Intermediate‐Volatility Organic Compounds Observed in a Coastal Megacity: Importance of Non‐Road Source Emissions

Abstract

Secondary organic aerosols (SOAs), which can account for 20%-95% of organic aerosols (OAs), significantly impact the global climate, regional air quality, and human health (Huang et al., 2014;Pöschl, 2005;Zhang et al., 2007). SOA remains the least understood composition of OA, and atmospheric models that only consider volatile organic compounds (VOCs) as SOA precursors significantly underestimate the SOA formed both in field observations and chamber experiments (

Contribution of Ship Emission to Volatile Organic Compounds Based on One‐Year Monitoring at a Coastal Site in the Pearl River Delta Region

“…Recent studies have shown that semi-/intermediate-VOCs (S/IVOCs) contributed significantly to SOA with generally higher SOA yields than VOCs (Robinson et al, 2007). A higher fraction of S/IVOCs and a higher SOA yield have been found for ship emissions when compared to other sources (Fang et al, 2022;Huang et al, 2018b). In this study, S/IVOCs were not measured and only VOCs were included for the calculation of SOAPF.…”

“…The reaction rates of VOCs with O 3 and NO 3 radical are slow. Therefore, the initial concentrations of VOCs were calculated only considering reactions involving OH radicals, as described by the following equations (Fang et al., 2022; Z. Zhang et al., 2016): $$${\left[{C}_{i}\right]}_{\text{observed}}={\left[{C}_{i}\right]}_{\text{initial}}\times \mathrm{exp}\left(-{\mathrm{k}}_{i}[\text{OH}]\Delta \mathrm{t}\right)$$$ $$$[\text{OH}]\Delta t=\frac{1}{{\mathrm{k}}_{\mathrm{X}}-{\mathrm{k}}_{\mathrm{E}}}\times \left(\mathrm{ln}{\left(\frac{[\mathrm{X}]}{[\mathrm{E}]}\right)}_{0}-\mathrm{ln}{\left(\frac{[\mathrm{X}]}{[\mathrm{E}]}\right)}_{t}\right)$$$ where [ C i ] observed (μg m −3 ) is the observed concentration of species i ; [ C i ] initial (μg m −3 ) is the initial concentration of species i ; k i (cm −3 molecule −1 s −1 ) is the rate constant for the reaction of species i with OH radicals. In this study, a highly significant correlation ( r 2 = 0.89, p < 0.01) was identified between m/p‐xylene (X) and ethylbenzene (E).…”

“…The reaction rates of VOCs with O 3 and NO 3 radical are slow. Therefore, the initial concentrations of VOCs were calculated only considering reactions involving OH radicals, as described by the following equations (Fang et al, 2022;Z. Zhang et al, 2016):…”

“…More importantly, a minor contribution to the whole region does not mean an insignificant role in the port areas. As a matter of fact, observations at an urban site in Guangzhou city, a central city in the PRD region and the capital city of Guangdong province, revealed that ship emissions could contribute 23% to intermediate‐volatility organic compounds (IVOCs) that are important SOA precursors (Fang et al., 2022). The stringent control of land emissions in the recent decade in China has significantly improved air quality (Lu et al., 2020).…”

Real-World Emission Characteristics of Full-Volatility Organics Originating from Nonroad Agricultural Machinery during Agricultural Activities

“…Mobile source emissions are a significant source of full-volatility organics and contribute to SOA formation. − Previous studies have been conducted on mobile source emissions of VOCs ,, and I/SVOCs. ,− In recent years, with the implementation of effective control of on-road mobile source emissions in China, pollution from nonroad mobile sources has become more prominent. − Zhao et al found that lower holding nonroad mobile sources emitted comparable amounts of IVOCs to on-road vehicles in China (2017). NRAM accounts for a large share of hydrocarbon (HC) emissions from nonroad mobile sources, while few studies have been conducted on their VOCs or I/SVOCs and the simultaneous testing of full-volatility organics .…”