Effects of Asian air pollution transport and photochemistry on carbon monoxide variability and ozone production in subtropical coastal south China

Abstract

[1] Surface ozone and carbon monoxide (CO) measured from a relatively remote coastal station in Hong Kong are analyzed to study the effects of pollutant transport and associated ozone production on CO and ozone variations in the subtropical south China region. CO and ozone concentrations show a common minimum in summer and in the maritime air masses from the South China Sea and Pacific Ocean. They have higher values in other seasons and in the continental air masses that have passed over mainland Asia and the East Asian coast. CO shows the maximum monthly median of 457-552 ppbv in winter while ozone shows a maximum of 40-50 ppbv in autumn and a distinct peak of 41-43 ppbv in spring. The CO concentrations especially in the continental air masses (median of 277 to 428 ppbv) are very high when compared with measurements in most parts of the world. This suggests that the south China region is under the strong influence of pollutant transport from the Asian continent and East Asian coast. Ozone and CO show strong positive correlations in the polluted maritime air masses and from late spring to early autumn (May-September) with the linear regression slopes of the ozone-CO plot from 0.08 to 0.22 (with respective standard errors from 0.01 to 0.03). The strong correlations and slopes plus the high CO levels indicate that there is substantial ozone production from pollution in the polluted maritime air masses and in the late spring to early autumn period.

Variations of surface ozone at Ieodo Ocean Research Station in the East China Sea and the influence of Asian outflows

“…The O 3 concentrations remained high during March-May, resulting in a broad spring peak which was in contrast to a sharp fall peak. This is in accordance with a typical pattern that has been observed in other remote sites over northeast Asia during the past decades (Chan et al, 2002;Jaffe et al, 1996;Kanaya et al, 2015;Kondo et al, 2008;Oltmans and Levy II, 1994;Tanimoto et al, 2005Tanimoto et al, , 2009Watanabe et al, 2005; Weiss-Penzias et al, 2004). In particular, the second peak of O 3 was the most noticeable at IORS along with Gosan in October, which was also observed in previous studies (Kanaya et al, 2015;Tanimoto et al, 2005).…”

Implications of regional surface ozone increases on visibility degradation in southeast China

“…Changes in CO and volatile organic compounds (VOCs) may also contribute to this trend through NO-peroxy radical reactions. Strong positive correlations between O 3 and CO concentrations were previously found in late spring to early autumn in this region (Chan et al, 2002), and O 3 formation in the Hong Kong region is VOC-limited (Huang et al, 2005 …”

Ozone pollution around a coastal region of South China Sea: interaction between marine and continental air

“…Numerous studies demonstrated that in addition to long-range transport (Chan, 2002;Guo et al, 2009;Wang et al, 2009) and local photochemical production (Ding et al, 2013b), tropical cyclones and mesoscale circulations are conducive to the occurrence of high-O 3 events (Yin, 2004;Huang et al, 2005;Yang et al, 2012;Jiang et al, 2015;Wei et al, 2016). In a number of studies, the tropical cyclone has been considered as the most conducive driver to the occurrence of O 3 episodes in Hong Kong (Yin, 2004;Ling et al, 2013) because it generally causes peripheral subsidence, stagnation air and inversion layers, which favor the production and accumulation of O 3 .…”