Aircraft measurements of O3, NOx, CO, VOCs, and SO2 in the Yangtze River Delta region

In this study, air pollutants, including ozone (O3), nitrogen oxides (NOx = NO + NO2), carbon monoxides (CO), sulfur dioxide (SO2), and volatile organic compounds (VOCs) measured in the Yangtze River Delta (YRD) region during several air flights between September/30 and October/11 are analyzed. This measurement provides horizontal and vertical distributions of air pollutants in the YRD region. The analysis of the result shows that the measured O3 concentrations range from 20 to 60 ppbv. These values are generally below the US national standard (84 ppbv), suggesting that at the present, the O3 pollutions are modest in this region. The NOx concentrations have strong spatial and temporal variations, ranging from 3 to 40 ppbv. The SO2 concentrations also have large spatial and temporal variations, ranging from 1 to 35 ppbv. The high concentrations of CO are measured with small variations, ranging from 3 to 7 ppmv. The concentrations of VOCs are relatively low, with the total VOC concentrations of less than 6 ppbv. The relative small VOC concentrations and the relative large NOx concentrations suggest that the O3 chemical formation is under a strong VOC-limited regime in the YRD region. The measured O3 and NOx concentrations are strongly anti-correlated, indicating that enhancement in NOx concentrations leads to decrease in O3 concentrations. Moreover, the O3 concentrations are more sensitive to NOx concentrations in the rural region than in the city region. The ratios of Δ[O3]/Δ[NOx] are −2.3 and −0.25 in the rural and in the city region, respectively. In addition, the measured NOx and SO2 concentrations are strongly correlated, highlighting that the NOx and SO2 are probably originated from same emission sources. Because SO2 emissions are significantly originated from coal burnings, the strong correlation between SO2 and NOx concentrations suggests that the NOx emission sources are mostly from coal burned sources. As a result, the future automobile increases could lead to rapid enhancements in O3 concentrations in the YRD region.