guest ::
| Home > Publications database > Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers? |
| Home > Publications database > Are dual isotope and isotopomer ratios of N2O useful indicators for N2O turnover during denitrification in nitrate-contaminated aquifers? |
| Journal Article | PreJuSER-22329 |
; ; ; ;
2012
Elsevier
New York, NY [u.a.]
This record in other databases: 
Please use a persistent id in citations: doi:10.1016/j.gca.2012.04.045
Abstract: Denitrifying aquifers are sources of the greenhouse gas N2O. Isotopic signatures reflect processes of production and reduction of N2O, but it is not clear to which extent these can be used to quantify those processes. We investigated the spatial distribution of isotopologue values of N2O (delta O-18, average delta N-15, and N-15 site preference, SP) in two denitrifying sandy aquifers to study N2O production and reduction and associated isotope effects in groundwater. For the first time, we combined this approach with direct estimation of N2O reduction from excess-N-2 analysis. Groundwater samples were collected from 15 monitoring wells and four multilevel sampling wells and analysed for NO3-, dissolved N2O, dissolved O-2, excess N-2 from denitrification and isotopic signatures of NO3- and N2O. Both aquifers exhibited high NO3- concentrations with average concentrations of 22 and 15 mg N L-1, respectively. Evidence of intense denitrification with associated N2O formation was obtained from mean excess-N-2 of 3.5 and 4.3 mg N L-1, respectively. Isotopic signatures of N2O were highly variable with ranges of 17.6-113.2 parts per thousand (delta O-18), 55.4 to 89.4 parts per thousand (delta N-15(bulk)) and 1.8-97.9 parts per thousand (SP). delta N-15 and delta O-18 of NO3- ranged from 2.1 parts per thousand to 65.5 parts per thousand and from -5 parts per thousand to 33.5 parts per thousand, respectively.The relationships between delta N-15 of NO3- , delta N-15(bulk) and SP were not in good agreement with the distribution predicted by a Rayleigh-model of isotope fractionation. The large ranges of delta O-18 and SP of N2O as well as the close correlation between these values could be explained by the fact that N2O reduction to N-2 was strongly progressed but variable.We confirm and explain that a large range in SP and delta O-18 is typical for N2O from denitrifying aquifers, showing that this source signature can be distinguished from the isotopic fingerprint of N2O emitted from soils without water-logging. We conclude that isotopologue values of N2O in our sites were not suitable to quantify production or reduction of N2O or the contribution of different processes to the total N2O flux, apparently because these values were not only governed by individual pathways but eventually also by the spatial distribution of substrates and activity within the aquifers. These observations could be explained by the dynamics of N2O production, reduction and transport in water-saturated systems with heterogenic distribution of microbial activity and by a combination of diffusive and enzymatic isotope effects. (C) 2012 Elsevier Ltd. All rights reserved.
Keyword(s): J
; JCR ; NCBI Molecular Biology Database ; Nationallizenz
; SCOPUS ; Science Citation Index ; Science Citation Index Expanded ; Thomson Reuters Master Journal List ; Web of Science Core Collection ; Zoological Record
|
The record appears in these collections: |