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Itatiaia, nestled in the Serra da Mantiqueira mountain range within the state of Rio de Janeiro, Brazil, occupies a geographically significant position. Located approximately 140 kilometers northwest of Rio de Janeiro city, its coordinates (-22.4914, -44.5592) place it within a region characterized by dramatic elevation changes and a diverse landscape. The city’s terrain is rugged, dominated by steep slopes and forested hills, contributing to a microclimate influenced by orographic lift and localized wind patterns. Itatiaia sits at an elevation ranging from roughly 800 to over 2,791 meters (Pico do Tanozo), significantly impacting air circulation and pollutant dispersion. The surrounding landscape is predominantly natural, comprising extensive Atlantic Forest biome, interspersed with small-scale agricultural plots and rural settlements. This proximity to extensive forest cover generally acts as a natural air filter, though agricultural practices can introduce localized pollutants. The urban–rural gradient is relatively sharp, with the city transitioning quickly into forested areas. While not directly adjacent to major rivers, Itatiaia benefits from several smaller streams and springs originating from the Mantiqueira range, influencing local humidity and temperature. The absence of large-scale industrial belts within the immediate vicinity is a positive factor for air quality, though transportation corridors connecting Itatiaia to larger urban centers can introduce external pollutants. The mountainous terrain creates valleys where pollutants can become trapped, particularly during periods of calm weather, influencing localized air quality variations.

Itatiaia’s subtropical highland climate dictates a distinct seasonal pattern influencing air quality. The region experiences a wet and dry season rather than four traditional seasons. The wet season, typically spanning from November to March, brings increased rainfall and higher humidity, generally leading to improved air quality due to atmospheric cleansing. Frequent rainfall washes particulate matter from the air, and increased humidity can help trap certain gaseous pollutants. However, heavy rainfall can also lead to soil erosion and runoff, potentially carrying dust and other pollutants into the air. The dry season, from April to October, is characterized by lower rainfall, higher temperatures, and increased sunshine. This period often sees a greater propensity for temperature inversions, particularly in the valleys and lower elevations surrounding Itatiaia. These inversions trap cooler air near the ground, preventing the vertical dispersion of pollutants. Agricultural burning, a common practice in the surrounding rural areas during the dry season to clear land for planting, significantly contributes to particulate matter pollution. Fog, common during the cooler months (June-August), can also exacerbate air quality issues by trapping pollutants close to the ground. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during periods of agricultural burning and when fog is present. Outdoor activities are generally more favorable during the wet season, particularly after rainfall events, but vigilance is still advised regarding potential runoff-related pollutants.