System dynamics modelling to simulate regional water-energy-food nexus combined with the society-economy-environment system in Hunan Province, China.

Nexus approaches provide an efficient way to analyze the dynamic evolution of the water-energy-food nexus (WEFN), yet there is a need to close the science-policy divide by making simulation models more practically relevant. This study incorporates society, economy and environment systems (SEE) into the WEFN, simulating a broad environmental system. A system dynamics model is constructed to simulate and dynamically track the development of the WEF-SEE system in Hunan Province, China. The developed model is applied to assess WEF-SEE system trajectories from 2021 to 2035 against nine policy goals formulated by the Hunan Provincial Government. Baseline results suggest that Hunan Province will have a surplus of grain production and will be in a state of "self-sufficiency" in water resources. The energy security situation is not as optimistic, with imports being required to meet demand. The sustainable development of the WEF Nexus will be constrained by resource shortages. As the future development of Hunan Province outpaces environmental protection policies, water pollution and CO2 emissions and are expected to increase. Intra-system trade-offs and synergies under the impacts of different policies indicate that the implementation of an indicative policy has the intended impact within its particular subsystem, but may lead to trade-offs in other subsystems. Due to system interconnectedness, the simultaneous implementation of multiple policies may increase or hinder progress towards certain goals. For example, expanding planting area increases food production, but increase agricultural water demand and water pollutant discharge, counter to water security goal and environmental protection goals. Cross-system impacts must be considered when choosing policies. This study advances environmental system analysis and evaluation, and contributes to practical policy recommendations, providing useful insights for Hunan Province, especially considering potential trade-offs and synergies. Such information could lead to more effective, holistic environmental policy formulation.

Assessment of PM2.5-related health effects: A comparative study using multiple methods and multi-source data in China.

In China, PM2.5 pollution has caused extensive death and economic loss. Thus, an accurate assessment of the spatial distribution of these losses is crucial for delineating priority areas for air pollution control in China. In this study, we assessed the PM2.5 exposure-related health effects according to the integrated exposure risk function and non-linear power law (NLP) function in 338 prefecture-level cities in China by utilizing online monitoring data and the PM2.5 Hindcast Database (PHD). Our results revealed no significant difference between the monitoring data and PHD (p value = 0.66 > 0.05). The number of deaths caused by PM2.5-related Stroke (cerebrovascular disease), ischemic heart disease, chronic obstructive pulmonary disease, and lung cancer at the national level estimated through the NLP function was 0.27 million (95% CI: 0.06-0.50), 0.23 million (95% CI: 0.08-0.38), 0.31 million (95% CI: 0.04-0.57), and 0.31 million (95% CI: 0.16-0.40), respectively. The total economic cost at the national level in 2016 was approximately US$80.25 billion (95% CI: 24.46-132.25). Based on a comparison of Z statistics, we propose that the evaluation results obtained using the NLP function and monitoring data are accurate. Additionally, according to scenario simulations, Beijing, Chongqing, Tianjin, and other cities should be priority areas for PM2.5 pollution control to achieve considerable health benefits. Our statistics can help improve the accuracy of PM2.5-related health effect assessments in China.

Multi-objective optimal water resources allocation in the middle and upper reaches of the Huaihe River Basin (China) based on equilibrium theory.

In the river basin water resources allocation (WRA) problem, an unbalanced WRA poses challenges to water resources management departments. Many studies focus on achieving a lower water shortage rate while ignoring the equilibrium relationship among the socio-economic system, water resources system and eco-environmental system, as well as the equilibrium relationship among different regions. In this study, a water resources allocation model(WRAM) based on equilibrium theory is constructed to achieve the balance between different systems and different spaces in a basin. First, the relationship among the water resources system, socio-economic system and eco-environmental system is described. Then, the regional equilibrium index and system equilibrium index are constructed. Finally, the first model based on equilibrium theory is constructed. The results show that: (1) the Pareto Front reflects the contradictory relationship between economic development and environmental sustainability; (2) with the restructuring of industry and cropping, both economic efficiency and water shortage rates improve; (3) the equilibrium of the basin could also be further improved if water resources utilisation is further improved. Therefore, this study improves the existing WRAM, which can be applied to guide the water resources management of river basin.

Study on Spatial and Temporal Distribution Characteristics of Coordinated Development Degree among Regional Water Resources, Social Economy, and Ecological Environment Systems.

Water resources utilization, social economy development, and ecological environment protection are key factors in regional sustainable development. Scientific evaluation of regional coordinated development status and diagnosis of regional uncoordinated development constraints will improve the management level of decision-makers. At present, most developing countries have the problem of unbalanced regional development caused by the one-sided pursuit of a certain system. Taking 14 prefecture-level cities in Hunan Province as cases, this paper analyzed the spatial and temporal distribution characteristics of the carrying capacity level of the water resources system, the development level of the social economy system and the protection level of the ecological environment system in each evaluation unit based on entropy weight method and order parameter analysis. Based on the theory of coordinated development, a calculation model of a coordinated development degree was constructed, and the corresponding evaluation criteria were formulated. The spatial and temporal distribution characteristics of a coordinated development degree in each research unit were analyzed and evaluated. The results showed that the average coordinated development degree of Hunan Province from 2004 to 2016 evolved from "Light disorder recession" to "Nearly disorder recession", then to "Reluctance coordinated development". Restricted by different systems, the coordinated development degree in each research unit presented spatial and temporal differences. According to different development stages and the characteristics of different regions, corresponding development strategies can be formulated to provide the guidance for coordinated the development of regions.

Capping experiments reveal multiple surface active sites in CeO2 and their cooperative catalysis.

Understanding of surface active sites (SAS) of CeO2 is crucial to its catalytic applications. In the present study, we have employed capping experiments, DFT calculations, and spectroscopic characterization to study pristine CeO2 catalyst. We find that multiple SAS coexist on the CeO2 surface: oxygen vacancies as redox sites and the coordinately unsaturated Ce cations near the oxygen vacancies and the neighboring oxygen ions as Lewis acid-base sites. Dimethylsulfoxide (DMSO), pyridine, and benzoic acid are utilized to cap the redox sites, Lewis acid sites, and base sites, respectively. Selective capping on the redox site does not have much effect on the acid-base catalysis, and vice versa, indicating the distinct surface proximity and independent catalysis of these SAS. We draw attention to a relationship between the well-known redox sites and the surface Lewis acid and Lewis base pairs on CeO2 surface, which are responsible for driving various heterogeneous catalytic reactions.

Preparation of Hollow Cu and CuO x Microspheres with a Hierarchical Structure for Heterogeneous Catalysis.

Diffusion is one of the most critical factors which affect the performance of porous catalysts in heterogeneous reactions. Hollow spheres with a hierarchical structure could significantly improve the mass transfer in the spherical catalyst. Therefore, preparation of such kind of microspheres is an important work in the field of inorganic synthesis. Herein, we combine microfluidic technology and electroless deposition to prepare hollow Cu and CuO x microspheres with a hierarchically porous structure. These microspheres have a controllable diameter (100-500 µm) and shell thickness (10-60 µm). Numerical simulation and experimental results indicate that the hollow structure is beneficial for the diffusion and utilization of the catalyst in heterogeneous reactions. The Cu and CuO x microspheres were used to catalyze the hydrogenation and Fenton-like reactions in a flow reactor, respectively. The conversion of all reactants can reach more than 95%, and catalysts can maintain their reactivity in long reaction times. Thus, the strategy in the present research should apply in the construction of other porous catalysts with high performance.

Direct catalytic hydrogenation of CO2 to formate over a Schiff-base-mediated gold nanocatalyst.

Catalytic transformation of CO2 to formate is generally realized through bicarbonate hydrogenation in an alkaline environment, while it suffers from a thermodynamic sink due to the considerable thermodynamic stability of the bicarbonate intermediate. Here, we devise a route for the direct catalytic conversion of CO2 over a Schiff-base-modified gold nanocatalyst that is comparable to the fastest known nanocatalysts, with a turnover number (TON) of up to 14,470 over 12 h at 90 °C. Theoretical calculations and spectral analysis results demonstrate that the activation of CO2 can be achieved through a weakly bonded carbamate zwitterion intermediate derived from a simple Lewis base adduct of CO2. However, this can only occur with a hydrogen lacking Lewis base center in a polar solvent. This finding offers a promising avenue for the direct activation of CO2 and is likely to have considerable implications in the fields of CO2 conversion and gold catalytic chemistry.

Bio-inspired immobilization of metal oxides on monolithic microreactor for continuous Knoevenagel reaction.

A facile method is reported to construct monolithic microreactor with high catalytic performance for Knoevenagel reaction. The microreactor is based on hierarchically porous silica (HPS) which has interconnected macro- and mesopores. Then the HPS is surface modified by pyrogallol (PG) polymer. Al(NO3)3 and Mg(NO3)2 are loaded on the surface of HPS through coordination with -OH groups of PG. After thermal treatment, Al(NO3)3 and Mg(NO3)2 are converted Al2O3 and MgO. The as-synthesized catalytic microreactor shows a high and stable performance in Knoevenagel reaction. The microreactor possess large surface area and interconnected pore structures which are beneficial for reactions. Moreover, this economic, facile and eco-friendly surface modification method can be used in loading more metal oxides for more reactions.

[Raman spectra of PAN-based carbon fibers during graphitization].

Laser Raman spectroscopy was employed to characterize the structure of PAN-based carbon fibers during graphitization (2 000-3 000 degrees C), and the spectra of the surface and the cross section of the fibers were compared. The results show that the Raman spectra of the fibers after graphitization can be separated as three bands (D, G and D'). The degree of disorder of the fibers can be measured by Raman spectra parameter, such as the full-widths at half maximum (FWHM) of D and G bands, Raman shift of G band, and the integrated intensity ratio in the form of R(I(D) I(G)). Further investigation demonstrated that the FWHM of D and G bands, Raman shift of G band and the value of R decrease with increasing heat treatment temperature (HTT). The D band can be seen and the value of R is 0.19 even after being heat treated at 3 000 V, indicting that the fibers still have disordered carbons. In addition, the value of R is linearly related to the reciprocal of the basal plane length of the crystallites (L(a)). The spectra of the surface and the cross-section of the fibers after graphitization show obvious difference. So the degree of graphitization and preferred orientation of carbon fibers can be quantitatively characterized by laser Raman spectroscopy.

A simple low-temperature growth of ZnO nanowhiskers directly from aqueous solution containing Zn(OH)42- ions.

One-dimensional (1D) needle-like ZnO nanowhiskers have been grown directly from aqueous solution containing Zn(OH)(4)(2-) ions produced by zinc chloride and sodium hydroxide, in the presence of sodium dodecyl sulfate (SDS).