Sources of organic carbon in fine particulate matter in northern European urban air

[摘要] A major fraction of fine particle matter consists of organic carbon (OC) butits origin is still inadequately known. In this study the sources of OC wereinvestigated in the northern European urban environment in Helsinki,Finland. Measurements were carried out over one year and they included bothfilter (PM₁) and online methods. From the filter samples OC, elementalcarbon (EC), water-soluble OC (WSOC), levoglucosan and major ions wereanalyzed. Filter data together with the concentrations of inorganic gaseswere analyzed by Positive matrix factorization (PMF) in order to find thesources of OC (and WSOC) on an annual as well as on a seasonal basis. Inorder to study the diurnal variation of sources, OC and EC were measured bya semicontinuous OC/EC analyzer and major ions were determined by aParticle-into-Liquid Sampler coupled to ion chromatographs. According toPMF, OC concentrations were impacted by four sources: biomass combustion,traffic, long-range transport and secondary production. On an annual basisthe OC concentration was dominated by secondary organic aerosol (SOA). Itscontribution to OC was as high as 64% in summer, which besidesanthropogenic sources may also result from the large biogenic volatileorganic carbon (VOC) emissions in the boreal region. In winter biomasscombustion constituted the largest fraction in OC due to domestic woodcombustion for heating purposes. Traffic contributed to OC from 15 to27%. Regarding the diurnal variation, the contribution from traffic washigher from 08:00 to 18:00 on weekdays than on weekends. The contributionfrom long-range transport to OC was 24% on average. All four sources alsoinfluenced the WSOC concentrations, however, the contribution of SOA wassignificantly larger for WSOC than OC.

[学科分类] 大气科学