| PM2.5 samples were collected at the seventh floor of Environment and Municipal Engineering Academy, in Xi`an University of Architecture and Technology of southern suburbs in December 15, 2009 to November 10, 2010, analyzed and studied for the pollution characteristics and relationship of water-soluble ions and heavy metal contaminated elements in PM2.5, and analyzed PM2.5 with the method of elemental enrichment factor. Followed is the main conclusion that there has got.The average concentration of PM2.5 was 95.72μg/m3, in the southern suburbs of Xi'an. Characteristics of the average concentration of PM2.5 by obvious seasonal variation: the highest level in winter, the lowest in summer, 100% of the mass concentration of PM2.5 have exceed the standard in winter, the pollution of PM2.5 in winter have serious in Xi'an. Time characteristics in weekly showed that higher concentrations of PM2.5 happened in 21:00-24:00 and 09:00-12:00 generally and presented bimodal distribution, but 15:00-18:00 was the lowest concentrations of PM2.5 in different seasons and time series.The mass concentration of PM2.5 showed a negative correlation respectively with wind, but presented a positively correlatively with relative humidity in different seasons. The water-soluble of SO42- and NO3- and the gaseous ex-product of SO2 and NO2 all have a good correlatively in summer. According both of the concentration curve, the conversion rate of NO2 is significantly lower than conversion rate of SO2. Represented in winter, time characteristics in weekly showed that SO42-, NO3-, Cl- in total PM2.5 were accounted for 13.6%, 12.7%, 3.8%, SO42- and NO3- were the main ions of water-soluble compoents in PM2.5, and the relative concentration in PM2.5 have the opposite time distribution pattern with PM2.5, the highest level in the 03:00-06:00 period, reflected timeliness characteristics of the secondary aerosol production from photochemical reactions in City. The average NO3-/SO42- in PM2.5 of Xi`an was 0.50, the average value of NO3-/SO42- (0.94) in winter, the air pollution of Xi'an has entered into the compound type pollution from soot and vehicle exhaust.In sampling period, the average concentration of various kinds of water-soluble heavy metals in PM2.5 has a large discrepancy, the average concentration of heavy metal Pb (0.1418μg/m3) was obviously higher than Cu, As and Cd. Characteristics by seasonal variation: Pb and Cu had similar distribution and the highest level in winter, the lowest in summer. The correlation analysis shows that Pb mainly comes from common contribution of NO2 and SO2. As to Cd, there has small influence from fuel and motor vehicle exhaust in winter. With the method of elemental enrichment factor to resolve heavy metals, the four heavy metals of Pb, Cu, As and Cd were mainly sourced in contribution from people. As mainly came from coal activities in winter, Cd had quite high enrichment degree in PM2.5, and mainly related with industrial production.
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