Diurnal Cycles of Acrolein and Other Small Aldehydes in Regions Impacted by Vehicle Emissions

This research determined the diurnal and seasonal differences in the ambient atmospheric concentrations of acrolein and several small aldehydes and attempted to link the chemicals to their potential sources. Two summertime and two wintertime sampling episodes were conducted in Roseville, CA at a site located near several busy roadways. One additional sampling episode was conducted at a remote site in the summer to estimate regional background concentrations of aldehydes. Each sampling episode consisted of duplicate samples collected every two hours around the clock for three days. Acrolein concentrations did not correlate with traffic density, ozone concentrations, or tracers of direct vehicle emissions, which argues against vehicles being a dominant source of ambient acrolein through primary emissions or secondary oxidation products. The results showed that wintertime acrolein concentrations correlated well with 2-furaldehyde, which is a tracer of biomass burning, thus suggesting that wood smoke is an important source of ambient acrolein. Other regularly detected carbonyls were tentatively assigned to different source classes (direct vehicle emissions, photochemical oxidation, wood smoke or transport from the Sierra Nevada Mountains) based on time series patterns and correlations with indicators of potential sources (e.g., ozone, traffic density, etc.).