Spatial And Temporal Change Of Soil Quality In The Artificially Disturbed Areas Of The Open-pit Coal Mine

The activities of open-pit coal mining strip all the rock formation and soil above coal,destroy vegetation and change the surface configuration.They bring severe damage to the ecosystem of the mining area.Soil is the basis for agricultural production,living and ecological restoration in the mining area.Soil quality is the key to build a healthy ecosystem in mining area.Taking Pingshuo open-pit coal mine as an example,this study focused on the quality of soil in artificially disturbed areas.Based on long-term data collection,analysis and soil sampling,we made the quantitative and qualitative analysis on soil quality changes and monitoring methods in the mine.The main contents contain two aspects:soil fertility quality and soil environmental quality.Specifically,we analyzed the mineral composition and the quality status of the geological strata in the mining area,monitored the changes of soil fertility quality in the soil profile,calculated the spatial characteristics and reasonable sampling quantity of soil fertility,and analyzed the changes of soil environment quality of the industrial site.Meanwhile,we proposed a proposal for classified management of soil in mining areas based on destroyed units.Through this study,the following conclusions are drawn:(1)When considering the mineral composition of geological strata,soils above 55m are more suitable for discharging to the surface.When considering pH and soil fertility indexes,soils above 69.72m are close to the background valued of Shanxi province,and the pH is suitable for vegetation growth,so they are more suitable for discharging to the surface.When considering the heavy metals,concentrations of As and Cr in soils at the depth of 22.74m are relatively high,and enough attention should be paid to this part of the soil.Concentrations of heavy metals in rock mass below 136m are high.So this part of rock mass is also not suitable for land reclamation.(2)Concentrations of most soil fertilities in the soil profile(0-100 cm)of the mine dump increased with reclamation time.However,concentrations of soil organic matter and total nitrogen in the reclaimed soils did not restore to the level of natural soils in the short term,especially in the surface layer.Land use types also have important effects on reclaimed soil.In the soil layer of 60-100 cm,soil properties and its trend lines of reclaimed forest land are closer to the corresponding values of the natural land compared with reclaimed cropland and grassland.The effect of reclamation time on soil properties varies between land use types.(3)The vegetation community structure has effects on the content and spatial distribution of most soil fertilities.When only considering the concentration and its spatial autocorrelation of soil fertilities,the reclamation model of "Pinus tabulaeformis + Robinia pseudoacacia" has more advantages.Except for soil bulk density and total nitrogen,the reasonable soil sampling numbers showed no significant difference among different soil fertilities at the given confidence intervals and relative error ranges.The sampling density can be reduced appropriately in the future soil sampling.However,enough attention should be paid to soil bulk density and total nitrogen when collecting soil samples.(4)In the 0-100 cm depth,most of the soil samples are seriously polluted by PAHs in the industrial site,and PAHs tend to accumulate in topsoil.Even in the same industrial site,the spatial distribution of PAHs varied greatly in different functional areas.In different land use types,the proportion of PAHs with high molecular weight was larger,especially the 4-ring and 5-ring PAHs.Although there are many sources of PAHs pollution,the burning of petroleum products is the main reason for PAHs accumulation in the study area.(5)Affected by the technologies of open-pit mining and land reclamation,areas and locations of different types of damaged land also dynamically change.Referencing the classification management standard of farmland,this paper proposed a preliminary idea of the classification management of mine soil based on different damage units.We divided mine soils into three classes based on soil quality in different damaged units,namely,priority protection class,safe use class,and strict control class.Soils belong to the priority protection class should be carefully prevented from pollution,and soils belong to strict control class should be prevented from agricultural use.