The unique urban form on the ground and the “city overlap city” phenomenon occurring underground at Kaifeng city, on the Yellow River floodplain, is investigated. Archaeological data and historical geographical analysis were used to study the form of surface remains. Primary data were collected from four 25 m long drill cores which were obtained from different locations at Kaifeng city and the sedimentary cycles were quantitatively divided-out and dated. The results show that the evolution of Kaifeng’s surface urban form mainly occurred over four periods, the first of which was before 225 BC; the second took place between 225 BC and 956 AD; the third between 956 AD and 1219 AD; and the fourth between 1219 AD and 1907 AD. The results support the view that the city wall of today has undergone continuous reconstruction on the basis of previous city walls and thus forming the special landscape sequence of overlapped walls as a result of the 1642 AD and 1841 AD floods. The results also substantiate the “city overlap city” phenomenon at Kaifeng city where there are at least “three and a half ancient cities” located underground today, and suggests the “city overlap city” landscape is a harmonious production comprising both natural and human heritages that are of worldwide significance in terms of authenticity and integrity. Our results contribute to understanding the effects of Yellow River flooding on shaping adaptive landscapes and human beings, and suggest that Kaifeng city as well as other lower Yellow River sites become World Heritage sites.

To explore the characteristics of PM_2.5 and assess the health risks to residents in Shijiazhuang before and during the heating period in 2019, 2020 and 2021, the hourly concentrations of PM_2.5 and its nine selected trace elements were determined. The results showed that the mass concentrations of PM_2.5 were 80.32 ± 50.21 μg m⁻³ (2019), 69.97 ± 41.91 μg m⁻³ (2020) and 58.70 ± 41.97 μg m⁻³ (2021) during the heating period, representing greatly improved air quality. The PM_2.5 levels in the heating period were 1.04~1.60 times greater than those before the heating period, while the total selected trace element concentrations were about 1.44~1.97 times higher, indicating that strict control for PM_2.5 in the heating period should be imposed. The overall hazard quotient (HQ) of the nine selected trace elements in the heating period were 1.08~1.42 times higher than those before the heating period, while the total cancer risks (CR) were decreased by 29.04% (2020) and 3.50% (2021). There were high health risks not only in local areas, but also in the south of Hebei, the north of Henan, and southern and central Shanxi. The health risks increased by 1.21~2.26 times from clean levels to heavy pollution levels. The leading element of HQ was Mn, while the dominant elements of CR varied from As to Co. Increases in PM_2.5 concentrations and HQ from before the heating period to during the heating period were observed, and there was even an inverse CR change between before the heating period and during the heating period, further identifying that air pollution control was efficient.

Fireworks burning (FB) constitutes a major but short-lived source of PM_2.5 during the Chinese Spring Festival, significantly deteriorating air quality in certain regions. This study was conducted to evaluate its impact through real-time monitoring of PM_2.5 chemical compositions in a forestry city (Xinyang) during the pre-fireworks and fireworks periods at the Spring Festival of 2023–2025. During the fireworks period, PM_2.5 concentrations increased by 10.5–226.4% compared to pre-fireworks levels, of which the concentrations of secondary inorganic aerosols (SIA), K and Cl⁻ rose by 1.6–4.8, 1.9–14.7 and 1.5–8.1 times, and they accounted for 33.2–47.7%, 6.7–12.5% and 3.8–6.4% of PM_2.5, respectively. Correspondingly, PM_2.5/CO and SIA/CO ratios in 2023–2025 elevated by factors of 1.4–2.3 and 1.1–3.4, indicating distinct enhancements in secondary inorganic aerosols formation. Additionally, acidity of PM_2.5, RH and O_x also increased during fireworks. Collectively, higher sulfur and nitrogen oxidation ratios (SOR and NOR) during the fireworks period under the combined effects of high RH, O_x and acidity conditions indicated a greater conversion of secondary inorganic aerosols. Positive Matrix Factorization (PMF) analysis confirmed that FB and secondary aerosols (SA) source levels during fireworks increased by 2.5–19.3 and 1.9–4.4 times compared to pre-fireworks values. This study underscores the need for implementing stringent management of fireworks and secondary formation mitigation to reduce PM_2.5 concentrations during the Spring Festival.

在黄河流域生态保护和高质量发展战略背景下，实施居民迁建工程是全面推动黄河滩区高质量发展与乡村振兴的必然选择。论文基于人地关系和区域高质量发展理论，运用多因素综合评价模型、地理探测器等定量分析方法，并结合实地调研、文本分析方法，对河南省黄河滩区居民迁建驱动力空间特征与机制进行研究。结果表明：① 滩区居民迁建驱动力存在显著的空间差异和等级分化特征，其中迁建动力较高的区域均集聚在滩区的中部，而迁建阻力较高的区域则主要位于滩区的东部；② 滩区居民迁建倾向整体以中、高水平为主，并呈现“以郑州为中心、向滩区东西两侧分别递减”的空间分布格局，且县域间差异显著；③ 二维平面映射分析显示，滩区尚有53.85%的研究单元居民迁建动力与阻力呈“双低”发展状态，而这种低水平的发展状态进一步加剧了潜在驱动力因子的隐蔽性，使其难以被及时有效地识别，从而给后续居民迁建工程带来较大的不确定性；④ 滩区居民迁建驱动力空间特征是多种影响因子相互演进、共同作用的结果，收入水平、地理区位、政策扶持力度、个体因素是主要驱动力因子。研究结果可为黄河滩区后续居民迁建政策的差异化制定与精准实施以及迁建风险评估提供科学参考。