Study On Soil Evolution Trend And Mechanism Of Xinqiu Open-pit Coal Mine Dump

Fuxin is rich in mineral resources,and a large number of abandoned mining areas are left over from mining.How to restore and rebuild the damaged ecosystem in mining areas has become a common issue urgently to be solved by experts and scholars.In this paper,different rocks and weathered materials and soil under different vegetation in the dump of Xinqiu open-pit mine were studied to analyze the formation and evolution law of the soil in the dump,aiming to provide a scientific basis for the ecological restoration of the dump.Six types of rocks and their weathering materials,four types of soil under different vegetation types and bare land were selected as five sample plots.They were P₁（tree:Ulmus pumila）,P₂（shrub:Periploca sepium Bunge）,P₃（herb:Setaria viridis）,P₄（herb:Salsola collina）and P₅（bare land）.The weathering rates of six kinds of rocks were analyzed by soaking and simulated rain tests with solutions of different p H values.The physical and chemical properties of rock weathering and soil,including particle composition and nutrient content,were analyzed.The results showed that:（1）The weathering rate of mudstone is the highest under soaking and simulated rain conditions;Followed by siltstone,fine sandstone,coal gangue,coarse sandstone,conglomerate.Compared with CK,water condition has an important influence on weathering,which can accelerate the disintegration of sedimentary rocks.p H value of water has an important influence on rock weathering rate,and acidic condition is more conducive to rock weathering.In general,the weathering rate of different rocks in the dump is acid>alkali>neutral.（2）The grain composition of rock weathering is mainly sand;Mudstone is mainly composed of silty clay and fine sand.In addition to mudstone,coarse sand（0.1-2 mm）is the highest in the grain composition of rock weathering material of siltstone,fine sandstone,coarse sandstone,conglomerate and coal gangue,which is 49.30%-67.31%（average 51.52%）.The content of powder（0.002-0.05 mm）ranged from 13.49%to 26.08%（average 21.75%）.Clay content（<0.002 mm）was relatively low,ranging from 9.47%to 20.95%（average 13.14%）.The fractal dimension of weathering particles of different rocks is mudstone>fine sandstone>siltstone>coarse sandstone>conglomerate>coal gangue.Therefore,mudstone and sandstone can provide more clay and silt during soil formation,thus improving soil quality.（3）The particle composition of soil under different vegetation of the dump is better than that of bare land.On the whole,the soil of the dump is sandy.The composition of soil particles under different vegetation was different.The soil of samples P₂and P₄was dominated by sand particles.The soil of P₁and P₃is dominated by silt clay.However,the content of silt and clay in soil under each vegetation was higher than that in bare land.P₅had the highest volume percentage of coarse sand,which was 72.95%,while the soil under Setaria had the lowest volume percentage of coarse sand,which was 28.39%.In terms of the proportion of clay content,the soil under Setaria was the highest,accounting for 28.78%,followed by Chlamydia porcini,accounting for 16.04%.This shows that vegetation has a significant effect on improving soil physical properties of the dump.From the soil layer of 20-40cm,the soil particle composition of P₁plot was significantly better than that of other plots.Therefore,trees and herbs can improve the quality of soil particle composition.Trees have a surface aggregation effect on the nutrients in the surface soil,and the roots absorb nutrients from different soil layers to form stems and leaves.After the dead leaves return to the soil surface,nutrients are enriched in the soil surface.The accumulation of organic matter both promotes rock weathering and prevents soil erosion,so the composition of soil particles changes and the proportion of clay particles increases.（4）The organic matter content of rock weathering is 2.7-155.6 g/kg;Total nitrogen content:0.12-1.6g/kg;Total phosphorus content:0.08-0.15g/kg;Total potassium content:12.08-27.39g/kg.In addition,the available phosphorus content of coarse sandstone is the highest.Siltstone has the highest available potassium content.（5）Vegetation restoration has an important effect on the content and distribution of organic matter,TN,TP and TK.The soil organic matter content under different vegetation types was P₄>P₁>P₂>P₃>P₅.Soil total nitrogen content was P₁>P₂>P₃>P₄>P₅.The total p content in soil was P₁>P₄>P₃>P₂>P₅.The total k content in soil was P₁>P₂>P₃>P₄>P₅.With the deepening of soil layer,the contents of organic matter,nitrogen,phosphorus and potassium in soil decreased.The correlation between different rock weathering materials and soil nutrients under different vegetation increased gradually,mainly because of the weakened influence of vegetation.Comparatively speaking,the contribution of rock weathering material to N,P and K is not great,but the effect of vegetation on the accumulation and distribution of N,P and K in soil is stronger.The paper has 37 pictures,9 tables,and 96 references.