Impact of biogenic volatile organic compounds on ozone production at the Taehwa Research Forest near Seoul, South Korea

Atmospheric Environment 70 (2013) 447e453 Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv Impact of biogenic volatile organic compounds on ozone production at the Taehwa Research Forest near Seoul, South Korea So-Young Kim a , Xiaoyan Jiang b , Meehye Lee c , Andrew Turnipseed b , Alex Guenther b , Jong-Choon Kim a , Suk-Jo Lee a , Saewung Kim b, * a b c National Institute of Environmental Research, Kyungseo-Dong, Seo-gu, Incheon 404-708, South Korea National Center for Atmospheric Research, 3090 Center Green Dr., Boulder, CO 80301, USA Department of Earth and Environmental Sciences, Korea University, 145 Anam Ro, Sungbuk-Gu, Seoul 136-701, South Korea h i g h l i g h t s < We presented trace gas observation results in the suburban Seoul Metropolitan Area. < We found BVOCs are dominant OH chemical sinks. < WRF-Chem modeling results show that BVOCs are important ozone precursors. a r t i c l e i n f o a b s t r a c t Article history: Received 13 June 2012 Received in revised form 31 October 2012 Accepted 5 November 2012 The importance of biogenic volatile organic compounds (BVOCs) in understanding of air-quality and climate on regional to global scales has been highlighted in a number of modeling and observational studies. At the same time, another important emerging research topic in atmospheric chemistry is the regional and global impacts of fast growing East Asian megacities. These two research topics must be integrated in order to adequately understand and address air quality challenges emerging from Eastern Asian megacities surrounded by planted or natural forest areas. We present initial measurement results for May, June and September 2011 from the Taehwa Research Forest (TRF) which has been developed to serve as a long term observatory for investigating biosphereeatmosphere interactions at the edge of the Seoul Metropolitan Area (population of w23.5 million). The comprehensive measurement datasets of ozone and its precursors such as CO, NO x , SO 2 and VOCs shows that high ozone episodes in the suburban site could not be explained by just anthropogenic pollutants alone. In addition, isoprene (C 5 H 8 ) and monoterpenes (C 10 H 16 ) were observed as two of the most important OH chemical sinks inside of the forest canopy. In order to understand the impacts of these BVOCs on ozone and related photochemistry, we conducted model sensitivity simulations using a coupled meteorology-chemistry model (WRF-Chem) for conditions including with and without BVOC emissions. The modeling results suggest that BVOC emissions could enhance regional daytime ozone production from 5 to 20 ppbv. The observed temporal variations in ozone correspond well with the variations in BVOCs, which likely reflects the influence of BVOCs on ozone formation. These findings strongly suggest that interactions between anthropogenic pollutants and BVOCs must be understood and quantified in order to assess photochemical ozone formation in the regions surrounding East Asian megacities. O 2012 Elsevier Ltd. All rights reserved. Keywords: Tropospheric ozone BVOCs WRF-Chem Asian megacities 1. Introduction Over the past three decades, the importance of biogenic volatile organic compounds (BVOCs) for tropospheric photochemistry has * Corresponding author. Present address: Department of Earth System Science, University of California, Irvine, Irvine, CA, USA. Tel.: þ1 949 824 4531. E-mail address: saewungk@uci.edu (S. Kim). 1352-2310/$ e see front matter O 2012 Elsevier Ltd. All rights reserved. http://dx.doi.org/10.1016/j.atmosenv.2012.11.005 been intensively studied. They are expected to have a major global role since BVOC emission is estimated to be much higher than anthropogenic volatile organic compound (AVOC) emission (Guenther et al., 2006; Goldstein and Galbally, 2007). The global dominance of BVOC is not only just in the total amount of emissions but also because BVOC reactivity with oxidants in the troposphere (e.g. hydroxyl radical (OH), ozone, and nitrate radical (NO 3 )) is usually much higher than for AVOCs. The reactivity contributions from ambient BVOC concentrations is often much higher than that