Spatiotemporal variation, sources, and secondary transformation potential of volatile organic compounds in Xi'an, China

Abstract

Abstract. As critical precursors of ozone (O3) and secondary organic aerosols, volatile organic compounds (VOCs) play a vital role in air quality, human health, and climate change. In this study, a campaign of comprehensive field observations and VOC grid sampling was conducted in Xi'an, China, from 20 June to 20 July 2019 to identify the spatiotemporal concentration levels, sources, and secondary transformation potential of VOCs. During the observation period, the average VOC concentrations at the Chanba (CB), Di Huan Suo (DHS), Qinling (QL), and gridded sampling sites were 27.8 ± 8.9, 33.8 ± 10.5, 15.5 ± 5.8, and 29.1 ± 8.4 ppb, respectively. Vehicle exhaust was the primary source of VOC emissions in Xi'an, and the contributions of vehicle exhaust to VOCs at the CB, DHS, and QL sites were 41.3 %, 30.6 %, and 23.6 %–41.4 %, respectively. While industrial emissions were the second-largest source of VOCs in urban areas, contributions from aging sources were high in rural areas. High potential source contribution function values primarily appeared in eastern and southern Xi'an near the sampling site, which indicates that Xi'an exhibits a strong local VOC source. Moreover, alkenes, aromatics, and oxygenated VOCs played a dominant role in secondary transformation, which is a major concern in reducing O3 pollution in Xi'an.

Volatile organic compounds: A proinflammatory activator in autoimmune diseases

“…However, there are differences in the sources that contribute to VOC emission across regions in China. In the cities of Langfang and Xiamen, paint solvents constitute the highest contributing factor to VOC emission (62), while vehicular exhaust and combustion are the primary sources of VOCs in Wuhan City (63). In another study (59), it was reported that about 40 VOCs were observed in more than 50% of air samples collected from residences of pregnant women in Northeastern British Columbia, a region of natural gas exploitation, while four VOCs were detected in more than 50% of the water samples tested.…”

Measurement report: Ambient volatile organic compound (VOC) pollution in urban Beijing: characteristics, sources, and implications for pollution control

“…The great changes in the mixing ratios of different species are mainly affected by photochemical processing, emission inputs, and ratios of VOC species having similar atmospheric lifetimes can reflect the source features (B. Li et al, 2019;Raysoni et al, 2017;Song et al, 2021). The ratio of ipentane to n-pentane is widely used to examine the impact of vehicle emissions, fuel evaporation, and combustion emissions within the i/n-pentane ratios of ranging 2.…”

Spatial variability of air pollutants in a megacity characterized by mobile measurements: Chemical homogeneity under haze conditions

“…During the clean day, both of the distributions show large spatial variabilities with high CV values ( hot spots for benzene and toluene are not the same, highlighting the difference in emissions from individual vehicles (Mo et al, 2016). The toluene-to-benzene concentration ratio (T/B) is widely used to differentiate the VOC sources (Song et al, 2021; and references therein). According to literature, traffic emissions have T/B ratios from 1 to 3 depending on vehicle type and fuel composition.…”

“…Moreover, grid sampling and simultaneous measurements at multiple sites are often used to investigate the spatial variations of air pollutants on sparse spatial scales. Previous studies show that the surface concentrations of VOCs and PM2.5 components vary because of different source contributions in metropolitan areas in China (Chen et al, 2020;Song et al, 2021).…”