Microorganisms in Dry Polar Snow Are Involved in the Exchanges of Reactive Nitrogen Species with the Atmosphere
International audience The snowpack is a complex photochemical reactor that emits a wide variety of reactive molecules to the atmosphere. In particular, the photolysis of nitrate ions, NO 3-, produces NO, NO 2 , and HONO, which affects the oxidative capacity of the atmosphere. We report measurements...
Published in: | Environmental Science & Technology |
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Main Authors: | , , , , , , , , , , |
Other Authors: | , , , , , , , , , , |
Format: | Article in Journal/Newspaper |
Language: | English |
Published: |
HAL CCSD
2010
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Subjects: | |
Online Access: | https://hal.archives-ouvertes.fr/hal-01686207 https://doi.org/10.1021/es9027309 |
Summary: | International audience The snowpack is a complex photochemical reactor that emits a wide variety of reactive molecules to the atmosphere. In particular, the photolysis of nitrate ions, NO 3-, produces NO, NO 2 , and HONO, which affects the oxidative capacity of the atmosphere. We report measurements in the European High Arctic where we observed for the first time emissions of NO, NO 2 , and HONO by the seasonal snowpack in winter, in the complete or near-complete absence of sunlight and in the absence of melting. We also detected unusually high concentrations of nitrite ions, NO 2-, in the snow. These results suggest that microbial activity in the snowpack is responsible for the observed emissions. Isotopic analysis of NO 2-and NO 3-in the snow confirm that these ions, at least in part, do not have an atmospheric origin and are most likely produced by the microbial oxidation of NH 4 + coming from clay minerals into NO 2-and NO 3-. These metabolic pathways also produce NO. Subsequent dark abiotic reactions lead to NO 2 and HONO production. The snow cover is therefore not only an active photochemical reactor but also a biogeochemical reactor active in the cycling of nitrogen and it can affect atmospheric composition all year round. |
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