Ozone and fine particle in the western Yangtze River Delta: An overview of 1 yr data at the SORPES station
This work presents an overview of 1 yr measure-ments of ozone (O 3) and fine particular matter (PM 2.5) and related trace gases at a recently developed regional back-ground site, the Station for Observing Regional Processes of the Earth System (SORPES), in the western part of the Yangtze River Delta (YRD) in eastern China. Ozone and PM 2.5 showed strong seasonal cycles but with contrast pat-terns: O 3 reached a maximum in warm seasons but PM 2.5 in cold seasons. Correlation analysis suggests a VOC-sensitive regime for O 3 chemistry and a formation of secondary aerosols under conditions of high O 3 in summer. Compared with the National Ambient Air Quality Standards in China, our measurements report 15 days of O 3 exceedance and 148 days of PM 2.5 exceedance during the 1 yr period, suggesting a severe air pollution situation in this region. Case studies for typical O 3 and PM 2.5 episodes demonstrated that these episodes were generally associated with an air mass trans-port pathway over the mid-YRD, i.e., along the Nanjing– Shanghai axis with its city clusters, and showed that syn-optic weather played an important role in air pollution, es-pecially for O 3 . Agricultural burning activities caused high PM 2.5 and O 3 pollution during harvest seasons, especially in June. A calculation of potential source contributions based on Lagrangian dispersion simulations suggests that emis-sions from the YRD contributed to over 70 % of the O 3 pre-cursor CO, with a majority from the mid-YRD. North-YRD and the North China Plain are the main contributors to PM 2.5 pollution in this region. This work shows an important envi-ronmental impact from industrialization and urbanization in the YRD region, and suggests an urgent need for improving air quality in these areas through collaborative control mea-sures among different administrative regions.