Temporal And Spatial Distribution And Chemical Composition Of Atmospheric Fine Particles PM_2.5 In Lanzhou

Atmospheric fine particles PM_2.5 known as respirable particles,ha-ve a certain influence to human health,visibility,and climate.In recent years,the haze weather have appeared frequently in many cities of China,which is mainly due to atmospheric particulates pollution.Therefore,to understand the spatial and temporal distribution and chemical composition of PM_2.5 is very important for source apportionment and controlling of PM_2.5.This study includes two parts:?1?The daily PM_2.5 concentration date in Lanzhou from March 2013 to February 2014 were collected,the spatial and temporal distribution of PM_2.5 in Lanzhou was investigated,the annual occerance frequency of primary pollutants in Lanzhou was counted,and the correlations between PM_2.5 and PM10,SO2,NO2 were studied.?2?The PM_2.5 samples were collected in October and December of 2013 in Chengguan and Xigu district of Lanzhou city.Meanwhile,meteorological parameters of sampling sites were recorded by portable meteorological instrument.Then the water-soluble inorganic ions?Na+?K+?NH4+?Cl-?NO3-?SO42-?and inorganic elements?Al?Ca?Cu?Fe?Mg?Mn?Pb?S?Ti?Zn?were analyzed by ion chromatography?IC?and inductively coupled plasma optical emission spectrometer?ICP-OES?respectively.In order to understand the characteristics of PM_2.5 concentration,the correlations between PM_2.5 and meteorological conditions,the chemical composition of PM2 5,the preliminary source apportionment of PM_2.5,the acid-base property of PM2 5 in non-heating and heating period in Lanzhou were also discussed in this study.The results and conclusion are listed as follows:Part One:?1?The daily average concentrations of PM_2.5 in Lanzhou ranged from 15.4?g/m3 to 247.8?g/m3 with a mean of 63.3?g/m3 in 2013.The number of days that the daily average concentration was less than the National Secondary Ambiemt Air Quality Standard?75?g/m3?is 76.7%of the total number of days.The temporal distributions of PM_2.5 in Lanzhou in 2013 were as follows:spring>winter>autumn>summer.For the spatial distributions,the highest PM2 5 concentration was in Lanyuan Hotel,followed by Shengjian Worker Hospital,Lanzhou Institute of Biology Products,Lanzhou Railway Bureau,and Yuzhong Campus of Lanzhou University,repectively.?2?Generally,the air quality of Lanzhou city in 2013 was good,and the number of days with excellent and good were up to 207.The occurrence frequency of PM2 5 as primary pollutants in Lanzhou was 23.6%in 2013,The correlations between PM_2.5 and PM10,SO2,NO2 were positive,however,PM_2.5 and PM10 in all seasons displayed positive correlation,the correlations between PM2 5 and SO2,NO2 were not obvious in spring and summer,and the correlations were very significant in autumn and winter.Part Two:?1?The concentration of PM2 5 in Lanzhou during the sampling period ranged from 64.8 to 228.9?g/m3 with the mean of 129.3?g/m3.For the temporal distribution of PM2 5 in Lanzhou,the concentration in heating period was obviously higher than that in non-heating period.In addition,spatial distribution of PM2 5 showed that the concentration in Chengguan district,non-industrial area,was almost as high as that in Xigu district,industrial area.Therefore,PM_2.5 in Lanzhou in sampling period negatively related with wind speed,temperature and humidity,which displayed the good correlations with wind speed and humidity,but it had a general ralation with temperature.?2?For chemical composition of PM2 5 in Lanzhou,the average concentraton of inorganic water-soluble ions inclulding Na+,K+,NH4+,Cl-,NO3-,and SO42-was 1.2?g/m3,1.5?g/m3,10.8?g/m3,5.9?g/m3,13.1?g/m3,15.5?pg/m3 respectively.The average content of inorganic water-soluble ions in PM2 5 was 37.0%.Overall,the concentration of inorganic water-soluble ions in heating period was higher than that in non-heating period.Except for K+,the concentration of the other ions in Xigu district,industrial area,was higher than that in Chengguan district,non industrial atea.In addition,the value of NO3/SO42-can be deduced the atmospheric pollution of Lanzhou tend to change to automobile exhaust type.The acid-base property of PM_2.5 is partial acid for Lanzhou.In addition,and NH4+ of PM2 5 was existed by?NH4?2SO4.?3?For inorganic elements?Al,Ca,Cu,Fe,Mg,Mn,Pb,S,Ti,Zn?in PM_2.5,the average concentration were 1125.8ng/m3,2756.8ng/m3,22.2ng/m3,2038.8ng/m3,725.7ng/m3,725.7ng/m3,356.6ng/m3,3505.6ng/m3,44.8ng/m3,255.5ng/m3 respectively.The content of inorganic elenmenst in PM2 5 was 8.6%in Lanzhou.The concentration of all inorganic element in heating period was higher than non-heating period.Except for S,the concentration of the other inorganic element in Chengguan district,non industrial area,were higher than that in Xigu district,industrial area.The results of element enrichment factor indicated that Pb,S,and Zn are mainly from the artificial sources,Al,Ca,Fe,Mn,and Cu are influenced by artificial and natural sources,and Mg and Ti are mainly from natural sources.