Dr. Edwige Demangeat

While the majority of current research focuses on biological reactions within N cycle, recent reports point out the importance of abiotic pathways in regulating soil N oxides (nitrous and nitric; N2O and NO) emissions in deserts. This work aims at (i) identifying N2O abiotic production and (ii) assessing the role of NH2OH and iron towards N2O emissions following a rewetting event in the Negev desert. Rewetting was performed with three different solutions (distilled water, 0.034 mM NH2OH and 1 g/L iron (III) oxides). Gas-tight jars and undisturbed soil cores experiments allowed to measure post-wetting soil emissions of NOx, N2O and CO2 (at 35% WHC, pH 7.3) in irradiated and non-irradiated soils. Preliminary measurements of nitrification potential confirmed that irradiation prevented microorganisms from performing nitrification in irradiated soils. The first set of experiments (gas-tight jars) showed that N2O emissions depend on the relative amounts between iron and hydroxylamine, and that change in iron concentration affects N2O emission to a greater extent than NH2OH does. It was also shown that after addition of NH2OH (i.e., irradiated soils, without iron addition), the soil still provides a reactive substrate for NH2OH oxidation and subsequent N2O release. Nitrous oxide production increased after addition of iron oxides together with NH2OH. These results were confirmed in the second set of experiments (undisturbed soil cores). NH2OH triggered high fluxes of N2O in both irradiated and control soil but the addition of iron oxides alone didn’t foster N2O production, suggesting that NH2OH wasn’t naturally released or not in sufficient amount.