Uranium (U) mining activities, which lead to contamination in soils and waters (i.e., leachate from U mill tailings), cause serious environmental problems. However, limited research works have been conducted on U pollution associated with a whole soil-water system. In this study, a total of 110 samples including 96 solid and 14 water samples were collected to investigate the characteristics of U distribution in a natural soil-water system near a U mining tailings pond. Results showed that U concentrations ranged from 0.09 ± 0.02 mg/kg to 2.56 × 10⁴± 23 mg/kg in solid samples, and varied greatly in different locations. For tailings sand samples, the highest U concentration (2.56× 10⁴ ± 23 mg/kg) occurred at the depth of 80 cm underground, whereas, for paddy soil samples, the highest U concentration (5.22 ± 0.04 mg/kg) was found at surface layers. Geo-accumulation index and potential ecological hazard index were calculated to assess the hazard of U in the soils. The calculation results showed that half of the soil sampling sites were moderately polluted. For groundwater samples, U concentrations ranged from 0.55 ± 0.04 mg/L to 3.36 ± 0.02 mg/L with a mean value of 2.36 ± 0.36 mg/L, which was significantly lower than that of percolating waters (ranging from 4.56 ± 0.02 mg/L to 12.05 ± 0.04 mg/L, mean 7.91 ± 0.98 mg/L). The results of this study suggest that the distribution of U concentrations in a soil-water system was closely associated with hydrological cycles and U concentrations decreased with circulation path.

6:2 Fluorotelomer sulfonate (6:2 FTS), a substitute for perfluorooctane sulfonate (PFOS), is frequently detected in aquatic environments, yet its reproductive toxicity remains incompletely understood. In this study, 480 adult female zebrafish were randomly assigned to five groups: DMSO control, PFOS (0.25 and 5 μg/L), and 6:2 FTS (0.25 and 5 μg/L), with 96 fish per group and three replicate tanks. After 42 days of exposure, PFAS bioaccumulation was assessed using three fish per group; separate sets of six fish per group were used for ovarian oxidative stress, HPG-axis-related hormones, HPG-axis-related gene expression, and reproductive performance; ovarian histopathology was examined using four fish per group; offspring development was assessed using 120 embryos per group; and integrated biomarker response version 2 (IBRv2) was applied. Data are presented as mean ± SEM, with significance set at p < 0.05. Compared with PFOS, 6:2 FTS showed lower bioaccumulation in the maternal liver, ovary, brain, and offspring, but still exhibited relative accumulation in ovarian tissue. Moreover, the ovarian oxidative stress induced by 6:2 FTS was relatively mild. Both compounds disrupted HPG-axis function, increasing gonadotropin releasing hormone (GnRH) and luteinizing hormone (LH) levels while decreasing follicle-stimulating hormone (FSH), testosterone (T), and estradiol (E2) levels. Consistently, gnrh-family genes and lhβ were upregulated, whereas fshβ and 17β-hsd were downregulated. These endocrine disturbances were associated with abnormal oocyte development, increased follicular atresia, reduced spawning output, and higher offspring malformation risk. IBRv2 analysis indicated that although 6:2 FTS caused lower overall toxicity than PFOS, it still impaired reproduction mainly through HPG-axis disruption. These findings demonstrate the reproductive risk of 6:2 FTS and support careful safety evaluation of PFAS alternatives.