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Tubarão, nestled in the heart of Santa Catarina state, Brazil, occupies a geographically significant position within the southern Brazilian coastal plain. Located at approximately -28.4669 latitude and -49.0069 longitude, the city’s terrain is characterized by gently rolling hills and valleys, a typical feature of the region’s sedimentary landscape. The elevation varies modestly, generally ranging from 20 to 80 meters above sea level, influencing local wind patterns and temperature distribution. The proximity to the Atlantic Ocean, roughly 30 kilometers to the east, moderates the climate and introduces a maritime influence on air quality, occasionally bringing in sea salt and moisture. Tubarão sits within a transitional zone between the coastal rainforest and the more temperate grasslands of the interior, resulting in a diverse surrounding landscape of both dense vegetation and agricultural land. The city is strategically positioned along the BR-101 highway, a major transportation artery, and is surrounded by a patchwork of agricultural fields – primarily sugarcane, soybeans, and dairy farms – contributing to potential localized emissions. The urban–rural gradient is relatively gradual, with smaller agricultural settlements and rural communities blending seamlessly into the city’s periphery. This interplay between urban development and intensive agriculture, coupled with the regional industrial activity concentrated further north along the coast, creates a complex interplay of factors impacting Tubarão’s air quality, particularly concerning particulate matter and volatile organic compounds. The Paraná River basin also influences the regional hydrology and, indirectly, atmospheric conditions.

Tubarão’s subtropical climate dictates a distinct seasonal pattern in its air quality. The wet season, typically spanning from November to March, brings frequent rainfall and higher humidity, generally leading to improved air quality as precipitation washes away pollutants. However, periods of prolonged fog, common during these months, can trap emissions close to the ground, creating localized pockets of poor air quality, especially in the mornings. The dry season, from April to October, presents a different challenge. Reduced rainfall and increased sunshine lead to drier conditions, promoting the build-up of particulate matter from agricultural activities like sugarcane burning, a common practice for land clearing and harvesting. Temperature inversions, where a layer of warm air sits above cooler air near the ground, are more frequent during the dry season, particularly in May and September, preventing pollutants from dispersing vertically. This phenomenon can significantly worsen air quality, trapping emissions from vehicles, industry, and agricultural sources. During the summer months (December-February), high temperatures and stagnant air can exacerbate ozone formation, a secondary pollutant. The autumn months (March-May) often see a transition period with fluctuating conditions. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly on days with visible haze or stagnant air. Outdoor activities are generally more favorable during the wet season, but vigilance regarding fog is advised. The agricultural cycle significantly influences air quality, with peak pollution often coinciding with sugarcane harvesting periods.