Analysis On The Distribution Of PAHs In PM₁₀and PM_2.5 In Chongqing

With the rapid development of industrialization and urbanizaiton,the atmospheric environment was deterioratting day by day. PM10and PM2.5, as the key indicator of atmospheric quality, were easy to become the carrier of all sorts of toxic pollutants in the air because of its small size,large specific surface area and strong adsorption ability,and then cause direct damage to human body with breathing into the human body and depositing in the lung;A variety of polycyclic aromatic hydrocarbons (PAHs) had been identified carcinogenic, terato genie, mutagenic activity, most on less than10microns particles.Therefore,to carry out the research of distribution characteristics and the main source of PAHs in PM10and PM2.5, and to grasp PAHs polution accuratly have an important guiding significance for pollution controlling and strategy formulation in chongqingThe research focused on the atmospheric particles of different functional areas and different seasons in Chongqing. PM10and PM2.5samples of4different functional areas were synchronous collected in April, Augusts October、December in2012.GC/MS was used to determine16polycyclic aromatic hydrocarbons (PAHs) which US EPA control preferentially.PAHs in PM10and PM2.5were comparatively analyzed to investigate the distribution characteristics and the rules of space-time changs in Chongqing.Characteristic ratios methord of several PAHs was used to preliminary analysis the source of the PAHs in PMioand PM2.5.Mainfy to obtain the following conclusions:(1) The daily average concentration of PM10were respectively130.97μg/m3in spring、101.40μg/m3in summer、113.25μg/m3in autumn and155.36μg/m3in winter,which exceeding standard rate was50%,and88.06μg/m、62.54μg/m3、75.76μg/m3,110.37μg/m3in PM2.5,which exceeding standard rate is57%. Annual particulate concentrations northern and some industrial cities were significantly higher than those in coastal cities, pollution in chongqing is medium level, was one more times than national secondary standard.(2) The concentration of PM10and PM2.5in chongqing has obvious seasonal and spatial variation, and showed significant correlation (R=0.9325), the atmospheric fine particles (PM2.5) in PM10accounted for about65%. In the seasonal aspect, PM10and PM2.5mass concentration from high to low in turn is:winter> spring> autumn> summer, PMi oand PM2.5concentration was highest in winter mainly becuase temperature inversion appearred frequently, which made the pollutants difficult to spread, and the summer due to high temperature, high humidity, atmospheric boundary layer thickness and poor atmospheric stability, pollutants can spread easily, resulting in low concentration. In space, in addition to concentrations in spring peak appeared in dadukou district (industrial area), four sampling point particle spatial distribution was consisten in other three seasons, in the order were:Shapingba district (traffic)> Dadukou district (industrial area)> Nanan distract (residential area)> Jinyun mountain (control part).(3)16PAHs in PM10and PM2.5total concentrations are20.27～234.12ng/m3and18.85～142.44ng/m3respectively in Chongqing main city zone,showing the characteristics of the four rich. Compared with other cities at home and abroad, pollution in chongqing was more serious. Average concentration of PAHs in winter was higher than other seasons, which was lowest in summer that was consistent with the results in many other cities in our country, the concentration was different was due to the emission of pollution source and meteorological conditions. The overall PAHs concentration of PM10and PM2.5in each function change trend was consistent, showed that the source of particulate matter are similar. In the order were shapingba district (traffic concentration areas)> dadukou district (industrial area)> nanan distract (residential area)> jinyun mountain(control part); Ratio method was used to analyse the sources of PAHs in PM10and PM2.5in Chongqing.Characteristic ratios of several PAHs showed that coal burning and vehicle emission were the major sources of PM10and PM2.5,wood such as combustion source contribution was smaller.