Experimental Study On Solute Migration Characteristics Of Unexplored Karst Slope Under Artificial Simulated Rainfall

The special geological conditions in karst area make the soil and water loss in this area very serious,soil erosion causes a large amount of soil nutrient loss,which results in the destruction of the local ecological environment,which seriously restricts the local agricultural production.In this paper,taking bare slope of karst as research object and lime soil as experimental soil,the characteristics of solute transport and nutrient loss in karst bare slope under different rainfall characteristics,topography,underground pore?crack?gap are studied by artificial simulated rainfall experiment.The main influencing factors of erosion and sediment yield and nutrient loss on karst sloping land were revealed and the corresponding mathematical models were established to provide theoretical basis for the control of non-point source pollution and the prediction of nutrient loss in karst area.The main findings are as follows:?1?The rainfall intensity has a significant positive correlation with the underground runoff and a significant positive correlation with the underground sediment yield.There is a significant negative correlation between slope and underground runoff,and a significant negative correlation between slope and underground sediment yield.There is a positive correlation between underground pore?crack?gap porosity and underground runoff,and a positive correlation between underground sediment yield and underground pore?crack?gap porosity.?2?nitrogen and phosphorus in surface runoff,water soluble organic carbon output concentration with the increase of rainfall intensity increases,the migration rate of the transfer and the overall nutrient and sediment surface in both increased with rainfall intensity increases;migration quantity of surface solute is about 2 times the amount of migration under the solute surface sediment transport capacity is about3 times of the underground,soil solute transport and sediment nutrient transport in surface migration.With the increase of slope surface sediment total nitrogen,total phosphorus,total potassium,total organic carbon increased,groundwater solute migration amount with the increase of slope decreased underground;sediment nutrient migration and slope The rate of underground solute migration generally showed an increasing trend along with the variation of underground pore?crack?gap degree.The total nitrogen,total phosphorus,total potassium,available potassium and soil organic carbon of underground sediment showed an increasing trend with the increase of underground pore fissure.?3?Rainfall intensity The solute migration in surface runoff showed a highly significant positive correlation?P<0.01?,and was significantly positively correlated with total nitrogen,total phosphorus,total potassium,available phosphorus,and soil organic carbon in surface sediments?P<0.01?;slope is positively correlated with surface solute migration,and slope is significantly positively correlated with surface phosphorus migration?P<0.01?,and there is a significant positive correlation between surface hydrolyzable nitrogen migration?P<0.05?.Underground pore?crack?gap is negatively correlated with surface solute migration,and is significantly negatively correlated with surface nitrogen,potassium and water-soluble organic carbon?P<0.01?.?4?Rainfall intensity The amount of solute migration in underground runoff was significantly positively correlated?P<0.01?,and was significantly positively correlated with total nitrogen,total phosphorus,total potassium,and soil organic carbon in the subsurface sediments?P<0.01?.The slope is negatively correlated with the solute migration in underground runoff,and the slope is significantly negatively correlated with the dissolved organic carbon of groundwater?P<0.05?;the slope is positively correlated with the amount of hydrolyzed nitrogen in surface sediment?P<0.05?,the slope has a significant positive correlation with the effective phosphorus migration in the subsurface sediment?P<0.05?.There was a significant negative correlation between underground porosity?fracture?gaps and total nitrogen,total phosphorus,total potassium,and soil organic carbon?P<0.01?,and a significant negative correlation with surface available potassium?P<0.05?.The underground hole?crack?porosity and underground sediment total nitrogen,total phosphorus,total potassium and soil organic carbon was positively correlated the relationship between?P<0.01?;a positive correlation with the underground hydrolysis of nitrogen.?5?The linear relationship between rainfall intensity and solute transport is better and the fitting degree is higher.The fitting equation between slope and total phosphorus in surface sediment is Y=211.17+28.996X-2.67X²+0.064X³?R²=0.794?,the fitting equation between slope gradient and water soluble organic carbon in underground sediment is Y=479.975X^-0.44?R²=0.765?,and the fitting equation between slope and total phosphorus in surface sediment is Y=347.886-39.195X+3.321X²-0.071X³?R²=0.833?.The fitting equation between slope and available phosphorus in underground sediment is Y=44.01-1.574X+0.06X²?R²=0.812?.The fitting equation between underground pore?crack?porosity and surface sediment total nitrogen is the best,and the fitting equation is Y=69.231X^-1.208?R²=0.825?.In general,the effect of rainfall intensity and underground pore?fissure?porosity is more significant,followed by slope.