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The environmental restoration and ecological treatment of abandoned mining areas are of great significance for the construction of ecological civilization. In view of the heavy metal pollution in soil caused by mining, it is particularly important to carry out the investigation of heavy metal pollution characteristics and health risk assessment for the design and construction of mining treatment schemes. The pollution characteristics of soil heavy metals(As, Cd, Cu, Mn and Ni)of Dafanshan abandoned alum mining area in Lujiang county of Anhui province were analyzed, and the pollution assessment and human health risk assessment were established by combining the site accumulation index method, potential ecological risk index method and health risk assessment model(USEPA).The results show that the contents of As and Cd in the soil of the abandoned alum mining area significantly exceed the standard, and compared with the risk screening value of agricultural land, the exceeding rates are 77% and 100%, respectively; Cu in soil is slightly polluted, and the exceeding rate is 16%; the contents of Mn and Ni do not exceed the standard; in addition, the above five heavy metal elements in the descending order of the coefficients of variation are Ni, Mn, Cu, Cd and As; the study area has strong potential ecological risk, and the potential ecological risk index shows that As and Cd are the main risk elements, and the soil is mainly in quite-strong and very-strong potential ecological risks. The health risk assessment model shows that the indirect oral intake of excessive heavy metals in soil is the main route of non-carcinogenic and carcinogenic risks; As and Cd are within the acceptable ranges of non-carcinogenic and carcinogenic risks for adults and children through oral ingestion, and there is no carcinogenic risk for adults and children through respiratory ingestion and skin contact. [ABSTRACT FROM AUTHOR]

High weathered soils in arid and semi-arid area are characterized by low soil fertility and high erosion potential. This paper evaluated the influences of nano-carbon on soil erosion and water loss on the sloping land (15°) of the Chinese Loess Plateau. Simulated rainfall experiments were performed on a natural, fallow loessial slope in the Shenmu Erosion and Environment Research Station, Institute of Soil and Water Conservation, Chinese Academy of Sciences, which locates in the Liudaogou watershed, Shenmu County, Shaanxi Province. Five application rates (i.e., 0, 0.1%, 0.5%, 0.7%, and 1.0%) of nano-carbon were selected during the simulated rainfall experiments (rainfall intensity of 60 mm/h); and 4 vegetation species (i.e., caragana, alfafa, bean, and maize) were planted on the slope to evaluate the vegetation effect on soil and water conservation with the bare as the control. A constant-intensity rainfall method was adopted under natural conditions. Field plots were established on the slope that had been fallow for 5 years. The rainfall simulator came from the independent design of Xi'an University of Technology. Under the 60 mm/h rainfall intensity, the simulated rainfall experiments were carried out for 50 times in the 25 different pretreated plots in order to estimate soil erosion and water loss for all the treatments. The main results were as follows: the initial runoff time was delayed with the increase of nano-carbon contents. Compared to the control treatment without nano-carbon application in bare land, the initial runoff time in alfalfa plot was delayed by 287.1%, which was the most obvious. Furthermore, with the increase of nano-carbon contents, the runoff in each treatment decreased obviously. The nano-carbon alfalfa coverage also had the most obvious effect in the reducing runoff, and the runoff was reduced by 66.47%; for other vegetation species, the reduction was between 31.5% and 33.6%. Moreover, the nano-carbon had a significant effect on soil loss controlling. The nano-carbon in alfalfa land showed the best effect for soil loss controlling, which was followed by caragana. Soybean land showed the highest soil loss. For the bare land (control) and alfalfa coverage, when the nano-carbon content was 1%, the lowest sediment yield was obtained; while for caragana, soybean and maize coverage, when the nano-carbon content was 0.5%, the sediment yield was the lowest. Based on the correlation analysis between nano-carbon and runoff and sediment yield, it could be concluded that nano-carbon has a significant impact on the experimental results. In the evaluation of soil and water loss control effect, the 0.5% nano-carbon had the obvious effect, which was similar with the 0.7% and 1.0% nano-carbon content, so considering the price, 0.5% nano-carbon content was appropriate on soil and water loss control in loess area. The results provide a guide for controlling soil water and nutrient loss on the sloping land. [ABSTRACT FROM AUTHOR]