High‐throughput 16S rRNA and 18S rRNA sequencing were performed to study the changes of soil microbial diversity and community structure under different heavy metal pollution levels in Chengxian lead–zinc mining area, Gansu Province. In this study, we characterized the main physicochemical properties, multiple heavy metal pollution, and microbial community structure of the soil in the tailings. The results show that the soil near the tailings pond was alkaline, barren and the heavy metals were seriously polluted. The microbial diversity and richness of S1 and S2 sites were significantly lower than that of CK2 site (P < 0·05), indicating that the heavy metal pollution could change the physicochemical properties and microbial community structure in soil. Among 97 identified core operating taxa of fungal communities, Ascomycota, Teguta and Basidiomycota were dominant at the phylum level, while among 1523 identified core operating taxa of bacterial communities, Actinomycota was dominant at the phylum level. In addition, the redundancy analysis and Spearman correlation analysis showed that the physicochemical properties and the heavy metal concentration had significant effects on the composition and distribution of soil microbial community. The basic characteristics of soil physicochemical properties, multiple heavy metal pollution and microbial community structure in the tailings were revealed, hoping to provide a basis for ecological rehabilitation of tailings by revealing the variance rule of microbial community diversity in the future.

Heavy metal (HM) pollution is a severe and common environmental problem in mining area soil. It is imperative to understand the micro ecological characteristics of mining area soil for HM contaminated soil remediation. This study described the effects of HM pollution level and soil physical and chemical parameters on microbial diversity. In this study, high-throughput sequencing technology was used to study the effects of HM pollution on the diversity and composition of the soil microbial community. The soil groups were barren, exhibiting alkaline pH, low total nitrogen (TN), and total potassium (TK) according to soil fertility standard. Compared with the control group, there was severe multiple HM pollution in the other five groups, including lead (Pb), cadmium (Cd), zinc (Zn), and copper (Cu). The dominant phyla accounting for more than 1% of the overall community in all soil groups were Proteobacteria (34.432 ± 7.478%), Actinobacteria (22.947 ± 4.297%), Acidobacteria (10.47 ± 2.439%), Chloroflexi (7.89 ± 2.980%), Planctomycetota (5.993 ± 1.558%), Bacteroidota (4.275 ± 1.980%), Cyanobacteria (3.478 ± 2.196%), Myxococcus (2.888 ± 0.822%), Gemmatimonadota (2.448 ± 0.447%), Firmicutes (1.193 ± 0.634%), Patescibacteria (0.435 ± 0.813%), and Nitrospirota (0.612 ± 0.468%). Proteobacteria and Actinobacteria were predominant at the phylum level, which showed a certain tolerance to HMs. In addition, redundancy analysis (RDA) results showed that Pb, Cu, Zn, and Cd were strongly correlated with each other (P < 0.01). Other nutrient elements (except for TK) were significantly positively correlated with each other. Cu and nutrient element TK had an important impact on bacterial community structure. Therefore, bacteria with the function of HM tolerance and bioremediation in extreme environments should be researched, which provides a foundation for future ecological remediation of contaminated soil by using microbial remediation technology.

The physiological mechanisms and phytoremediation effects of three kinds of native quinoa in a desert mining area were studied. We used two different types of local soils (native soil and tailing soil) to analyze the changes in the heavy metal content, leaf physiology, photosynthetic parameters, stem hydraulics, and anatomical characteristics of potted quinoa. The results show that the chlorophyll content, photosynthetic rate, stomatal conductance, and transpiration rate of Kochia scoparia were decreased, but intercellular CO2 concentration (Ci) was increased under heavy metal stress, and the net photosynthetic rate (Pn) was decreased due to non-stomatal limitation. The gas exchange of Chenopodium glaucum and Atriplex centralasiatica showed a decrease in Pn, stomatal conductance (Gs), and transpiration rate (E) due to stomatal limitation. The three species showed a similar change in heavy metal content; they all showed elevated hydraulic parameters, decreased vessel density, and significantly thickened vessel walls under heavy metal stress. Physiological indicators such as proline content and activity of superoxide dismutase (SOD) and peroxidase (POD) increased, but the content of malondialdehyde (MDA) and glutathione (GSH), as well as catalase (CAT) activity, decreased in these three plants. Therefore, it can be concluded that these three species of quinoa, possibly the most dominant 30 desert plants in the region, showed a good adaptability and accumulation capacity under the pressure of heavy metal stress, and these plants can be good candidates for tailings remediation in the Jinchang desert mining area.

Mining activities have led to serious environmental (soil erosion, degradation of vegetation, and groundwater contamination) and human health (musculoskeletal problems, diarrheal conditions, and chronic diseases) issues at desert mining areas in northwest China. Native plant species grown naturally in desert regions show a unique tolerance to arid and semiarid conditions and are potential candidates for soil phytoremediation. Here, an ex situ experiment involving pot planting of seedlings of three native plant species (Suaeda glauca, Artemisia desertorum, and Atriplex canescens) was designed to explore their phytoremediation potential and the underlying physiological mechanism. For Zn and Cu, the three plants were all with a biological accumulation coefficient (BAC) greater than 1. For Cd, Ni, and Pb, Atriplex canescens had the highest bioaccumulation concentrations (521.52, 862.23, and 1734.59 mg/kg), with BAC values (1.06, 1.30, 1.25) greater than 1, which indicates that Atriplex canescens could be a broad-spectrum metal extraction plant. Physiological analysis (antioxidation, extracellular secretions, photosynthesis, and hydraulics) showed that the three desert plants exploited their unique strategy to protect against the stress of complex metals in soils. Moreover, the second growing period was the main heavy metal accumulation and extraction stage concomitant with highest water use efficiency (iWUE). Taken together, the three desert plants exhibited the potent heavy metal extraction ability and physiological and ecological adaptability to a harsh polluted environment in arid desert areas, providing potential resources for the bioremediation of metal-contaminated soils in an arid and semiarid desert environment.

YZB_1 85.79%±16.44% ab 7.75%±6.55% c 4.17%±3.11% b 0.00%±0.00% b 3.75%±2.21% b 1.83%±1.22% a 0.00%±0.00% b 0.05%±0.02% b YZB_2 51.79%±5.42% bc 6.23%±5.74% c 2.99%±0.08% b 28.42%± 14.32% a 9.42%±1.92% a 0.00%±0.00% a 1.52%±1.15% a 0.14%±0.08% b YZB_3 75.11%±11.49% abc 19.71%±12.24% c 2.12%±1.24% b 0.00%±0.00% b 0.17%±0.10% b 2.71%±1.98% a 0.00%±0.00% b 1.15%±0.95% a YZB_4 92.26%±13.18% a 7.73%±13.18% c 0.00%±0.00% b 0.00%±0.00% b 0.00%±0.00% b 0.00%±0.00% a 0.00%±0.00% b 0.00%±0.00% b YZB_NT 64.46%±4.64% bc 26.17%±3.94% bc 1.79%±1.22% b 0.00%±0.00% b 6.42%±2.06% a 0.41%±0.26% a 0.15%±0.13% b 0.58%±0.04% a