An activity based emission inventory was prepared for mobile sources in an urban center, Izmir, Turkey. The
vehicles were counted and categorized into four main vehicle categories; motorcycles, passenger cars, light–duty vehicles
and heavy–duty vehicles by a portable vehicle classifier system at 19 major streets in the city. The vehicles were also
counted continuously for 24 hours during a week in order to determine the daily and hourly fluctuations on vehicle
numbers. The seasonal changes of the vehicle numbers were also studied at all sampling points by repeating the counting
campaigns in two different weeks representing summer and winter seasons. Emissions of five main pollutants; nitrogen
oxides (NOx), carbon monoxide (CO), non-methane volatile organic compounds (NMVOCs), particulate matter (PM10)
and sulfur dioxide (SO2), were estimated using hourly traffic activity data on the streets and the customized emission
factors from COPERT methodology. The CALMET/CALPUFF dispersion modeling system was also performed for the
prediction of pollutant concentrations from exhaust emissions of mobile sources near the studied streets. The results
indicated that totally 160 000-180 000 vehicles in the rush hours (08:00-09:00 am, and 18:00-19:00 pm) were active on
the streets in the city. These numbers equal to 21% of the registered vehicle fleet in the city. It was estimated that total
annual emissions were 5590 tons for CO, 754 tons for NMVOC, 2496 tons for NOx, 104 tons for PM10 and 338 tons for
SO2. When these emissions were compared with the emissions emitted from industrial plants and residential heating
sources in the city, NOx emissions from traffic were found higher than the emissions from both sectors. Dispersion model
runs were mainly focused for the two episodes (August 16 and December 4, 2007) in the year 2007. According to
modeling results, maximum concentrations occurred on the streets or on a few hundred meters away from the streets.
Mobile source, air quality, vehicle counting, emission inventory, CALPUFF, Izmir.
Dokuz Eylul University, Dept. of Environmental Engineering, Tinaztepe Campus, 35160 Izmir, Turkey.