Understanding Soil Microbial Sources of Nitrous Acid and their Effect on Carbon-Nitrogen Cycle Interactions
- Indiana Univ., Bloomington, IN (United States)
Descriptions of soil emissions of reactive nitrogen (NOy) in climate models are underdeveloped or non-existent, due to the fact that details of the mechanisms leading to nitrous acid (HONO) and nitrogen di-oxide (NO2) formation in soil are lacking. This represents a major gap in our understanding of a significant land-atmosphere interaction that prevents us from scaling these processes from the laboratory scale to the ecosystem and global scales. There is a critical need to include these mechanisms into climate models since NOy controls the oxidative capacity of the atmosphere and the lifetime of greenhouse gases and the rate of secondary aerosol formation that directly and indirectly affect climate. The first objective of this proposal is to conduct laboratory and field measurements of NOy fluxes from diverse soil types and determine the mechanism of biogenic NOy formation. The working hypothesis based on preliminary data is that soil HONO and NO2 is ultimately derived from ammonia-oxidizing archaea (AOA) and bacteria (AOB) that are widespread, but whose abundance varies across ecosystems. In the case of NO2, reactive oxygen species derived from iron-containing minerals and heterotrophic bacteria drive NO-to-NO2 conversion. The approach is to link soil fluxes of HONO and NO2 to AOA, AOB, and other heterotrophs using a combination of laboratory and field experiments, isotopic analysis, and molecular techniques to address how variability in land surfaces and edaphic properties impact emissions. In addition, we will determine the effect of HONO and NO2 on nitrogen immobilization and the photo-oxidative capacity of soil. The working hypothesis is that HONO uptake in soil will be a source of nitrosonium and hydroxyl radical that will lead to thermal- and photodegradation of soil organic matter to CO2 and CO, and the incorporation of N in soil organic matter. We will use surface-sensitive mass spectrometry techniques and gas phase detection to study N-immobilization in soil and subsequent enhancements in reactivity that lead to decomposition of organic matter. The results will be used to reduce the uncertainty in projections from the Community Earth System Model (CESM) stemming from inaccurate representations of soil NOy emissions. The proposed research is significant because, in addition to demonstrating new mechanisms of NOy formation and loss, it will be a crucial first step towards modeling the land-atmosphere exchange of HONO and NO2 in the CESM. Improved model treatment of land-air exchange of NOy is key for understanding feedbacks between human activity and climate, and addressing societal concerns about the fate of N and C emitted to the atmosphere.
- Research Organization:
- Indiana Univ., Bloomington, IN (United States)
- Sponsoring Organization:
- USDOE Office of Science (SC), Biological and Environmental Research (BER)
- Contributing Organization:
- Pacific Northwest National Laboratory (PNNL), Richland, WA (United States). Environmental Molecular Sciences Laboratory (EMSL); USDOE Joint Genome Institute (JGI), Berkeley, CA (United States)
- DOE Contract Number:
- SC0014443
- OSTI ID:
- 2529047
- Report Number(s):
- DOE-IUB--14443
- Country of Publication:
- United States
- Language:
- English
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