University of Oulu

Bhattarai, H.R., Wanek, W., Siljanen, H.M.P. et al. Denitrification is the major nitrous acid production pathway in boreal agricultural soils. Commun Earth Environ 2, 54 (2021).

Denitrification is the major nitrous acid production pathway in boreal agricultural soils

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Author: Bhattarai, Hem Raj1,2; Wanek, Wolfgang3; Siljanen, Henri M. P.1;
Organizations: 1Department of Environmental and Biological Sciences, University of Eastern Finland, Kuopio, Finland
2Natural Resources Institute Finland, Production systems, Milk Production Unit, Maaninka, Finland
3Department of Microbiology and Ecosystem Science, Center of Microbiology and Environmental Systems Science, University of Vienna, Vienna, Austria
4Water, Energy and Environmental Engineering Research Unit, University of Oulu, Oulu, Finland
5Natural Resources Institute Finland, Production systems, Oulu, Finland
6Lawrence Berkeley National Laboratory (LBNL), Berkeley, CA, USA
Format: article
Version: published version
Access: open
Online Access: PDF Full Text (PDF, 1.7 MB)
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Language: English
Published: Springer Nature, 2021
Publish Date: 2021-09-17


Nitrous acid (HONO) photolysis produces hydroxyl radicals—a key atmospheric oxidant. Soils are strong HONO emitters, yet HONO production pathways in soils and their relative contributions are poorly constrained. Here, we conduct ¹⁵N tracer experiments and isotope pool dilution assays on two types of agricultural soils in Finland to determine HONO emission fluxes and pathways. We show that microbial processes are more important than abiotic processes for HONO emissions. Microbial nitrate reduction (denitrification) considerably exceeded ammonium oxidation as a source of nitrite—a central nitrogen pool connected with HONO emissions. Denitrification contributed 97% and 62% of total HONO fluxes in low and high organic matter soil, respectively. Microbial ammonium oxidation only produced HONO in high organic matter soil (10%). Our findings indicate that microbial nitrate reduction is an important HONO production pathway in aerobic soils, suggesting that terrestrial ecosystems favouring it could be HONO emission hotspots, thereby influencing atmospheric chemistry.

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Series: Communications earth & environment
ISSN: 2662-4435
ISSN-E: 2662-4435
ISSN-L: 2662-4435
Volume: 2
Issue: 1
Article number: 54
DOI: 10.1038/s43247-021-00125-7
Type of Publication: A1 Journal article – refereed
Field of Science: 1172 Environmental sciences
Funding: This study was funded by the Academy of Finland under the project “The origin of nitrous acid (HONO) emissions from northern soils and linkages to nitrogen cycle processes” (grant no. 297735) and the doctoral program of the University of Eastern Finland (grant to H. R Bhattarai). We also thank the Academy of Finland Center of Excellence program (project no. 307331) for supporting this study.
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