Quantifying hydrological-ecological response relationships based on zooplankton index of biotic integrity and comprehensive habitat quality index - A case study of typical rivers in Xi'an, China.

With the accelerated development of urbanization, rivers in urban areas have become the most closely synergized water ecosystem between human activities and natural processes. To achieve the restoration goal of using hydrological regime change-ecological response relationship to advance the sustainable development of regulated river ecosystems, this study collected ecohydrological data at four tributaries of the Wei River system (Ba, Chan, Feng, and Hei Rivers) at a total of 24 stations in October 2020 and June 2021. Taking ecological flow as hydrological parameter and zooplankton as indicator organism, combined with habitat data scored on-site, the indicator system of zooplankton index of biological integrity and comprehensive habitat quality index was established to explore the hydrological-ecological response relationship in a multi-dimensional way. The results showed that during the ebb stage, the ecological health of the Feng River was better overall, with an average ecological flow value of 267.09 ± 348.62. The ecological health of the Hei River was the worst, with an average ecological flow value of 37.80 ± 38.80. During the abundant water period, the ecological health of the Chan River was optimal with an average ecological flow value of 189.25 ± 190.10, while the ecological health of the Hei River remained unimproved, but the average ecological flow value increased by 283.12 ± 197.76. There was a clear negative correlation relationship between the comprehensive habitat quality index and ecological flow. The correlation between zooplankton index of biological integrity and ecological flows is extremely strong and threshold values exist, but there is strong heterogeneity in the interaction of disturbance factors across water systems, which may not provide a predictable response to flow changes. This study aims to provide a case reference for flow management in watersheds that also lack long-time series hydrological data and to contribute new thinking to the wide application of the hydrological-ecological response relationship.

Electrode Potential Regulation of Carbon Fiber Based on Galvanic Coupling and Its Application in Electrochemical Grafting.

The reaction behavior of carbon fiber in electrochemical grafting is related to its electrode potential. In this paper, carbon fiber and metals with different electrode potentials were used to form combined electrodes to regulate the electrode potential of carbon fiber. The results showed that galvanic coupling was formed in the combined anode when the potential difference between carbon fiber and the metal (Δϕ = ϕCF0 - ϕmetal) was higher than 0.05 V. The electrode potential of carbon fiber was reduced due to cathodic polarization. The electrode potential of carbon fiber after galvanic coupling was proportional to the self-corrosion potential of metals. By applying the electrode potential regulation of carbon fiber in the electrochemical grafting of poly(glycidyl methacrylate) onto the carbon fiber surface, the grafting effect was significantly improved with the decrease of the electrode potential of carbon fibers. The grafting amount of carbon fibers increased from 0.83 to 69.86% as the electrode potential of carbon fibers dropped from 0.55 to -0.72 V. Consequently, the interfacial shear strength of the carbon fiber composite was remarkably promoted from 47.59 to 81.41 MPa, increasing by 71.07%.

A novel comprehensive model of set pair analysis with extenics for river health evaluation and prediction of semi-arid basin - A case study of Wei River Basin, China.

The accelerated development of urbanization in semi-arid areas is easy to cause varying degrees of disturbance to its fragile aquatic ecosystem. To find a general method for assessing the health status in semi-arid basins in China, and to provide theoretical basis for river health management and sustainable development, this study is that health evaluation index system is established in the Wei River Basin, covering a huge semi-arid area, and analyzed the biological structure of plankton obtained by field sampling and identified in laboratory, chemical conditions including dissolved oxygen, water temperature, ammonia nitrogen, pH, chlorophyll and other water physical and chemical factors determined by field instruments and sediment heavy metals analyzed in laboratory, physical habitat scored on site and social factors including water resource utilization rate and water consumption per 10,000 yuan of GDP collected in local water resource bulletin. Based on the idea of game theory, an improved coupling model of set pair analysis with extenics is established to assess and predict health. The results show that Wei River System and Jing River System are healthy, Beiluo River System is sub-healthy, and the whole Wei River Basin is also healthy; most of the cross-sections have a tendency to change to a bad level. Compared with simple weighting, set pair analysis and variable fuzzy set methods based on the corresponding sampling data and the weight in this paper, the coupling model can explain the transition and its trend between levels, reflect the certainty and uncertainty, and get more accurate results. It is suggested that daily monitoring and management should be strengthened in most sections to improve their health. And improve the development level of ecological function and social service function, give priority to the development of downstream water resources economy.

Electrochemical grafting of poly(glycidyl methacrylate) on a carbon-fibre surface.

In this work, glycidyl methacrylate (GMA) was polymerised and grafted onto the surface of carbon fiber (CF) by using electrochemical grafting to improve the interfacial properties between the fibre and epoxy resin. The optimised conditions for electrochemical grafting and the reaction mechanism were also investigated. Results showed that GMA was covalently grafted to the CF surface by the assistance of aluminium chloride, which is a good electrolyte for electrochemical grafting. The GMA grafting ratio on the CF surface increased with electrolyte concentration and reaction time, and an optimal current intensity for the electropolymerisation was determined. On the basis of the strong correlation between the grafting ratio and the carboxyl content in the CF, a two-step mechanism of electrochemical grafting on the CF surface was proposed: first, the surface of CF was anodised to produce oxygen-containing functional groups, mainly including COOH, OH and C[double bond, length as m-dash]O. Next, when CF was used as the anode in the electrical grafting reaction, the COOH on the surface of CF would lose electrons and then remove carbon dioxide to generate carbon radicals on the surface of CF. The carbon radical would attack the carbon-carbon double bond in GMA to initiate the radical polymerisation of GMA monomers and graft polymers would be formed on the CF surface. Compared with untreated CF, the interfacial shear strength (IFSS) test proved the improvement of the interface adhesion of the modified carbon fibre (mCF) composites. This work provided a controllable electrochemical approach that could simply and quickly graft poly(glycidyl methacrylate) (PGMA) on the surface of CF.