煤矸石充填复垦地理化特性与重金属分布特征

为研究煤矸石充填复垦地农作物产量达到最佳时的覆土厚度及煤矸石充填复垦地重金属分布状况,该文以新庄孜矿煤矸石充填复垦地作为研究对象,采取室外田间小区试验和室内试验分析方法,选取不同覆土厚度50~60,60~70,70~80,80~90 cm的4类试验地块及对照地块对其土壤理化性质及农作物根系分布、长势产量、重金属元素含量进行调查分析,发现复垦地块各项指标与对照地块差异显著,劣于对照地块;煤矸石充填基质土壤理化性质较差;70~80 cm的厚度是煤矸石充填复垦造地较经济合理的覆土厚度。煤矸石复垦地重金属元素有向上迁移的趋势;复垦土壤及煤矸石基质中Pb、Zn、Cr元素含量处于安全水平;大部分监测的Cu、Ni、Cd元素含量高于淮南土壤背景值,低于中国土壤环境质量标准二级标准,对复垦土壤已构成潜在的威胁性,应予以重视;覆土厚度50~60 cm地块的煤矸石基质中Cu、Ni元素含量处于安全水平,煤矸石基质中Cd元素含量高于淮南土壤土壤背景值,低于中国土壤环境质量标准二级标准,应予以重视。结果表明70~80 cm的厚度是煤矸石充填复垦造地最佳覆土厚度;新庄孜煤矸石充填复垦地重金属有向上迁移的趋势,复垦土壤中重金属含量符合国家二级标准,未出现重金属污染情况,但部分重金属元素含量高于淮南市土壤背景值,应予以重视。

Physical and chemical properties and distribution characteristics of heavy metals in reclaimed land filled with coal gangue

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.