Ourinhos Air Quality Index (AQI)

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Ourinhos, nestled in the interior of São Paulo state, Brazil, occupies a gently undulating terrain within the Paraná sedimentary basin. Located at coordinates -22.9789, -49.8708, the city’s elevation is approximately 540 meters above sea level, contributing to relatively stable atmospheric conditions. The surrounding landscape is dominated by agricultural lands, primarily sugarcane and soybean cultivation, interspersed with patches of *cerrado* vegetation – a tropical savanna ecoregion. This agricultural intensity is a key factor influencing local air quality. Ourinhos isn’t directly adjacent to large bodies of water, though smaller rivers and streams crisscross the region, providing limited dispersion for pollutants. The city functions as a regional hub for agricultural processing and distribution, leading to moderate industrial activity concentrated around the urban core. The urban-rural gradient is relatively sharp; transitioning quickly from denser built-up areas to expansive farmland. This proximity to agricultural sources, combined with the basin’s topography, can trap pollutants, particularly during periods of low wind speed. The city’s position within a larger agricultural belt means it’s susceptible to long-range transport of pollutants from burning activities elsewhere in the state. Understanding this geographic context is crucial for interpreting air quality trends in Ourinhos.

Ourinhos experiences a distinct wet and dry season, rather than traditional four seasons. Air quality generally improves during the wet season (October to April) due to rainfall effectively scavenging particulate matter and suppressing dust from agricultural lands. However, increased humidity can also promote the formation of secondary pollutants. The dry season (May to September) consistently presents the poorest air quality. This is largely due to increased agricultural burning for land preparation, releasing significant amounts of smoke and particulate matter. Low wind speeds during these months exacerbate the problem, allowing pollutants to accumulate. Temperature inversions, common during cool, clear nights in the dry season, trap pollutants near the ground. August and September are typically the worst months for outdoor activity, particularly for individuals with respiratory conditions. Sensitive groups – children, the elderly, and those with asthma – should limit strenuous outdoor exercise during these periods. Even during the wet season, periods of drought or reduced rainfall can lead to localized air quality issues. Monitoring wind patterns is crucial; winds from the southwest often carry pollutants from larger agricultural operations.