基于CT分析露天煤矿复垦年限对土壤有效孔隙数量和孔隙度的影响

露天煤矿排土场由于排土过程中大型机械压实等作用会对土壤的孔隙结构产生影响,重构适合于植被生长的土壤孔隙结构是排土场土地复垦的重要工作。为对排土场重构土壤孔隙结构进行定量分析,该文采用高精度无损计算机断层扫描技术(CT)对山西平朔矿区安太堡露天煤矿排土场平台全黄土母质覆盖的不同复垦年限(0、20、23 a)以及原地貌的土壤进行分层扫描成像,并利用Photoshop和Arcgis软件对扫描图像进行处理和统计分析,探讨了排土和复垦对土壤孔隙数量和孔隙度的影响,分析了排土场重构土壤大、中和小孔隙的变化。结果表明:原地貌土壤孔隙数量和孔隙度最大,其次是复垦23和20 a的土壤,排土后未复垦土壤孔隙数量和孔隙度最小。采矿和排土等活动由于大型机械压实作用降低了土壤孔隙数量和孔隙度,尤其是大孔隙数量和大孔隙度;土地复垦对增加土壤孔隙数量和孔隙度有一定的作用,但是过程比较缓慢。采矿和排土等活动对表层土壤孔隙数量和孔隙度的影响要高于底层土壤。该研究可为黄土区大型露天煤矿排土场重构土壤结构的优化与土地复垦措施选择提供依据。

Effects of land reclamation time on soil pore number and porosity based on computed tomography images in opencast coal mine dump

Abstract: Opencast coal mining is an anthropogenic activity that changes the antecedent soil profile, and the physical, chemical and biological properties. The compaction activities of large machinery play a great effect on reconstructed soil pore structure in opencast coal-mine dump, so it is an important work to reconstruct a suitable soil pore structure for vegetation growth during the land reclamation for dump. In order to make a quantitative analysis on the pore number and porosity of reconstructed soils in dump, high precision and lossless computed tomography (CT) was used to study the effect of opencast coal-mining, land reclamation and dumping on soil pore number and porosity by scanning the soils in Antaibao opencast coal mine in Pingshuo mining area, Shanxi Province, China. The soils were taken from the dump platform covered by loess parent material, which were the ones with different reclamation time (0, 20 and 23 a) and the one of original landform. The softwares, including Photoshop 7.0, ArcGIS 10 and AutoCAD 2010, were used to process the scanned image and carry out statistical analysis for soil pore properties, and the image characteristics of soil pores and the changes in the number of soil pores and the porosity were analyzed. The changes in macropores, mesopores and micropores of reconstructed soils were also studied in this paper. The results indicated that: 1) Applying the combination method of high precision CT scan imaging technology and computer graphics software could accurately analyze the size, number and distribution of reconstructed soil in opencast coal-mine dump; 2) The number of soil pores and the porosity in original landform were the largest, followed by the soils reclaimed for 23 and 20 years, and the soils after dumping before reclamation were the lowest; 3) Opencast coal-mining and dumping activities reduced the number of soil pores and the porosity because of the effects of large mechanical compaction, especially for macrospores, and land reclamation had a certain function of increasing soil pore size and improving soil porosity; 4) The effect of mining, dumping and other activities on the number of soil pores and the soil porosity for surface soils was higher than that for the bottom soils. During the land reclamation process, subsoiling, planting green manure, applying organic fertilizer and other land reclamation measures should be used to increase the number of reclaimed soil pores and the porosity of macropore on surface soils. This research can provide theoretical reference for the quantitative expression of reconstructed soil pores'' distribution, the selection of land reclamation measures, and the optimization of reconstructed soil structure in opencast coal-mine dumps in loess areas.