Currently, more than ten ultrahigh arch dams have been constructed or are being constructed in China. Safety control is essential to long-term operation of these dams. This study employed the flexibility coefficient and plastic complementary energy norm to assess the structural safety of arch dams. A comprehensive analysis was conducted, focusing on differences among conventional methods in characterizing the structural behavior of the Xiaowan arch dam in China. Subsequently, the spatiotemporal characteristics of the measured performance of the Xiaowan dam were explored, including periodicity, convergence, and time-effect characteristics. These findings revealed the governing mechanism of main factors. Furthermore, a heterogeneous spatial panel vector model was developed, considering both common factors and specific factors affecting the safety and performance of arch dams. This model aims to comprehensively illustrate spatial heterogeneity between the entire structure and local regions, introducing a specific effect quantity to characterize local deformation differences. Ultimately, the proposed model was applied to the Xiaowan arch dam, accurately quantifying the spatiotemporal heterogeneity of dam performance. Additionally, the spatiotemporal distribution characteristics of environmental load effects on different parts of the dam were reasonably interpreted. Validation of the model prediction enhances its credibility, leading to the formulation of health diagnosis criteria for future long-term operation of the Xiaowan dam. The findings not only enhance the predictive ability and timely control of ultrahigh arch dams’ performance but also provide a crucial basis for assessing the effectiveness of engineering treatment measures.
Although big data is publicly available on water quality parameters, virtual simulation has not yet been adequately adapted in environmental chemistry research. Digital twin is different from conventional geospatial modeling approaches and is particularly useful when systematic laboratory/field experiment is not realistic (e.g., climate impact and water-related environmental catastrophe) or difficult to design and monitor in a real time (e.g., pollutant and nutrient cycles in estuaries, soils, and sediments). Data-driven water research could realize early warning and disaster readiness simulations for diverse environmental scenarios, including drinking water contamination.
This study synthesized a ferric oxide–nanographite (NG) nanocomposite (Fe2O3@NG) from waste toner powder through carbonization. Subsequently, a TiO2/Fe2O3@NG nanohybrid was fabricated using the sol–gel technique to improve the photocatalytic degradation of dyes. TiO2/Fe2O3@NG nanocomposites were prepared at TiO2:Fe2O3@NG ratios of 2:1 (Ti:T-21), 1:1 (Ti:T-11), and 1:2 (Ti:T-12). The porosity, morphology, surface chemistry, and chemical interactions between TiO2, Fe2O3, and graphite in the prepared TiO2/Fe2O3@NG nanocomposites were characterized using the Brunauer–Emmett–Teller (BET) method and microscopic and spectroscopic analyses. The TiO2/Fe2O3@NG nanohybrid exhibited a reduced bandgap (2.4–2.9 eV) and enhanced charge carrier separation through charge transfer at the junction of the hetero-structured TiO2/Fe2O3@NG nanohybrid. Preliminary experiments revealed that Ti:T-21 was the most effective photocatalyst for degrading acid blue-25 (AB-25) compared to Ti:T-11, Ti:T-12, sole TiO2, and Fe2O3@NG. This study also investigated the impacts of catalyst dose and initial dye concentration on the AB-25 photocatalytic degradation. Notably, 97% of 5-mg/L AB-25 was removed using 1.25-g/L Ti:T-21 at an unmodified pH of 6.4 within 120 min. Furthermore, Ti:T-21 exhibited remarkable recyclability in its immobilized form, achieving degradation ratios of 74.7%–71.8% over five consecutive runs, compared to removal efficiencies of 85.0%–62.3% in the suspended mode. Trapping experiments identified hydroxyl radicals, holes, and superoxide as the principal reactive radicals. The TiO2/Fe2O3@NG/light system was effective in disintegrating and mineralizing other synthetic dyes such as Congo red, methylene blue, and methyl red, indicating its potential for industrial-scale degradation of authentic dye wastewater. The utilization of waste toner for water treatment is highlighted as a strategy to promote environmental sustainability, foster a circular economy, and contribute to pollution remediation.

