities, decreased by 66.9%, 61.7%, 65.4%, and 65.3% since 1986, but still exceed the national standards. From 1986 to 2015, soil pH increased significantly, with available concentrations of Zn, Pb, Cu and Cd decreasing by 13%, 81%, 77%, and 67%, respectively, and potential ecological risk indexes (Er) of the determined metals decreasing by more than 60%. Horizontally, total contents and percentages of available concentrations of Zn, Pb, Cu, and Cd decreased with the distance from the tailing heap in SD village, while pH values showed the reverse pattern. Vertically, Zn and Cd, Pb, and Cu showed similar vertical distribution patterns in the soil profiles. There was a slight downward migration for the determined metals in soil of M and H area and the mobility was in the order of Cd > Zn > Pb > Cu. It can be concluded that although concentrations and ecological risks of Cd, Cu, Pb, and Zn in soil decreased significantly, SD village is still a high risk area, and the priority pollutant is Cd.
Highlights
Metal pollution is covert, persistent, and irreversible [1]
A recent survey showed that 33.4% of soils from the survey mining regions were contaminated by cadmium, lead, arsenic, and polycyclic aromatic hydrocarbons in China [8]
Adding 25 mL of cooled-down boiled ultrapure water to 10 g soil passed through the 20-mesh sieve in a small beaker, stirring for 1 min with a glass rod, sitting for half an hour at room temperature, soil pH was measured by a pH meter with a glass electrode (INESA PHSJ-3F, INESA INSTRUMENT, Shanghai, China)
Summary
Persistent, and irreversible [1] This kind of pollution degrades the quality of the atmosphere, water bodies, soil, and food crops, and threatens the health of animals and human beings [2,3]. Mineral resources is one of the basic sources for production and living, and the exploitation of mineral resources plays an important role in national economic development. A recent survey showed that 33.4% of soils from the survey mining regions were contaminated by cadmium, lead, arsenic, and polycyclic aromatic hydrocarbons in China [8]
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