Air quality diagnosis from comprehensive observations of total OH reactivity and reactive trace species in urban central Tokyo

Abstract

Atmospheric Environment 49 (2012) 51e59 Contents lists available at SciVerse ScienceDirect Atmospheric Environment journal homepage: www.elsevier.com/locate/atmosenv Air quality diagnosis from comprehensive observations of total OH reactivity and reactive trace species in urban central Tokyo Ayako Yoshino a, * , Yoshihiro Nakashima a , Koji Miyazaki a , Shungo Kato a , Jeeranut Suthawaree a , Nobuo Shimo b , Sou Matsunaga b , Satoru Chatani b, c , Eric Apel d , James Greenberg d , Alex Guenther d , Hiroyuki Ueno e , Hiroyuki Sasaki e , Jun-ya Hoshi e , Hisashi Yokota e , Koichiro Ishii e , Yoshizumi Kajii a a Department of Applied Chemistry, Graduate School of Urban Environmental Sciences, Tokyo Metropolitan University, 1-1 Minami-Osawa, Hachioji, Tokyo 192-0397, Japan Auto Oil and New Fuels Department, Japan Petroleum Energy Center, 4-3-9 Toranomon, Minato-ku, Tokyo 105-0001, Japan Toyota Central RD Tajima et al., 2010). The concen- tration of NO x (NO x ¼ NO þ NO 2 ) and non-methane hydrocarbons (NMHCs) has decreased by 10%e20%, while in contrast, O 3 has increased by 2% per year between 1992 and 2002 in Japan (Akimoto, 2006). Tropospheric O 3 makes a significant contribution to global warming because of its large radiative forcing, which is nearly equal to that of methane (CH 4 ). Thus there is a need within * Corresponding author. Present address: Faculty of Agriculture, Tokyo University of Agriculture and Technology, 3-5-8 Saiwaicho, Fuchu, Tokyo 183-8509, Japan. Tel./ fax: þ81 42 367 5620. E-mail address: ayoshino@cc.tuat.ac.jp (A. Yoshino). 1352-2310/$ e see front matter O 2011 Elsevier Ltd. All rights reserved. doi:10.1016/j.atmosenv.2011.12.029 the atmospheric science community to investigate the cause of this increase in tropospheric O 3 . Recent research has suggested that factors responsible for this increase in O 3 may include the presence of unknown VOCs (Sadanaga et al., 2005; Kajii et al., 2006) which facilitate highly efficient O 3 production following the decrease in NO x , the acceleration of O 3 production by the heat island phenom- enon, and the transport of O 3 and its precursors from the Asian continent (Ohara and Sakata, 2003). However, the most significant causative factors of this increase in O 3 in the urban atmosphere have yet to be identified. In order to completely understand the mecha- nism of tropospheric O 3 production, simultaneous observations of all the precursors of O 3 and an understanding of their reaction pathways are necessary, but this is not a practical approach. A great number of reactions contribute to the formation of tropospheric O 3 . Lewis et al. (2000) reported that there are more than several hundred kinds of VOCs in the troposphere, and Goldstein and Galbally (2007) reported that there are probably more than 10 5 different VOCs in the troposphere, which underscores the difficulty in fully characterizing all tropospheric O 3 reaction pathways.