Spatial and Seasonal Variation of Dissolved Nitrous Oxide in Wetland Groundwater

Abstract

Understanding the spatial and temporal pattern of dissolved nitrous oxide (N 2 O) in groundwater is essential to estimate the N 2 O emissions from groundwater to the unsaturated zone and to the atmosphere. In order to study the spatial distribution and seasonal change of dissolved N 2 O in wetland, a headwater wetland in Ichikawa, Chiba Prefecture, Japan, was chosen. Variations of nitrate (NO 3-), dissolved N 2 O and δ 15 N-NO 3 indicated that the dissolved N 2 O in the groundwater of study wetland consists of two parts, one from denitrification within the wetland, and another from nitrification at upland. Principal component analysis (PCA) was used to assess the shallow groundwater parameters in the wetland. And t-test was conducted to find statistically significant differences of the variables between the ASW and NS, warm season and cool season. The concentrations of dissolved N 2 O increased from the upland to the zone of adjacent area between slope and wetland (ASW) and then decreased at the zone near the stream (NS). In sight of dissolved N 2 O associated nitrogen migration, groundwater in the study area can be divided into three stages: upland as the stage 1, ASW as the stage 2, and NS as the stage 3. Higher temperature results in higher denitrification rate, lower dissolved oxygen (DO) and oxidation-redox potential (ORP), yielding higher concentration of N 2 O in the warm season. Therefore, the seasonal change of dissolved N 2 O in study wetland can be mainly interpreted by the variation of temperatures of groundwater.

Dissolved nitrous oxide (N2 O) dynamics in agricultural field drains and headwater streams in an intensive arable catchment

“…Compared to the field drains, stream samples contained significantly ( p < .05) lower N 2 O concentrations, a consequence of N 2 O being rapidly degassed from field drain water once it has come into contact with the atmosphere upon discharge into the stream. This degassing of supersaturated N 2 O from subsurface drainage and groundwater after discharge to surface water has also been reported in previous studies (e.g., Bowden & Bormann, ; Reay, Smith, & Edwards, ; Minamikawa, Hayakawa, Nishimura, Akiyama, & Yagi, ; Li et al, ). For comparison, in a 13‐month study at nine sites on the eutrophic San Joaquin River, California, Hinshaw and Dahlgren () reported a mean dissolved N 2 O concentration in surface waters of 0.91 μg N L −1 , whilst Outram and Hiscock () recorded a mean N 2 O concentration of 1.7 μg N L −1 in the lowland River Thurne, eastern England.…”

Isotopic composition of nitrogen species in groundwater under agricultural areas: A review

“…In general, it appears that the final δ 15 N of NO 3 − derived via nitrification from manure-N would be more positive than that from fertilizer-N (Choi et al, 2003). The influence of the nitrification on the δ 15 N-NO 3 − of groundwater was detected in the Sichuan Basin (China) (Li et al, 2007), Ichikawa city (Japan) (Li et al, 2014a(Li et al, , 2014b, shallow groundwater in Wexford (Ireland) (Baily et al, 2011), in the Cretaceous Chalk aquifer in Cambridgeshire and Norfolk, UK (Hiscock et al, 2003) and in the hydrogeological formation in Zunyi (China) (Li et al, 2010).…”

“…Consequently, it can be expected that the isotopic composition of N species exhibits pronounced seasonal patterns (Bedard-Haughn et al, 2003). The optimal temperature range for mineralization is 25-40°, for nitrification -15-35°and for anammox -30-40° (Li et al, 2014a(Li et al, , 2014bGuntiñas et al, 2012;Shammas, 1986;Jin et al, 2012).…”

Effects of Soil Temperature, Flooding, and Organic Matter Addition on N2O Emissions from a Soil of Hongze Lake Wetland, China

“…Soil temperature directly impacts production and consumption of N 2 O though microorganism's activity, soil aeration, substrate availability, and redistribution. Soil moisture is a key determinant of the microbial processes [ 13 ]. Organic matter fractions have been also found to enhance N 2 O emissions as they supply substrates for nitrification and denitrification and augment microbial O 2 consumption [ 14 ].…”