Evidence for NO_x Control over Nighttime SOA Formation

摘要

Laboratory studies have established a number of chemical pathways by which nitrogen oxides (NO_X) affect atmospheric organic aerosol (OA) production. However, these effects have not been directly observed in ambient OA. We report measurements of paniculate organic nitrates in Bakersfield, California, the nighttime formation of which increases with NO_x and is suppressed by high concentrations of organic molecules that rapidly react with nitrate radical (NO_3)-evidence that multigenerational chemistry is responsible for organic nitrate aerosol production. This class of molecules represents about a third of the nighttime increase in OA, suggesting that most nighttime secondary OA is due to the NO_3 product of anthropogenic NO_x emissions. Consequently, reductions in NO_x emissions should reduce the concentration of organic aerosol in Bakersfield and the surrounding region.