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Mendes, nestled in the Paraíba do Sul River Valley within the state of Rio de Janeiro, Brazil, occupies a geographically significant position. Located approximately 120 kilometers northwest of Rio de Janeiro city, it sits within the Zona da Mata, a transition zone between the Atlantic Forest biome and the Cerrado savanna. The city’s terrain is characterized by rolling hills and fertile plains, a consequence of the river’s alluvial deposits, resulting in a relatively low average elevation of around 280 meters. This valley setting, while agriculturally productive, presents unique challenges for air quality. The surrounding landscape is a mosaic of agricultural land – sugarcane plantations and fruit orchards are prominent – interspersed with patches of remaining Atlantic Forest. Mendes’ proximity to the industrial belt of São Paulo, though not immediately adjacent, means it can be affected by long-range transport of pollutants. The Paraíba do Sul River itself influences local climate and can contribute to humidity, potentially trapping pollutants under certain atmospheric conditions. The urban–rural gradient is relatively sharp; the city transitions quickly into agricultural areas and forested hills. This close interaction between urban development and agricultural practices, combined with the valley’s topography which can impede air circulation, creates a localized environment where air quality is susceptible to both regional and local sources of pollution, including vehicle emissions, agricultural burning (particularly during land clearing), and industrial activity further afield.

Mendes experiences a tropical savanna climate, characterized by distinct wet and dry seasons, significantly impacting its air quality profile. The dry season, typically spanning from April to September, often sees a marked increase in particulate matter. This is largely attributable to agricultural practices; farmers frequently employ controlled burns to clear land for planting, releasing substantial amounts of smoke and ash into the atmosphere. Reduced rainfall during this period also limits the natural cleansing effect of precipitation, allowing pollutants to persist. Temperature inversions, common during the cooler, drier months, trap pollutants near the ground, exacerbating the problem. Conversely, the wet season (October to March) brings increased rainfall and higher humidity, which generally leads to improved air quality as pollutants are washed out of the atmosphere. However, periods of intense rainfall can also mobilize dust and soil particles, temporarily degrading air quality. Fog, particularly during the transition months, can also contribute to pollutant accumulation. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the dry season, limiting outdoor activities on days with visible smoke or haze. While the wet season generally offers respite, periods of heavy rain and subsequent dust storms warrant similar precautions. The interplay of agricultural practices, meteorological conditions, and the valley’s topography creates a dynamic air quality environment in Mendes, demanding vigilance and proactive mitigation strategies.