Preliminary assessment of particulate matter air quality associated with traffic Emissions in Nakhon Si Thammarat, Thailand

Abstract

Urbanization results in increasing traffic density which is in turn a major cause of air quality deterioration. For the past decade, number of new registered vehicles in Thailand was increased around 3 times as of 2011 while levels of air pollutants occasionally exceeded the national ambient air quality standards (NAAQS). Various policies and measures toward better air quality have been implemented in the country, particularly Bangkok to strive against the air pollution problems. The overall situation has been reported to be improved; however, a problem related to the particular pollutants, i.e. particulate matter and ozone is remained. Nakhon Si Thammarat is, in term of population, the biggest province in Southern Thailand and ranks in top ten of the country as of 2011 record. Similarly to the country traffic data, number of new registered vehicles in Nakhon Si Thammarat was increased around 3.5 times for the past decade. Lack of permanent air quality monitoring stations in this city causes a questionable level of air quality. This study was design to assess levels of particulate matter air quality as PM10 and PM2.5 in the city of Nakhon Si Thammarat at three main traffic connections: Tha Wang; Ku Khwang; and Lak Muang for four consecutive days on 11th-14th July 2012. Results revealed that measured 3-hour average PM10 concentrations ranged from around 60 to 140 μg/m3 and 40 to 170 μg/m3, respectively in the morning and evening while those for PM2.5 ranged from 40 to 110 μg/m3 and 40 to 160 μg/m3, respectively. Overall, estimated PM10 and PM2.5 at 24-hour and annual average concentrations met the NAAQS of Thailand; however, several values of 24-hour average PM10 exceeded the guideline values of the World Health Organization (WHO). Concentrations of 24-hour average PM2.5 also exceeded the guideline values of WHO recommending the implementation of stringent measures to tackle the situation. Further study should include field survey of traffic volume, engine type and fuel consumption as well as measurement of other pollutant emissions to assess the association between air pollutants and traffic density.