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Nandazhang, nestled within Hebei Province, China, occupies a geographically complex position significantly influencing its air quality. Located at approximately 38.08°N, 114.76°E, the city sits on a gently undulating plain, part of the North China Plain, a vast alluvial expanse formed by the Yellow River’s sediment deposition over millennia. Its elevation averages around 40 meters above sea level, contributing to a low atmospheric mixing layer, which can trap pollutants. Nandazhang’s proximity to the Taihang Mountains to the west creates a rain shadow effect, reducing precipitation and further hindering pollutant dispersal. The surrounding landscape is a mosaic of agricultural land – primarily wheat and corn cultivation – interspersed with small villages and increasingly, light industrial zones. This agricultural activity, coupled with the burgeoning industrial sector, represents a significant source of emissions. The urban–rural gradient is relatively sharp, with the city transitioning quickly into agricultural fields and scattered settlements. The city’s location within the Beijing-Tianjin-Hebei economic region places it within a major industrial belt, exposing it to transboundary pollution from larger urban centers. The lack of substantial bodies of water nearby limits natural air purification processes. Prevailing winds often originate from the northwest, carrying pollutants from the mountains and surrounding industrial areas directly towards Nandazhang, exacerbating local air quality challenges. The flat terrain and limited topographical relief further impede the natural dispersion of airborne contaminants.

Nandazhang’s air quality follows a distinct seasonal pattern dictated by meteorological conditions and human activity. Winter (November – February) consistently presents the most challenging period. Cold temperatures lead to frequent temperature inversions, where a layer of warm air traps cooler air near the ground, preventing vertical mixing and concentrating pollutants. Reduced sunlight hours also limit photochemical reactions that can break down some pollutants. Agricultural burning, a common practice for clearing fields in the autumn, contributes significantly to particulate matter during this time. Spring (March – May) brings increased dust storms originating from the Gobi Desert and Mongolia, adding to the particulate load. While temperatures rise, allowing for some dispersion, the influx of dust often overwhelms this effect. Summer (June – August) is generally the most favourable season, with increased rainfall and stronger winds helping to flush out pollutants. However, periods of stagnant weather can still lead to localized air quality degradation. Autumn (September – October) sees a transition period, with decreasing temperatures and increasing agricultural burning, mirroring the winter pattern. Sensitive groups, including children, the elderly, and individuals with respiratory conditions, should exercise caution during winter and spring, limiting outdoor exposure and wearing appropriate masks. During periods of high dust, staying indoors with windows closed is advisable. Summer offers the best window for outdoor activities, but vigilance is still required during stagnant weather events. Careful monitoring of local conditions and adherence to public health advisories are crucial for minimizing exposure risks.