Study On Morphologies And Chemical Compositions Of Atmospheric Aerosols Related To Traffic

At present,with the gradual deepening of urbanization and the rapid upgrading of roads and other infrastructures,particle pollution related to traffic has become an important factor affecting the quality of atmospheric environment in the whole city.Furthermore,it makes great influences on human health because there are many harmful substances in the particulate matters.In this study,morphologies and compositions of single particles from traffic atmospheric environment of winter and summer(corresponding to the heating and non-heating period)in Taiyuan City and brake,tire wear of vehicles were analyzed using quantitative electron microprobe analysis technology(low-Z particle EPMA)respectively,to provide science basis for the source apportionment of particles in urban traffic environment and air pollution control.The research contents include:(1)Particle samples were collected Using the Dekati sampler at the intersection of Bingzhou North Road and Shaungta Western Street in Yingze District on Dec.19-23,2011(heating period)and the intersection of Wucheng Road and Xuefu Street in Xiaodian District on Jul.22-26,2016(non-heating period),respectively.The sizes,morphologies and Compositions of particles were determined by a SEM equipped with an Oxford Link SATW ultrathin window EDX detector,different sources and the factors influence the formation and transformation of particles related to traffic in different periods were analysied and compared.(2)Simulate the emission process of tyre,brake wear particles in road environment using a set of rolling resistance experimental system,samples were collected using a seven-stage MAY cascade impactor(aerodynamic diameter of 8,4,2,1,0.5and 0.25?m for stages 2-7,respectively)on Jun.10,2016 in Cheonan city,Korean.Various types of particles were classified according to the secondary electron images(SEIs)and X-ray spectrum,and compositions and sources of particles were analyzed also.Results showed that:(1)The sources of particles related to traffic in heating period were complex,affected by the construction site dust,road dust,coal-fired heating and vehicle emissions,in addition to primary source,can also be reproduced by chemical reactions among pollutants.The contents of various types of particles in samples also showed different variation rules.Compared with heating period,the sources of particles in non-heating period were comparatively simple,The backward trajectory showed that generated particles at the sampling site were mainly affected by air masses from the South and north direction.The single particle analysis showed that Alsi accounted for relatively large proportion in samples of non-heating period due to the strong effect of surface dust,a small amount of Fe,EC and OC were mainly produced by vehicles wear,exhaust and non-exhaust emissions.(2)Brake wear particles included heavy metal particles,EC,OC,CaCO3,(P,Si)OX,FeOX,CuSO4,CaSO4,BaSO4,Sb2S3,Si O2,respectively.With the exception of the first five types were same with brake particles,tire wear particles also included AlSi and organic matter.Analysis about wear particles indicated that brake wear particles generated mainly from the reinforced fiber,filler,adhesive,abrasive and high-temperature lubricant.The sources of Heavy metal particles,CaCO3,SiO2 in tire wear particles were Consistent with brake particles,organic matter may come from rubber softener.In addition,the NaCl and Al2O3 found in the samples may be carried by the sea breeze and the friction of the grinding wheel surface,respectively.These results suggested that there were different variation rules for the types and Compositions of atmospheric particles related to traffic in heating and non-heating periods.a large number of heavy metal,organic and inorganic particles were produced in the course of driving,its impact on the environment and human health can not be ignored.component analysis of particles emissioned from exhaust and non-exhaust gaseous was important for studies on the generation mechanism of traffic-related atmospheric aerosols,with the gradually deepening of tail gas treatment and continuous improvement of exhaust pollution and control policy,the study on the contribution of non-exhaust to aerosol formation in traffic environment needs to be improved.