Atmospheric Chemistry and Physics www.atmos-chem-phys.net 1680-7316 1680-7324 9 19 2009 10.5194/acp-9-7343-2009 http://www.atmos-chem-phys.net/9/7343/2009/ http://www.atmos-chem-phys.net/9/7343/2009/acp-9-7343-2009.html http://www.atmos-chem-phys.net/9/7343/2009/acp-9-7343-2009.pdf 7343 7360 2009-10-02 Concurrent observations of air pollutants at two sites in the Pearl River Delta and the implication of regional transport H. Guo ceguohai@polyu.edu.hk F. Jiang H. R. Cheng I. J. Simpson X. M. Wang A. J. Ding T. J. Wang S. M. Saunders T. Wang S. H. M. Lam D. R. Blake Y. L. Zhang M. Xie Air Quality Studies, Department of Civil and Structural Engineering, the Hong Kong Polytechnic University, Hong Kong School of Atmospheric Sciences, Nanjing University, Nanjing, China Department of Chemistry, University of California at Irvine, California, USA Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou, China School of Biomedical, Biomolecular and Chemical Sciences, University of Western Australia, Perth, Australia An intensive field measurement study was conducted simultaneously at a site within the inland Pearl River Delta (PRD) region (WQS) and a site in Hong Kong (TC) between 22 October and 1 December 2007. Ambient air pollutants measured included O₃, NO_x, CO, SO₂, NMHCs, and carbonyls. The purpose is to improve our understanding of the interplay among local and regional air pollutants in the Hong Kong area, and the influence of regional transport on local air pollutants. The results indicate that the mean levels of air pollutants at the WQS site were much higher than those at the TC site, except NO_x. Thirteen O₃ episode days (daily O₃ peak in excess of 122 ppbv) were monitored at WQS during the study period, while only 2 days were recorded at TC. Diurnal variations of O₃ showed higher nighttime levels of O₃ at TC than at WQS as well as more photochemical activity at WQS than TC. Remarkable differences in diurnal variations were also found between high and low O₃ pollution days at each site, implying that Hong Kong is more acutely VOC-limited than the inland PRD region. Ratio analyses for trace gases and VOCs and back trajectory calculation revealed that the air masses arriving at WQS were more aged due to regional influence, whereas the air masses at TC were mainly affected by local emissions and/or regional transport. 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