Comment on acp-2021-959

doi:10.5194/acp-2021-959-rc2

Abstract

Abstract. The increasing ozone (O3) pollution and high fraction of secondary organic aerosols (SOA) in fine particle mass has highlighted the importance of volatile organic compounds (VOCs) in air pollution control. In this work, four intensive field measurements of VOCs during winter of 2018 (from 1Â DecemberÂ 2018 to 17Â JanuaryÂ 2019), spring (15Â April to 27Â May), summer (17Â June to 13Â July), and autumn (22Â September to 27Â November) of 2019 were conducted at an urban site in Beijing to characterize VOC sources and their contributions to air pollution. The total mixing ratio of the 95 quantified VOCs (TVOC) observed in this study ranged from 5.5â118.7âppbv with the mean value of 34.9âppbv. Alkanes, OVOCs, and halocarbons were the dominant chemical groups, accounting for 75â%â81â% of the TVOC across the sampling months. The molar ratios of VOCs to NOx indicated that O3 formation was limited by VOCs during the whole sampling period. Positive matrix factorization (PMF) analysis showed that diesel vehicle exhaust, gasoline vehicle exhaust, and industrial emissions were the main VOC sources during both the O3-polluted and PM2.5-polluted months. On the basis of O3 formation impact, VOCs from fuel evaporation and diesel exhaust, particularly toluene, xylenes, trans-2-butene, acrolein, methyl methacrylate, vinyl acetate, 1-butene, and 1-hexene, were the main contributors, illustrating the necessity of conducting emission controls on these pollution sources and species to alleviate O3 pollution. Instead, VOCs from diesel exhaust as well as coal and biomass combustion were found to be the dominant contributors to secondary organic aerosol formation potential (SOAFP), particularly the VOC species of toluene, 1-hexene, xylenes, ethylbenzene, and styrene, and top priority should be given to these for the alleviation of haze pollution. This study provides insights for the government to formulate effective VOC control measures for air pollution in Beijing.

Highlights

The ozone (O3) and fine particulate matter (PM2.5) pollution has restricted improvements in air quality in China.Observation data from the Chinese Ministry of Environment and Ecolgy (MEE) network has witnessed an upward trend for O3 across the country over the period 2013-2019 (Fu et al, 2019; Li et al, 2017; Li et al, 2020; Shen et al, 2019; Fan et al, 2020)
Major Volatile organic compounds (VOCs) compositions were generally consistent during the whole measurement period
(44 μg m-3) > low-PM2.5 months (29 μg m-3). These results suggested that apart from meteorological factors, emissions play a role in deteriorating PM2.5 and O3 pollution, and reducing anthropogenic emissions is essential for improving air quality

Summary

Introduction

The ozone (O3) and fine particulate matter (PM2.5) pollution has restricted improvements in air quality in China.Observation data from the Chinese Ministry of Environment and Ecolgy (MEE) network has witnessed an upward trend for O3 across the country over the period 2013-2019 (Fu et al, 2019; Li et al, 2017; Li et al, 2020; Shen et al, 2019; Fan et al, 2020). The ozone (O3) and fine particulate matter (PM2.5) pollution has restricted improvements in air quality in China. Haze pollution occurred in urban sites were commonly characterized by high fractions of secondary organic aerosols (SOA) in fine particles (Guo et al, 2014; Huang et al, 2014). Volatile organic compounds (VOCs) are key precursors for the formation of O3 via multiphase reactions (Odum et al., 1997; Atkinson, 2000; Sato et al, 2010; Huang et al, 2014). The VOCs compounds including aromatics and biogenic species have significant impact on SOA formation which play an important role in haze formation (Hallquist et al, 2009; Huang et al, 2014). VOCs emission abatement is imperative for improving air quality in China

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Conclusion