The Long-term Characteristics of PM10 and PM2.5 in Bangkok, Thailand

The long-term characteristics of non-roadside (residential) PM10 and PM2.5 in Bangkok, Thailand was analyzed by using hourly concentrations of PM10 and PM2.5 which had been collected from 10 monitoring stations by the Pollution Control Department (PCD) of Thailand from 2006 to 2016. The results showed that most of the stations showed either the decreasing trend or no trend characters. The PM2.5 and PM10 during weekdays and dry season were higher than during weekends and wet season, respectively. The diurnal variations of both PM2.5 and PM10 exhibited multi-peaks characteristic, mostly 2 peaks during a day for PM2.5 and 2 to 3 peaks depending on the locations for PM10. The PM2.5 to PM10 ratio of our residential monitoring stations was 0.61 in average which was in the same range as the PM2.5/PM10 ratio from the roadside monitoring stations. This shows that the common sources of PM2.5 and PM10 at both types of monitoring station were similar, probably mainly from the traffic and transportations. However, it was found that PM2.5/PM10 ratio during wet season was lower than during dry season indicating the role of emission sources and removal process in each season.