The overexploitation of mineral resources in northwestern China has resulted in severe ecological degradation and even desertification in certain mining areas. To support ecological restoration in these arid mining regions, we conducted a study on water conservation and ecological water demand using Bayan Obo as a case study. Based on remote sensing, geographic information systems, and the Integrated Valuation of Ecosystem Services and Trade-offs InVEST model, our study found that the mining area has lost its capacity for water production, with the water source conservation showing negative values. In addition, precipitation levels are far lower than evapotranspiration, making it difficult to retain precipitation. We predicted ecological water demand for the planning years (2025, 2030, and 2035) by combining qualitative and quantitative forecasting methods, with 2019 serving as the base year. The results indicated a downward trend in natural ecological water demand, while artificial ecological water demand exhibited the opposite trend. Changes in natural grassland and artificial green areas in the mining region were identified as the main drivers of changes in ecological water demand.

In this study, aged biochar (CCB350 and CCB650) were obtained from pyrolysis of corn stalk biochar (CB350 and CB650) at the degree of 350 °C and 650 °C by artificial oxidation with hydrogen peroxide (H2O2). Also, the mechanism of Pb2+ and Cd2+ on fresh and aged biochars was analyzed qualitatively and quantitatively by batch adsorption experiments combined with characterization. The adsorption isotherm results showed that aging treatment decreased the adsorption capacity of Pb2+ and Cd2+ and inhibited the competitive adsorption behavior of heavy metals. In the single-metal system, precipitation and cation exchange were considered as the main adsorption mechanisms for CB350 and CB650, with a ratio of 40.07–48.23% and 38.04–57.19%, respectively. Competition between Pb2+ and Cd2+ increased the relative contribution of mineral precipitation, but decreased the contribution of cation exchange mechanism. Aging resulted in the rise of the contribution of surface complexation to the adsorption of Pb2+ and Cd2+ on biochars, especially in low-temperature biochars, but weakened the contribution of mineral precipitation to the adsorption. Further, the contribution of other adsorption mechanisms was significantly enhanced for high-temperature aged biochars. These results are important to evaluate its long-term application prospects in the natural environment.

No abstract