Determination of Particle-bound PAH Concentrations within a Heavily-trafficked Street Canyon in Chiang Mai, Thailand

Abstract

The aim of this study was to identify pollutant sources by characterizing polycyclic aromatic hydrocarbons (PAHs) during the month of important public holidays in Chiang Mai City that is the main province of Thailand’s tourism. Twice daily sampling was performed throughout the month of April including early-, mid- and late- month. The 16 PAHs were observed in respirable particulate matter (PM10). The average concentration of PAHs was 31.35 ng/m3. Moreover, it was found that the high concentrations were ranging from 25.24-62.81 ng/m3 (mid-month), while those were 20.89-27.04 ng/m3 (early- and late-month). Most of PAHs concentrations were not different between morning and afternoon except the afternoon of recently post-public holidays. The average carcinogenic polycyclic aromatic hydrocarbons (c-PAHs) was 56.80 %. High range of c-PAHs was obtained in mid-month (54.85-67.75 %), while normal period was 51.51-55.23% (early- and late-month). The ratios of polycyclic aromatic hydrocarbons indicate that vehicle emission was the main source in this period. The values of health risk assessment of PAHs-bound PM10 (i.e. TEQ, MEQ. BaPE and ICR) indicate that a high potential risk for travelers, street vendors and pedestrians was observed after the exposure to particulate matters in the urban area of Chiang Mai City, especially mid-month, which is the period of public holidays of Thailand, while the early-and late-month were found in the similar concentration. Therefore, it can be concluded that the distribution of pollutants inside urban areas was not different between morning and afternoon due to urban street canyon. Moreover wind speed was not a significantly influencing factor on PM10 level. This study points out the air quality during public holidays period for a city of tourism and it further demonstrates that tourism should pay more attention to implement serious improvement measures of air pollution and have a thorough system optimization.