Analytical Chemistry Seminar

Analytical & Environmental Chemistry Division and Atmospheric Chemistry Program Seminar
Jointly sponsored by the Department of Chemistry and Biochemistry, CIRES, and the Environmental Program
Atmospheric Chemistry of Nitrogen Oxides at Soil-Air Interfaces
by Jonathan Raff, Associate Professor, Indiana University
There remain large uncertainties in the terrestrial sources and sinks of reactive oxides of nitrogen (NOy = NO, NO2, and HONO)—gases that play an important role in regulating the oxidizing capacity of the atmosphere. Most terrestrial surfaces are covered in soil particles, either as fine coatings of air-blown dust or as topsoil in which countless organisms live. In addition, soil particles possess large intrinsic surface areas and myriad reactive surface sites on which chemical reactions occur. These properties make soil a potentially important consideration in understanding the heterogeneous reactions that control the atmospheric NOy budget. In this presentation I will discuss results of laboratory experiments conducted on soil and individual soil constituents aimed at testing the hypothesis that redox couples involving soil organic matter and minerals mediate HONO conversion from NO 2 at night and from nitrate during the daytime. In addition, we carried out kinetics studies using a coated wall flow reactor and surface composition studies using nano-DESI and nanoSIMS [at the Environmental Molecular Sciences Laboratory (EMSL), Pacific Northwest National Laboratory] to explore the role of minerals and organic matter as sinks for HONO in soil.