ACPD Atmospheric Chemistry and Physics Discussions ACPD 1680-7375 Copernicus GmbH Göttingen, Germany 10.5194/acpd-9-10429-2009 Increasing surface ozone concentrations in the background atmosphere of southern China, 1994–2007 Wang T. 1 Wei X. L. 1 Ding A. J. 1 Poon C. N. 1 Lam K. S. 1 Li Y. S. 1 Chan L. Y. 1 Anson M. 2 Department of Civil and Structural Engineering, The Hong Kong Polytechnic University, Hong Kong, China Faculty of Construction and Land Use, The Hong Kong Polytechnic University, Hong Kong, China 28 04 2009 9 2 10429 10455 This is an open-access article ditributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited. This article is available from http://www.atmos-chem-phys-discuss.net/9/10429/2009/acpd-9-10429-2009.html The full text article is available as a PDF file from http://www.atmos-chem-phys-discuss.net/9/10429/2009/acpd-9-10429-2009.pdf

Tropospheric ozone is of great importance with regard to air quality, atmospheric chemistry, and climate change. In this paper we report the first continuous record of surface ozone in the background atmosphere of South China. The data were obtained from 1994 to 2007 at a coastal site in Hong Kong, which is strongly influenced by the outflow of Asian continental air during the winter and the inflow of maritime air from the subtropics in the summer. Overall, the ozone concentration increased by an averaged rate of 0.55 ppbv/yr, with a larger increase in autumn (0.68 ppbv/yr). We also examine the trend in air masses from various source regions in Asia. Using local wind and concurrently measured carbon monoxide (CO) data to filter out local emissions, the mean ozone in air masses from eastern China, using the pooled averaging method, increased by 0.64 ppbv/yr, while ozone levels in other air-mass groups showed a positive trend (0.29–0.67 ppbv/yr) but with lower levels of statistical significance. An examination of the nitrogen dioxide (NO<sub>2</sub>) column concentration data obtained from GOME and SCIAMACHY reveals an increase in atmospheric NO<sub>2</sub> in the three fastest developing coastal regions of China, whereas NO<sub>2</sub> in other parts of Asia decreased during the same period. It is believed that the observed increase in background ozone in Hong Kong is primarily due to the increased emissions of NO<sub>2</sub> (and possibly volatile organic compounds (VOCs) as well) in the upwind coastal regions of mainland China, which is supported by the observed positive CO trend (5.23 ppbv/yr) at the site. The increase in background ozone contributed two thirds of the annual increase in ''total ozone'' in the downwind urban areas of Hong Kong, suggesting the need to consider distant sources when developing long-term strategies to mitigate local ozone pollution, although short-term strategies should be aimed at sources in Hong Kong and the adjacent Pearl River Delta.

 References Chameides,~W L., Li,~X S., Tang,~X Y., Zhou,~X J., Luo,~C., Kiang,~C. ~S., St John,~J., Saylor,~R D., Liu,~S C., Lam,~K S., Wang,~T., and Giorgi,~F.: Is ozone pollution affecting crop yields in China?, Geophys. Res. Lett., 26, 867–870, 1999. Chan,~C Y., Chan,~L Y., and Harris,~J M.: Urban and background ozone trend in 1984-1999 at subtropical Hong Kong, South China, Ozone-Sci. Eng., 25, 513–522, 2004. Cheung,~V T F., and Wang,~T.: Observational study of ozone pollution at a~rural site in the Yangtze Delta of China, Atmos. Environ., 35, 4947–4958, 2001. Chou,~C C K., Liu,~S C., Lin,~C Y., Shiu,~C J., and Chang,~K H.: The trend of surface ozone in Taipei, Taiwan, and its causes: Implications for ozone control strategies, Atmos. Environ., 40, 3898–3908, 2006. Cohen,~D D., Garton,~D., Stelcer,~E., Hawas,~O., Wang,~T., Poon,~S., Kim, ~J., Choi,~B C., Oh,~S N., Shin,~H J., Ko,~M Y., and Uematsu,~M.: Multielemental analysis and characterization of fine aerosols at several key ACE-Asia sites,~J. Geophys. Res.-Atmos., 109, D19S12, doi:10.1029/2003JD003569, 2004. Collins,~W J., Derwent,~R G., Garnier,~B., Johnson,~C E., Sanderson,~M. ~G., and Stevenson,~D S.: Effect of stratosphere-troposphere exchange on the future tropospheric ozone trend,~J. Geophys. Res.-Atmos., 108, 8528, doi:10.1029/2002JD002617, 2003. Crutzen,~P.: Discussion of chemistry of some minor constituents in stratosphere and troposphere, Pure Appl. Geophys., 106, 1385–1399, 1973. Danielsen,~E.: Stratospheric-tropospheric exchange based on radioactivity ozone and potential vorticity,~J. Atmos. Sci., 25, 502–518, 1968. Ding,~A J., Wang,~T., Thouret,~V., Cammas,~J P., and Nédélec,~P.: Tropospheric ozone climatology over Beijing: analysis of aircraft data from the MOZAIC program, Atmos. Chem. Phys., 8, 1–13, 2008. Dorling,~S R., Davies,~T D., and Pierce,~C E.: Cluster-analysis – a~technique for estimating the synoptic meteorological controls on air and precipitation chemistry – method and applications, Atmos. Environ., 26, 2575–2581, 1992. Draxler,~R R. and Hess,~G D.: An overview of the HYSPLIT_4 modelling system for trajectories, despersion, and deposition, Austral. Meterol. Mag., 47, 295–308, 1998. Fiore,~A M., Jacob,~D J., Logan,~J A., and Yin,~J H.: Long-term trends in ground level ozone over the contiguous United States, 1980–1995,~J. Geophys. Res.-Atmos., 103, 1471–1480, 1998. Gao,~J., Wang,~T., Ding,~A J., and Liu,~C B.: Observational study of ozone and carbon monoxide at the summit of mount Tai (1534 \unitm a.s.l.) in central-eastern China, Atmos. Environ., 39, 4779–4791, 2005. IPCC: Climate change 2007 – Synthesis Report, 2007. Jacob,~D J., Logan,~J A., and Murti,~P P.: Effect of rising Asian emissions on surface ozone in the United States, Geophys. Res. Lett., 26, 2175–2178, 1999. Jaffe,~D. and Ray,~J.: Increase in surface ozone at rural sites in the western US, Atmos. Environ., 41, 5452–5463, 2007. Lam,~K S., Wang,~T J., Chan,~L Y., Wang,~T., and Harris,~J.: Flow patterns influencing the seasonal behavior of surface ozone and carbon monoxide at a~coastal site near Hong Kong, Atmos. Environ., 35, 3121–3135, 2001. Naja,~M. and Akimoto,~H.: Contribution of regional pollution and long-range transport to the Asia-Pacific region: Analysis of long-term ozonesonde data over Japan,~J. Geophys. Res.-Atmos., 109, D21306, doi:10.1029/2004JD004687, 2004. Novelli,~P C., Masarie,~K A., Lang,~P M., Hall,~B D., Myers,~R C., and Elkins,~J W.: Reanalysis of tropospheric CO trends: Effects of the 1997–1998 wildfires,~J. Geophys. Res.-Atmos., 108(D15), 4464, doi:10.1029/2002JD003031, 2003. Novelli,~P C.: Observational evidence for long-term trends in carbon monoxide, American Geophysical Union, Fall Meeting, abstract#A11C-0600, 2007. NRC, Committee on Tropospheric Ozone: Rethinking the Ozone Problem in Urban and Regional Air Pollution, 1991. Oltmans,~S J., Lefohn,~A S., Harris,~J M., Galbally,~I., Scheel,~H E., Bodeker,~G., Brunke,~E., Claude,~H., Tarasick,~D., Johnson,~B J., Simmonds, ~P., Shadwick,~D., Anlauf,~K., Hayden,~K., Schmidlin,~F., Fujimoto,~T., Akagi,~K., Meyer,~C., Nichol,~S., Davies,~J., Redondas,~A., and Cuevas,~E.: Long-term changes in tropospheric ozone, Atmos. Environ., 40, 3156–3173, 2006. Parrish,~D D., Dunlea,~E J., Atlas,~E L., Schauffler,~S., Donnelly,~S., Stroud,~V., Goldstein,~A H., Millet,~D B., McKay,~M., Jaffe,~D A., Price,~H U., Hess,~P G., Flocke,~F., and Roberts,~J M.: Changes in the photochemical environment of the temperate North Pacific troposphere in response to increased Asian emissions, J. Geophys. Res.-Atmos., 109, D23S18, doi:10.1029/2004JD004978, 2004. Richter,~A., Burrows,~J P., Nuss,~H., Granier,~C., and Niemeier,~U.: Increase in tropospheric nitrogen dioxide over China observed from space, Nature, 437, 129–132, 2005. Shao,~M., Tang,~X Y., Zhang,~Y H., and Li,~W J.: City clusters in China: air and surface water pollution, Front. Ecol. Environ., 4, 353–361, 2006. Tanimoto,~H., Mukai,~H., Sawa,~Y., Matsueda,~H., Yonemura,~S., Wang,~T., Poon,~S., Wong,~A., Lee,~G., Jung,~J Y., Kim,~K R., Lee,~M H., Lin,~N. ~H., Wang,~J L., Ou-Yang,~C F., Wu,~C F., Akimoto,~H., Pochanart,~P., Tsuboi,~K., Doi,~H., Zellwegern,~C., and Klausenn,~J.: Direct assessment of international consistency of standards for ground-level ozone: strategy and implementation toward metrological traceability network in Asia, J. Environ. Monitor., 9, 1183–1193, 2007. Taylor,~J K., and Cihon,~C.: Statistical Techniques for data analysis, 2nd edn, Chapman and Hall/CRC, 2004. USEPA: EPA's Report on the Environment 2008, EPA/600/R-07/045F, Washington, DC 20460, 2008. Vingarzan,~R.: A~review of surface ozone background levels and trends, Atmos. Environ., 38, 3431–3442, 2004. Wang,~T., Lam,~K S., Chan,~L Y., Lee,~A S Y., and Carroll,~M A.: Trace gas measurements in coastal Hong Kong during the PEM-West B,~J. Geophys. Res.-Atmos., 102, 28575–28588, 1997. Wang,~T., Lam,~K S., Lee,~A S Y., Pang,~S W., and Tsui,~W S.: Meteorological and chemical characteristics of the photochemical ozone episodes observed at Cape D'Aguilar in Hong Kong,~J. Appl. Meteorol., 37, 1167–1178, 1998. Wang,~T., Cheung,~V T F., Anson,~M., and Li,~Y S.: Ozone and related gaseous pollutants in the boundary layer of eastern China: Overview of the recent measurements at a~rural site, Geophys. Res. Lett., 28, 2373–2376, 2001. Wang,~T., Ding,~A J., Blake,~D R., Zahorowski,~W., Poon,~C N., and Li,~Y. ~S.: Chemical characterization of the boundary layer outflow of air pollution to Hong Kong during February–April 2001,~J. Geophys. Res.-Atmos., 108, 8787, doi:10.1029/2002JD003272, 2003. Wang,~T., Guo,~H., Blake,~D R., Kwok,~Y H., Simpson,~I J., and Li,~Y S.: Measurements of trace gases in the inflow of South China Sea background air and outflow of regional pollution at Tai O, Southern China,~J. Atmos. Chem., 52, 295–317, 2005. Wang,~T., Ding,~A J., Gao,~J., and Wu,~W S.: Strong ozone production in urban plumes from Beijing, China, Geophys. Res. Lett., 33, 1–5, 2006a. Wang,~Z F., Li,~J., Wang,~X Q., Pochanart,~P., and Akimoto,~H.: Modeling of regional high ozone episode observed at two mountain sites (Mt. Tai and Huang) in East China,~J. Atmos. Chem., 55, 253–272, 2006b. Xu,~X., Lin,~W., Wang,~T., Yan,~P., Tang,~J., Meng,~Z., and Wang,~Y.: Long-term trend of surface ozone at a~regional background station in eastern China 1991–2006: enhanced variability, Atmos. Chem. Phys., 8, 2595–2607, 2008. Zhang,~J., Wang,~T., Chameides,~W L., Cardelino,~C., Kwok,~J., Blake,~D. ~R., Ding,~A., and So,~K L.: Ozone production and hydrocarbon reactivity in Hong Kong, Southern China, Atmos. Chem. Phys., 7, 557–573, 2007. Zhang,~Y H., Su,~H., Zhong,~L J., Cheng,~Y F., Zeng,~L M., Wang,~X S., Xiang,~Y R., Wang,~J L., Gao,~D F., Shao,~M., Fan,~S J., and Liu,~S C.: Regional ozone pollution and observation-based approach for analyzing ozone-precursor relationship during the PRIDE-PRD2004 campaign, Atmos. Environ., 42, 6203–6218, 2008.