Nitrous oxide, dinitrogen and methane emission in a subsurface flow constructed wetland

Abstract

N2O, N2 and CH4 fluxes were measured from a horizontal subsurface flow (HSSF) constructed wetland (CW) for wastewater treatment in Estonia. The closed chamber method was used in the field and the He-O method (intact soil core analyses) in the lab throughout the period from October 2001 to June 2002. The average flux of N2O-N, N2-N and CH4-C from various microsites ranged from 0.1 to 59, 4.1 to 1,458 and -0.04 to 2,094 mg m(-2) d(-1), respectively. A significantly higher flux of N2O was found in chambers installed above the inlet pipes, while the methane flux was higher in the inlet part of the bed with wetter conditions. The groundwater table significantly correlates with gas emission rates of all the gases studied; N2 emission was enhanced by higher temperature of wastewater. PO4(3-) and NH4+ content significantly enhanced, and NO2- and NO3- content inhibited, both N2O and CH4 fluxes. NH4+ showed a negative correlation with N2 flux. Nitrification and denitrification are the main processes of the N removal in the CW covering 42.9%. The specific global warming potential was highest in the wet bed and lowest in the dry bed with lowered water table (32 and 9 g CO2 pe(-1) d(-1), respectively).

Water quality and emission rates of greenhouse gases in a treatment reedbed

“…Values of N 2 O-N emission from our study are significantly lower than the values observed in various CWs for wastewater treatment (up to 17,000 μg N 2 O m -2 h -1 ; [13,14,16,17,72]), lower than those reported from drained boreal Grasslands [76] and wetlands with altered water regime [77] show higher N 2 O-N emission (up to 184 μg N 2 O m -2 h -1 ). Forests emit low amounts of nitrous oxide (from low consumption up to 35 μg N 2 O m -2 h -1 ; [78,79]), whereas deciduous forests tend to emit more than coniferous forests [80].…”

“…Dinitrogen (N 2 ) emission was measured using the He-O method [17,19,33,34]. Intact soil cores (diameter 6.8 cm and height 6 cm) for analysis using the H-O method were taken from the topsoil (0-10 cm) under the gas sampler (closed chamber) sites after gas sampling was completed.…”

“…Many species of emergent macrophytes such as Phragmites australis possess a convective flow mechanism; oxygen is transported to the roots, and gaseous microbial by-products are emitted into the atmosphere from plant roots [12]. Constructed and (semi-) natural wetlands are claimed to be effective water purifiers that have lower maintenance costs than conventional systems [4], but at the same time wetlands can contribute to global warming by emitting three important greenhouse gases (GHG): carbon dioxide (CO 2 ), methane (CH 4 ) and nitrous oxide (N 2 O) [13][14][15][16][17][18][19][20][21][22][23][24]. Nevertheless, we have not found in the literature data on GHG fluxes in reedbeds or other (semi-)natural wetland ecosystems used for the long-term after-treatment of municipal wastewater.…”

Nitrogen mineralization and gaseous nitrogen losses from waterlogged and drained organic soils in a black alder (<i>Alnus glutinosa</i> (L.) Gaertn.) forest

“…This requires the presence of efficient electron acceptors (e.g., NO − 3 ) to prevent the reduction of N 2 O to N 2 (Bremner and Blackmer, 1981;Speir et al, 1995;Jungkunst et al, 2004). Due mainly to analytical difficulties in the determination of microbially produced N 2 , to date the denitrification potential from waterlogged peat soils has rarely been estimated (Watts and Seitzinger, 2000;Mander et al, 2003;Teiter and Mander, 2005;Wray and Bayley, 2007;Roobroeck et al, 2010;Soosaar et al, 2011;Uri et al, 2011). The substitution of ambient N 2 by Helium (He) in laboratory studies possibly represents the most reliable method for the direct and simultaneous determination of N 2 O and N 2 exchange rates (Butterbach-Bahl et al, 2002;Roobroeck et al, 2010;Butterbach-Bahl et al, 2013).…”

“…For measurements of N 2 , N 2 O, CO 2 and CH 4 fluxes, we applied the helium-oxygen (He-O) method (Butterbach-Bahl et al, 2002;Mander et al, 2003;Roobroeck et al, 2010;Uri et al, 2011) using four different incubation temperatures (0, 5, 15 and 25 • C). Five replications per site and moisture content were simultaneously placed in special gas-tight incubation vessels inside a climate chamber.…”