Rate constant and secondary organic aerosol formation from the gas-phase reaction of eugenol with hydroxyl radicals

Changgeng Liu,Jun Liu,Hong He,Tianzeng Chen,Yongchun Liu

doi:10.5194/acp-19-2001-2019

Abstract

Abstract. Methoxyphenols are an important organic component of wood-burning emissions and considered to be potential precursors of secondary organic aerosol (SOA). In this work, the rate constant and SOA formation potential for the OH-initiated reaction of 4-allyl-2-methoxyphenol (eugenol) were investigated for the first time in an oxidation flow reactor (OFR). The rate constant was 8.01±0.40×10-11 cm3 molecule−1 s−1, determined by the relative rate method. The SOA yield first increased and then decreased as a function of OH exposure and was also dependent on eugenol concentration. The maximum SOA yields (0.11–0.31) obtained at different eugenol concentrations could be expressed well by a one-product model. The carbon oxidation state (OSC) increased linearly and significantly as OH exposure rose, indicating that a high oxidation degree was achieved for SOA. In addition, the presence of SO2 (0–198 ppbv) and NO2 (0–109 ppbv) was conducive to increasing SOA yield, for which the maximum enhancement values were 38.6 % and 19.2 %, respectively. The N∕C ratio (0.032–0.043) indicated that NO2 participated in the OH-initiated reaction, subsequently forming organic nitrates. The results could be helpful for further understanding the SOA formation potential from the atmospheric oxidation of methoxyphenols and the atmospheric aging process of smoke plumes from biomass burning emissions.

Highlights

Wood combustion is a major contributor to atmospheric fine particulate matter (PM) (Bruns et al, 2016), which could contribute approximately 10 %–50 % of the total organic fraction of atmospheric aerosols (Schauer and Cass, 2000)
No secondary organic aerosol (SOA) formation was observed by the scanning mobility particle sizer (SMPS) and HR-ToF-AMS
In order to investigate the possible photolysis of eugenol and reference compounds at 254 nm UV light in the oxidation flow reactor (OFR), the comparative experiments were conducted with the UV lamp turned on and turned off when eugenol and reference compounds were introduced into the OFR

Summary

Introduction

Wood combustion is a major contributor to atmospheric fine particulate matter (PM) (Bruns et al, 2016), which could contribute approximately 10 %–50 % of the total organic fraction of atmospheric aerosols (Schauer and Cass, 2000). In some regions with cold climates, woodsmoke-associated aerosols are estimated to account for more than 70 % of PM2.5 in winter (Jeong et al, 2008; Ward et al, 2006). The significant potential for secondary organic aerosol (SOA) formation from woodsmoke emissions has been reported (Bruns et al, 2016; Gilardoni et al, 2016; Tiitta et al, 2016; Ciarelli et al, 2017; Ding et al, 2017). Wood combustion has multifaceted impacts on climate, air quality, and human health

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