|Title||Probing molecular associations of field-collected and laboratory-generated SOA with nano-DESI high-resolution mass spectrometry|
|Publication Type||Journal Article|
|Year of Publication||2013|
|Authors||O'Brien RE, Nguyen TB, Laskin A, Laskin J, Hayes PL, Liu S, Jimenez JL, Russell LM, Nizkorodov SA, Goldstein AH|
|Journal||Journal of Geophysical Research-Atmospheres|
|Type of Article||Article|
|Keywords||atmospheric aerosols; chemical-characterization; composition; elemental; fulvic-acids; isoprene; major components; Oligomers; photooxidation; secondary organic aerosol; smog chamber|
Aerosol samples from the 2010 CalNex field study in Bakersfield (BF) and Pasadena (LA) were analyzed using positive mode nanospray-desorption electrospray ionization mass spectrometry. Secondary organic aerosol (SOA) produced in a photochemical chamber by photooxidation of diesel (DSL) fuel and isoprene (ISO) under humid, high-NOx conditions, was analyzed for comparison. Three groups of organic compounds with zero, one, or two nitrogen atoms in their molecular formulas (0N, 1N, 2N) were compared in detail. The composition of ambient SOA exhibited greater overlap with DSL than with ISO. The overlap of the chamber experiments with the BF data was relatively consistent throughout the day while the overlap with LA data increased significantly in the noon to 6 P. M. sample, consistent with the SOA plume arriving from downtown Los Angeles. BF samples were more oxidized, contained more organic nitrogen, and had more overlap with the chamber data compared to LA samples. The addition of gaseous ammonia (NH3) to the DSL experiment was necessary to generate many of the 2N compounds observed in BF. This analysis demonstrates that DSL and ISO were important sources but cannot account for all of the observed ambient compounds indicating that other sources of organics were also likely important.