Experimental Study On Adsorption Of Total Nitrogen, Ammonium Nitrogen And Nitrate Nitrogen From Biogas Slurry In Unsaturated Homogeneous Soil

With the optimal adjustment of the structure of rural energy, biogas engineering is developing rapidly, meanwhile it will produce a large amount of biogas slurry, if these biogas slurry will not be rational utilization, it must be harmful to the soil environment and the groundwater environment, however, farmland utilization is one of the most easy to implement and effective solutions. Using the normal application of biogas slurry as the research object, Through one-dimensional biogas slurry adsorption characteristic experiment with unsaturated homogeneous soil column in the condition of constant room temperature was conducted in order to analyze total nitrogen, ammonium nitrogen and nitrate nitrogen of biogas slurry in unsaturated homogeneous soil in migration law, and explore the effects of different factors on the migration law, at the same time, CXTFIT2.0 software is used to solve the migration parameters. In order to biogas slurry instead of a variety of organic fertilizer, and combined with the integrated management of water and fertilizer, to provide certain scientific basis for improving the soil environment.（1）All of the changed curves of percolate conductivity showed this phenomenon, which first increased and then decreased and the last gradually leveled off. The curves of percolate conductivity in soil bulk density of 1.35g·cm-3 was significantly shifted to the right than soil bulk density of 1.30g·cm-3, the peak point of percolate conductivity in soil bulk density of 1.35g·cm-3 was less than that in soil bulk density of 1.30g·cm-3 under all treatments; the deviations between the percolates conductivity of peak point and that after peak point increased with biogas slurry concentration increase.（2）Total nitrogen of biogas slurry adsorption curve showed the initial stage of percolate relative concentrations were greater, then sharply decline and then slowly rose finally flattening under the condition of different treatment. The initial stage the percolate relative concentration in soil bulk density of 1.30g·cm-3decreased significantly than that in soil bulk density of 1.35g·cm-3,and The time required for the adsorption to reach saturation was 1.35 g·cm^-3 larger than1.30g·cm-3.（3） Biogas slurry in ammonium nitrogen and nitrate nitrogen adsorption curve showed: percolate concentrations began was larger, then sharply decreased and then slowly decreased the final leveling off under the condition of different treatment. with the soil bulk density increased, the content of nitrate nitrogen and ammonium nitrogen assumed 1.35 g·cm^-3>1.30 g·cm^-3 when biogas slurry start stage to adsorption equilibrium.（4）With the increase of biogas slurry concentration, the adsorption curves of total nitrogen, nitrate nitrogen and ammonium nitrogen gradually moved towards downward and right, total nitrogen adsorption turning point corresponding time increases with the increase of biogas slurry concentration and density. the percolate relative concentration in（C/C0） gradually decreased from start to adsorption equilibrium. The relative concentration of 4cm head exudates was higher than that of 2cm head, but The time required for the adsorption to reach saturation was 2cm head is greater than 4cm.（5） All of the nitrate nitrogen content less than 10 mg·l-1,except for 1.35 g·cm^-3, 1:1concentration and 4cm water head treatment which nitrate nitrogen content is12.62 mg·l-1 beyond the national standard（10mg·l-1） under the conditions of different treatments when nitrate nitrogen adsorption equilibrium in soil.（6） with the soil column height increased, the content of total nitrogen, nitrate nitrogen and ammonium nitrogen assumed the nitrogen content in the percolate of 20 cm soil column was the least,but the amount of nitrogen intercepted in the soil was the highest, 10 cm soil column was maximum, the amount of nitrogen intercepted in the soil was the lowest when biogas slurry start stage to adsorption equilibrium..（7） Using CXTFIT2.0 to simulate the slurry of nitrate nitrogen and ammonium nitrogen adsorption curve with measuring adsorption curve is in good consistency. With the increase of biogas slurry concentration, the average prove-water velocity（V）and hydrodynamic dispersion coefficient（D） decreased. the average prove-water velocity of 2cm heads and hydrodynamic dispersion coefficient less than 4cm under the different heads, with the soil bulk density increased the average prove-water velocity assumed1.35g·cm-3<1.30g·cm-3,but hydrodynamic dispersion coefficient assumed 1.35 g·cm^-3>1.30 g·cm^-3.