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Land use significantly affects the rate and amount of groundwater recharge. To understand these patterns, stable isotope analyses (δ 2 H and δ 18 O) and hydrochemical methods were employed to study the recharge and evolution of groundwater.MixSIAR Bayesian mixture modelling and statistical regression techniques were utilized to investigate the influence of land-use type on groundwater recharge and to calculate the contribution of various water sources to different groundwater types.These findings are important for effective management and conservation of groundwater resources. The groundwater in all studied areas displayed a magnesium bicarbonate type with notable cation exchange, and also demonstrated the dissolution of carbonate and weathering of silicate. Results from the Bayesian mixture model indicate that 69.3% of the groundwater in the Loess Plateau region was recharged by precipitation, while 86.9% of the groundwater in the loess hilly-gully region was recharged from the surface water. Groundwater recharge was more rapid in the loess hilly-gully region than in the Loess Plateau and was less sensitive to the land use type in the former. Dryland-moderate coverage grassland was found to be most conducive to groundwater infiltration, whereas monotypic dryland and high-coverage grassland inhibited infiltration to some degree. To maintain balanced soil erosion control, an increase the area of moderate-coverage grasslands in the Loess Plateau region is recommended.

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We conducted a study of the leaf-deposited particles and magnetism of plant leaves in different functional areas (tra c areas, parks and residential areas) in Lanzhou, China. The saturation isothermal remanence (SIRM) of the washed and unwashed leaves of 23 plant species (including evergreen shrubs, deciduous shrubs, deciduous liana species and deciduous trees) at three sampling heights (0.5 m, 1.5 m and 2.5 m) was measured. In addition, the mass of the leaf-deposited particles was measured using the elution-ltration method and the leaf morphological characteristics were determined by scanning electronic microscope (SEM) analysis. The results revealed signi cant differences in particles retention capacity among the 23 plant species, with evergreen shrub species at the heights of 0.5 m and 1.5 m having higher particles concentrations. Buxus sinica, Buxus megistophylla, Prunus cerasifera and Ligustrum×vicaryi were the most effective plant species for accumulating particles. The SEM results showed that leaves with a relatively complex adaxial surface (such as deep grooves and protrusions)were more effective at accumulating particles. The SIRM of washed leaves, unwashed leaves and leafdeposited particles were signi cantly higher in tra c areas than in parks and residential areas. In addition, signi cant correlations were found between SIRM of unwashed leaves and leaf-deposited particles and the mass of leaf-deposited particles, and therefore the leaf magnetic properties effectively re ect levels of PM pollution under different environmental conditions. Overall, our results provide a valuable reference for the selection of plant species with high particle retention capacity that suitable for urban greening and pollution mitigation.

The direct ingestion of indoor dust particles at historical heritage sites is a primary exposure pathway for employees to heavy metals. Water-soluble ions (WSIs) and heavy metal levels, sources, bioaccessibility, and health risks associated with indoor dust in the Mogao Grottoes were analyzed using comprehensive methods to determine the differences in the concentrations and distribution characteristics of WSIs and heavy metals between statue dust and floor dust. The concentrations of WSIs and heavy metals and the magnetic values of χ lf and SIRM in indoor dust were higher than those in street dust and topsoil. The mean χ lf and SIRM of statue dust particles were 100.3 × 10 − 8   m 3 k g − 1 and 1686.9 × 1 0 − 5   Am 2 k g − 1 . Specifically, the concentration of Pb was 277   mg   k g − 1 , 15-fold higher than the background value, indicating the continual receipt of heavy metals with high magnetic minerals during dust deposition. WSIs mainly originate from the weathering of surrounding rocks and earthen plaster; Pb originates from the shedding of paint of murals and sculptures; and Zn, Cu, and magnetic minerals originate from traffic sources. The bioaccessibility of heavy metals is high in the gastrointestinal phases of indoor dust. Overall, the health risks posed by heavy metals in indoor dust were low, with moderate to high risks in individual caves. Ingestion presents the highest noncarcinogenic and carcinogenic risk to employees. These results provide essential knowledge on indoor dust characteristics in the Mogao Grottoes, facilitating strategies for dust pollution mitigation and employee health risk control.