TY - JOUR

T1 - Soil HONO emissions at high moisture content are driven by microbial nitrate reduction to nitrite: tackling the HONO puzzle

AU - Wu, Dianming

AU - Horn, Marcus A.

AU - Behrendt, Thomas

AU - Müller, Stefan

AU - Li, Jingsong

AU - Cole, Jeff A.

AU - Xie, Baohua

AU - Ju, Xiaotang

AU - Li, Guo

AU - Ermel, Michael

AU - Oswald, Robert

AU - Fröhlich-Nowoisky, Janine

AU - Hoor, Peter

AU - Hu, Chunsheng

AU - Liu, Min

AU - Andreae, Meinrat O.

AU - Pöschl, Ulrich

AU - Cheng, Yafang

AU - Su, Hang

AU - Trebs, Ivonne

AU - Weber, Bettina

AU - Sörgel, Matthias

N1 - Funding information: We thank J. Cui and M. Badawy for helping to collect the soil samples. We also thank G. Braker and L.R. Bakken for providing pure bacteria cultures. We are grateful to J. Kesselmeier, F. X. Meixner, and H.L. Drake for allowing us to complete experiments in their laboratories. We are also grateful to M. Welling, D. Plake, U. Parchatka, A. Moravek, A. Dallinger, S. Hetz, M. Morawe, N. Roßbach, R. Mertel, and A. Wieczorek for supporting techniques in our experiments. This work was supported by the Max Planck Society and the Chinese Academy of Sciences. D. Wu was sponsored by the National Natural Science Foundation of China (41807449), Shanghai Pujiang Program (18PJ1403500), and “the Fundamental Research Funds for the Central Universities”. M. Liu was supported by the National Natural Science Foundation of China (41761144062). B. Weber would like to thank Paul Crutzen for awarding her a Nobel Laureate Fellowship (2013–2015).

PY - 2019/7

Y1 - 2019/7

N2 - Nitrous acid (HONO) is a precursor of the hydroxyl radical (OH), a key oxidant in the degradation of most air pollutants. Field measurements indicate a large unknown source of HONO during the day time. Release of nitrous acid (HONO) from soil has been suggested as a major source of atmospheric HONO. We hypothesize that nitrite produced by biological nitrate reduction in oxygen-limited microzones in wet soils is a source of such HONO. Indeed, we found that various contrasting soil samples emitted HONO at high water-holding capacity (75–140%), demonstrating this to be a widespread phenomenon. Supplemental nitrate stimulated HONO emissions, whereas ethanol (70% v/v) treatment to minimize microbial activities reduced HONO emissions by 80%, suggesting that nitrate-dependent biotic processes are the sources of HONO. High-throughput Illumina sequencing of 16S rRNA as well as functional gene transcripts associated with nitrate and nitrite reduction indicated that HONO emissions from soil samples were associated with nitrate reduction activities of diverse Proteobacteria. Incubation of pure cultures of bacterial nitrate reducers and gene-expression analyses, as well as the analyses of mutant strains deficient in nitrite reductases, showed positive correlations of HONO emissions with the capability of microbes to reduce nitrate to nitrite. Thus, we suggest biological nitrate reduction in oxygen-limited microzones as a hitherto unknown source of atmospheric HONO, affecting biogeochemical nitrogen cycling, atmospheric chemistry, and global modeling.

AB - Nitrous acid (HONO) is a precursor of the hydroxyl radical (OH), a key oxidant in the degradation of most air pollutants. Field measurements indicate a large unknown source of HONO during the day time. Release of nitrous acid (HONO) from soil has been suggested as a major source of atmospheric HONO. We hypothesize that nitrite produced by biological nitrate reduction in oxygen-limited microzones in wet soils is a source of such HONO. Indeed, we found that various contrasting soil samples emitted HONO at high water-holding capacity (75–140%), demonstrating this to be a widespread phenomenon. Supplemental nitrate stimulated HONO emissions, whereas ethanol (70% v/v) treatment to minimize microbial activities reduced HONO emissions by 80%, suggesting that nitrate-dependent biotic processes are the sources of HONO. High-throughput Illumina sequencing of 16S rRNA as well as functional gene transcripts associated with nitrate and nitrite reduction indicated that HONO emissions from soil samples were associated with nitrate reduction activities of diverse Proteobacteria. Incubation of pure cultures of bacterial nitrate reducers and gene-expression analyses, as well as the analyses of mutant strains deficient in nitrite reductases, showed positive correlations of HONO emissions with the capability of microbes to reduce nitrate to nitrite. Thus, we suggest biological nitrate reduction in oxygen-limited microzones as a hitherto unknown source of atmospheric HONO, affecting biogeochemical nitrogen cycling, atmospheric chemistry, and global modeling.

UR - http://www.scopus.com/inward/record.url?scp=85062476001&partnerID=8YFLogxK

U2 - 10.15488/15944

DO - 10.15488/15944

M3 - Article

VL - 13

SP - 1688

EP - 1699

JO - The ISME journal

JF - The ISME journal

SN - 1751-7362

IS - 7

ER -