露天矿上覆岩土层中表土替代材料的筛选

Selection of topsoil alternatives from overburden of surface coal mines

在表土缺乏地区,筛选适宜的表土替代材料是露天矿复垦的关键。通过对内蒙古某露天煤矿上覆岩土层的基本特征的分析,以当地表土作为对照,比较分析了表土层下Ⅱ层黄土(18.4 m厚)和Ⅲ层亚黏土(16 m厚)的原状基质及其风化物的理化性质与营养成分、重金属含量,同时采用盆栽试验研究了各基质出苗率及土壤表层的结皮情况。试验结果表明:表土层下Ⅱ层风化与原状基质分别属于粉黏土和黏土,pH值偏高,缺乏有机质、速效磷、速效钾等营养成分,As、Cr、Cu、Ni、Zn、Pb等重金属含量较低,表层结皮严重对紫花苜蓿的出苗率影响较大;Ⅲ层风化与原状基质属于重黏土,pH值适中,营养成分含量不均衡,速效钾含量丰富,As、Cr、Cu、Ni、Zn、Pb等重金属含量较低,表层稍有结皮对紫花苜蓿出苗率的影响较小。分析结果表明:Ⅲ层基质在酸碱性、电导率、含盐量、出苗率等方面均接近当地表土,较为适宜作为表土替代材料,其风化后的土壤特性更优。

Selection of topsoil alternatives is very important for surface mined land reclamation in the region of topsoil shortage. This paper conducted research on the selection of topsoil alternatives from overburden of a surface coalmine in Inner Mongolia, which is located in the famous Hulunbaier grassland. The analysis of geological profile indicated the potential capability of Layers II and III to become topsoil alternatives. The samples of Layers II and III were taken from its original places, the weathering materials of Layers II and III were taken from dumps, and the original topsoil was also taken as control for comparison. Thus, five treatments including original topsoil, Layer II weathering material, Layer II, Layer III weathering material and Layer III were selected. The physical, chemical properties and heavy metal contents of these five soil materials were determined based on samples＇ analysis. Seeds germination of alfalfa and surface crust situation of these soil materials were also obtained from pot experiments to check their effectiveness as topsoil. The results showed that soil textures of Layer II and its weathering material contained 94.75% and 62.32% of clay respectively, which were clay and silty clay. Such soil could be relatively good topsoil alternatives, but the aggregate contents were lower, the pH values were slightly higher （8.02 and 9.22 respectively）, and some nutrients such as organic matter contents, rapidly available K and available P were deficient. The serious surface crust of Layer II and its weathering material decreased emergence rate of seeds. Layer III and its weathering material contained almost 100% of clay, which were brown and heavy clay soil, but they had lower aggregate contents, moderate pH values （7.75 and 7.83 respectively）, rich available K and lower other nutrient contents. All the samples of the five soil materials had lower contents of heavy metalS such as As, Cr, Cu, Ni, Zn and Pb, meeting with the first class of the national soil environment standard. The surface crust situation of Layer III and its weathering material were not serious and had better emergence rate of seeds, which were all larger than 55%, compared with the 65% of control treatment and the 25% of Layer II. The results indicated that Layer IIl had similar soil chemical and physical properties and better seed germination compared with the original topsoil, and could be good topsoil alternatives. The Weathering material of Layer III was the best for topsoil alternatives.