Research On Soil Reconstruction Of Eastern Grassland Surface Scarce Mining Area Based On Mining Solid Waste

Coal resources are the most important fossil energy in China and even the world,providing a powerful driving force for global economic development.However,the large-scale mining of coal has also brought a series of ecological and social problems.Under the current background of ecological civilization construction,how to realize the win-win situation of production and protection has been paid more and more attention,so land reclamation and ecological restoration are imperative.In the actual process,land reclamation work is limited by local natural resource conditions,so it is necessary to follow the principle of one mine and one policy,and to formulate land reclamation strategies according to local conditions.The eastern grassland mining area is an important coal and power base in China,but at the same time it is also an ecologically fragile area.Intense mining activities make the already fragile ecological environment more fragile,while the thin topsoil layer seriously restricts the land reclamation work of the mining area.Focusing on solving the problem of scarcity of topsoil in the mining area and realizing the utilization of solid waste,we used industrial solid waste as a substitute for topsoil to achieve a win-win situation between production and ecology in the mining area,in which field survey,field sampling method,analysis of variance,pot test method and other methods were used.On the basis of fieldwork,coal gangue,fly ash and rock-soil stripping materials were selected as top soil substitute materials,and pot experiments were carried out in the greenhouse.By analyzing the differences of physicochemical characteristics and comparing plant growth status and drought tolerance of reconstructed soils,the reconstituted soil formula based on mining solid waste suitable for eastern grassland mining areas was selected.The result showed:(1)Compared with the original surface soil,the soil nutrient condition is effectively improved,especially for the organic matter content when coal gangue and other mining solid waste were used as the surface soil substitute material.The addition of coal gangue effectively improved the chemical properties of soil,while the addition of fly ash to a certain extent made the chemical properties of soil worse,and the high content of rock and soil stripping also caused the chemical properties worse.(2)The addition of rock and soil stripping improved the sand property of soil,while the addition of fly ash increased the content of sand in the soil.On the fourth day,the soil moisture content of reconstructed soil was higher than that of original soil,and the soil moisture content of original soil decreased the fastest in a four-day irrigation cycle,with soil moisture content decreasing from 16% to 6%.(3)According to the four selected indicators of sweet clover growth,it was feasible to use mining solid waste as the replacement of topsoil.The biomass of sweet clover was the highest when the ratio of overburden: gangue: rock and soil was 3:3:4,with good performance of leaf width,plant height and root length.The biomass of sweet clover was higher than that of pure topsoil when the reconstructed soil and coal gangue are placed in layers,with the thickness of upper layer more than 10 cm.When the amount of coal gangue was controlled at 30%,the biomass of sweet clover was the best,with good performance of other indicators.The overall biomass of the treatments with fly ash was lower than that of the control scheme,but the growth status of single plant was better,so better growth status was achieved when the amount of fly ash was controlled at 10% or below.Four indicators of sweet clover showed better performance when the amount of rock and soil was controlled at 40% or below,which was more suitable for sweet clover growth.(4)Using the method of coal gangue in the lower layer and covering the reconstituted soil in the upper layer can keep more water under the condition of drought,but the thickness of reconstituted soil in the upper layer should be more than 20 cm.Compared with the control scheme,the reconstructed soil can provide more water for plant growth under drought condition,and the survival rate of plant was higher under drought condition.In terms of single surface soil substitute material,coal gangue showed better performance on moisture retention,while the excessive content of fly ash led to excessive wilting of plants.and the effect of rock soil stripping was similar to that of surface soil.Therefore,when the content of coal gangue and fly ash was about 30% and less than 30% in the reconstructed soil,it was beneficial to the growth of plants under the condition of drought.It was feasible to use coal gangue as the substitute material for topsoil.Coal gangue and reconstructed soil layered reconstruction method can be used,30% coal gangue,30% topsoil and 40% rock soil stripping material was the best growth condition of reconstituted soil for sweet clover,the physical and chemical properties of soil and the drought resistance of sweet clover were also better than that of original soil.