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Nelmadūr, nestled in the Thanjavur district of Tamil Nadu, India, occupies a geographically significant position within the Cauvery Delta, a fertile and densely populated region. Located at approximately 9.51°N, 78.30°E, the city’s terrain is predominantly flat, characteristic of the deltaic plains formed by the Cauvery River. Its elevation is minimal, rarely exceeding 15 meters above sea level, contributing to a low dispersion potential for pollutants. The surrounding landscape is overwhelmingly agricultural, dominated by rice paddies and other crops, a vital component of Tamil Nadu’s economy. This proximity to intensive agricultural practices introduces sources of air pollution, including ammonia emissions from fertilizers and particulate matter from crop residue burning, particularly during post-harvest seasons. Nelmadūr’s location within the delta also means it’s susceptible to flooding during the monsoon season, which can temporarily exacerbate air quality issues by mobilizing dust and pollutants. The urban–rural gradient is gradual; Nelmadūr itself is a small town, but it’s situated within a larger network of villages and towns, and is relatively close to Thanjavur city, which introduces potential for industrial and vehicular pollution to drift into the area. The lack of significant topographical features—hills or valleys—further limits natural air circulation, potentially trapping pollutants within the local atmosphere. The region's humid subtropical climate, with hot summers and a distinct monsoon season, also influences atmospheric stability and pollutant behaviour.

Nelmadūr’s air quality experiences a distinct seasonal cycle heavily influenced by the region’s tropical climate and agricultural practices. The pre-monsoon season (March-May) typically sees the poorest air quality. High temperatures and minimal rainfall create stable atmospheric conditions, often leading to temperature inversions that trap pollutants near the ground. Agricultural burning of crop residue after the harvest season significantly contributes to particulate matter pollution during this period. The monsoon season (June-September) brings relief, with heavy rainfall washing away pollutants and strong winds dispersing them. However, periods of intense rainfall can also lead to localized flooding, stirring up dust and impacting air quality temporarily. The post-monsoon season (October-November) is generally characterized by improved air quality as agricultural burning decreases and wind patterns become more favourable. However, fog can form during cooler nights, trapping pollutants and reducing visibility. The winter months (December-February) are typically the most pleasant for outdoor activities, with cooler temperatures, lower humidity, and generally better air quality. Sensitive groups, such as children, the elderly, and individuals with respiratory conditions, should exercise caution during the pre-monsoon season and be mindful of potential fog events in the post-monsoon period. Avoiding strenuous outdoor activity during peak pollution episodes is advisable. Local authorities should monitor agricultural burning closely and implement measures to minimize its impact on air quality, particularly during the pre-monsoon months.