Seasonal Variations of Carbonyls and Their Contributions to the Ozone Formation in Urban Atmosphere of Taiyuan, China

Zeqian Liu,Xueying Gao,Lili Guo,Yuhang Wang,Yang Cui,Xinming Wang,Yanli Feng,Qiusheng He

doi:10.3390/atmos12040510

Abstract

Ambient carbonyls are critical precursors of ozone (O3) and secondary organic aerosols (SOA). To better understand the pollution characteristics of carbonyls in Taiyuan, field samplings were conducted, and 13 carbonyls were detected in an urban site of Taiyuan for the four seasons. The total concentration of carbonyls in the atmosphere was 19.67 ± 8.56 μg/m3. Formaldehyde (7.70 ± 4.78 μg/m3), acetaldehyde (2.95 ± 1.20 μg/m3) and acetone (5.57 ± 2.41 μg/m3) were the dominant carbonyl compounds, accounting for more than 85% of the total carbonyls. The highest values for formaldehyde and acetone occurred in summer and autumn, respectively, and the lowest occurred in winter. The variations for acetaldehyde were not distinct in the four seasons. Formaldehyde and acetone levels increased obviously in the daytime and decreased at night, while acetaldehyde did not show significant diurnal variations. Higher temperature and stronger sunlight intensity could facilitate the photochemical reaction of volatile organic compounds (VOCs) and enhance the O3 levels in summer. Formaldehyde and acetaldehyde contributed 70–95% of carbonyls’ ozone formation potential (OFP) caused by carbonyls with the highest totals of 268.62 μg/m3 and 38.14 μg/m3, respectively. The highest concentrations of carbonyls from south and southwest winds in summer suggest that the coke industries in the southern Taiyuan Basin should be, firstly, controlled for the alleviation of ozone pollution.

Highlights

Carbonyls play an essential role in atmospheric chemistry
According to the report from the World Health Organization’s International Agency for Research on Cancer, formaldehyde is classified as a Group I human carcinogen for its carcinogenicity and acetaldehyde is a Group II carcinogen for its suspected carcinogenicity
Formaldehyde, acetaldehyde and acetone were the most abundant carbonyls in the atmosphere, and different energy and industrial structures resulted in the different composition proportions of carbonyls in those cities

Summary

Introduction

Carbonyls play an essential role in atmospheric chemistry. They are critical precursors of various oxidative radicals, ozone (O3), peroxyacetyl nitrate (PAN) and secondary organic aerosols (SOA) in the atmosphere. Formaldehyde, acetaldehyde and acetone were the most abundant carbonyls in the atmosphere, and different energy and industrial structures resulted in the different composition proportions of carbonyls in those cities. Formaldehyde was the most abundant species in the atmosphere in Beijing [13], while acetaldehyde and acetone were the highest in Nanning and Wuhan, respectively [15,16]. Qian et al (2019) reported that carbonyls exhibited the highest concentrations in summer, and primary anthropogenic emissions contributed 61% and 69% of total carbonyls in summer and winter, respectively [17]. A previous study in Shenzhen found that carbonyl levels were relatively higher in summer and autumn than those in spring and winter, and biogenic sources and secondary formation contributed 41% and 38% of formaldehyde in summer, respectively [18]. The difference in industrial structure, vegetational coverage, transportation and meteorological conditions could result in distinct characteristics of carbonyls in different areas and seasons [19,20]

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