Analysis of Particulate Concentrations at Highway Areas in Ulsan

Concentrations of participate matter (PM) on highway areas in Ulsan of Korea were analyzed using a portable PM sampler and a low volume PM10 sampler during a summer sampling period. This study analyzed the air concentrations of PM1.0, PM2.5, PM7.0, PM10, and TSP (total suspended particulate) at 4 places, having quite different environment, located at highway areas in Ulsan. The PM measurements on 2 week days and 2 weekend days were conducted during the four different time zones (morning rush hour, day time, evening rush hour, midnight hour) of each measurement day, respectively. The highest average concentrations of PM1.0, PM2.5, PM7.0, PM10, and TSP were observed at the bridge on the Kyungbu highway followed by the start point of Ulsan highway with a busy traffic rotary. The PM concentrations at the toll gate and the bus stop of Ulsan highway were similar; however, they were much lower than those at the bridge or start point. The PM concentrations during the midnight and morning rush hours were much higher than those of the day time or evening rush hours. All the PM concentrations and the concentration ratio of PM 1.0 to PM2.5 at the three sites (highway start point, bus stop, bridge) during the weekend days significantly decreased as compared to their concentrations during the week days. In particular, the smaller particle sizes, the larger decrease in PM concentrations were observed at the highway start point and bus stop. However, all the PM concentrations and the concentration ratio of PM 1.0 to PM2.5 at the toll gate increased as compared to those during the week days. The smaller particle sizes, the larger increase in PM concentrations were observed at the highway toll gate. The PM concentrations increased with the increase of relative humidity level during the measurement periods showing significant correlation coefficients. The PM concentrations also increased with the increase of the total traffic density and diesel vehicle volume during day time and evening rush hours. However, they may not be significantly related to the traffic density but the humidity level during midnight time and morning rush hours which usually shows stable atmospheric conditions. The PM concentrations seem to be decreased with the average wind speed during the measurement periods.