Characteristics Of Atmospheric Particles PM_2.5 And Component In The Southern Suburbs Of Xi’an

There was a PM2.5 automatic monitoring station in Xi’an University of Architecture and Technology of southern suburbs of Xi’an, we studied the dependence relation between spatio-temporal and meteorological factors on the average concentration and water-soluble ions and TOC of PM2.5 in this paper. All data based on real-time monitoring and experimental test data from December 1,2008 to November 30,2009.The average concentration of PM2.5 was 102.2μg/m3,in monitoring period. Characteristics of the average concentration of PM2.5 by seasonal variation:the largest daily average concentration,343.6μg/m3 of PM2.5 happened in winter, and the smallest in summer with the concentration of 5.2μg/m3 when the data in winter apparently higher than other seasons. Characteristics of PM2.5 by time interval variation:higher concentrations occured in 09:00-12:00 and 21:00-00:00 generally and presented doublet, but from15:00 to 18:00 was the lowest concentrations of PM2.5 in different seasons and different time interval.Visibility and the daily average pressure showed a negative correlation respectively with PM2.5, but PM2.5 and the total radiation presented the positively correlativity in the different seasons. The water-soluble ions of NH+, NO3-, SO42- and visibility showed good negative correlation.The larger concentration difference of day and night occurred in spring and summer frequently, but the smaller was in autumn from water-soluble components of atmospheric particulate PM2.5. Represented in winter, study on the time interval concentration of water-soluble ions, we emphasized NH4+, NO3-, SO42- were the main ions of water-soluble components in PM2.5, and quality proportion of these three was 10.225%,13.698%,15.650% respectively, and the highest proportion was from 06:00 to 09:00, from 03:00 to 06:00, from 18:00 to 21:00 respectively. Water-soluble ammonium salt, nitrate salt and sulfate salt components may be combined as NH4NO3 or (NH4)2SO4 of atmospheric particles PM2.5 in the southern suburbs of Xi’an, moreover water-soluble potassium salt and calcium salt may be combined as KNO3 or KCl and CaCl2 respectively.The specific value of TOC/PM2.5 was 18.253% with annual average, so TOC is an important component of PM2.5.