Abstract
Abstract. Secondary organic aerosols (SOAs) formed from biogenic volatile organic compounds (BVOCs) constitute a significant fraction of atmospheric particulate matter and have been recognized to significantly affect the climate and air quality. Atmospheric SOA particulate mass yields and chemical composition result from a complex mixture of oxidation products originating from a diversity of BVOCs. Many laboratory and field experiments have studied SOA particle formation and growth in the recent years. However, a large uncertainty still remains regarding the contribution of BVOCs to SOA. In particular, organic compounds formed from sesquiterpenes have not been thoroughly investigated, and their contribution to SOA remains poorly characterized. In this study, a Filter Inlet for Gases and Aerosols (FIGAERO) combined with a high-resolution time-of-flight chemical ionization mass spectrometer (CIMS), with iodide ionization, was used for the simultaneous measurement of gas-phase and particle-phase oxygenated compounds. The aim of the study was to evaluate the relative contribution of sesquiterpene oxidation products to SOA in a springtime hemiboreal forest environment. Our results revealed that monoterpene and sesquiterpene oxidation products were the main contributors to SOA particles. The chemical composition of SOA particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified for both situations. Surprisingly, sesquiterpene oxidation products were the predominant fraction in the particle phase in some periods, while their gas-phase concentrations remained much lower than those of monoterpene products. This can be explained by favorable and effective partitioning of sesquiterpene products into the particle phase. The SOA particle volatility determined from measured thermograms increased when the concentration of sesquiterpene oxidation products in SOA particles was higher than that of monoterpenes. Overall, this study demonstrates that sesquiterpenes may have an important role in atmospheric SOA formation and oxidation chemistry, in particular during the spring recovery period.
Highlights
Volatile organic compounds (VOCs) are ubiquitous constituents of Earth’s atmosphere that are emitted from both biogenic and anthropogenic sources (e.g., Kansal, 2009)
The chemical composition of secondary organic aerosol (SOA) particles was compared for times when either monoterpene or sesquiterpene oxidation products were dominant and possible key oxidation products for SOA particle formation were identified for both situations
Barreira et al.: The importance of sesquiterpene oxidation products for SOA formation ceeds that of Anthropogenic VOCs (AVOCs) by an order of magnitude, implying that biogenic volatile organic compounds (BVOCs) dominate on the global scale (e.g., Guenther et al, 1995; Kansal, 2009) and often even in urban environments (e.g., Barreira et al, 2021)
Summary
Volatile organic compounds (VOCs) are ubiquitous constituents of Earth’s atmosphere that are emitted from both biogenic and anthropogenic sources (e.g., Kansal, 2009). F. Barreira et al.: The importance of sesquiterpene oxidation products for SOA formation ceeds that of AVOCs by an order of magnitude, implying that BVOCs dominate on the global scale (e.g., Guenther et al, 1995; Kansal, 2009) and often even in urban environments (e.g., Barreira et al, 2021). BVOCs play an important role in atmospheric physics and chemistry They react with atmospheric oxidants, which results in the formation of secondary products (e.g., Kavouras et al, 1999). Aerosols in the atmosphere have adverse effects on public health, since they cause or enhance respiratory, cardiovascular, infectious and allergic diseases (Pöschl, 2005)
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