High-resolution Pollution Characteristics And Weather Impact Analysis Of Carbon Fractions In PM_2.5 At Typical Period In Xi’an

With the recent decline in air quality, haze event multiple more concern aboutPM_2.5,it particle size small to easily enter the lungs through breathing and cause seriousharm to human health. In this study, the observed experimental study for PM_2.5carriedout in2009.11～2012.12, high resolution system distribution sequence ambient PM_2.5inXi’an. On this basis, the high-resolution acquisition of a typical winter period （duringthe Spring Festival, the fine weather, dust process） of PM_2.5samples, explores thereal-time variation of the carbon component, the impact of weather conditions onaerosol, fine scale atmospheric carbon aerosol processes, the use of mathematical andstatistical methods to source apportionment of PM_2.5and its carbon component, analysisof meteorological factors on PM_2.5pollution.The monitoring period of three years PM_2.5daily average concentrationrespectively to73.470±55.357,107.208±75.626and110.010±77.449μg/m3in Xi’an.Contrast to the national standard, the three-year average daily concentrations exceededsuperscalar multiples were2.10,3.06,3.14. Four Seasons concentration distribution offurther analysis of the three PM_2.5the concentration of more than two of each season（75μg/m3） the standard limit percentage as follows: winter（64.09%）>autumn（62.40%）>spring（50.05%）>summer（38.00%）. The four seasons of PM_2.5concentrations areincreasing every year. PM_2.5daily average concentration of the three-year heating periodwere108.605±75.893,112.217±84.354,146.160±94.550μg/m3. Three winter PM_2.5daily average concentration of over one standard threshold exceedances:1.45,1.50，1.95from2010to2012. PM_2.5pollution overall trend is gradually increased in Xi’an.Sampling period OC,EC and WSOC concentration mean48.651μg/m3,12.921μg/m3and19.900μg/m3in Xi’an, the three components of the average concentration distribution in the three periods differ: OC and WSOC was Ⅱ>Ⅰ> Ⅲ,EC wasⅠ> Ⅱ> Ⅲ. On three components distributed in each period there are differences,which the EC distribution is more stable, sooner or later, in three periods exhibited abimodal distribution, indicating relatively stable in the winter EC sources, mainly fromcoal-fired emissions; OCⅠ period and III period the EC changes similar, this time thetwo have the same source, Ⅱperiod OC was circadian distribution, indicating that theperiod due to the strong the Bai Tianguang chemical reaction and generate secondaryorganic carbon. WSOC and WSOC/OC changes with OC，the alien transmission sourceof the carbon fractions. The relationship of the three components that winter OC, ECsources, mainly from the coal and automobile exhaust, of WSOC and OC goodcorrelation with EC lowest correlation WSOC more secondary organics. Winter OC/ECminimum value method to estimate mean SOC concentration20.164μg/m3, accountingfor36.549%proportion of OC the SOC concentration distribution in the three periodswas Ⅱ>Ⅰ>Ⅲ changes simultaneous sampling ofSOC concentration daytime22.548μg/m3much higher than17.718μg/m3in nighttime, and that winter Clear conducive tothe occurrence of photochemical reactions is formed the SOC, SOC is the importantpart of the atmospheric organics.PM_2.5and carbon components about meteorological factors correlation differences,the meteorological factors PM_2.5complex. There is located in the valley, low-altitudeatmospheric flow is slow, weak vertical flow and turbulence, atmospheric stratification,high stability, low mixing layer height, atmospheric dispersion capability is weak, theaccumulation of PM_2.5in the land. Geographical topography of the special weatherconditions in Xi’an, is not conducive to the spread of particulate matter, easy to formhaze.The control should be focused on anthropogenic sources of PM_2.5pollution inXi’an.