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Nova Granada, nestled within the state of São Paulo, Brazil, at coordinates -20.5339, -49.3139, presents a fascinating case study in urban air quality. The city’s relatively small population of 19,419 is situated within a broader, intensely agricultural region, dominated by sugarcane and soybean cultivation. This surrounding landscape significantly influences local air quality, with seasonal burning for land preparation releasing substantial particulate matter. The terrain is gently undulating, characteristic of the broader Paulista plateau, with elevations ranging between 500-600 meters. This moderate elevation contributes to temperature inversions, trapping pollutants near the ground, particularly during calmer periods. While not directly on a major waterway, Nova Granada is within the watershed of the Rio Tietê, a river historically impacted by industrial and agricultural runoff. The urban-rural gradient is quite sharp; the city itself is compact, quickly giving way to extensive farmland. The proximity to larger industrial centres within São Paulo state, such as Ribeirão Preto and São José do Rio Preto, means the city can experience long-range transport of pollutants. Prevailing winds, generally from the south-southeast, can carry these pollutants into the region, exacerbating local emissions. The city’s limited public transport infrastructure encourages vehicle use, adding to the localized pollution burden.

Nova Granada experiences a distinct wet and dry season, heavily influencing its air quality. The dry season, typically from May to September, sees a significant deterioration in air quality. This is primarily due to increased agricultural burning for sugarcane harvesting and land preparation, releasing large quantities of particulate matter (PM2.5 and PM10). Lower humidity during these months also means dust and other airborne particles remain suspended for longer. Temperature inversions are more frequent during the cooler, drier nights, trapping pollutants close to the ground. October and November mark the transition to the wet season, with increased rainfall gradually washing away accumulated pollutants. December to April, the wet season, generally offers the best air quality, as rainfall suppresses dust and dilutes emissions. However, even during the wet season, localized pollution from vehicle exhaust and small-scale burning can occur. Sensitive groups – children, the elderly, and those with respiratory conditions – should be particularly cautious during the dry season, limiting outdoor activity on days with visible haze. Monitoring wind patterns is crucial; winds from the southeast can bring pollutants from larger industrial areas. Fog, common during cooler months, can also trap pollutants, worsening conditions.