10:15 AM - 10:30 AM
[AHW27-06] Understanding Nitrogen Cycling and Nitrous Oxide Emission in Constructed Wetlands: A Mesocosm Study
Keywords:nitrogen cycle, constructed wetland, 15N stable isotope tracer, mesocosm
Constructed wetlands are increasingly recognized as an effective wastewater treatment method, with microbial nitrogen cycling playing a crucial role in pollutant removal. However, the environmental factors regulating nitrogen transformation processes remain unclear, particularly under varying nutrient loads.
This study investigates nitrogen cycling dynamics in a controlled mesocosm experiment conducted in a greenhouse, focusing on the effects of different ammonia-nitrogen influent concentrations. Using 18 mesocosms planted with common reed (Phragmites australis), artificial wastewater with three different ammonium levels (2.2, 22.0, and 100.0 mg N L-1) was introduced to simulate different nutrient conditions, with a hydraulic retention time (HRT) of five days. Nitrous oxide (N2O) flux was monitored using a trace gas analyzer to assess the impact of nutrient levels on greenhouse gas emissions.
Results indicate that higher ammonia-nitrogen concentrations significantly increase N2O emissions, with emission fluxes ranging from 6.98 to 350 μg m-2 hr-1 in the highest concentration group. Statistical analyses show that N2O emissions are positively correlated with temperature and salinity but negatively correlated with pH, suggesting that microbial nitrification and denitrification dynamics are influenced by these environmental factors.
To further elucidate nitrogen transformation pathways, a complementary 15N tracer experiment is underway, aiming to quantify the relative contributions of nitrification and denitrification to total nitrogen removal. These findings will enhance our understanding of nitrogen cycling mechanisms in constructed wetlands and provide insights for optimizing wastewater treatment strategies to balance pollutant removal efficiency with greenhouse gas mitigation.
This study investigates nitrogen cycling dynamics in a controlled mesocosm experiment conducted in a greenhouse, focusing on the effects of different ammonia-nitrogen influent concentrations. Using 18 mesocosms planted with common reed (Phragmites australis), artificial wastewater with three different ammonium levels (2.2, 22.0, and 100.0 mg N L-1) was introduced to simulate different nutrient conditions, with a hydraulic retention time (HRT) of five days. Nitrous oxide (N2O) flux was monitored using a trace gas analyzer to assess the impact of nutrient levels on greenhouse gas emissions.
Results indicate that higher ammonia-nitrogen concentrations significantly increase N2O emissions, with emission fluxes ranging from 6.98 to 350 μg m-2 hr-1 in the highest concentration group. Statistical analyses show that N2O emissions are positively correlated with temperature and salinity but negatively correlated with pH, suggesting that microbial nitrification and denitrification dynamics are influenced by these environmental factors.
To further elucidate nitrogen transformation pathways, a complementary 15N tracer experiment is underway, aiming to quantify the relative contributions of nitrification and denitrification to total nitrogen removal. These findings will enhance our understanding of nitrogen cycling mechanisms in constructed wetlands and provide insights for optimizing wastewater treatment strategies to balance pollutant removal efficiency with greenhouse gas mitigation.