No abstract

The soil heavy metal pollution around the mine threatens crop growth and human health. Intensively studies of the distribution characteristics and source of soil heavy metals around some typical mines are very crucial for environmental management and green development of mine. A total of eighty-nine soil samples, twenty-one sediment samples, five waste rock samples and two tailing sand samples were sampled to investigate copper (Cu), lead (Pb), zinc (Zn), arsenic (As), cadmium (Cd), chromium (Cr) and mercury (Hg) in soil, sediment, waste rocks and tailings sand around Dexing Copper Mine, Jiangxi Province, China. The concentrations of the seven heavy metals were determined using inductively coupled plasma mass spectrometry ICP-MS/atomic fluorescence spectroscopy (AFS). The Igeo values of soil heavy metal showed that 100% of Cu were at an unpolluted-to-moderately-polluted level (Igeo > 0), more than 50% of Cu were heavily polluted (Igeo > 3), 65.16%, and 22.47%, 7.86% and 7.87% of the soil samples for Cd, Hg, As and Zn were overly moderately polluted (Igeo > 1). A total of 13.48% and 11.24% of the soil samples for Pb and Cr, respectively, were moderately polluted (1 < Igeo < 2). The concentrations of heavy metals in soil were Compared with Risk Screening Values for Contamination of Agricultural Land (RSVCAL), with the concentration of 97.75% soil samples for Cu, and 69.21% of soil samples for Cd were higher than RSVCAL. In Dawu river basin the concentration of 50% soil samples for Pb were higher than RSVCAL. According to Igeo and RSVCAL, the soils around Dexing Copper Mine were polluted by heavy metals to some extent, with especially the Cu pollution of soil being the most serious. These heavy metal concentrations exceeding RSVCAL have threatened the safety of agricultural products. The results of soil profile analysis, principal component analysis (PCA) and cluster analysis (CA) indicated that the mining activities of Dexing copper mine should be the main source of Cu in the soil. High As concentration in soil obviously caused by the copper mine as well. In addition, Dexing Copper Mine should partly account for soil pollution by Zn, Pb, Cd, Hg and Cr around the mine.

During mining, some of the essential metal(loid)s for plants or humans are discharged into the environment with non-essential metal(loid)s. Thus, comprehensive investigations of their distribution and the health risk of consuming food crops near mines are significant. A total of 26 soils and 25 food crops (soybean grains and wheat grains) were sampled to investigate arsenic (As), cadmium (Cd), chromium (Cr), copper (Cu), mercury (Hg), lead (Pb), zinc (Zn), selenium (Se), molybdenum (Mo), and manganese (Mn) in soils and crops in a typical non-ferrous metal mine area in Northeast China. The distribution patterns of soil heavy metal(loid)s and principal component analysis (PCA) results indicated that Cd, Cu, Zn, Mo, and Mn in soils were significantly affected by mining activities and were mainly or partly derived from the mines. Moreover, these soil heavy metal(loid)s (except Se) in the Tongshan copper mine area were attenuated with distance in the downstream direction. The BCF (bioconcentration factor) values of non-essential elements (Se, Hg, Cr, As, Cd, Pb) were relatively lower and positively related to soil nutrients. On the contrary, higher BCF values of essential elements (Cu, Zn, and Mo) and a weak relationship between the BCF of essential elements and soil nutrients were found. The mean Igeo values of soil heavy metal(loid)s indicated that As and Cu were at an unpolluted-to-moderately-polluted level (Igeo > 1), while other heavy metal(loid)s all presented an unpolluted level (Igeo < 1). Nevertheless, some soil samples were obviously polluted (Igeo > 1), such as KQ, D1, D3, D5, D6, and T1. The HQ (hazard quotient) and HI (hazard index) values of As and Mn both exceeded 1, indicating the higher potential health risks of consuming soybean grains and wheat grains for all people groups.

The in-situ stabilization remediation of Hg-contaminated soil in Qianyang, Dehua County, Fujian Province, was studied through the pre-experiments (stabilization orthogonal experiment and pot experiment) and field plot experiments for two consecutive years. The pre-experiments results showed that the main factors of the stabilization were the initial concentration of Hg in the soil and the amount of amendment added, followed by the amendment type, while the aging time had less effect. When the initial concentration of Hg in the soil was less than 10 mg·kg−1 and the amendment (modified biochar with modified attapulgite) added ratio was 0.2–0.4%, indicating optimized stabilization effect. After one-time application of 6750 and 11,250 kg·hm−2 amendment in low (1.38 mg·kg−1), medium (2.46 mg·kg−1), and high (8.52 mg·kg−1) Hg-contaminated soils, it could accelerate the transformation of Hg from exchangeable to residual and oxidizable Hg, enhance the activities of catalase, urease, and invertase in the soil. After one year of remediation, the case of adding 6750 kg·hm−2 amendment showed a significant stabilization effect. Compared to the control group, the available Hg content in the soil and Hg content in the water spinach reduced to 52.1–62.0% and 58.2–66.6%, respectively. When the application amount was increased to 11,250 kg·hm−2, the reduction rates were 43.2–46.0% and 58.2–62.0%, respectively. After two years of remediation, the stabilization effect was weakened, but the available Hg content in the soil and the water spinach was still significantly lower than that of the control, indicating that the persistence of the stabilization was good. For the soil contaminated slightly by Hg, the Hg content in the water spinach within two years was lower than the limit value of the Chinese standard (0.01 mg·kg−1). Although the Hg content in the water spinach for the soil contaminated highly by Hg was higher than the limit value, it could reduce to 67.3%, indicating an acceptable stabilization effect on heavily contaminated soil.