Measurements of some low molecular-weight oxygenated, aromatic, and chlorinated hydrocarbons in ambient air and in vehicle emissions

Abstract

Low-molecular-weight oxygenated, aromatic, and chlorinated organic air pollutants were measured at different sites in urban air and in motor vehicle emissions. The analytical method used is based upon cryogenic sampling using a thermogradient over a packed, well-deactivated sampling tube. Analysis of the samples was made by two-dimensional gas chromatography. Formaldehyde was trapped on molecular sieve 13 × and analyzed by gas chromatography with photoionization detection. At sites near dense traffic a strong correlation was found between vehicle exhaust components such as CO and NO with aromatic compounds (benzene, toluene, ethyl benzene, m/ p-xylene), formaldehyde, acrolein, methacrolein, and 3-buten-2-one. At the dense traffic sites, significant amounts of methanol (0.58–72 nL/L), ethanol (1.5–247 nL/L), 2-propanol (0.28–44 nL/L), acetone (1.0–129 nL/L), 2-butanone (0.26–32 nL/L), ethylacetate (0.15–21 nL/L), trichloroethylene (0.03–37 nL/L), tetrachloroethylene (0.04–53 nL/L), butanal (0.06–3.1 nL/L), pentanal (0.04–1.9 nL/L), and 3-methylbutanal (0.01–0.45 nL/L) were measured. However, these compounds did not generally correlate to typical vehicle exhaust compounds. Other potential sources such as solvent usage, dry cleaning, and bakeries are plausible sources for these compounds. For the low molecular weight aldehydes (C 4C 5), photochemical production as well as natural emissions may be significant sources.