Abstract:
Abstract: Coal gangue is a solid waste with the largest emissions during the process of coal mining, processing, and utilization in Huainan mining areas. Many coal emissions have caused worsening situations dealing with land occupation and the problem of ecological environment damage in mining areas. The utilization of coal gangue for filling and land reclamation is not only able to recover the value of mining subsidence land, but it can handle coal gangue, which has significant economic and environmental benefits. The key problems for land reclamation based on using coal gangue as the main substrate are designing the best and economical depth of top soil for meeting the needs of crop growth and the possibility that the utilization of coal gangue for land reclamation will cause soil pollution. For studying the depth of top soil when optimum crop yields can be achieved and the possibilities of pollution to the environment caused by the filling reclaimed soil, this paper introduced the establishment of outside field plots, regarded as Xin Zhuangzi coal gangue reclaimed land, as the research object. The winter wheat had been planted on both control plots and four test plots, which were designated A, B, C, and D, with the top-soil depth of 50-60 cm, 60-70 cm, 70-80 cm and 80-90 cm, respectively. Soil, coal gangue and wheat samples had been collected. The analysis of indicators were as follows: the pH values of soil and coal gangue samples, the content of organic matter, the contents of total nitrogen, total phosphorus and total potassium, natural water content of soil, particle density; the root density, height and production of winter wheat; and the content of these elements: Cu, Cd, Pb, Zn, Ni and Cr. All the indicators had been analyzed by using statistical methods. The experimental results showed that reclaimed land has notable differences of each indicator compared with the control plots. The physical-chemical properties of the soil, the root density, height of crops, and production of winter wheat are poorer than those of the control plots. The substrate made of coal gangue has more inferior physical-chemical properties. Considering the indicators, the conclusion is that several indicators of B test plot are better than the others, so a soil depth of 70-80 cm is a more economical and rational top-soil depth for reclaimed land when using coal gangue as a filler. The elements in coal gangue substrate for filling, such as Cu, Cd, Pb, Zn, Ni, and Cr, has a trend of migrating to the upper surface. At a safe level, the contents of Pb, Zn, Cr in reclaimed soil and coal gangue matrix are below the background values of the soil in Huainan (30.5 mg/kg, 80.8 mg/kg, 64.9 mg/kg). In a significant cumulative effect, the contents of Cu, Ni, Cd elements in reclamation soil are above the background values of Huainan soil but lower than the primary standard of the soil environmental quality standards in China (35mg/kg). Though these elements would not pollute the soil singly, this situation constitutes a potential threat on reclaimed soil and more attention to the threat should be paid. The contents of Cu, Ni in the coal gangue matrix of test A plot are below the background values of Huainan soil (24.2 mg/kg) and at a safe level. The content of Cd is higher than the background value of Huainan soil (0.06 mg/kg) and lower than the minor standard of Chinese soil environmental quality (0.6 mg/kg), and deserves more attention because of the cumulative effect in coal gangue matrix.