Bio-physical Improvement And Ecological Effects Of Open-pit Mining Associated Clay In The Eastern Grassland Of China

There are abundant coal reserves in the grassland open-pit coal mine area in the east of China.The open-pit mining will not only promote the economic development,but also affect the local ecological environment.The ecological reconstruction of the open-pit waste dump has become the most urgent task of grassland ecological restoration in the eastern mining area.The top soil of the eastern grassland is poor,and mining intensifies the soil desertification and nutrient loss.In the process of ecological reconstruction of waste dump,there is not enough topsoil,coupled with the cold climate conditions,vegetation is difficult to build,so it is necessary to study the soil matrix which can replace the representative soil,and improve the matrix for use in the ecological reconstruction of open-air waste dump to obtain better ecological improvement effect.In the mining process of Baorixile open pit coal mine,it is found that there is a 16m-20 m thick mining associated clay.The physical characteristics of the clay are high clay content,low organic matter content,high total nutrient content,but low effective nutrient content,and few microorganisms.Soil modification is the basis of the utilization of the clay resources.Through physical and biological improvement of the clay,it is revealed that its ecological restoration is improved Effect.In order to find the best ratio,sand and clay were used as the ratio to lay the foundation for the later biophysical utilization;a series of studies on the dynamics of clay nutrients were carried out to obtain the potential for the effective utilization of nutrients in clay;biological improvement was carried out by using microbial technology,which was popularized and applied to the ecological reconstruction of the waste dump of the open-pit mine in the eastern grassland,and the preliminary ecological restoration effect was achieved.The main conclusions are as follows:(1)Study on physical improvement technology and proportion of clay matrix.The results show that the holding capacity of water and potassium by the mixture of clay and sand is the most similar to that of topsoil.The 1:1 mixture of sandy soil and clay can effectively reduce the evaporation of water compared with other proportions;the analysis of soil mechanical composition shows that after the 1:1 mixture of sandy soil and clay,it becomes: clay 48.14%,silt 2.8%,sand 49.06%,texture is loamy clay,which is similar to the top soil.The XRD results show that the main clay mineral is montmorillonite,and the mineral characteristic peak of 1:1 mixed matrix is similar to that of topsoil.Therefore,the 1:1 mixture ratio of sand and clay should be the best physical improvement technology and ratio.(2)The dynamic characteristics of phosphorus in clay and soil matrix with different proportion were studied to reveal the potential characteristics of clay for nutrient utilization.The adsorption parameters of phosphorus in soil were calculated to provide theoretical basis for physical improvement.The adsorption capacity of sand and clay is2.2 times of that of topsoil after 1:1 mixing,and the desorption rate is 38.6%,which is most similar to 40.9% of that of topsoil.Because of the large basic adsorption capacity,the desorption rate is 1.51 times of that of topsoil.Therefore,the 1:1 mixture of clay and sandy soil has the potential to be used as the top soil substitute material in the open pit dump.(3)The improvement of clay by different microorganisms was studied.It was found that arbuscular mycorrhizal fungi(AMF)could effectively promote plant growth and increase soil enzyme activity in pure clay matrix,while PSB could not improve soil matrix.The aboveground biomass of maize inoculated with AMF was 1.14 times that of CK,and there was no significant difference between PSB and CK.The plant phosphorus absorption of AMF was 10.12 mg,which was significantly higher than that of PSB 8.67 mg and CK 8.58 mg.The contribution rate of AMF is 16.9%,higher than0.6% of PSB.Inoculation of AMF promoted the increase of soil protein related to urease and coccidiomycin in clay and the content of water stable aggregates in clay.AMF can be used as microbial improver of mining associated clay to improve clay matrix.(4)The improvement effect of the combination of microorganism and physics on clay.Combining physical improvement with biological improvement,AMF inoculation significantly increased the biomass of the mixture of topsoil,sandy soil and sandy soil:Clay 1:1(S?C1:1),in which the aboveground part increased by 28.3%,34.8%,24.4%,and the biomass of the underground part increased by 37.3%,20.6%,34.8%.The contribution rate of mycorrhiza was the highest(34.83%),followed by 29.45% of topsoil.After AMF inoculation,urease and phosphatase activities in topsoil,sandy soil and S?C1:1 increased significantly.The level of IAA and CTK were significantly increased,and ABA was inhibited.The structure equation model(SEM)was used to analyze that the physical improvement process and AMF inoculation were the most important factors affecting the plant biomass.The combination of biological and physical improvement could effectively improve the mining associated clay and promote the plant growth.(5)Study on ecological effect of plant microorganism clay combined improvement in open pit dump.Through microbial improvement,it was found that AMF could effectively promote the transformation of nutrients in the soil,and the proportion of available phosphorus in the clay inoculated area was 1.29-1.36 times of that in the control area;AMF could significantly promote the activities of urease,phosphatase,ee-grsp and t-grsp in the soil.It was found that the mixture of seabuckthorn and alfalfa could effectively increase soil enzyme activity,and the growth of seabuckthorn was better than that of single species.The results showed that there were 23.3 new species in the top soil + AMF area,6.6 more than the top soil control area,there were17.3 new species in the clay soil + AMF area,6.3 more than the clay soil control area area,and intercropping area had 5 more than new species the Seabuckthorn area.The most important species are Kochia scoparia(L.)Schrad.var.sieversiana(Pall.)Ulbr.ex Aschers et Graebn.and Salsolacollina Pall;the biomass of grass production is mainly the invasive annual plant alkali groundsel and lard.The inoculation can effectively reduce the invasion of alkali groundsel and lard,the biomass of the sample in the surface soil inoculation area is 34% lower than that in the control area,and the biomass of the sample in the clay inoculation area is 26% lower than that in the clay control area.Combined improvement can effectively promote the nutrient release of mining associated clay,promote the growth of plants,enrich the number of species,increase the use of water by plants,which is of great significance for the ecological reconstruction of waste dump.