Background Characteristics Of Surface Ozone And Carbon Monoxide At Zhongshan Station Over Antarctica

The Antarctic area is regarded as the background of global atmosphere, because it isminimally affected or polluted by human activities. Consequently, the trends and variation ofthe atmospheric compositions over Antarctica are of particular value for assessing theanthropogenic influence in global changing. In the end of 2007, an atmosphere monitoringstation was built at Zhongshan Station, bythe 24th Antarctic scientific expeditionteam. In thispaper, surface ozone and carbon monoxide data observed at Zhongshan Station in 2008 wereused to analyze the relationship of the observed data and local wind, the backgroundconcentration and their seasonal variations. The research also involves the analysis of thesurface ozone depletion events (ODE) at Zhongshan Station. And the Hybrid Single-ParticleLagrangian Integrated TrajectoryModel (HYSPLIT) was used to find the potential sources ofsurfaceozoneandcarbonmonoxide.Mainconclusionsareasfollows:1. The wind frequency from the station area was only 2%, while the prevailing windfrequency was much larger (79.2%). This indicates that the surface ozone and carbonmonoxide observations were not affected by the human activities at the station, and thereforecouldbecountedasbackgroundconcentrationsalongAntarcticcoast.2. The concentration of surface ozone shows a distinct annual variation with the yearlymean of 25.0 ppb and the maximum in winter (July), the minimum in summer (December).ThisvariationissimilartothoseobservedatothercoastalstationsoverAntarctica.Thesurfaceozone concentrationhada strongnegativecorrelationwithultraviolet radiation,whichimpliesthatphotochemicaldestructionofozonedominatesoverAntarctica.3.Thecarbonmonoxideconcentrationhas anobviouslyasymmetricseasonal variation.Itpeaks in September, with a monthly mean value of 66.4 ppb, and reaches the bottom inJanuary, with amonthlymean valueof37.7ppb. This seasonal variationmaybe relatedtothetropical biomassburning.ThefeatureofcarbonmonoxideatZhongshanStationis inlinewiththoseatotherAntarcticsites.4. During the spring of 2008, the surface ozone concentration experienced two mainsurface ozone depletion events (ODE). The results show that the ozone depletion events atZhongshan Station were obviously related to lower temperature and wind speed. Backwardtrajectory analysis reveals that the ozone depletion events are predominately caused by thehigh BrOconcentrations.5. There is no obvious seasonal variation in the trajectories ending at Zhongshan Station. And the trajectories are affected by the Katabatic wind, the circumpolar westerlies and thecyclones. Theairmasswithlowozoneconcentrationgenerallycomesfromthesouthernoceanand the coastal area, while the high ozone concentration air mass comes from the inland area.Differently, the trajectories along the coastline and from the ocean bring high carbonmonoxideconcentrationtoZhongshanStation.