engleski

PM1.0 levels in the vicinity of residential street under various traffic density conditions

Airborne particulate matter (PM) comprises dust, dirt soot, smoke, and liquid droplets suspended in the atmosphere. Particle sizes and their physical and chemical characteristics are determined by the formation processes and subsequent reactions in the atmosphere. Typically, urban aerosol can be divided into two main fractions ; fine (with diameter less than 2  m) and coarse particles (diameter of more than 2  m). Fine particles mainly originate from combustion, and, they comprise sulfates, organic ammonium, nitrates, carbon, lead, and some trace constituents. Coarse fraction is produced by mechanical processes, and it contains crustal material (i.e. silicon compounds, iron, aluminum), sea salt and plant particles. There are number of studies addressing to particles with diameter less than 10 and 2.5  m (PM10 and PM2.5, respectively), compared to relatively sparse literature on PM PM1.0 (particles smaller than 1.0  m in aerodynamic diameter). The aim of the study was to assess pedestrian’ s exposure to the PM1.0 fractions in a residential part of Zagreb, Croatia under various traffic density conditions. Continuous PM1.0 concentrations were measured using Model 8520 DUSTTRAKTM Aerosol Monitor (TSI Inc., Shoreview, MN, USA). The instrument is portable, and provides the real-time data at the temporal resolution of 1 s. In order to assess pedestrians’ exposure, the DUSTTRAKTM was placed at the sidewalk of a road, at the height of 1.7 m above the ground, half meter away from the road edge and with the inlet perpendicular to the roadway. The road has two lanes of opposite direction, separated by the centerline. The traffic is generally low-speed (up to 50 km / h), and its density varies from low to moderate (at the most up to about 30 vehicles per minute). Measurements of PM1.0 concentration at the resolution of 1 s were performed during ten time intervals of 45 min. Simultaneously, meteorological data (air pressure, air temperature, horizontal and vertical wind, global radiation and relative humidity were recorded by automatic meteorological station META 2000 (AMES, Brezovica, Slovenia) approximately 50 m far from the road at the temporal resolution of 1 min. Measured PM1.0 concentrations at 1 s resolution varied from 4 to 413  g m-3, and they were on the average 38.8  g m-3. Investigation of relationships between the PM1.0 levels and various meteorological parameters and traffic density revealed the strongest correlation of PM1.0 concentrations with relative humidity and wind direction, where the latter suggest the importance of distant pollution sources. While wind speed and traffic density affect the concentrations of the ambient fine particles, temperature and global radiation do not seem to influence the PM1.0 levels.

ambient concentrations; DUSTTRAKTM Aerosol Monitor; particulate matter; moderate traffic density

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