The correlation between the photocatalytic degradability of polycyclic aromatic hydrocarbons (PAHs) over Pt/TiO₂‐SiO₂ in water and their quantitative molecular structure was studied. Six PAHs, namely, naphthalene, fluorene, phenanthrene, pyrene, benzo[a]pyrene, and dibenzo[a,h]anthracene, were tested in Pt/TiO₂‐SiO₂ suspension under UV irradiation. The results showed that the degradation efficiencies of the higher molecular weight PAHs were enhanced significantly in the presence of Pt/TiO₂‐SiO₂, while the degradation efficiencies of the lower molecular weight PAHs were decreased in the presence of Pt/TiO₂‐SiO₂. Both the photolysis and photocatalysis of all PAHs fit the pseudo‐first‐order equation very well, except FL. Quantitative analysis of molecular descriptors of energy of the highest occupied molecular orbital (E_homo), energy of the lowest unoccupied molecular orbital (E_lumo), and the difference between E_lumo and E_homo, GAP (GAP = E_lumo − E_homo), suggested that the GAP was significant for predicting a PAHs’ photocatalytic degradability. Through comparison against the maximum GAP (7.4529 eV) of PAHs (dibenzo[a,h]anthracene) that could be photocatalytically degraded and the minimum GAP (8.2086 eV) of PAHs (pyrene) that could not be photocatalytically degraded in this study, the photocatalytic degradability of 67 PAHs was predicted. The predictions were partly verified by experimental photocatalytic degradation of anthracene and Indeno[1.2.3.cd]pyrene.

This article investigates the energy intensity and related impacts of the Eastern Route of China's South-North Water Transfer Project, based on the concept of the water–energy nexus. It finds that from November 2013 to May 2017 a total of 2.35 billion kWh of energy was consumed to transfer 15.5 billion m3 water driven by a large-scale system of pumping stations. This energy production required 7.4 million m3 of virtual water and emitted 1.93 MtCO2e of carbon. An average water–energy nexus ratio of 0.05% indicates that transferring 100 m3 of water consumes 0.05 m3 of virtual water due to the electricity consumption of the Eastern Route's pumping stations. It is estimated that to transfer 7.3 billion m3 water by 2030, this mega project will consume 1.35 billion kWh of energy, 4.6 million m3 of virtual water and emit 0.94 MtCO2e of carbon. These findings and scenario analysis demonstrate that strategies are needed for mitigating the energy intensity of the Eastern Route, such as improved pumping efficiency, reduced water loss during water delivery, decreased water quotas, and promotion of other, less carbon-intensive water sources in destination provinces.

Evapotranspiration is one of the most important hydrological variables in the context of water resources management. An attempt was made to understand and predict the dynamics of reference evapotranspiration from a nonlinear dynamical perspective in this study. The reference evapotranspiration data was calculated using the FAO Penman-Monteith equation with the observed daily meteorological data for the period 1966–2005 at four meteorological stations (i.e., Baotou, Zhangbei, Kaifeng, and Shaoguan) representing a wide range of climatic conditions of China. The correlation dimension method was employed to investigate the chaotic behavior of the reference evapotranspiration series. The existence of chaos in the reference evapotranspiration series at the four different locations was proved by the finite and low correlation dimension. A local approximation approach was employed to forecast the daily reference evapotranspiration series. Low root mean square error (RSME) and mean absolute error (MAE) (for all locations lower than 0.31 and 0.24, resp.), high correlation coefficient (CC), and modified coefficient of efficiency (for all locations larger than 0.97 and 0.8, resp.) indicate that the predicted reference evapotranspiration agrees well with the observed one. The encouraging results indicate the suitableness of chaotic approach for understanding and predicting the dynamics of the reference evapotranspiration.

River pollution is a major issue in China’s urbanization process. Understanding the effects of river morphology and constructed wetlands on the self-purification capacity is crucial for water quality improvement. This study takes the Shiwuli River, a main tributary of Chaohu Lake, as an example. By monitoring the concentration changes of five water quality indicators—total nitrogen (TN), total phosphorus (TP), ammonia nitrogen (NH₃-N), chemical oxygen demand (COD), and dissolved oxygen (DO)—in the river section for the years 2017 and 2024, we conducted a comparative analysis of the relationship between river morphology and self-purification capacity, as well as influencing factors. The results show that meandering rivers possess self-purification capabilities under natural conditions. There is a positive correlation between river sinuosity and the reduction rates of TP, TN, NH₃-N, and COD, as well as the increase rate of DO—the greater the sinuosity, the stronger the purification capacity. Wetlands enhance both the self-purification capacity and the purification rate of river channels, reducing the required sinuosity for effective self-purification from 1.49 to 1.30. This study also discusses the mechanisms by which meandering rivers influence water self-purification, and proposes that increasing river sinuosity and constructing wetlands can enhance the self-purification capacity. This measure will increase the length and width of the river, prolong the purification time, improve the DO level, and enhance the exchange between the riverbed and groundwater. The findings of this study can provide a reference for river restoration and management in the context of urbanization.