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Don Sak, Surat Thani, occupies a strategically important coastal location in southern Thailand, serving as a vital ferry terminal connecting the mainland to Koh Samui and other islands in the Gulf of Thailand. Situated at approximately 9.3168° N, 99.6918° E, the town’s geography is characterized by a gently sloping coastal plain transitioning into low-lying hills inland. The terrain is largely flat near the coastline, facilitating the port infrastructure and surrounding residential areas, while the hinterland gradually rises, influencing local drainage patterns and microclimates. The proximity to the Gulf of Thailand is a defining feature, moderating temperatures and influencing humidity levels, but also potentially impacting air quality through sea breezes carrying pollutants or salt spray. Don Sak’s regional position places it within a zone of mixed land use – a gradual urban–rural gradient. To the west, agricultural lands, primarily rubber plantations and coconut groves, dominate the landscape, while to the east lies the sea. While Don Sak itself is a relatively small town, it’s part of a larger Surat Thani province, which includes industrial zones further inland, potentially contributing to regional air pollution transported by prevailing winds. The elevation is relatively low, generally below 30 meters above sea level, which can exacerbate the trapping of pollutants during periods of stable atmospheric conditions. The surrounding landscape is a mosaic of coastal mangroves, agricultural fields, and scattered rural settlements, all contributing to the local environmental context.

Don Sak’s tropical climate dictates a distinct wet and dry season pattern, significantly influencing air quality dynamics. The dry season, typically spanning from February to May, often sees a slight improvement in air quality compared to the wetter months, although this is not always consistent. During this period, reduced rainfall minimizes the scrubbing effect of precipitation, and lower humidity can lead to increased particulate matter concentrations, particularly if agricultural burning practices are prevalent in surrounding areas. Temperature inversions, common during the cooler nights of February and March, can trap pollutants close to the ground, leading to localized episodes of poorer air quality. The monsoon season, from June to November, brings frequent rainfall, which naturally helps to cleanse the atmosphere, reducing pollutant levels. However, the increased humidity can also contribute to the formation of ground-level ozone under certain conditions. November to January represents a transitional period, with fluctuating rainfall and wind patterns. Fog, particularly during the cooler months, can also reduce visibility and trap pollutants. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should be mindful of potential air quality fluctuations, especially during the dry season and periods of fog. Outdoor activities are generally more favorable during the monsoon season, but it’s advisable to monitor local conditions and avoid strenuous activity during periods of elevated humidity or potential agricultural burning.