| Wei, J; Amelung, W; Lehndorff, E; Schloter, M; Vereecken, H; Brüggemann, N: N2O and NOx emissions by reactions of nitrite with soil organic matter of a Norway spruce forest, Biogeochemistry, 132, 325-342 (2017), doi:10.1007/s10533-017-0306-0 | |
| Abstract: Nitrite (NO2 −) as an important intermediate of the biological nitrogen cycle is particularly reactive in acidic soils and acts as a source of N2O and NOx (NO and NO2). However, abiotic and biotic pathways of NO2 −-driven N2O and NOx production in forest soil and the role of soil organic matter (SOM) in these processes are still unclear. In this study, NO2 − was applied to both unsterile and sterilized soil samples as well as to different SOM fractions from a Norway spruce forest. Biotic and abiotic N2O emission was measured with an infrared absorption analyzer and gas chromatography, while NOx emission was quantified with a chemiluminescence analyzer. Isotopic signatures of N2O (δ15Nbulk, δ18O, and 15N-N2O site preference) were analyzed with an isotope ratio mass spectrometer. After NO2 − addition, a large amount of NOx was emitted immediately, while N2O emission occurred 15–60 min later and was much lower compared to NOx. Sterilization of soil decreased N2O emission significantly, but not NOx emission. The 15N site preference of N2O ranged from 7.98 to 11.58‰ for abiotic and 4.69–7.42‰ for biotic sources. The fulvic acid fraction contributed the most to abiotic N2O emission, while the fastest NO and N2O emission occurred after NO2 −application to the humin fraction, followed by the humic acid fraction. These results are important for the future understanding of NOx and N2O sources, as well as the use of isotopic signatures for source-partitioning N2O emission from soil. |
