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  • Organic nitrogen aerosol plays a vital role in global nitrogen deposition.

    Organic nitrogen aerosol plays a vital role in global nitrogen deposition.

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    Newswise — This study, led by Dr Yumin Li of Southern University of Science and Technology (SUSTech), was a collaboration between Professor Tzung-May Fu’s team at SUSTech and Professor Jian Zhen Yu’s team at Hong Kong University of Science and Technology (HKUST). The research emphasized the previously underestimated significance of atmospheric ON aerosol depositions on ecosystems. Additionally, the ecological effects of ON aerosol depositions are anticipated to increase due to global warming and the decrease in nitrogen oxide emissions from human activities.

    Atmospheric deposition of organic nitrogen (ON) plays a crucial role in the global nitrogen cycle. Surface measurements showed that 2% to 70% of the local atmospheric deposition flux of total nitrogen was organic. However, previous models have largely neglected the spatial and chemical variations of atmospheric ON, leading to inadequate assessment of its global impacts.

    The scientists from SUSTech and HKUST developed a comprehensive global model of atmospheric gaseous and particulate ON, incorporating the latest knowledge on emissions and secondary formations. Their simulated surface concentrations of atmospheric particulate ON (ONp) were highly consistent with global observations, a feat that had not been achieved previously. Additionally, their simulated atmospheric deposition flux aligned with global observations within an order of magnitude. The scientists estimated that the global atmospheric ON deposition was 26 Tg N yr-1. This majority of this deposition (23 Tg N yr-1) occurred in the form of ON aerosol and accounted for 19% of the global atmospheric total N deposition (124 Tg N yr-1). The main sources of ON aerosols were wildfires, ocean emissions, and secondary formation.

    “Our simulation showed that the deposition of ON aerosol from the atmosphere is a crucial external source of nitrogen to nitrogen-limited ecosystems worldwide, such as the boreal forests, tundras, and the Arctic Ocean,” Fu says. In a future warming climate, wildfires will likely become more frequent and intense. Climate warming will also lead to surface ocean stratification, making atmospheric ON deposition an increasingly important source of nitrogen to these ecosystems. “We need to further examine the environmental impacts of atmospheric ON aerosol and how those impacts respond to climate change.”

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  • Trees outcompete shrubs in the race to the top

    Trees outcompete shrubs in the race to the top

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    Newswise — The findings from this study, led by Professor Eryuan Liang (Institute of Tibetan Plateau Research, Chinese Academy of Sciences), were published as a research article in the journal National Science Review. The study also involved researchers from, CREAF, CSIC, Global Ecology Unit CREAF-CSIC-UAB, Instituto Pirenaico de Ecología (IPE-CSIC), Spain and Université du Québec à Chicoutimi, Canada.

    Climatic warming is altering the structure and function of alpine ecosystems, including shifts of vegetation boundaries. The upward shift of alpine treelines, the uppermost limit of tree growth forming the boundary between montane forest and alpine communities, is strongly modulated by shrub-tree interactions. But little is known on the responses of such coexisting life forms to a warmer climate.

    Based on unique 8- and 10-year in situ observations of cambial phenology in sympatric trees and shrubs at two treelines on the southeastern Tibetan Plateau, researchers found an opposite pattern of cambial phenology between shrub and tree species in response to warming. Under a spring warming of +1°C, xylem resumption advances by 2-4 days in trees, but delays by 3-8 days in shrubs. The divergent phenological response to warming was due to shrubs being 3.2 times more sensitive than trees to chilling accumulation.

    “Under the same amount of chilling, shrubs required more forcing accumulation than trees, leading to a delayed onset of cambial phenology. For trees, however, forcing was less dependent on chilling, thus resulting in an earlier cambial phenology under warmer spring,” Liang says.

    The researchers further performed a global meta-analysis combined with a process-based growth model to explore drivers of phenological growth shifts in response to warming, from 344 shrubs and 575 trees paired across 11 alpine treelines in the Northern Hemisphere. Based on the cambial phenological records derived from the growth model, they further infer divergent effects of spring temperature on cambial phenology between trees and shrubs in the treelines of the northern hemisphere. Model outputs indicate trees show a higher sensitivity to spring warming than shrubs as expected. Shrubs are instead more influenced by chilling accumulation than trees. “Our meta-analysis confirmed the same mechanism across continental scales,” Liang says.

    Regardless of whether shrubs and trees at alpine treelines interact through facilitation or competition, climate warming has the potential to drive divergent shifts in their phenology. This would involve shortening the growing season for shrubs while extending it for trees. Consequently, the resulting phenological mismatch due to warming could confer a competitive advantage to trees over shrubs by increasing growth, carbon gain and improving resource availability, potentially promoting upward treeline shifts in cold mountainous regions (Figure 1).

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  • Garnet solid electrolytes can be recycled via thermal healing

    Garnet solid electrolytes can be recycled via thermal healing

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    Newswise — Metallic lithium is considered as the ultimate anode material of next-generation high-performance energy storage system, owing to its ultrahigh theoretical specific capacity (3860 mA h g-1), ultralow electrochemical potential (-3.04 V vs. the standard hydrogen electrode), and low density (0.534 g cm-3). Employing Li metal as high-capacity anode, solid-state lithium-metal batteries (SSLMBs) are becoming one of the most promising candidates for next-generation energy storage devices, due to their high safety and potential high energy density. SSLMBs are expected to be the future for conventional lithium-ion batteries. However, the development of SSLMBs is still limited, due to the severe safety issues caused by the uncontrolled Li dendrite formation and growth. Besides, the strategies focusing on healing or recycling solid electrolytes with Li dendrite penetration are rarely reported.

    Recently, a study is led by the group of Prof. Wei Liu (School of Physical Science and Technology, ShanghaiTech University). In this study, they demonstrate a facile method for healing and recycling garnet electrolytes (Ta doped Li7La3Zr2O12: LLZTO) with Li dendrites through heat treatment. Excitingly, the recycled garnet ceramic pellets have increased ionic conductivity with higher relative density, which is due to the dendrite-derived species (LiOH and Li2CO3) in the grain boundaries are able to promote further densification of garnet electrolyte pellets during thermal healing process as sintering aids (Figure). Compared with pristine garnet electrolyte pellets, the relative density of the recycled garnet pellets is improved from 90.9% to 95.3%, and ionic conductivity is improved from 0.39 to 0.62 mS cm-1. Benefited from the enhanced relative density and ionic conductivity, a higher critical current density (CCD) is achieved, suggesting a better suppression effect on Li dendrite penetration.

     

    See the article:

    Recycling of garnet solid electrolytes with lithium-dendrite penetration by thermal healing

    https://link.springer.com/article/10.1007/s40843-022-2371-9

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  • Superscattering of water waves – breaking the single channel scattering limit

    Superscattering of water waves – breaking the single channel scattering limit

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    Newswise — Recently, the National Science Review published the study of Huaping Wang’s group at Zhejiang University online. Inspired by electromagnetic metamaterials, the research team designed and fabricated a water wave superscattering device based on degeneracy resonance by using the similarity of water wave equation and electromagnetic wave equation under shallow water conditions, which was realized it experimentally.

    Water waves are a very intuitive fluctuating phenomenon that is widely observed in the natural world. Understanding and controlling the propagation of water waves is significant for both hydrodynamics and marine engineering. In recent years, metamaterials have developed rapidly and become a beneficial tool to manipulate electromagnetic waves, elastic waves, acoustic waves and water waves. Enhanced water wave scattering using metamaterials has a wide range of promising applications in marine energy harvesting and coastal protection.

    Inspired by the superscattering in electromagnetic and acoustic waves, it is possible to design water wave superscatterers based on transformation optics to achieve an increase in the scattering intensity of a given object. However, its experimental implementation remains a great challenge due to the extreme requirements on anisotropic parameters and in water wave conditions.

    Based on the degenerate resonant superscattering mechanism, the researchers theoretically designed and experimentally verified the superscatterer structure of water waves in an experimental water tank. The subwavelength superscatterer is composed of multiple concentric cylinders with different heights, and the geometry and operating frequency of the superscatterer are optimized by a simulated annealing algorithm. By designing resonances with different angular momentum channels, the total scattering cross section can break the limit of single-channel scattering by several times and also far exceed the scattering intensity of ordinary scatterers of the same size. For an ordinary scatterer, the resonances are spread out and the total scattering cross section is limited by the single channel.

    In the experiments, the research group measured the near-field patterns of the water-wave superscatterers, which were in agreement with the theoretical predictions and numerical simulations, and further measured the superscattering effects under different boundary conditions, water depths, and frequencies.

    This study provides a simple and low-cost method to enhance the scattering of water waves, which can be used to enhance the scattering of small sub-wavelength objects, and this is highly relevant for marine engineering, offshore coastal protection, etc., and may be used in marine energy harvesting devices and coastal protection facilities in the future.

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    See the article:

    Superscattering of water waves

    https://doi.org/10.1093/nsr/nwac255

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