Informations et ressources scientifiques
sur le développement des zones arides et semi-arides

Accueil du site → Doctorat → Australie → 2021 → Isotopic evidence for the cycling of nitrate and nitrous oxide in aquifers beneath an irrigated agricultural district using established and emerging measurement techniques

University of New South Wales (UNSW) 2021

Isotopic evidence for the cycling of nitrate and nitrous oxide in aquifers beneath an irrigated agricultural district using established and emerging measurement techniques

Harris, Stephen

Titre : Isotopic evidence for the cycling of nitrate and nitrous oxide in aquifers beneath an irrigated agricultural district using established and emerging measurement techniques

Auteur : Harris, Stephen

Université de soutenance : University of New South Wales (UNSW)

Grade : Doctor of Philosophy (PhD) 2021

Résumé partiel
Modern agricultural fertiliser application rates often result in groundwater contamination with nitrogen compounds such as nitrate (NO3-) and nitrous oxide (N2O). Groundwater isotopic measurements can elucidate the hydrogeochemical controls on NO3- and N2O, leading to improved land management practices. Although most groundwater isotopic measurement techniques are well-established, laser spectroscopic methods to acquire groundwater N2O isotopic data are still evolving. However, if proven robust, they may provide potential benefits in terms of cost, ease of use and immediacy of results when compared to the conventional method using isotope-ratio mass-spectrometry (IRMS). The primary aim of this thesis was to use established multiple stable and radioactive isotope tracers to elucidate the hydrogeochemical controls on the production and reduction of NO3- and N2O in aquifers beneath the Emerald Irrigation Area (EIA), Queensland, Australia. Isotopic evidence indicates that NO3- in EIA aquifers is derived from fertiliser N which is retained in the soil organic N pool prior to mineralisation, nitrification and leaching. Groundwater NO3- occurrence is linked to irrigated agriculture beginning in the 1970s. N2O isotope data acquired via IRMS shows that groundwater N2O is a mixture of nitrification- and denitrification-derived N2O that has undergone reduction. The reduction of NO3- and N2O occurs under two contrasting scenarios : progressively, as groundwater flows from the upgradient oxic basalt aquifer to the downgradient suboxic alluvial aquifer ; and beneath leaking irrigation channels, where electron donor-rich suboxic hyporheic zones have manifested

Présentation

Version intégrale (21 Mb)

Page publiée le 5 avril 2022