Elemental and organic carbon in urban canyon and background environments in Budapest, Hungary

Abstract

Abstract As part of an international research project, aerosol samples were collected by several filter-based devices on Nuclepore polycarbonate membrane, Teflon membrane and quartz fibre filters over separate daylight periods and nights, and on-line aerosol measurements were performed by TEOM and aethalometer within an urban canyon (kerbside) and at a near-city background site in Budapest, Hungary from 23 April–5 May 2002. Aerosol masses in PM2.0, PM10–2.0, PM2.5, PM10 size fractions and of TSP were determined gravimetrically; atmospheric concentrations of organic (OC) and elemental carbon (EC) for PM2.5 (or PM2.0), PM10 fractions and for TSP were measured by thermal–optical transmission method. Repeatability of the mass determination by Nuclepore filters seems to be 5–6%. Collections on Teflon filters yielded smaller mass on average by 8(±12)% than that for the Nuclepore filters. Quartz filters overestimated the PM10 mass in comparison with the Nuclepore filters due primarily to sampling artefacts on average by 10(±16)% at the kerbside. Tandem filter set-ups were utilised for correcting the sampling artefacts for OC by subtraction method. At the kerbside, the aerosol mass was made up on average of 35(±4)% of organic matter (OM) in the PM10 fraction, while the contribution of OM to the PM2.5 mass was 43(±9)%. At the background, OM also accounted for 43(±13)% of the PM2.0 mass. On average, EC made up 14(±6)%, 7(±2)% and 4.5(±1.1)% of the mass in the PM2.5, PM10 fractions and TSP, respectively, at the kerbside; while its contribution was only 2.1(±0.5)% in the PM2.0 fraction in the near-city background. Temporal variability for PM mass, OC and EC concentrations was related to road traffic, local meteorology and long-range transport of air masses. It was concluded that a direct coupling between the atmospheric concentration levels and vehicle circulation can be identified within the urban canyon, nevertheless, the local meteorology in particular and long-range transport of air masses have much more influence on the air quality than changes in the source intensity of road traffic. Concentration ratios of OC/EC were evaluated, and the amount of secondary organic aerosol (SOA) was estimated by using EC as tracer for the primary OC emissions. Mean contribution and standard deviation of the SOA to the OM in the PM2.5 size fraction at the kerbside over daylight periods and nights were of 37(±18) and 46(±16)%, respectively.