Xunyang is rich in various metal minerals and is one of the four major metal mining areas in Shaanxi province, China. To explore the effects of soil heavy metals and metalloid pollution on the environment and human health around the mining areas, four places—Donghecun (D), Gongguan (G), Qingtonggou (Q) and Nanshagou (N)—were selected as the sampling sites. Potential ecological risk (PER) and health risk assessment (HRA) models were used to analyze the environmental and health risks around the mining areas. The concentration of heavy metals (Cd, Cr, Pb, Zn, Ni, Cu, Hg) and metalloid (As) in cultivated land in the vicinity of Xunyang mining areas indicated that, except for Cu, the remaining elements detected exceeded the threshold values at some sites. The geo-accumulation index (I_Geo) revealed that soils in G and Q could be identified as being extremely contaminated. PER indicated that there was significantly high risk at G and Q for Hg. In N, Pb recorded the highest $E_r^i$ , which also demonstrates a considerable pre-existing risk. HRA indicated that the hazard index (HI) for both carcinogenic and non-carcinogenic risks was much higher among children than among adults, and the ingestion pathway contributed the greatest risk to human health, followed by the dermal pathway and inhalation. Because the HI values of the metals and metalloid in the study areas were all lower than 1, there was no significant non-carcinogenic risk. However, the carcinogenic risk for Cr is relatively higher, surpassing the tolerable values in G, Q, and N. This study analyzed the ecological risks and human health risks of heavy metals and metalloid in farmland soils near the sampling mining areas, and demonstrated the importance of environmental changes caused by land development in the mining industry.

Mercury (Hg) and arsenic (As) are toxic and harmful heavy metals, with exceedance rates of 1.6% and 2.7%, respectively, in soils across China. Compared to soils contaminated with Hg or As alone, co-contaminated soils pose complex environmental risks and are difficult to remediate. Biochar is widely used as a soil amendment to adsorb and immobilize pollutants such as heavy metals. However, only a few studies have explored the efficiency of biochars produced from different crop straws to reduce the bioavailability of heavy metals in co-contaminated soils, and the effects on soil biological properties are often overlooked. The aim of this study was to investigate changes to the physicochemical properties, enzyme activities, and heavy metal bioavailability of an industrial soil co-contaminated with Hg and As upon the addition of different biochars from reed, cassava, and rice straws (REB, CAB, and RIB, respectively). The soil was amended with 1% biochar and planted with spinach in pots for 30 days. RIB was more effective than REB and CAB in increasing the soil pH, organic matter content, and cation exchange capacity. RIB and CAB exhibited similar positive effects on the soil dehydrogenase, catalase, invertase, and urease activities, which were higher than those of REB. The exchangeable fraction of both metals decreased upon biochar addition, and the residual fraction showed the opposite trend. All biochar amendments reduced the bioconcentration factors of heavy metals (especially Hg) in plants and decreased the metal bioavailability in soil. RIB is the optimal amendment for the stabilization of soil co-contaminated with Hg and As.

Northern Shaanxi is the birthplace of the oil industry. In the process of large-scale oil and gas transportation and extraction, oil leakage and inevitability will inevitably result, causing some pollution to soil and groundwater. The purpose of this study is to investigate the impact of oil pollution on soil moisture characteristics. In this study, the loessial soil in northern Shaanxi was used as the research object to determine the wettability, capillary water rise and saturated hydraulic conductivity of soils under five different pollution gradients (0%, 0.5%, 1%, 2% and 4%). The results showed that when the soil was polluted by oil, the wettability of the soil will change, resulting in a certain degree of water repellence. In the same rising period, the uncontaminated soil capillary water rose significantly higher than the oil-contaminated soil, and the higher the degree of pollution, the smaller the capillary water rise. Oil pollution made soil saturated hydraulic conductivity decrease with the increase of pollution concentration, although saturated hydraulic conductivity decreases, but for loessial, it was within an order of magnitude.

Atmospheric nitrogen deposition is one of the most important elements in nitrogen biogeochemical cycles. It is not only one of the major processes for removing nitrogenous pollutants in the air, but also an important way for the ecosystem to obtain nitrogen from the atmosphere. In recent years, due to the combustion of minerals, the use of chemical fertilizers and the rapid development of livestock husbandry, human activities have led to the continuous increase of atmospheric active nitrogen concentration, which has aroused widespread concern of all parties. This paper introduces the types and sources of atmospheric nitrogen deposition and focuses on the response of atmospheric nitrogen deposition to different ecosystems.

Mu us sandy land is a typical ecologically fragile area in our country, which will bring remarkable comprehensive benefits to its rational development and utilization. This research systematically explored the comprehensive improvement technology of Mu Us sandy land through indoor experiment, plot test and field demonstration, and refined the soft rock and sand combined sand-fixing ability improvement technology, efficient irrigation water-saving technology, water and fertilizer management technology, and developed a comprehensive development scale decision support system, which can provide decision support for the development of Mu Us sandy land. Through the integration of technologies, demonstration application has been carried out in Mu Us sandy land of northern Shaanxi and good ecological, social and economic benefits have been achieved.