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Abstract: Low molecular weight dicarboxylic acids exhibit a semivolatile behavior and partition between gas and aerosol phases in the atmosphere. Here we present an approach for sample collection, which provides information about the gas/particle distribution of the investigated acids, but with less effort compared to commonly used denuder systems. The procedure was applied for the investigation of C2–C9 dicarboxylic acids at a continental background site in central Europe (Mt. Rax) and the urban site Vienna. The averaged gas phase contribution determined for individual low molecular weight dicarboxylic acids varied between 4% (malonic acid) and 37% (glutaric acid) of the total collected amounts. Using the observed gas/particle distributions effective Henry''s law constants were estimated. Between the carbon chain length of the investigated dicarboxylic acids and the magnitude of a dependence was observed — showing higher values for C2/C3 dicarboxylic acids (averaged ) and lower values for C4/C5 compounds (averaged ). [Copyright &y& Elsevier]

Size segregated emissions of particle-phase species from on-road motor vehicles were investigated in the Kaisermühlen Tunnel (Vienna, Austria) during April and May 2005. Emission factors were calculated from concentration differences between tunnel inside and tunnel outside samples, the distance between tunnel entrance and sampling location, the ventilation rate and the number of vehicles passing the tunnel. For a mixed car fleet with an average contribution of 9.6% heavy duty vehicles (HDVs) mean particle mass emissions of 26±10mgveh−1 km−1 in PM2.5, 62±18mgveh−1 km−1 in PM10 and 129±45mgveh−1 km−1 for total suspended particulates (TSPs) were observed. The released particles mainly consisted of elemental carbon (EC), organic carbon (OC) and the mineral components (MC=Si, Fe, Ca, Al, Mg). They accounted for 34.4% (EC), 30.3% (OC) and 18.2% (MC) of total PM10 emissions and 68.5%, 8.7% and 14.9% of PM2.5 emissions, respectively. Trace metal emissions (As, Ba, Cd, Co, Cr, Cu, Mn, Ni, Pb, Sb, Sn, Sr, Ti, V, Zn) contributed for less than 1% of total emissions in all size fractions. Emissions of coarse particles were found to be dominated by resuspended matter as well as by brake wear, whereas fine particles were mainly derived from combustion processes. On weekends for some components distinctly reduced emissions were observed which could be explained with changes in the driving conditions and/or fleet composition. [Copyright &y& Elsevier]

Total and size-segregated Pt and Pd emission factors from on-road vehicles were measured in the Kaisermühlen Tunnel in Vienna, Austria. Aerosol sampling was performed simultaneously inside and outside the tunnel during April and May 2005. Analysis of the acid-digested aerosol samples was performed using a preconcentration procedure with subsequent on-line detection by electro-thermal atomic absorption spectrometry (ETAAS). Inside the tunnel distinctly increased Pt and Pd concentrations were found with highest levels in total suspended particulate matter samples and reduced concentrations in the size-segregated PM10 and PM2.5 samples. Emission factors were calculated from concentration differences between tunnel inside and tunnel outside samples, the distance between tunnel entrance and sampling location, the ventilation rate, and the number of vehicles passing through the tunnel. Emission rates observed for Pt ranged from 38 +/- 5.9 to 146 +/- 13 ng veh(-1) km(-1), whereas the emission factors of Pd varied between 13 +/- 2.1 and 42 +/- 4.1 ng veh(-1) km(-1). Variations in the emission rates were assumed to originate from alterations in traffic conditions. Size-segregated investigations revealed that the major part of Pt and Pd emissions were released in the coarse aerosol mode (size fraction > PM10), nevertheless a considerable fraction (approximately 12% and approximately 22% respectively) was emitted in the inhalable PM2.5 fraction.