| As an important energy base in China,Huaibei mining area has a long history of coal mining.Long-term coal mining activities have caused land damage and ecological damage.Subsidence land reclamation is an important measure to repair the damaged land in the mining area.An in-depth understanding of the change characteristics of soil moisture and the law of soil nutrient loss in the process of reclamation is of great significance to scientifically guide the reclamation and ecological reconstruction of subsidence land in the mining area.Taking the collapse and reclaimed soil of Haizi coal mine in Huaibei mining area as the research object,this paper explores the law of soil water movement in the study area based on field investigation and experiment;The distribution characteristics of soil nutrient content were tested and analyzed by collecting surface and profile soil samples at different collapse and reclamation depths;Adsorption process is the main means for soil to retain adsorbable nutrient elements.Phosphorus is used as an adsorbable element.At the same time,considering the shortcomings of soil types and nitrogen and potassium as adsorbed elements in the study area,the occurrence forms and adsorption properties of soil phosphorus are analyzed;With the help of indoor soil column simulation test,the influence of different soil column filling materials(soil column filling materials are topsoil,guest soil,fly ash and coal gangue)on the law of soil nutrient loss under rainfall runoff is simulated and explored,in order to provide some guiding significance for the reclamation and ecological restoration of collapsed land in mining area.The main research contents and conclusions of this paper are as follows:(1)By consulting relevant data,the variation characteristics of annual rainfall(December 2020～November 2021)in the study area were obtained,and the water potential sensor was used to monitor the soil moisture of different collapse reclamation depth profiles(0～60cm)for one year.The annual rainfall in the study area reached1039.61 mm,mainly in summer,of which the average rainfall in July was the largest,reaching 407.33 mm,accounting for 39.18% of the annual rainfall.There is a certain correlation between rainfall and soil volume moisture content.The average volume moisture content of different points of surface soil in subsidence area(referred to as area s)is S1 > S2 > S3 > S4,and the average volume moisture content of different points of surface soil in reclamation area(referred to as area R)is R3 > R4 > R2 > R1;With the increase of months,the soil volume moisture content at different points in the study area varies significantly with months.It fluctuates greatly in spring and summer,and fluctuates less in autumn and winter.On the whole,it shows an upward trend,which is mainly related to rainfall and collapse reclamation depth.With the increase of soil depth,the soil volume moisture content at different points shows an upward trend.Among them,the soil volume moisture content at various points in area s changes significantly with soil depth,while the change in area R is not significant.On the whole,the soil volume moisture content of each soil layer in area R is less than that in area s,which is mainly related to the soil type and reclamation method used for reclamation.(2)The distribution characteristics of soil nutrient content were obtained by collecting soil samples from different sections in s area and R area.The soil nutrient content in the study area is mainly concentrated in the surface soil,in which the average content of soil SOM is 14.95g/kg,the average content of TK is 18.21g/kg,the average content of AK is 252.57mg/kg,the average content of TN is 0.73g/kg,the average content of TP is 0.73g/kg,and the average content of AP is 24.48mg/kg;With the increase of soil depth,the change of AK content is significant,showing a change trend of first increasing and then decreasing;The content of other nutrients had no significant difference with the depth of soil layer,and showed a downward trend as a whole.Comparing the nutrient contents of different points in s area and R area,it can be seen that the contents of SOM,AK and TN in different soil layers in s area are higher than those in R area,TP and TK have no significant difference,while the content of AP in R area is higher than that in S area.(3)Taking phosphorus(P)as an example,the occurrence forms and adsorption characteristics of P in S and R regions were studied.The results showed that the total phosphorus of S1,S2,S3,S4,R1,R2,R3 and R4 soil at 8 sampling points in the mining area ranged from 210.30 to 442.74 mg/kg,mainly Ca-P,Al-P and residual P.The total phosphorus content of soil in s area decreases with the increase of soil depth,Fe-P and Ca-P increase with the increase of collapse depth,and Al-P decreases with the increase of collapse depth.The overall adsorption capacity of soil in area R is greater than that in area s.The adsorption range of soil in area R and area s to P is 438.52～1650.82mg/kg and482.33～1366.13mg/kg respectively.(4)Five reclamation modes of 60 cm topsoil,60 cm guest soil,20 cm topsoil + 20 cm guest soil + 20 cm guest soil,20 cm topsoil + 20 cm guest soil + 20 cm coal gangue,20 cm topsoil + 20 cm guest soil + 20 cm fly ash are set to simulate soil columns and simulate the nutrient loss law of each soil column under rainfall runoff.The results show that the leaching concentrations of total potassium,ammonium nitrogen and orthophosphate in different columns and different soil layers have different trends in the leaching process,and the nutrient loss is related to the nature of the soil itself,rainfall and other external environment.The concentrations of total potassium,ammonium nitrogen and orthophosphate decreased with the increase of leaching times,and there was no obvious law between different soil layers of each column.The leaching concentrations of soil potassium and ammonium nitrogen of different filling materials decrease with the increase of leaching times,and the leaching concentration of orthophosphate is far less than that of potassium and ammonium nitrogen,indicating that phosphorus is easy to be adsorbed by soil and fixed in the leaching process.(5)The occurrence forms and adsorption characteristics of phosphorus(P)in different filling materials of simulated column were further studied.The total content of inorganic P in topsoil,guest soil,fly ash and coal gangue is 462.33 mg/kg,338.93 mg/kg,562.28 mg/kg and 174.51 mg/kg respectively.The phosphorus in topsoil,guest soil and coal gangue mainly exists in the form of Ca-P,followed by residual P and Al-P;The adsorption capacity of filling materials for P is as follows: topsoil > guest soil > coal gangue > fly ash,and the adsorption characteristics accord with Langmuir model;Due to multiple leaching of different filling materials in soil column due to fertilization and rainfall,the leaching P is mainly adsorbed as Fe-P and Al-P.Figure [33] Table [15] Reference [104]... |
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