Source apportionment of VOCs and their impacts on surface ozone in an industry city of Baoji, Northwestern China.

Level of surface ozone (O3) has been increasing continuously in China in recent years, while its contributors and formation pathways are less understood. In this study, distributions of volatile organic compounds (VOCs) and the roles on O3 pollution have been investigated in a typical industrial city of Baoji in Northwestern China by means of monitoring of their concentrations and other trace gases. The air samples have been collected at three sites according to urban function area. Concentration of VOCs in Weibin site, which near to industrial zone, was higher than most of other cities in China, and the ambient VOCs were dominated by aromatics and alkenes. The temporal variations of VOCs and O3 coincided with the surface wind, implying that the formation of O3 was impacted by both exports of plumes upwind and local photochemical reactions. Result of source apportionment indicated that industrial emission, vehicular exhaust, and solvent evaporation were three major pollution origins. Alkenes and aromatics contributed to the largest fractions of photochemical reactivity, suggesting the strong influences from industrial and traffic sectors. The study presents the characteristic VOCs and other factors in the contribution of O3 formation in China.