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Amparo, nestled within the Serra do Mar mountain range in São Paulo state, Brazil, occupies a geographically significant position within the broader Southeast region. Located approximately 110 kilometers northwest of São Paulo city, its coordinates (-22.7031, -46.7650) place it at an elevation of around 870 meters above sea level, contributing to a relatively cool and humid climate compared to the coastal plains. The city’s terrain is characterized by undulating hills and valleys, typical of the Serra do Mar, influencing local wind patterns and air circulation. Surrounding Amparo is a mosaic of landscapes: to the east, the dense Atlantic Forest dominates, providing a natural filter for some pollutants but also contributing to localized fog formation. To the west and north, agricultural lands, including coffee plantations and cattle ranches, extend, introducing biogenic volatile organic compounds (BVOCs) and potential dust sources, particularly during dry periods. The urban–rural gradient is relatively sharp, with the city transitioning quickly into agricultural and forested areas. Amparo’s proximity to the larger industrial belt of São Paulo, while offering economic opportunities, also exposes it to long-range transport of pollutants. The Serra do Mar acts as a barrier, sometimes trapping pollutants and creating localized air quality challenges, especially during periods of stagnant air. The Paraíba do Sul river flows nearby, influencing humidity and potentially affecting the dispersion of particulate matter. The city’s compact urban form, combined with the surrounding topography, creates microclimates that can exacerbate air quality issues in specific areas.

Amparo’s air quality experiences a distinct seasonal pattern dictated by its tropical climate and the interplay of meteorological factors. The wet season, typically from October to March, brings frequent rainfall, which naturally helps to cleanse the atmosphere by removing particulate matter and gaseous pollutants. However, increased humidity can also promote the formation of ground-level ozone under certain conditions, particularly when sunlight is strong. The dry season, from April to September, is characterized by lower rainfall and higher temperatures, often leading to periods of stagnant air and temperature inversions, especially during the months of July and August. These inversions trap pollutants near the ground, resulting in poorer air quality. Agricultural activities intensify during the dry season, potentially increasing dust emissions from soil preparation and harvesting. Fog, common during the cooler months (June-August), further restricts air dispersion and can worsen air quality. The Atlantic Forest surrounding Amparo releases biogenic volatile organic compounds (BVOCs) year-round, but their impact on ozone formation is heightened during periods of intense sunlight and warm temperatures. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, particularly during periods of stagnant air or fog. Outdoor activities are generally more favorable during the wet season, although vigilance regarding ozone levels on sunny days is still advised. The transition months of September and October often see a gradual improvement in air quality as rainfall increases and temperatures begin to moderate.