Aircraft measurements of O 3, NO x, CO, VOCs, and SO 2 in the Yangtze River Delta region

Abstract

In this study, air pollutants, including ozone (O 3), nitrogen oxides (NO x = NO + NO 2), carbon monoxides (CO), sulfur dioxide (SO 2), 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 O 3 concentrations range from 20 to 60 ppbv. These values are generally below the US national standard (84 ppbv), suggesting that at the present, the O 3 pollutions are modest in this region. The NO x concentrations have strong spatial and temporal variations, ranging from 3 to 40 ppbv. The SO 2 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 NO x concentrations suggest that the O 3 chemical formation is under a strong VOC-limited regime in the YRD region. The measured O 3 and NO x concentrations are strongly anti-correlated, indicating that enhancement in NO x concentrations leads to decrease in O 3 concentrations. Moreover, the O 3 concentrations are more sensitive to NO x concentrations in the rural region than in the city region. The ratios of Δ[O 3]/Δ[NO x ] are −2.3 and −0.25 in the rural and in the city region, respectively. In addition, the measured NO x and SO 2 concentrations are strongly correlated, highlighting that the NO x and SO 2 are probably originated from same emission sources. Because SO 2 emissions are significantly originated from coal burnings, the strong correlation between SO 2 and NO x concentrations suggests that the NO x emission sources are mostly from coal burned sources. As a result, the future automobile increases could lead to rapid enhancements in O 3 concentrations in the YRD region.