Predictions of prospectivity based on remote sensing were developed using alteration mineral indicative hyperspectral mapping and remote sensing anomaly filtering, combined with geological characteristics and anomalous mineral field verification. Based on the results of the hyperspectral mineral mapping and the actual geological ground conditions, the results of mapping of altered minerals, such as chlorite, muscovite, kaolinite, and iron oxide were validated, and gold, silver, copper, nickel, and other geochemical anomaly areas were identified for verification work. The results of hyperspectral mineral extraction show that the mineral assemblage closely related to gold deposits in shear zones is muscovite + chlorite + epidote + kaolinite. This alteration mineral assemblage can be used as regional search criteria for shear zone gold mineralisation and was the basis for the discovery of mineralised hydrothermal alteration centres and delineation of four prospective targets. Established on a spectral prospectivity model of the study area, prospective ore-bearing areas have been delineated, which indicate the direction for further geological and mineral resource surveys.

Despite significant improvements in air quality during and after COVID-19 restrictions, haze continued to occur in Zhengzhou afterwards. This paper compares ionic compositions and sources of PM_2.5 before (2019), during (2020), and after (2021) the restrictions to explore the reasons for the haze. The average concentration of PM_2.5 decreased by 28.5% in 2020 and 27.9% in 2021, respectively, from 102.49 μg m⁻³ in 2019. The concentration of secondary inorganic aerosols (SIAs) was 51.87 μg m⁻³ in 2019, which decreased by 3.1% in 2020 and 12.8% in 2021. In contrast, the contributions of SIAs to PM_2.5 increased from 50.61% (2019) to 68.6% (2020) and 61.2% (2021). SIAs contributed significantly to PM_2.5 levels in 2020–2021. Despite a 22~62% decline in NO_x levels in 2020–2021, the increased O₃ caused a similar NO₃⁻ concentration (20.69~23.00 μg m⁻³) in 2020–2021 to that (22.93 μg m⁻³) in 2019, hindering PM_2.5 reduction in Zhengzhou. Six PM_2.5 sources, including secondary inorganic aerosols, industrial emissions, coal combustion, biomass burning, soil dust, and traffic emissions, were identified by the positive matrix factorization model in 2019–2021. Compared to 2019, the reduction in PM_2.5 from the secondary aerosol source in 2020 and 2021 was small, and the contribution of secondary aerosol to PM_2.5 increased by 13.32% in 2020 and 12.94% in 2021. In comparison, the primary emissions, including biomass burning, traffic, and dust, were reduced by 29.71% in 2020 and 27.7% in 2021. The results indicated that the secondary production did not significantly contribute to the PM_2.5 decrease during and after the COVID-19 restrictions. Therefore, it is essential to understand the formation of secondary aerosols under high O₃ and low precursor gases to mitigate air pollution in the future.

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.

This study investigated rubber additives and relevant transformation products (RARTPs) in surface waters of Kaifeng, a city linking the Yellow River and Huaihe River basins. Seven of fifteen target analytes were detected in >10% of samples. The hydrolysis product 4-hydroxydiphenylamine (4OH) showed the highest detection frequency (70%), followed by 1,2-Dihydro-2,2,4-trimethylquinoline (TMQ, 57%) and N-(1,3-Dimethylbutyl)-N′-phenyl-p-phenylenediamine (6PPD, 27%). TMQ had the highest average concentration (6.16 ± 4.17 ng·L⁻¹). Urban rivers (14.20 ± 4.72 ng·L⁻¹) were contamination hotspots, driven by management practices (e.g., dredging of urban lakes). Although detected at lower levels (0.09 ± 0.21 ng·L⁻¹), 6PPD-quinone (6PPD-Q) was associated with elevated risk (risk quotient, RQ ≥ 1) at 19% of sites. The chronic daily intake assessment showed that drinking water ingestion contributed 66.7% of total exposure in daily use, whereas dermal absorption dominated during swimming. Children, especially girls, were the most vulnerable subgroup. Although estimated chronic daily intakes (CDIs) from surface water accounted for only a negligible proportion of the daily urinary excretion of p-phenylenediamine antioxidants (PPDs) reported in a Chinese population, the ecological risk of 6PPD-Q warrants continued attention. These findings highlight the need for improved management of water bodies receiving urban runoff and aquaculture inputs, and further health risk assessment of RARTPs.

Exploring the pollution characteristics and ecological risks of urbanization on lakes in urban fringe areas has guiding significance for the control and scientific management of heavy metal pollution in lakes in urban fringe areas. Taking the West Lake in Kaifeng city as an example, the samples of the sediments and surface water of the lake were collected, and the contents of heavy metals (As, Cd, Cr, Cu, Ni, Pb, and Zn) were measured, assessing the degree and ecological risk of heavy metal pollution using the Geo-Accumulation Index (I_geo) and Potential Ecological Risk Index methods (RI); and the sources of pollution were identified. The results show that the heavy metal concentrations in the surface water of the West Lake in Kaifeng city are generally low; average concentrations of Cd, Cu, Zn, Cr, Ni, Pb, and As in sediments are 3.120, 1.810, 1.700, 1.540, 1.000, 0.990, and 0.430 times higher than the background value of fluvo-aquic soil, respectively. The sequence of the average I_geo from high to low is Cd (1.020) > Cu (0.220) > Zn (0.160) > Cr (0.000) > Pb (−0.610) > Ni (−0.640) > As (−1.850). Among them, contaminations with Pb are classed as moderately polluted; As pollution is relatively light, while other heavy metals are unpolluted. The average Potential Ecological Risk Coefficient (E) values for seven heavy metals are Cd (93.500) > Cu (9.040) > Ni (4.990) > Pb (4.950) > As (4.290) > Cr (3.080) > Zn (1.700). Cd is at a considerable potential ecological risk, while other heavy metals are at low ecological risks. Heavy metal pollution in sediment of West Lake in Kaifeng mainly comes from traffic activities such as yacht machinery wear and gasoline burning. The research findings provide a scientific foundation for developing effective mitigation strategies against heavy metal contamination in peri-urban lacustrine ecosystems.