Sources of organic carbon in fine particulate matter in northern European urban air
- ISSN: 1680-7316
A major fraction of fine particle matter consists of organic carbon\n(OC) but its origin is still inadequately known. In this study the\nsources of OC were investigated in the northern European urban environment\nin Helsinki, Finland. Measurements were carried out over one year\nand they included both filter (PM1) and online methods. From the\nfilter samples OC, elemental carbon (EC), water-soluble OC (WSOC),\nlevoglucosan and major ions were analyzed. Filter data together with\nthe concentrations of inorganic gases were analyzed by Positive matrix\nfactorization (PMF) in order to find the sources of OC (and WSOC)\non an annual as well as on a seasonal basis. In order to study the\ndiurnal variation of sources, OC and EC were measured by a semicontinuous\nOC/EC analyzer and major ions were determined by a Particle-into-Liquid\nSampler coupled to ion chromatographs. According to PMF, OC concentrations\nwere impacted by four sources: biomass combustion, traffic, long-range\ntransport and secondary production. On an annual basis the OC concentration\nwas dominated by secondary organic aerosol (SOA). Its contribution\nto OC was as high as 64% in summer, which besides anthropogenic\nsources may also result from the large biogenic volatile organic\ncarbon (VOC) emissions in the boreal region. In winter biomass combustion\nconstituted the largest fraction in OC due to domestic wood combustion\nfor heating purposes. Traffic contributed to OC from 15 to 27%.\nRegarding the diurnal variation, the contribution from traffic was\nhigher from 08:00 to 18:00 on weekdays than on weekends. The contribution\nfrom long-range transport to OC was 24% on average. All four sources\nalso influenced the WSOC concentrations, however, the contribution\nof SOA was significantly larger for WSOC than OC.