Atmos. Chem. Phys. Discuss., 12, 32795-32823, 2012
© Author(s) 2012. This work is distributed
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Evidence and quantitation of aromatic organosulfates in ambient aerosols in Lahore, Pakistan
S. Kundu1, T. A. Quraishi2, G. Yu3, C. Suarez3, F. N. Keutsch3, and E. A. Stone1
1Department of Chemistry, University of Iowa, Iowa City, IA 52242, USA
2Institute of Environmental Engineering and Research, University of Engineering and Technology, Lahore, Pakistan
3Department of Chemistry, University of Wisconsin-Madison, Madison, Wisconsin 53706, USA

Abstract. Organosulfates are important components of atmospheric organic aerosols, yet their structures, abundances, sources and formation processes are not adequately understood. This study presents the identification and quantitation of benzyl sulfate in atmospheric aerosols, which is the first reported atmospheric organosulfate with aromatic carbon backbone. Benzyl sulfate was identified and quantified in fine particulate matter (PM2.5) collected in Lahore, Pakistan during 2007–2008. An authentic standard of benzyl sulfate was synthesized, standardized, and identified in atmospheric aerosols using ultra-performance liquid chromatography (UPLC) coupled with quadrupole time-of-flight (Q-ToF) mass spectrometry (MS). Benzyl sulfate was quantified in aerosol samples using UPLC coupled to negative electrospray ionization triple quadrupole (TQ) MS. The highest benzyl sulfate concentrations were recorded in November and January 2007 (0.50 ± 0.11 ng m−3) whereas the lowest concentration was observed in July (0.05 ± 0.02 ng m−3). To evaluate matrix effects, benzyl sulfate concentrations were determined using external calibration and the method of standard addition; comparable concentrations were detected by the two methods, which ruled out significant matrix effects in benzyl sulfate quantitation. Three additional organosulfates with m/z 187, 201 and 215 were qualitatively identified as aromatic organosulfates with additional methyl substituents by high-resolution mass measurements and tandem MS. The observed aromatic organosulfates form a homologous series analogous to toluene, xylene, and trimethylbenzene, which are abundant anthropogenic volatile organic compounds (VOC), suggesting that aromatic organosulfates may be formed by secondary reactions. Further studies are needed to elucidate the sources and formation pathways of aromatic organosulfates in the atmosphere.

Citation: Kundu, S., Quraishi, T. A., Yu, G., Suarez, C., Keutsch, F. N., and Stone, E. A.: Evidence and quantitation of aromatic organosulfates in ambient aerosols in Lahore, Pakistan, Atmos. Chem. Phys. Discuss., 12, 32795-32823, doi:10.5194/acpd-12-32795-2012, 2012.
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