Fine organic aerosols collected in a humid, rural location (Great Smoky Mountains, Tennessee, USA): Chemical and temporal characteristics

Fine organic aerosols collected at the Great Smoky Mountain National Park, Tennessee (USA) during 15 July –25 August 1995 as part of the Southeastern Aerosol and Visibility Study (SEAVS) were chemically characterized. The water-soluble organic species (WSOS) often dominated over the solvent-soluble organic species (SSOS) at this remote, humid sampling site, contributing 76–98% of the total identified organic mass in 17 out of the 21 daytime samples analyzed. Nighttime samples tended to have slightly larger concentrations of total SSOS than the daytime, with nocturnal/diurnal organic mass ratios greater than 1.0 in 7 out of the 10 paired samples. However, for total WSOS mass, the nocturnal-to-diurnal ratios were less than 0.3 in 7 out of the 10 paired samples, reflecting much more substantial depletion and/or less production of the more polar organics during nighttime. Based on identified species, the organic-mass-to-organic-carbon (OM–OC) ratios at the SEAVS site are estimated as 2.0, 2.2, and 1.3 for the daytime total organics, WSOS, and SSOS, respectively. For the nighttime samples, the OM–OC ratio for total identified organics is estimated to be 1.8, slightly lower than the daytime ratio due to the smaller mass fraction of WSOS present at night.