Noise and Air Quality from Traffic in Mueang Nakhon Si Thammarat, Nakhon Si Thammarat Province

Abstract

Noise pollution and poor air quality are growing environmental concerns in rapidly developing Thai cities. This study assessed traffic-generated noise levels and ambient air quality at four signalized intersections in Mueang Nakhon Si Thammarat district, Nakhon Si Thammarat Province, in September 2022. Measurements were conducted at three peak-hour periods (07:00–09:00, 11:00–13:00, and 15:00–17:00) on both weekdays and weekends. Parameters included equivalent continuous noise level (Leq), oxygen (O₂), carbon monoxide (CO), carbon dioxide (CO₂), sulfur dioxide (SO₂), relative humidity, wind speed, and temperature. All four sites exceeded the Thai national noise standard (24-hr average ≤70 dB(A)) on weekdays, with Site 1 (Hua Thanon) recording the highest average of 73.5 dB(A). On weekends, Site 2 (Fountain Circle–Kanlayanee School) was the only site within the standard at 69.9 dB(A). CO concentrations at all sites (26.0–27.3 ppm) exceeded the Thai 8-hour ambient standard of 9 ppm, though they remained within the 1-hour limit of 30 ppm. O₂ levels were below the atmospheric reference of 20.9% at every site, while SO₂ was undetectable throughout. Environmental factors—particularly relative humidity, wind speed, and temperature—influenced both noise propagation and pollutant dispersion. Site 3 (Khu Khwang) showed the highest CO and CO₂ concentrations, attributed to the dense surrounding buildings, which restricted ventilation. These findings highlight the need for continuous environmental monitoring and traffic management interventions in Nakhon Si Thammarat's urban core.