Effects Of Nano-Biochar On Soil-Water Loss And Nutrient Transport Characteristics On Loess Slope

Based on the serious soil-water and nutrient loss in the Loess area as the background,this paper studied the research progress of nano-biochar at home and abroad,Established the purpose of applying soil modifier to improve soil structure environment on loess slope and controlling soil and water loss.In this paper,we adopted laboratory soil structure experiment,simulated rainfall experiment and combined with theoretical analysis to study regulation mechanism of nano-biochar on soil-water and nutrient loss along Loess slope land.Furthermore,we proposed mathematical models to describe the transport of overland flow and nutrients under nano-biochar,and also provided the way of parameters estimation.The obtained results as follows:?1?Nano-biochar could effectively change the distribution of soil pore structure and the number of water stable aggregates.Applied nano-biochar reduced the soil porosity in the 0.01⁰.05mm³interval and increased the proportion of the macropores?>0.05mm³?in the pore structure.Nano-biochar had a significant reduction in soil infiltration,and nano-biochar contents had a positive correlation with the inhibition of water infiltration.Applied nano-biochar could change the relationship between soil water content and soil suction,and improved the water suction of the whole soil.With the nano-biochar content increased,the soil water suction would be greater,the soil moisture absorption capacity would be stronger.?2?Nano-biochar had s significant effect on the initial runoff time of rainfall.The cumulative runoff and sediment decreased with the nano-biochar content increased,and nano-biochar had obvious effect on reducing sediment.With the increase of nano-biochar content,the average water depth of runoff gradually increased,however the Reynolds number and Froude number gradually decreased.The analysis between the average flow power and the sediment content showed that the slope sediment decreased with the nano-biochar content increased in the early stage of runoff.Through the comparative analysis of the water content in the profiles,the nano-biochar mixed layer increased the water content of the soil deep section,further increased the capacity of soil to accommodate rainfall and rapid infiltration.The Hydrus-3D model could be applied to the process of soil moisture movement in the simulated rainfall,and the fitting effect was good.There was a significant relationship between the nano-biochar contents with the hydraulic parameters in the nano-biochar layer.The intake suction(?^-1),shape coefficient?n?and saturated water conductivity?K_s?had a linear relationship with the nano-biochar contents.With the increase of nano-biochar contents,the hydraulic parameters in the applied nano-biochar treatment had moderate variation.The effect of nano-biochar on soil water properties was greater than that of soil structure during soil water movement;?3?The cumulative nitrate loss in runoff and sediment had a negative correlation with nano-biochar contents.After simulated rainfall,the distribution of nitrate in the section showed a single peak,and nano-biochar could promote the migration of nitrate to the deep layer.The equivalent mixed depth model based on power function had the better fitting effect on the nitrate loss of runoff process,among the relationship between the mixing depth with the nano-biochar contents was a power function.With the nano-biochar contents increased,mixing depth h_m?h_m?and H₀were decreased.That is,soil depth whcih involved in runoff nutrient loss was reducing.