Is atmospheric oxidation capacity better in indicating tropospheric O_(3) formation?

Tropospheric ozone(O_(3))concentration is increasing in China along with dramatic changes in precursor emissions and meteorological conditions,adversely affecting human health and ecosystems.O_(3) is formed from the complex nonlinear photochemical reactions from nitrogen oxides(NOx=NO+NO_(2))and volatile organic compounds(VOCs).Although the mechanism of O_(3) formation is rather clear,describing and analyzing its changes and formation potential at fine spatial and temporal resolution is still a challenge today.In this study,we briefly summarized and evaluated different approaches that indicate O_(3) formation regimes.We identify that atmospheric oxidation capacity(AOC)is a better indicator of photochemical reactions leading to the formation of O_(3) and other secondary pollutants.Results show that AOC has a prominent positive relationship to O_(3) in the major city clusters in China,with a goodness of fit(R^(2))up to 0.6.This outcome provides a novel perspective in characterizing O_(3) formation and has significant implications for formulating control strategies of secondary pollutants.

Investigating missing sources of glyoxal over China using a regional air quality model (RAMS-CMAQ)

Currently, modeling studies tend to significantly underestimate observed space-based glyoxal （CHOCHO） vertical column densities （VCDs）, implying the existence of missing sources of giyoxal. Several recent studies suggest that the emissions of aromatic compounds and molar yields of glyoxal in the chemical mechanisms may both be underestimated, which can affect the simulated glyoxal concentrations. In this study, the influences of these two factors on glyoxal amounts over China were investigated using the RAMS-CMAQ modeling system for January and July 2014. Four sensitivity simulations were performed, and the results were compared to satellite observations. These results demonstrated significant impacts on glyoxal concentrations from these two factors. In case 1, where the emissions of aromatic compounds were increased three-fold, improvements to glyoxal VCDs were seen in high anthropogenic emissions regions. In case 2, where molar yields of glyoxal from isoprene were increased five-fold, the resulted concentrations in July were B-B-fold higher, achieving closer agreement between the modeled and measured glyoxal VCDs. The combined changes from both cases 1 and 2 were applied in case B, and the model succeeded in further reducing the underestimations of glyoxal VCDs. However, the results over most of the regions with pronounced anthropogenic emissions were still underestimated. So the molar yields of giyoxal from anthropogenic precursors were considered in case 4. With these additional mole yield changes （a two-fold increase）, the improved concentrations agreed better with the measurements in regions of the lower reaches of the Yangtze River and Yellow River in January but not in July.