Characterization of Speciated Acyl Peroxy Nitrates Above and Within a Forest Canopy

Anthropogenic pollution generated in California’s Central Valley is thought to impact air quality goals of rural regions downwind such as the Sierra Nevada foothills. To better understand the impact of anthropogenic pollution and biogenic emissions on photochemistry at the urban-rural interface, observations of speciated acyl peroxy nitrates (APNs), a substantial component of atmospheric reactive nitrogen, were collected over two seasons as part of the BEARPEX campaign using thermal dissociation chemical ionization mass spectrometry (TD-CIMS). Vertical concentration gradients of eight APN species were collected within and above a Ponderosa Pine forest during the late summer and early fall of 2007 as well as the summer of 2009. The TD-CIMS technique allows us to study less well-known and less abundant APN species. Many of these species are precursor-specific, allowing them to be used as tracers for biogenic and anthropogenic influences within an air mass and for constraining Lagrangian models of the chemical evolution of an urban plume. Using linear combination models and factor analysis we glean insights into the chemical and atmospheric processes responsible for local formation of ozone and organic aerosol on diurnal and seasonal time scales approximately 75km downwind of Sacramento.