Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers?

Well, Reinhard; Eschenbach, Wolfram; Flessa, Heinz; Heide, C. von der; Weymann, Daniel

doi:10.1016/j.gca.2012.04.045

Cited by 85 publications

(129 citation statements)

References 75 publications

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“…There were similar covariance results from N 2 O reduction to N 2 during denitrification (JinuntuyaNortman et al, 2008;Well and Flessa, 2009 (Figure 2) was within the slope range reported for residual N 2 O after partial reduction to N 2 (Well et al, 2012). This similarity might further complicate the distinction of N 2 O from nitrification and denitrification in environments.…”

Section: Aoa Strainssupporting

confidence: 79%

Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Well²,

et al. 2013

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N 2 O gas is involved in global warming and ozone depletion. The major sources of N 2 O are soil microbial processes. Anthropogenic inputs into the nitrogen cycle have exacerbated these microbial processes, including nitrification. Ammonia-oxidizing archaea (AOA) are major members of the pool of soil ammonia-oxidizing microorganisms. This study investigated the isotopic signatures of N 2 O produced by soil AOA and associated N 2 O production processes. All five AOA strains (I.1a, I.1a-associated and I.1b clades of Thaumarchaeota) from soil produced N 2 O and their yields were comparable to those of ammonia-oxidizing bacteria (AOB). The levels of site preference (SP), d 15 N bulk and d 18 O -N 2 O of soil AOA strains were 13-30%, À 13 to À 35% and 22-36%, respectively, and strains MY1-3 and other soil AOA strains had distinct isotopic signatures. A 15 N-NH 4 þ -labeling experiment indicated that N 2 O originated from two different production pathways (that is, ammonia oxidation and nitrifier denitrification), which suggests that the isotopic signatures of N 2 O from AOA may be attributable to the relative contributions of these two processes. The highest N 2 O production yield and lowest site preference of acidophilic strain CS may be related to enhanced nitrifier denitrification for detoxifying nitrite. Previously, it was not possible to detect N 2 O from soil AOA because of similarities between its isotopic signatures and those from AOB. Given the predominance of AOA over AOB in most soils, a significant proportion of the total N 2 O emissions from soil nitrification may be attributable to AOA.

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Section: Aoa Strainssupporting

confidence: 79%

Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Well²,

et al. 2013

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“…Correspondingly, the ratio of ε 18 :ε SP in this study is smaller than 1, which has only been observed in one study looking at reduction in soils (K€ oster et al, 2013a) (see Table S2). A potential explanation for this is oxygen isotope exchange during the formation of N 2 O, as observed in a number of studies (Casciotti et al, 2002;Kool et al, 2007Kool et al, , 2009Well et al, 2012); although a 'normal' slope of 1.1e1.2 was seen by Well et al (2012) following extensive O isotope exchange during N 2 O Fig. 2.…”

Section: Isotopic Composition Of N 2 O Produced Under Baseline Conditmentioning

confidence: 92%

Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor

et al. 2015

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Nitrous oxide (N2O) production pathways in a single stage, continuously fed partial nitritation-anammox reactor were investigated using online isotopic analysis of offgas N2O with quantum cascade laser absorption spectroscopy (QCLAS). N2O emissions increased when reactor operating conditions were not optimal, for example, high dissolved oxygen concentration. SP measurements indicated that the increase in N2O was due to enhanced nitrifier denitrification, generally related to nitrite build-up in the reactor. The results of this study confirm that process control via online N2O monitoring is an ideal method to detect imbalances in reactor operation and regulate aeration, to ensure optimal reactor conditions and minimise N2O emissions. Under normal operating conditions, the N2O isotopic site preference (SP) was much higher than expected - up to 40‰ - which could not be explained within the current understanding of N2O production pathways. Various targeted experiments were conducted to investigate the characteristics of N2O formation in the reactor. The high SP measurements during both normal operating and experimental conditions could potentially be explained by a number of hypotheses: i) unexpectedly strong heterotrophic N2O reduction, ii) unknown inorganic or anammox-associated N2O production pathway, iii) previous underestimation of SP fractionation during N2O production from NH2OH, or strong variations in SP from this pathway depending on reactor conditions. The second hypothesis - an unknown or incompletely characterised production pathway - was most consistent with results, however the other possibilities cannot be discounted. Further experiments are needed to distinguish between these hypotheses and fully resolve N2O production pathways in PN-anammox systems.

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“…18−26 A better understanding of the processes is, however, required in order to improve mitigation strategies. 23,27 Denitrification is considered the most important reaction for NO 3 − remediation in aquifers. This process occurs in O 2 depleted layers with available electron donors.…”

Section: ■ Introductionmentioning

confidence: 99%

“…33 O 19,20,38 and clear correlation between these signatures have been shown to be indicative for denitrification with N 2 as main product. 23 Especially, isotopologue-based data on the relative contribution of the saturated and unsaturated zones to total fluxes and on lateral N 2 O fluxes with groundwater flow to open water bodies are provided by very few studies. 23 The main objective of our study is to compare two differently loaded riparian alder stands in terms of gaseous N fluxes from soil and N turnover in the near-surface groundwater.…”

Section: ■ Introductionmentioning

confidence: 99%

“…23 Especially, isotopologue-based data on the relative contribution of the saturated and unsaturated zones to total fluxes and on lateral N 2 O fluxes with groundwater flow to open water bodies are provided by very few studies. 23 The main objective of our study is to compare two differently loaded riparian alder stands in terms of gaseous N fluxes from soil and N turnover in the near-surface groundwater. For that purpose we did (1) measure N 2 O and N 2 emission using closed chamber and He−O incubation techniques, respectively; (2) investigate N 2 O accumulation in shallow groundwater in order to estimate the riparian forest's potential to emit N 2 O into the atmosphere via the lateral convective pathway; (3) compare N 2 O accumulation in groundwater to N 2 from denitrification in order to reveal the dynamics of that process; (4) discuss sources of N 2 O using stable isotope signatures of N 2 O.…”

Section: ■ Introductionmentioning

confidence: 99%

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Isotopologue Ratios of N₂O and N₂ Measurements Underpin the Importance of Denitrification in Differently N-Loaded Riparian Alder Forests

Mander

Well²,

Weymann

et al. 2014

Environ. Sci. Technol.

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Known as biogeochemical hotspots in landscapes, riparian buffer zones exhibit considerable potential concerning mitigation of groundwater contaminants such as nitrate, but may in return enhance the risk for indirect N2O emission. Here we aim to assess and to compare two riparian gray alder forests in terms of gaseous N2O and N2 fluxes and dissolved N2O, N2, and NO3(-) in the near-surface groundwater. We further determine for the first time isotopologue ratios of N2O dissolved in the riparian groundwater in order to support our assumption that it mainly originated from denitrification. The study sites, both situated in Estonia, northeastern Europe, receive contrasting N loads from adjacent uphill arable land. Whereas N2O emissions were rather small at both sites, average gaseous N2-to-N2O ratios inferred from closed-chamber measurements and He-O laboratory incubations were almost four times smaller for the heavily loaded site. In contrast, groundwater parameters were less variable among sites and between landscape positions. Campaign-based average (15)N site preferences of N2O (SP) in riparian groundwater ranged between 11 and 44 ‰. Besides the strong prevalence of N2 emission over N2O fluxes and the correlation pattern between isotopologue and water quality data, this comparatively large range highlights the importance of denitrification and N2O reduction in both riparian gray alder stands.

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Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers?

Cited by 85 publications

References 75 publications

Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor

Isotopologue Ratios of N₂O and N₂ Measurements Underpin the Importance of Denitrification in Differently N-Loaded Riparian Alder Forests

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Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers?

Cited by 85 publications

References 75 publications

Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Isotopic signatures of N2O produced by ammonia-oxidizing archaea from soils

Isotopic evidence for nitrous oxide production pathways in a partial nitritation-anammox reactor

Isotopologue Ratios of N2O and N2 Measurements Underpin the Importance of Denitrification in Differently N-Loaded Riparian Alder Forests

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Isotopologue Ratios of N₂O and N₂ Measurements Underpin the Importance of Denitrification in Differently N-Loaded Riparian Alder Forests