Abstract
The Korea-United States Air Quality Study (KORUS-AQ) took place in spring 2016 to better understand air pollution in Korea. In support of KORUS-AQ, 2554 whole air samples (WAS) were collected aboard the NASA DC-8 research aircraft and analyzed for 82 C1–C10 volatile organic compounds (VOCs) using multi-column gas chromatography. Together with fast-response measurements from other groups, the air samples were used to characterize the VOC composition in Seoul and surrounding regions, determine which VOCs are major ozone precursors in Seoul, and identify the sources of these reactive VOCs. (1) The WAS VOCs showed distinct signatures depending on their source origins. Air collected over Seoul had abundant ethane, propane, toluene and n-butane while plumes from the Daesan petrochemical complex were rich in ethene, C2–C6 alkanes and benzene. Carbonyl sulfide (COS), CFC-113, CFC-114, carbon tetrachloride (CCl4) and 1,2-dichloroethane were good tracers of air originating from China. CFC-11 was also elevated in air from China but was surprisingly more elevated in air over Seoul. (2) Methanol, isoprene, toluene, xylenes and ethene were strong individual contributors to OH reactivity in Seoul. However methanol contributed less to ozone formation based on photochemical box modeling, which better accounts for radical chemistry. (3) Positive Matrix Factorization (PMF) and other techniques indicated a mix of VOC source influences in Seoul, including solvents, traffic, biogenic, and long-range transport. The solvent and traffic sources were roughly equal using PMF, and the solvents source was stronger in the KORUS-AQ emission inventory. Based on PMF, ethene and propene were primarily associated with traffic, and toluene, ethylbenzene and xylenes with solvents, especially non-paint solvents for toluene and paint solvents for ethylbenzene and xylenes. This suggests that VOC control strategies in Seoul could continue to target vehicle exhaust and paint solvents, with additional regulations to limit the VOC content in a variety of non-paint solvents.
Highlights
Air pollution is an environmental and human health concern throughout the world
The air samples collected during KORUS-AQ showed distinct volatile organic compounds (VOCs) distributions and signatures depending on their source origins
Because the separation of paint and non-paint solvents was evident in simple correlation analysis, and because the 5-factor solution was more reasonable for the biogenic and long-range source factors, we suggest that the 5-factor solution can be used with appropriate uncertainty considerations
Summary
Air pollution is an environmental and human health concern throughout the world. As well as impacting respiratory and heart diseases, the International Agency for Research on Cancer (IARC) has classified outdoor air pollution as a carcinogen (IARC, 2013). Gasoline-fueled vehicles in South Korea have been subject to California’s Non Methane Organic Gases Fleet Average System since 2009, and diesel-fueled vehicles have been regulated under Euro 6 emission standards since 2014. VOCs have additional sources in South Korea such as organic solvents and production processes, and emission control strategies include the establishment of nation-wide VOC content limits for paints in 2013 (KMOE, 2017). While these emission control measures have led to an overall reduction in VOC levels in Seoul over the past twenty years, understanding the contributions of VOCs to ozone and aerosol formation in the Seoul Metropolitan Area (SMA) remains a high research priority (Kim and Lee, 2018)
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