Changming Li

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.

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.

Jinchang mining area, as a metal mine with a long history of arid and semi-arid mining in western China, has brought a great risk of heavy metal pollution to the local environment. In this experiment, tailings, slag and native soil are mixed in equal proportions for the pot experiment settings. 9 species of sand plants unique to the arid region of the western inland were planted to screen the varieties with green remediation value. After six months of plant growth, the concentration of Zn in the plant was the highest, ranging from 103.27 to 467.63mg/kg, followed by Cu, ranging from 25.07 to 200.35mg/kg. In the early stage (2 months), POD was the main defense, and in the later stage (4\6 months), SOD and CAT were the main defense, accompanied by unknown proteins up-regulated. The results of net photosynthetic rate showed that it was inhibited by metal stress in the early stage, and it was high in the late stage to provide material basis for the accumulation and secretion of adaptable and resistant substances. Seven species of plants, such as Suaeda glauca, Bassia scoparia, Halogeton glomeratus, Kalidium foliatum, Medicago falcata, Atriplex canescens, Artemisia desertorum can be used as enrichment materials for Zn and Cu. While, Atriplex canescens has the highest metal enrichment potential, and can be used as a planting variety to enrich Cd, Ni and Pb in a broad spectrum of metals including Zn and Cu. This study lays a solid scientific foundation for green remediation of contaminated soil in arid desert area of western China.