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Châu Đốc, nestled in the heart of An Giang province, Vietnam, occupies a strategically vital position within the Mekong Delta. Situated at approximately 10.7000° N, 105.1167° E, the city’s geography is profoundly shaped by its proximity to the Mekong River and the vast, fertile floodplains characteristic of the region. The terrain is predominantly flat, with elevations rarely exceeding 5 meters above sea level, making it exceptionally vulnerable to flooding and influencing atmospheric circulation patterns. Châu Đốc acts as a significant trading hub, connecting Vietnam to Cambodia via the Hau River, a major distributary of the Mekong. This location fosters a blend of urban and rural landscapes; the city itself exhibits a moderate urban character with markets, residential areas, and some light industry, while the surrounding area is dominated by intensive agricultural land – primarily rice paddies and fruit orchards. The landscape is a mosaic of waterways, canals, and agricultural fields, creating a humid, tropical environment. Upstream, the river carries sediment and potential pollutants from across the Mekong basin. Downstream, the delta’s low-lying nature can trap stagnant air, particularly during periods of reduced wind. The urban–rural gradient is gradual, with agricultural activities directly impacting the city’s air quality through seasonal burning practices and fertilizer use. The surrounding landscape, while visually appealing, contributes to the complex interplay of factors affecting Châu Đốc’s atmospheric conditions.

Châu Đốc’s tropical climate dictates a distinct wet and dry season, significantly influencing air quality patterns. The dry season, typically from November to April, often sees a build-up of pollutants. Reduced rainfall and lower humidity contribute to the concentration of particulate matter, exacerbated by agricultural burning practices used to clear fields for the next planting season. The prevailing winds during this period are often light and variable, hindering the dispersion of pollutants, and temperature inversions can occasionally trap emissions close to the ground. Fog, common in the early mornings during the dry season, further restricts visibility and concentrates pollutants. The wet season, from May to October, brings increased rainfall and higher humidity, naturally cleansing the atmosphere and reducing particulate concentrations. Monsoon winds become more frequent, dispersing pollutants more effectively. However, heavy rainfall can also lead to increased levels of ozone, a secondary pollutant formed through photochemical reactions. The months of January and February often experience the poorest air quality due to the combination of agricultural burning and stagnant air. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should limit outdoor activity during these periods, particularly during early morning hours when fog is prevalent. During the wet season, while overall air quality improves, those with sensitivities to pollen or mold should remain vigilant, as increased humidity can promote their growth.