Research Summary

It is essential that we understand atmospheric processes to provide policymakers with accurate information they need to address rapid alteration of Earth’s climate in a timely and cost-effective manner.  Most policy decisions are based on predictive atmospheric models that have become necessarily complex as they are extended to answer global-scale questions.  Unfortunately, current models are unable to accurately represent all of the important chemical components due to challenges in identifying details of biogeochemical processes occurring within the terrestrial environment that have a significant impact on the atmosphere above. This is especially true for abiotic transformations of reactive N and soil microbial emissions of reactive nitrogen (e.g., nitrous acid, nitric oxide, and nitrogen dioxide), which directly and indirectly affect climate by controlling the oxidative capacity of the atmosphere, lifetime of greenhouse gases, and formation rate of aerosols. 

My group seeks to provide an improved mechanistic understanding of the fate of reactive nitrogen in soil that will enable these processes to be more accurately scaled from the laboratory to the ecosystem and global scales. We take a unique multidisciplinary approach to examine how variability in land surfaces and soil properties impact reactive nitrogen emissions, and to link soil fluxes of these gases to their chemical and microbial sources using a combination of laboratory and field studies, isotopic analysis, and genomic techniques.  We often do this in collaboration with other chemists, theorists, modellers, ecologists, geologists, engineers at IU, internationally, and at other academic institutions and national laboratories.

Research projects in the Raff group rely on an interdisciplinary and collaborative approach that provides group members with a strong background in:

  • analytical chemistry (e.g., spectroscopy, mass spectrometry, systems design),
  • synthetic chemistry (e.g., mechanisms of inorganic and organic chemical reactions; preparation of analytical standards and gaseous reactants),
  • heterogeneous chemistry (mechanistic studies of reactions occurring at the air-solid and air-liquid interface).
  • biogeochemistry (e.g., studying interactions of gases with soil minerals, assessing microbial activity with genomics)

  • Measuring terrestrial-atmospheric exchange of gases in the field and laboratory and elucidating mechanisms of their release and parameterizing this exchange for use in atmospheric chemistry and climate models.
  • Elucidating microbial and abiotic sources (both thermal and photochemical) of reactive nitrogen (NOy = NO, NO2, N2O5, HONO, HNO3, etc), N2O, and other gases of formed on environmental surfaces that impact climate and the oxidizing capacity of the atmosphere and soil.
  • Elucidating photochemical mechanisms that form highly reactive oxidants and their precursors on soil and in airborne particles.
  • Through or work we hope to obtain a basic understanding of the molecular and biogeochemical processes that are essential for answering key environmental questions and developing effective solutions to problems related to pollution, human health, and climate.

  • Chemical ionization mass spectrometry (CIMS): For detection of gaseous small molecules at ppt levels.
  • Chemiluminescence: For NOx and HONO detection at ppt levels; reactive oxygen detection at pM levels.
  • Tunable infrared laser direct absorption spectroscopy (TILDAS): For ppt level detection of N2O; ppm levels of N2O isotopomers.
  • Cavity ring-down spectroscopy (for ppb levels of CH4 and its isotopomers)
  • Broad band cavity-enhanced absorption spectroscopy (BB-CEAS) for ppb level detection of NO2 and HONO)
  • FT-IR spectroscopy (with capabilities to study gas phase and surface chemistry)
  • Coated-wall flow tube reactors (for studying kinetics of heterogeneous (gas/surface) chemistry)
  • Dynamic flux chambers (for measuring exchange fluxes of trace gases between air and soil)