Air Quality at Night Markets in Taiwan

Abstract

In Taiwan, there are more than 300 night markets and they have attracted more and more visitors in recent years. Air quality in night markets has become a public concern. To characterize the current air quality in night markets, four major night markets in Kaohsiung were selected for this study. The results of this study showed that the mean carbon dioxide (CO₂) concentrations at fixed and moving sites in night markets ranged from 326 to 427 parts per million (ppm) during non-open hours and from 433 to 916 ppm during open hours. The average carbon monoxide (CO) concentrations at fixed and moving sites in night markets ranged from 0.2 to 2.8 ppm during non-open hours and from 2.1 to 14.1 ppm during open hours. The average 1-hr levels of particulate matter with aerodynamic diameters less than 10 µm (PM₁₀) and less than 2.5 µm (PM_2.5) at fixed and moving sites in night markets were high, ranging from 186 to 451 µg/m³ and from 175 to 418 µg/m³, respectively. The levels of PM_2.5 accounted for 80–97% of their respective PM₁₀ concentrations. The average formaldehyde (HCHO) concentrations at fixed and moving sites in night markets ranged from 0 to 0.05 ppm during non-open hours and from 0.02 to 0.27 ppm during open hours. The average concentration of individual polycyclic aromatic hydrocarbons (PAHs) was found in the range of 0.09 × 10⁴ to 1.8 × 10⁴ ng/m³. The total identified PAHs (TIPs) ranged from 7.8 × 10¹ to 20 × 10¹ ng/m³ during non-open hours and from 1.5 × 10⁴ to 4.0× 10⁴ ng/m³ during open hours. Of the total analyzed PAHs, the low-molecular-weight PAHs (two to three rings) were the dominant species, corresponding to an average of 97% during non-open hours and 88% during open hours, whereas high-molecular-weight PAHs (four to six rings) represented 3 and 12% of the total detected PAHs in the gas phase during non-open and open hours, respectively.