| The arid region in the northwest has the characteristics of dry climate,lack of water resources,and the reconstructed soils of coal gangue mountain has poor structural and poor water and fertilizer retention properties,which limits the ecological recovery process of the mining area.In order to find suitable proportions of modifying agent in reconstructing soil of mining areas,the physicochemical properties and enzyme activities of coal gangue matrix mixed with coal gangue and raw soil of Lingwu mining area of Ningxia under the mixed application of different proportion of biochar(1%,2% and 5%)and polyacrylamide(PAM)(0.01%,0.02% and 0.05%)were studied by using a simulated soil column method and culture experiment.The results indicated that:(1)The soil bulk density of the coal gangue matrix under mixed application of biochar and PAM was significantly reduced,and the total porosity and capillary porosity of the coal gangue matrix were higher than the control group;With the rate of biochar and PAM addition increased,the saturated water content,capillary moisture capacity and field moisture capacity of matrix increased;Compared to the control group,the water cumulative infiltration of coal gangue matrix under the mixed addition of 5% biochar and 0.01% PAM decreased significantly by 55.10%,which was conducive to water retention;The water cumulative evaporation of coal gangue matrix under the mixed addition of 2% biochar and 0.05% PAM decreased significantly by 37.26% when comparing with the control group,which effectively suppresses the evaporation of water.(2)Mixed application of biochar and PAM could lower the p H of coal gangue matrix and increased the EC value of coal gangue matrix;Compared with the control group,the total organic carbon content of coal gangue matrix under the mixed addition of 5% biochar and 0.01% PAM increased by 50.46%,and active organic carbon content increased with the increase of the addition ratio of biochar and PAM;There was no significant difference in content of total nitrogen and dissolved total nitrogen between the treatments of mixed addition of biochar and PAM,but both were higher than those of the control group;The content of available phosphorus and available potassium under the treatment with 5% biochar were significantly higher than those of the control group;Cluster analysis showed that the difference in the chemical properties of the matrix between the treatments with the same application rate of biochar and different application rates of PAM was not significant.(3)The mixed application of different amounts of biochar and PAM could improve the dissolved organic carbon,total nitrogen,available phosphorus,easily oxidizable carbon and total organic carbon of coal gangue matrix,thereby increasing the soil enzyme activity of coal gangue matrix.Among them,compared to the control group,the activities of ?-glucosidase,N-acetyl-glucosaminidase and alkaline phosphatase of coal gangue matrix under the mixed addition of 5% biochar and 0.05% PAM increased by 107.23%,233.77% and 108.26%,respectively;The activities of ?-glucosidase,leucine aminopeptidase and glycine aminopeptidase of coal gangue matrix under the mixed application of 5% biochar and 0.02% PAM increased by 111.02%,51.96% and 260.46% when comparing with the control group,respectively;And the activities of cellobiohydrolase of coal gangue matrix under the mixed application of 2% biochar and 0.05% PAM increased by 86.84% when comparing with the control group.In summary,the mixed application of biochar and PAM could improve the quality of coal gangue matrix.The mixed application of 5% biochar and 0.02% PAM could significantly improve the porosity of the matrix,reduced water infiltration and evaporation,and improved the water storage performance;It also has a significant effect on improving the content of matrix organic carbon nitrogen,available phosphorus,available potassium and enzyme activity.The research results have a certain guiding role for the ecological restoration of reconstructed soil in the mining area. |
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