Study On Soil Reconstruction In Lingquan Closed Open-pit Coal Mine

The eastern grassland region of China is rich in coal resources that are suitable for open-pit mining due to the characteristics of shallowly buried coal seams.Although the development of coal resources has promoted social and economic development,it has also caused a certain degree of negative ecological and environmental effects.In response to the situation where the surface mine drainage field and slopes have insufficient topsoil,poor nutrients,water,and fertilizer leakage,and are prone to erosion,in this study,straw,sheep slab dung,binder,diatomaceous earth and fly ash were combined in different proportions to reconstruct the soil using sandy mudstone from the mining area as the substrate.They explored the erosion resistance,soil aggregate composition,nutrient changes in soil aggregates,and the effects on plants of the reconstructed soil through artificial simulated rainfall tests and potting tests.The following main results were obtained:（1）Soil reconstitution material ratios were optimised through single-factor experiments and response surface methodology.By comparing the physicochemical properties of the compounded soils,the T1 combination of sandy mudstone with 2.5%straw,15%sheep dung,0.2%binder,8%diatomaceous earth and 4%fly ash was considered to be the best ratio for soil reconstruction,followed by T2（2%straw,10%sheep dung,0.2%binder,9%diatomaceous earth and 3%fly ash）and T3（2%straw,10%sheep dung,0.2%binder,8%diatomaceous earth and 4%fly ash）is the next best.（2）The erosion resistance of the reconstructed soil was significantly improved.Compared to sandy mudstone without amendments,soil restructuring measures reduced the cumulative runoff volume,cumulative sediment volume and relative loss of nutrients from the slope,with the T1 treatment having the most significant reduction in flow and erosion for 20°slope and 45 mm/h rainfall intensity,by 38.86%and 53.27%respectively.The relative loss rates of organic matter,total nitrogen and total phosphorus were all lowest under this condition.（3）The composition and nutrient content of soil aggregates were significantly improved by soil restructuring measures.Soil restructuring measures can change the distribution of soil water-stable aggregates and promote the transformation of microaggregates into large aggregates;improve the stability of aggregates,increasing the content of>0.25 mm aggregates(R_0.25),the mean weight diameter（MWD）and the geometric mean diameter（GWD）,and decreasing the fractal dimension（D）parameter;increase the nutrient content of water-stable aggregates of all particle sizes.（4）Soil reconstitution measures significantly promoted plant growth and improved soil properties.Seedling emergence,plant height and biomass of alfalfa were significantly higher under the three soil reconstitution ratios than the control treatment,indicating that reconstituted soil is feasible as a topsoil alternative;the reconstituted soil improved p H,organic matter,total nitrogen and total phosphorus significantly,with the T1 treatment having higher soil enzyme activity,microbial community richness and diversity.In summary,this study has greater reference value for the ecological restoration of the closed open-pit mine at Lingquan and open-pit mines in similar conditions.This paper has 39 figures,11 tables and 123 references.