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Potassium (K) metal batteries have attracted great attention owing to their low price, widespread distribution, and comparable energy density. However, the arbitrary dendrite growth and side reactions of K metal are attributed to high environmental sensitivity, which is the Achilles’ heel of its commercial development. Interface engineering between the current collector and K metal can tailor the surface properties for K-ion flux accommodation, dendrite growth inhibition, parasitic reaction suppression, etc. We have designed bifunctional layers via prepassivation, which can be recognized as an O/F-rich Sn–K alloy and a preformed solid-electrolyte interphase (SEI) layer. This Sn–K alloy with high substrate-related binding energy and Fermi level demonstrates strong potassiophilicity to homogeneously guide K metal deposition. Simultaneously, the preformed SEI layer can effectually eliminate side reactions initially, which is beneficial for the spatially and temporally KF-rich SEI layer on K metal. K metal deposition and protection can be implemented by the bifunctional layers, delivering great performance with a low nucleation overpotential of 0.066 V, a high average Coulombic efficiency of 99.1%, and durable stability of more than 900 h (1 mA cm–2, 1 mAh cm–2). Furthermore, the high-voltage platform, energy, and power densities of K metal batteries can be realized with a conventional Prussian blue analogue cathode. This work provides a paradigm to passivate fragile interfaces for alkali metal anodes.

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This study was conducted in the Taizi River catchment, located in northeastern China. Six representative streams in three regions (upper mountains, middle hills, lower plains) with different levels of anthropogenic disturbances were surveyed to describe the structure of fish assemblages and their relationship to environmental parameters. The results showed that the fish assemblages were significantly different among the three regions in the Taizi River catchment. Indicator species analysis found ten representative fish species in the Taizi River catchment and four species in the upper, four species in the middle, and two species in the lower regions. The ecological traits of the representative fish species were generally in agreement with the physiochemical features of the streams located within different regions. Multivariate analysis indicated that altitude, water temperature, and total nitrogen were the three most significant environmental parameters influencing the fish assemblage structure in the Taizi River catchment. Based on the different environmental features and fish assemblages found in each region, fish management and conservation strategies should be tailored to the specific characteristics of each region.

Biological functional traits help to understand specific stressors that are ignored intaxonomic data analysis. A combination of biological functional traits and taxonomic data ishelpful in determining specific stressors which are of significance for fish conservation and riverbasin management. In the current study, the Taizi River was used as a case study to understand therelationships between the taxonomic and functional structure of fish and land use and waterquality, in addition to determining the thresholds of these stressors. The results showed thattaxonomic structure was significantly affected by the proportion of urban land and specificconductivity levels, while functional metrics were influenced by the proportions of farmland andforest. Threshold indicator taxa analysis found that Phoxinus lagowskii, Barbatula barbatula nuda,Odontobutis obscura, and Cobitis granoei had negative threshold responses along the gradients ofurban developments and specific conductivity. There was a significant change in fish taxonomiccomposition when the proportion of urban land exceeded a threshold of 2.6–3.1%, or specificconductivity exceeded a threshold of 369.5–484.5 μS/cm. Three functional features—habitatpreference, tolerance to disturbances, and spawning traits—showed threshold responses to theproportion of farmland and forest. The abundance of sensitive species should be monitored as partof watershed management, as sensitive species exhibit an earlier and stronger response to stressorsthan other functional metrics. Sensitive species had a positive threshold response to the proportionof forest at 80.1%. These species exhibited a negative threshold response to the proportion offarmland at 13.3%. The results of the current study suggest that the taxonomic and functionalstructure of fish assemblages are affected by land use and water quality. These parameters shouldbe integrated into routine monitoring for fish conservation and river basin management in the TaiziRiver. In addition, corresponding measures for improving river habitat and water quality shouldbe implemented according to the thresholds of these parameters.

Fish species tolerance used as a component of fish-index of biological integrity (F-IBI) can be problematic as it is usually classified using the historical data, data from literature or expert judgments. In this study, fish assemblages, water quality parameters and physical habitat factors from 206 sampling sites in the Huntai River Basin were analyzed to develop tolerance indicator values (TIVs) of fish based on a (Fb-TIVs) and the weighted averaging (WA) method (FW-TIVs). The two quantitative methods for fish tolerance were then compared. The FW-TIVs and Fb-TIVs of fish species were calculated separately using a WA inference model based on ten water quality parameters (WT, pH, DO, SC, TDS, NH3, NO2−, NO3−, TP, Cl−, and SO42−), and six biological traits (lithophilic spawning, benthic invertivores, cold water species, equilibrium or periodic life history strategies, families of Cottidae, and species distribution range). Fish species were then classified into biological traits approach three categories (tolerant species, moderately tolerant species, and sensitive species). The results indicated that only 30.3% fish species have the same classification based on FW-TIVs and Fb-TIVs. However, the proportion of tolerant species based on two methods had a similar response to environmental stress, and these tolerant species were correlated with PCA axes 1 site scores obtained by (FW-TIVs, p < 0.05, R2 = 0.434; Fb-TIVs, p < 0.05, R2 = 0.334) and not correlated with PCA axis 2 site scores (FW-TIVs, p > 0.05, R2 = 0.001; Fb-TIVs, p > 0.05, R2 = 0.012) and PCA axis 3 site scores (FW-TIVs, p > 0.05, R2 = 0.000; Fb-TIVs, p > 0.05, R2 = 0.013). The results of linear regression analyses indicated that Fb-TIVs can be used for the study of fish tolerance. Fish tolerance assessments based on FW-TIVs requires long-term monitoring of fish assemblages and water quality parameters to provide sufficient data for quantitative studies. The Fb-TIV method relies on the accurate identification of fish traits by an ichthyologist. The two methods used in this study can provide methodological references for quantitative studies of fish tolerance in other regions, and are of great significance for the development of biological assessment tools.