Effect Of Biochar And Nitrogen,Biological Activity,and Stability Aggregates In Post-Mining Areas

Coal mining has caused disturbance of soil layer,soil erosion and the decrease of soil nutrient.At the same time,thepost-mining land is also a huge source of carbon emission.Biochar is a carbon rich material with dense porosity,high specific surface area and high chemical stability,it is important for improving soil fertility,stabilizing soil carbon pool and improving soil structure.In this study,effects of biochar with additions of 0%(CK),1%(BC1),3%(BC2),5%(BC3)on soil carbon and nitrogen components and soil enzyme activity were investigated by lab experiments.Soil samples were fractionated into different aggregate sizes using the wet sieving method,and then the contents of soil carbon and nitrogen components and enzyme activity in different aggregates were measured.The main results are as follows:1.Biochar addition significantly increased contents of aggregates>2 mm and2?0.25 mm,but significantly reduced contents of aggregates<0.053 mm.Biochar significantly increased contents of>0.25 mm aggregates(R_0.25),the mean weight diameter(MWD)and the geometric mean diameter(GMD).This indicated that the application of biochar to the soil increased the stability of the soil structure.The effect of different treatment on the stability index of soil aggregates was generally expressed as BC3>BC2>BC1>CK.2.Biochar addition significantly increased the activities of invertase,urease and catalase,while significantly decreased phosphatase activity.Biochar addition increased the activities of invertase,urease,and catalase in different aggregates sizes,and inhibited the activity of phosphatase in the aggregates.The enzyme activity in aggregates increased,then decreased with the increase of soil aggregates sizes under different different processing methods.Biochar addition did not change the aggregates size distribution of enzyme activity.The effect of different treatment on the invertase,urease and catalase activity of soil were generally expressed as BC3>BC2>BC1>CK,and the effects on phosphatase was BC3<BC2<BC1<CK.3.Biochar addition significantly increased the contents of soil organic carbon(SOC),total nitrogen(N),and easily oxidizable organic carbon(EOC)in the post-mining area.At the same time,the biochar addition reduced EOC/SOC in soil.Biochar addition also increased the contents of SOC,N,and EOC in different aggregates sizes.Biochar significantly increased the SOC and N contribution of soil aggregates>2 mm and 2?0.25 mm,while decreased the soil aggregates contribution of 0.25?0.053 mm and<0.053 mm.4.Correlation analysis showed that there were significant correlations between the different types of enzyme activities and SOC and N contents.Soil D_0.25,MWD and GMD all showed significant correlations with soil SOC,N,EOC and different enzyme activities.The stability of soil structure was affected by soil enzyme activity and soil carbon and nitrogen components.Organic carbon was the primary factor affecting the stability of soil aggregates.In sum,bochar addition significantly increased the carbon and nitrogen components and enzyme activity in the soil and soil aggregates of the mining area,and increased the stability of the soil structure.The results suggested that 5%biochar addition is the most effective method among all the experiments to improve the quality of the post-mining soil.