Measured and modelled concentrations and vertical profiles of airborne particulate matter within the boundary layer of a street canyon

Concentrations and vertical profiles of various fractions of airborne parti culate matter (suspended particulate matter (SPM), PM10 and PM2.5) have bee n measured over the first three metres from ground in a street canyon. Meas urements were carried out using automated near rear-time apparatus called t he Kinetic Sequential Sampling (KSS) system. KSS system is essentially an e lectronically-controlled lift carrying a real-time particle monitor for sam pling air sequentially, at different heights within the breathing zone, whi ch includes all heights within the surface layer of a street canyon at whic h people may breathe. Data is automatically logged at the different recepto r levels, for the determination of the average vertical concentration profi le of airborne particulate matter. For measuring the airborne particle conc entration, a Grimm Dust Monitor 1.104/5 was used. The recorded data also al lows for time series analysis of airborne particulate matter concentration at different heights. Time series data and hourly-average vertical concentr ation profiles in the boundary layer of the confines of a street are though t to be mainly determined by traffic emissions and traffic associated proce sses. Hence the measured data were compared with results of a street canyon emission-dispersion model in time and space. This Street Level Air Quality (SLAQ) model employs the plume-box technique and includes modules for simu lating vehicle-generated effects such as thermally- and mechanically-genera ted turbulence and resuspension of road dust. Environmental processes, such as turbulence resulting from surface sensible heat and the formation of su lphate aerosol from sulphur dioxide exhaust emissions, are taken into accou nt. The paper presents an outline description of the measuring technique an d model used, and a comparison of the measured and modelled data. (C) 1999 Elsevier Science B.V. All rights reserved.