Impact of isoprene and HONO chemistry on ozone and OVOC formation in a semirural South Korean forest

Abstract

Abstract. Rapid urbanization and economic development in East Asia in past decades has led to photochemical air pollution problems such as excess photochemical ozone and aerosol formation. Asian megacities such as Seoul, Tokyo, Shanghai, Guangzhou, and Beijing are surrounded by densely forested areas, and recent research has consistently demonstrated the importance of biogenic volatile organic compounds (VOCs) from vegetation in determining oxidation capacity in the suburban Asian megacity regions. Uncertainties in constraining tropospheric oxidation capacity, dominated by hydroxyl radical, undermine our ability to assess regional photochemical air pollution problems. We present an observational data set of CO, NO x , SO 2 , ozone, HONO, and VOCs (anthropogenic and biogenic) from Taehwa research forest (TRF) near the Seoul metropolitan area in early June 2012. The data show that TRF is influenced both by aged pollution and fresh biogenic volatile organic compound emissions. With the data set, we diagnose HO x (OH, HO 2 , and RO 2 ) distributions calculated using the University of Washington chemical box model (UWCM v2.1) with nearexplicit VOC oxidation mechanisms from MCM v3.2 (Master Chemical Mechanism). Uncertainty from unconstrained HONO sources and radical recycling processes highlighted in recent studies is examined using multiple model simulations with different model constraints. The results suggest that (1) different model simulation scenarios cause systematic differences in HO x distributions, especially OH levels (up to 2.5 times), and (2) radical destruction (HO 2 + HO 2 or HO 2 + RO 2 ) could be more efficient than radical recycling (RO 2 + NO), especially in the afternoon. Implications of the uncertainties in radical chemistry are discussed with respect to ozone-VOC-NO x sensitivity and VOC oxidation product formation rates. Overall, the NO x limited regime is assessed except for the morning hours (8 a.m. to 12 p.m. local standard time), but the degree of sensitivity can significantly vary depending on the model scenarios. The model results also suggest that RO 2 levels are positively correlated with oxygenated VOCs (OVOCs) production that is not routinely constrained by observations. These unconstrained OVOCs can cause higher-than-expected OH loss rates (missing OH reactivity) and secondary organic aerosol formation. The series of modeling experiments constrained by observations strongly urge observational constraint of the radical pool to enable precise understanding of regional photochemical pollution problems in the East Asian megacity region.

Atmospheric mixing ratios of methyl ethyl ketone (2-butanone) in tropical, boreal, temperate and marine environments

“…Its occurrence in the atmosphere has been reported over a wide range of environments (Cecinato et al, 2002;Hellén et al, 2004;Ho et al, 2002;Kim et al, 2015;McKinney et al, 2011;Singh et al, 2004) with typical mixing ratios of 0.03-4 ppb (Ciccioli and Mannozzi, 2007;Kim et al, 2015). Although often being measured alongside other volatile organic compounds (VOCs), atmospheric MEK has received little attention to date.…”

“…Terrestrial vegetation (BrachoNunez et al, 2013;Brilli et al, 2014;Davison et al, 2008;De Gouw et al, 1999;Isidorov et al, 1985;Jardine et al, 2010;Kirstine et al, 1998;König et al, 1995;McKinney et al, 2011;Ruuskanen et al, 2011;Song and Ryu, 2013;Steeghs et al, 2004;Wilkins, 1996;, fungi (Wheatley et al, 1997) and bacteria (Song and Ryu, 2013;Wilkins, 1996) are known to emit MEK. It is also emitted directly by several anthropogenic sources, including anthropogenic biomass burning (Andreae and Merlet, 2001), solvent evaporation (Kim et al, 2015;Legreid et al, 2007) and vehicle exhaust (Bon et al, 2011;Brito et al, 2015;Liu et al, 2015;Verschueren, 1983). In addition, MEK can be formed via the atmospheric oxidation of other compounds (de Gouw et al, 2003;Jenkin et al, 1997;Neier and Strehlke, 2002;Sommariva et al, 2011).…”

Diagnosis of Photochemical Ozone Production Rates and Limiting Factors in Continental Outflow Air Masses Reaching Fukue Island, Japan: Ozone-Control Implications

“…More specifically, in-situ ozone production rates can be assessed based on a photochemical box model calculation, constraining the precursor concentrations to observations [observation-based model (OBM)]. This methodology, originally established for the study of urban photochemistry in the United States (e.g., Cardelino and Chameides, 1995;Kleinman, 2000), has been applied to Asian megacities (Zhang et al, 2008;Shao et al, 2009) and suburban and rural areas (e.g., Kanaya et al, 2009;Kim et al, 2014). The rates were also determined for the Asian outflow captured by aircraft-borne observations over the western Pacific region during Pacific Exploration of Asian Continental Emission campaigns and near California during the Intercontinental Transport and Chemical Transformation 2002 campaign (Hudman et al, 2004).…”

Variation of OC and EC in PM_2.5 at Mt. Taehwa

“…이렇듯 OC 는 EC에 비해 생성원과 전구물질이 다양하고 생성과 정 또한 복잡하므로 특히 SOC에 대한 이해는 매우 부 족하다 (Turpin et al, 2000). 따라서 대부분 POC를 추 정하여 이를 기반으로 SOC의 농도를 간접적으로 계산 하는 방법들이 개발되었다 (Chou et al, 2010 Kim et al, 2015a;Kim et al, 2015b;Kim et al, 2013a;Kim et al, 2013b (Ham, 2015). Kim et al, 2007), 상해 (e.g., Feng et al, 2009) …”