Research on Migration and Degradation of Nitrogen Based on 15N Trace Technique in Semi-Aerobic Landfill

Simulated semi-aerobic landfill equipment and anaerobic landfill equipment were constructed. In-situ trace and contrast experiment based on the ¹⁵N isotope technique was developed when the landfills were stably working for 12 months. Each equipment was respectively added with 4 g standard ¹⁵NH₄Cl tracer, and the leachate samples at the spaces and bottom of the equipments were taken, to detect ¿(NH₄ ⁺-N), ¿(TN), the abundance of ¹⁵N in leachate TN, and the abundance of ¹⁵N in leachate NH₄ ⁺-N. The dynamic variation characteristics, migration rules and degradation principles of leachate nitrogen during the semi-aerobic landfill process were researched. Results showed that, most of ¹⁵NH₄CL solution rapidly went through the upper layer of landfill to the middle layer, lower layer and underlayer for eluviation, migration and accumulation after the tracer was added; compared with point positions far from the airway, the point positions near the airway in the middle layer of the semi-aerobic treatment reached nitrogen's degradation balance and stability more rapidly, and ¿(NH₄ ⁺-N) in the lower layer was maintained at a higher level; the migration and conversion of NH₄ ⁺-N in leachate were the main contributory factors to the change of total nitrogen content at the bottom area; compared with anaerobic landfill structure, semi-aerobic treatment could earlierly reach a migration balance and a stable degradation status of nitrogenous pollutant of the system.