[Effect of seasonal distribution in precipitation on soil nitrogen mineralization in a subtropical forest]. / é™æ°´å­£èŠ‚æ€§åˆ†é å¯¹äºšçƒ­å¸¦æ£®æž—åœŸå£¤æ°®çŸ¿åŒ–çš„å½±å“.

Soil N mineralization is a key process of nutrient cycling in ecosystems. The mechanism of the seasonal distribution of precipitation on soil N mineralization remains unclear. We conducted a precipitation manipulation experiment in a subtropical forest in the middle and lower reaches of the Yangtze River in China from 2020 to 2022, with three treatments, including control (CK), decreased precipitation in the dry season with extremely increased precipitation in the wet season (T1), and decreased precipitation in the dry season with proportionally increased precipitation in the wet season (T2). With in situ resin core method, we explored the effect of seasonal distribution of precipitation on soil N mineralization. The results showed that T1 and T2 significantly decreased dry season net nitrification rate by 57.9% and 72.5% and the net N mineralization rate by 82.5% and 89.6%, respectively, and significantly increased wet season net nitrification rate by 64.3% and 79.5% and net N mineralization rate by 64.2% and 81.1%, respectively. Proportionally increased precipitation in the wet season was more conducive to soil N mine-ralization process than extremely increased precipitation in the wet season. Results of the structural equation model showed that change in seasonal distribution of precipitation could significantly affect soil N mineralization processes in the subtropical forest by changing soil water content, ammonium nitrogen, microbial biomass nitrogen, and soil C:N. Our results had important reference for understanding soil nitrogen cycling and other ecological processes, and were conducive to more accurate assessment on the impacts of future changes in seasonal precipitation pattern on subtropical forest ecosystems.

Highly Aligned Cellulose/Polypyrrole Composite Nanofibers via Electrospinning and In Situ Polymerization for Anisotropic Flexible Strain Sensor.

Flexible strain sensors have recently attracted great attention due to their promising applications in human motion detection, healthcare monitoring, human-machine interfaces, and so forth. However, traditional uniaxial strain sensors can only detect strain in a single direction. Herein, an anisotropic flexible strain sensor is fabricated based on conductive and highly aligned cellulose composite nanofibers, via facile electrospinning cellulose acetate, deacetylation, and in situ polymerization of pyrrole, to detect complex multidimensional strains. Benefiting from the unique well-ordered structure of conductive composite nanofibers, the obtained strain sensor shows extraordinary anisotropic sensing performance with a sensitivity of 0.73 and 0.01 for the tensile applied perpendicular and parallel to the nanofiber alignment, respectively. The sensor also exhibits outstanding durability (2000 cycles) due to the strong hydrogen bonding between cellulose nanofibers and polypyrrole. Moreover, the flexible strain sensors exhibit promising potentials for application in motion detection, as demonstrated by the detection of various joint movements in the human body.

Effects of green infrastructure on the dispersion of PM2.5 and human exposure on urban roads.

Urban green infrastructure (GI) has been widely demonstrated to effectively improve air quality in the built environment. However, due to the lack of comparative studies of the effects of different GI forms on PM2.5 dispersion, optimal GI designs suitable for different urban road types currently remain unclear. In this study, we adopted different roadside GI types in Hangzhou city as case studies and used the ENVI-met model to compare the effects of the different GI forms on PM2.5 dispersion and human exposure to PM2.5. The results indicated that 1) In open roads, the concave-shaped GI type could effectively reduce PM2.5 aggregation and human exposure on motorways, and the all-tree GI type performed the best in terms of sidewalk PM2.5 purification. 2) In street canyons, green roof and green screen were highly conducive to PM2.5 concentration reduction under commuter exposure compared with traditional green solutions. 3) There were trade-offs in the GI-PM2.5 interaction. GI types which can reduce pedestrian exposure tend to increase exposure in motorways. The same GI type deployed along the two different road types could yield completely opposite dispersion effects. Novel GI types had better environmental performance and relatively high economic cost. All decision-making should be based on the trade-offs between the advantages and disadvantages of GI. Our study also highlights the importance of comprehensive consideration of GI and road types and local wind conditions in future urban road planning and GI applications.

Janus Biopolymer Sponge with Porous Structure Based on Water Hyacinth Petiole for Efficient Solar Steam Generation.

Solar-driven steam generation for desalination is a facile, sustainable, and energy-saving approach to produce clean freshwater. However, the complicated fabrication process, high cost, potential environmental impact, and salt crystallization of conventional evaporators limit their large-scale application. Herein, we present a sustainable Janus evaporator based on a biopolymer sponge from the water hyacinth petiole (WHP) for high-performance solar steam generation. The freeze-dried WHP maintained its original porous structure and aligned channels well, and therefore holds the capability for rapid water transport due to strong capillary action. The WHP coated with carbon nanotubes/ethyl cellulose paste on its surface (WHP-C) gains a good photothermal property, thus achieving an efficient solar steam generation with a rate of 1.50 kg m-2 h-1 under 1 sun irradiation. Moreover, the WHP-C after hydrophobic modification by fluorocarbon (WHP-CH) is endowed with high water repellency and exhibits good salt resistance during long-term solar desalination. Additionally, we demonstrate that a stable wet surface that enables efficient water supply and vapor escape is also significant to the successive desalination of a solar evaporator. Our work provides new insights into the high-value utilization of biomass waste, i.e., water hyacinth, and the development of sustainable interfacial solar evaporators for the environmentally friendly production of freshwater.

Direct-Ink-Write Printing and Electrospinning of Cellulose Derivatives for Conductive Composite Materials.

The aim of this study is to realize the controlled construction and modulation of micro-/nanostructures of conductive composite materials (CCMs) in a facile way. Herein, interdigital electrodes are prepared by direct-ink-write printing co-blended inks made of ethyl cellulose and carbon nanotubes on cellulose paper. The cellulose nanofibers (CFs) are prepared by electrospinning cellulose acetate on to an aluminum foil, followed by deacetylation in NaOH/ethanol. All co-blended inks exhibit a typical non-Newtonian shear thinning behavior, enabling smooth extrusion and printing. The above electrodes and the conductive CF films with excellent thermal stability are assembled into a pressure sensor, which has a high sensitivity (0.0584 KPa-1) to detect the change in external loading pressure. The obtained porous CFs film is further endowed with conductivity by in situ polymerization of polypyrrole (PPy), which are uniformly distributed on the CFs surface as particles; a triboelectric nanogenerator is constructed by using the CF@PPy film as a tribo-positive friction layer to achieve efficient energy harvesting (output voltage = 29.78 V, output current = 2.12 µA). Therefore, the construction of CCMs with micro-/nanostructures based on cellulose derivatives have essential application prospects in emerging high-tech fields, such as green electronics for sensing and energy harvesting.

Three-dimensional building morphology impacts on PM2.5 distribution in urban landscape settings in Zhejiang, China.

Three-dimensional (3D) urban landscape patterns and building morphology are crucial for urban planning and essential for urban landscape functions. In this study, fixed and mobile monitoring sites were used to determine the spatial distribution of PM2.5 concentrations in Hangzhou. Six 3D metrics were selected to analyze the response of PM2.5 pollution to landscape patterns and building morphology, while their two-dimensional (2D) counterparts' metrics were also analyzed to contrast the differences. A variance partitioning analysis (VPA) was performed to measure the combined and relative contribution of 3D and 2D metrics to the changes in PM2.5 concentrations. The results showed that: (1) on the 3D scale, forming a building pattern with a combination of different building heights can eliminate the accumulation of PM2.5; (2) on the 2D scale, fragmentation and decentralization of landscapes and building patches alleviate PM2.5 pollution; and (3) 3D building morphology indicators have the highest explanatory power (40.94%) for the changes of PM2.5 concentrations. It turns out that the explanatory power of 3D metrics for PM2.5 concentrations changes is much greater than that of 2D metrics. In addition, when compared to building morphology indicators from a single dimension, the combination of 2D and 3D metrics is better able to reflect urban PM2.5 pollution. The results of this study expand our understanding of how PM2.5 pollution responds to 2D and 3D metrics and provide useful information for urban planning.