Thia-arenes as pollution source tracers in urban air particulate

Abstract

<p>A method to distinguish coke oven emissions from diesel exhaust emissions in ambient samples has been developed. Sulfur-containing polycyclic aromatic compounds (thia-arenes) and polycyclic aromatic hydrocarbons (PAH) were determined in source samples, standard reference samples and ambient samples using gas chromatography/mass spectrometry. A total of 92 ambient respirable air particulate samples that were collected at four locations upwind and downwind of the steel industries in Hamilton, Ontario in 1995, were analyzed for their total particulate mass, 15 PAH and a number of thia-arene compounds. The steel industries were found to contribute the majority of PAH pollution in Hamilton air particulate above the urban background of approximately 1.5 ng/m3 . Particulate concentrations in Hamilton air indicate several major sources of particulate, including vehicle emissions. Profiles of alkylated dibenzothiophene isomers, 234 amu this-arene isomers and 258 amu thia-arene isomers were examined in Hamilton air particulate, Toronto air particulate, coke oven condensate, Diesel Exhaust Particulate Standard Reference Material (SRM 1650), Urban Dust Standard Reference Material (SRM 1649) and Coal Tar Standard Reference Material (SRM1597). Selected thia-arenes were also examined in a variety of other environmental samples. Principal component analysis (PCA) was used to select suitable thia-arene tracer compounds and examine the relationship between a variety of environmental samples. A thia-arene index was developed using a combination of ratios of selected 234 amu and 258 amu isomers. The suitability of thia-arene tracers for distinguishing coke oven emissions from diesel emissions is demonstrated with Hamilton air particulate and source samples. Ambient samples with particulate bound PAH levels below 1.6 ng/m3 were classified as petrogenic in origin in all cases, while samples with PAH levels above about 3.6 ng/m3 were shown to have significant coke oven impacts. The quality of the thia-arene criteria is discussed in comparison to PAH criteria found in the literature. Four gas chromatography stationary phases were evaluated for the separation of thia-arenes and PAH. Retention index values are reported for 49 PAH and 66 thia-arene compounds. The 50% phenyl-substituted methylpolysiloxane stationary phase provided the best overall separation of thia-arenes and PAH.</p>