Risk assessment and microbial community structure in agricultural soils contaminated by vanadium from stone coal mining.

High health risks of vanadium (V) released by the mining of vanadium titanomagnetite (VTM) have been widely recognized, but little is known about the risks and microbial community responses of V pollution as a consequence of the stone coal mining (SCM), another important resource for V mining. In this study, the topsoils and the profile soils were collected from the agricultural soils around a typical SCM in Hunan Province, China, with the investigation of ecological, health risks and microbial community structures. The results showed that ∼97.6% of sampling sites had levels of total V exceeding the Chinese National standard (i.e., 130 mg/kg), and up to 41.1% of V speciation in the topsoils was pentavalent vanadium (V(V)). Meanwhile, the proportions of HQ > 1 and 0.6-1 in the topsoils were ∼8.3% and ∼31.0% respectively, indicating that V might pose a non-carcinogenic risk to children. In addition, the microbial community varied between the topsoils and the profile soils. Both sulfur-oxidizing bacteria (e.g. Thiobacillus, MND1, Ignavibacterium) and sulfate-reducing bacteria (e.g. Desulfatiglans, GOUTB8, GOUTA6) might have been involved in V(V) reductive detoxification. This study helps better understand the pollution and associated risks of V in the soils of SCM and provides a potential strategy for bioremediation of the V-contaminated environment.

Heavy metal pollution in a black shale post-mining site of southern China: Pollution pattern, source apportionment and health risk assessment.

Source apportionment is critical but remains largely unknown for heavy metals in the soil surrounding black shale mining areas. Herein, the distribution, potential hazards, and sources of heavy metals in the soil around a black shale post-mining site were investigated. The content of Cadmium (Cd) in topsoil samples (0.77-50.29 mg/kg, N = 84) all exceeded the Chinese agricultural soil standard (0.3 mg/kg). The majority of Cd in the soil existed in the mobile fraction posing a high potential risk to the local ecosystem. and Zn and V in soils existed in the residual form. The percentages of HQing > 1 and 0.6-1 for Vanadium (V) in soil were 8.3% and 31.0%, respectively, and the percentages of HQing > 0.5 for Cd in soil were 3.7% showed that V and Cd were the main factors that increased the potential non-cancer risk. Five potential sources were identified using the geostatistical and positive matrix factorization (PMF) model, among which Cd was mainly derived from the short-term weathering process of black shale (81.06%), most Zinc (Zn) was from the long-term weathering of black shale (67.35%), whereas V was contributed by many factors including long-term weathering of black shale (42.99%), traffic emissions (31.12%) and agricultural activities (21.05%). This study reveals the potential risk and identifies the sources of heavy metals, which is helpful to manage the contaminated soil in black shale mining areas.