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Rongcheng, a small city in Hebei Province, China, occupies a crucial position within the broader North China Plain. Located at coordinates 39.0525° N, 115.8603° E, the city’s terrain is largely flat, characteristic of the alluvial plain formed by the Hai River basin. This flatness contributes to limited natural air dispersion. Rongcheng’s elevation is relatively low, further exacerbating potential for pollutant accumulation. The city is situated inland, approximately 150km southeast of Beijing and 100km north of the Bohai Sea, meaning coastal influences are minimal. Surrounding Rongcheng are extensive agricultural lands, primarily dedicated to wheat and corn cultivation, alongside emerging industrial zones focused on manufacturing and processing. The urban-rural gradient is relatively sharp; the city centre is densely populated, transitioning quickly to farmland. This proximity to both agricultural activity (potential ammonia emissions from fertilizers) and industry (sources of particulate matter and sulfur dioxide) significantly impacts local air quality. The regional climate, a typical continental monsoon climate, features cold, dry winters and hot, humid summers, influencing pollutant behaviour. The surrounding landscape offers limited topographic features to break up wind patterns and disperse pollutants, making Rongcheng vulnerable to air stagnation events.

Rongcheng’s air quality follows a distinct seasonal pattern. Winter, from November to March, typically sees the poorest air quality. Cold temperatures create stable atmospheric conditions, often with temperature inversions trapping pollutants near the ground. Reduced wind speeds further limit dispersion. Heating demands, reliant on coal in surrounding areas, contribute significantly to particulate matter (PM2.5 and PM10) concentrations. Spring (April-May) brings increased dust storms originating from the Gobi Desert, adding to particulate pollution, though temperatures begin to rise, offering some improvement. Summer (June-August) generally experiences better air quality due to increased rainfall, which helps to wash pollutants from the atmosphere, and stronger monsoon winds that promote dispersion. However, high temperatures can also lead to increased ozone formation. Autumn (September-October) is a transitional period; air quality initially remains relatively good, but deteriorates as heating season approaches. Sensitive individuals – children, the elderly, and those with respiratory conditions – should avoid strenuous outdoor activity during winter and spring. Monitoring wind direction is crucial, as pollutants often drift from nearby industrial centres. Months of July and August generally offer the most favourable conditions for outdoor activities.