Nalbāri, nestled in the heart of Assam, India, occupies a geographically significant position within the Brahmaputra River Valley. Located at approximately 26.4450° N, 91.4400° E, the city’s terrain is predominantly alluvial, a direct consequence of the Brahmaputra’s sediment deposition over millennia. The surrounding landscape is characterized by fertile plains, punctuated by pockets of dense tropical forests and interspersed with agricultural fields – primarily rice and jute cultivation. Nalbāri’s elevation is relatively low, averaging around 25 meters above sea level, contributing to a humid subtropical climate and influencing atmospheric stability. The city’s proximity to the Brahmaputra River itself plays a crucial role; while providing a vital water source, it can also exacerbate air pollution through the transport of pollutants downstream and the potential for stagnant air conditions during periods of low wind. The urban–rural gradient around Nalbāri is gradual, with agricultural activities and smaller villages blending seamlessly into the urban fabric. While Nalbāri isn't directly adjacent to major industrial belts, it serves as a regional trading hub for agricultural produce, leading to vehicular traffic and associated emissions. The flat topography limits natural ventilation, potentially trapping pollutants, especially during cooler months. The region's geology, composed largely of unconsolidated sediments, also means dust resuspension is a common occurrence, particularly during the dry season, further impacting air quality. The surrounding tea gardens, while economically important, can contribute to localized emissions from burning agricultural waste.

Nalbāri’s air quality follows a distinct seasonal pattern dictated by the region’s monsoonal climate. The monsoon season, typically spanning June to September, brings relief from accumulated pollutants due to frequent rainfall and strong winds that disperse contaminants. However, this period also sees increased humidity, which can trap certain pollutants close to the ground. The pre-monsoon months (March-May) often experience a build-up of pollutants, exacerbated by rising temperatures and decreasing rainfall. This period is frequently characterized by stagnant air conditions and the potential for temperature inversions, where cooler air becomes trapped beneath a layer of warmer air, preventing vertical mixing and concentrating pollutants near the surface. The dry season (November-February) presents a mixed picture. While winds are generally lighter than during the monsoon, the cooler temperatures can lead to fog formation, particularly in the mornings, which traps particulate matter and reduces visibility. Agricultural burning, a common practice for clearing fields after the harvest, significantly contributes to pollution during this time. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon and dry season months, limiting outdoor activity during peak pollution hours. The post-monsoon period (October) offers a transitional phase with gradually improving air quality as rainfall decreases and winds pick up. Maintaining indoor air quality through ventilation and air purification can be beneficial during periods of elevated pollution, and awareness campaigns promoting cleaner agricultural practices are crucial for mitigating seasonal spikes.