Photochemistry at night: Dark reactions of photochemically generated species

PHYS 19

Steven S. Brown, steven.s.brown@noaa.gov1, William P. Dubé1, Hans D. Osthoff2, Harald Stark1, and James M. Roberts1. (1) Chemical Sciences Division, NOAA Earth System Research Laboratory, 325 Broadway, Boulder, CO 80305, (2) Department of Chemistry, University of Calgary, Calgary, AB T2N 1N4
Tropospheric ozone formation is a photochemical process. However, its daytime production increases the oxidative capacity of the nighttime atmosphere through dark reactions that produce peroxy (RO2), hydroyl (OH) and nitrate (NO3) radicals. This talk will present results from recent field campaigns on oxidation reactions of NO3. Nocturnal oxidation rates for both biogenic and highly reactive anthropogenic VOC can be substantial, but depend on the timing of VOC emissions, co-location between VOC and NOx emissions, and vertical mixing within the stratified nighttime atmosphere. Dimethyl sulfide (DMS), emitted from the ocean surface, undergoes rapid nocturnal oxidation in polluted marine environments, a process that may perturb the yield of sulfate aerosol from this naturally occurring sulfur compound. Finally, heterogeneous uptake of N2O5 on sea salt aerosol activates halogen radicals through the nighttime production and sunrise photolysis of ClNO2.
 

Physical Chemistry of Atmospheric Processes
8:00 AM-12:00 PM, Sunday, April 6, 2008 Morial Convention Center -- Rm. 343, Oral

Division of Physical Chemistry

The 235th ACS National Meeting, New Orleans, LA, April 6-10, 2008