Rates and regimes of photochemical ozone production over Central East China in June 2006: a box model analysis using comprehensive measurements of ozone precursors

摘要

An observation-based box model approach was undertaken to estimateconcentrations of OH, HO, and RO radicals and the netphotochemical production rate of ozone at the top of Mount Tai, located inthe middle of Central East China, in June 2006. The model calculation wasconstrained by the measurements of O, HO, CO, NO, NO,hydrocarbon, HCHO, and CHCHO concentrations, and temperature and values. The net production rate of ozone was estimated to be 6.4 ppb has a 6-h average (09:00–15:00 CST), suggesting 58±37 ppb ofozone is produced in one day. Thus the daytime buildup of ozone recorded atthe mountain top as ~23 ppb on average is likely affected by in situphotochemistry as well as by the upward transport of polluted air mass inthe daytime. On days with high ozone concentrations (hourly values exceeding100 ppb at least once), in situ photochemistry was more active than it wason low ozone days, suggesting that in situ photochemistry is an importantfactor controlling ozone concentrations. Sensitivity model runs for whichdifferent NO and hydrocarbon concentrations were assumed suggestedthat the ozone production occurred normally under NO-limitedconditions, with some exceptional periods (undervolatile-organic-compound-limited conditions) in which there was freshpollution. We also examined the possible influence of the heterogeneous lossof gaseous HO radicals in contact with aerosol particle surfaces onthe rate and regimes of ozone production.