Laboratory study on nitrate removal and nitrous oxide emission in intact soil columns collected from nitrogenous loaded riparian wetland, Northeast China

Abstract

Nitrate pollution of surface and groundwater systems is a major problem globally. For some time now wetlands have been considered potential systems for improving water quality. Nitrate dissolved in water moving through wetlands can be removed through different processes, such as the denitrification process, where heterotrophic facultative anaerobic bacteria use for respiration, leading to the production of nitrogen (N 2 ) and nitrous oxide (N 2 O) gases. Nitrate removal and emission of N 2 O in wetlands can vary spatially, depending on factors such as vegetation, hydrology and soil structure. This study intended to provide a better understanding of the spatial variability and processes involved in removal and emission of N 2 O in riparian wetland soils. We designed a laboratory experiment simulating surface water flow through soil columns collected from different sites dominated by different plant species within a wetland. Water and gas samples for and N 2 O analyses were collected every 5 days for a period of 30 days. The results revealed significant removal of in all the soil columns, supporting the role of riparian wetland soils in removing nitrogen from surface runoff. Nitrate removal at 0 and 10cm depths in sites dominated by Phragmites australis and Carex schnimdtii was significantly higher than in the site dominated by Calamagrostis epigeio . Nitrous oxide emissions varied spatially and temporally with negative flux observed in sites dominated by P . australis and C . schnimdtii . These results reveal that in addition to the ability of wetlands to remove , some sites within wetlands are also capable of consuming N 2 O, hence mitigating not only agricultural nitrate pollution but also climate change.

Copper availability governs nitrous oxide accumulation in wetland soils and stream sediments

“…Denitrification, an anoxic process in which nitrate (NO3 -) is reduced to N2, is a key biogeochemical process that regulates the amount of N2O released from both terrestrial and aquatic ecosystems into the atmosphere (Makowski, 2019;Tian et al, 2020;Martinez-Espinosa et al, 2021). Natural aquatic systems, especially those that display vertical redox gradients, such as wetlands and hyporheic zones in streams, are active sites for denitrification (Merill and Tonjes, 2014;Nag et al, 2017;Mwagona et al, 2019;Martinez-Espinosa et al, 2021). Oxic regions above redox transition zones favor the oxidation of ammonia (NH3) to NO3via nitrification, and the anoxic regions below redox transition zones promote denitrification with NO3being reduced to nitrite (NO2 -), nitric oxide (NO), N2O, and N2.…”

Greenhouse gas emissions (CO2, CH4 and N2O) in saline-alkaline systems of the Pantanal of Nhecolândia/MS

“…Consequently, NO3limitation may be one of the factors responsible for N2O consumption during denitrification and nitrification in the crystalline lake (07SR) (Audet et al, 2014;Mwagona et al, 2019). Plants can compete for the nitrogen source, so an abundance of macrophytes can promote changes in nitrogen-related processes and increase N2O consumption (Mwagona et al, 2019;Mander et al, 2021).…”