OH reactivity in urban and suburban regions in Seoul, South Korea – an East Asian megacity in a rapid transition

Abstract

South Korea has recently achieved developed country status with the second largest megacity in the world, the Seoul Metropolitan Area (SMA). This study provides insights into future changes in air quality for rapidly emerging megacities in the East Asian region. We present total OH reactivity observations in the SMA conducted at an urban Seoul site (May–June, 2015) and a suburban forest site (Sep, 2015). The total OH reactivity in an urban site during the daytime was observed at similar levels (∼15 s−1) to those previously reported from other East Asian megacity studies. Trace gas observations indicate that OH reactivity is largely accounted for by NOX (∼50%) followed by volatile organic compounds (VOCs) (∼35%). Isoprene accounts for a substantial fraction of OH reactivity among the comprehensive VOC observational dataset (25–47%). In general, observed total OH reactivity can be accounted for by the observed trace gas dataset. However, observed total OH reactivity in the suburban forest area cannot be largely accounted for (∼70%) by the trace gas measurements. The importance of biogenic VOC (BVOCs) emissions and oxidations used to evaluate the impacts of East Asian megacity outflows for the regional air quality and climate contexts are highlighted in this study.

Shipborne measurements of total OH reactivity around the Arabian Peninsula and its role in ozone chemistry

“…The range and composition of OH reactivity (and the ozone mixing ratios) around the Arabian Peninsula were, despite the 5 marine measurement locations, broadly comparable to observations from highly populated urban areas, except for an unusually large contribution of OVOCs (Kovacs et al, 2003;Mao et al, 2010;Dolgorouky et al, 2012;Kim et al, 2016;Williams et al, 2016;Praplan et al, 2017;Yang et al, 2017). The "urban-like" OH reactivity is related to intensive international ship traffic in the seaways in the Arabian Basin and to major emissions from oil and gas industries on sea platforms and at the coasts.…”

Response to review

“…The OH reactivities measured at the Wangdu site in the North China Plain show diurnal profiles that are comparable to those reported for other polluted environments all over the world (see review by Yang et al, 2016). The total reactivities lie within the range of values observed during summertime at other locations that were mainly influenced by anthropogenic emissions, like Nashville (Kovacs et al, 2003), New York and Houston (Mao et al, 2010) in the US, Tokyo in Japan (Chatani et al, 2009), Beijing in China, Seoul in South Korea (Kim et al, 2016), and London (Whalley et al, 2016) in Great Britain. Also, the shapes of the diurnal profiles were similar, with peak values between 15 and 50 s −1 in the early morning and minimum values in the afternoon.…”

OH reactivity at a rural site (Wangdu) in the North China Plain: contributions from OH reactants and experimental OH budget

“…The total reactivities lie within the range of values observed during summertime at other locations that were mainly influenced by anthropogenic emissions, like Nashville (Kovacs et al, 2003), New York and Houston (Mao et al, 2010) in the US, Tokyo in Japan (Chatani et al, 2009), Beijing in China, Seoul in South Korea (Kim et al, 2016), and London (Whalley et al, 2016) in Great Britain. Also, the shapes of the diurnal profiles were similar, with peak values between 15 and 50 s −1 in the early morning and minimum values in the afternoon.…”