Microplastics (plastics < 5 mm, including nanoplastics which are < 0.1 μm) originate from the fragmentation of large plastic litter or from direct environmental emission. Their potential impacts in terrestrial ecosystems remain largely unexplored despite numerous reported effects on marine organisms. Most plastics arriving in the oceans were produced, used, and often disposed on land. Hence, it is within terrestrial systems that microplastics might first interact with biota eliciting ecologically relevant impacts. This article introduces the pervasive microplastic contamination as a potential agent of global change in terrestrial systems, highlights the physical and chemical nature of the respective observed effects, and discusses the broad toxicity of nanoplastics derived from plastic breakdown. Making relevant links to the fate of microplastics in aquatic continental systems, we here present new insights into the mechanisms of impacts on terrestrial geochemistry, the biophysical environment, and ecotoxicology. Broad changes in continental environments are possible even in particle-rich habitats such as soils. Furthermore, there is a growing body of evidence indicating that microplastics interact with terrestrial organisms that mediate essential ecosystem services and functions, such as soil dwelling invertebrates, terrestrial fungi, and plant-pollinators.

Therefore, research is needed to clarify the terrestrial fate and effects of microplastics. We suggest that due to the widespread presence, environmental persistence, and various interactions with continental biota, microplastic pollution might represent an emerging global change threat to terrestrial ecosystems.

https://onlinelibrary.wiley.com/doi/pdf/10.1111/gcb.14020

Microplastics as an emerging threat to terrestrial ecosystems

Two-dimensional MXenes: From morphological to optical, electric, and magnetic properties and applications

Polymer carbon dots (PCDs) are proposed as a new class of room-temperature phosphorescence (RTP) materials. The abundant energy levels in PCDs increase the probability of intersystem crossing (ISC) and their covalently crosslinked framework structures greatly suppress the nonradiative transitions. The efficient methods allow the manufacture of PCDs with unique RTP properties in air without additional metal complexation or complicated matrix composition. They thus provide a route towards the rational design of metal-free RTP materials that may be synthesized easily. Furthermore, we find that RTP is associated with a crosslink-enhanced emission (CEE) effect, which provides further routes to design improved PCDs with diverse RTP performance. Our results show the potential of PCDs as a universal route to achieve effective metal-free RTP.

/pdf/design-of-metal-free-polymer-carbon-dots-a-new-class-of-room-49055zqhx6.pdf

Design of Metal‐Free Polymer Carbon Dots: A New Class of Room‐Temperature Phosphorescent Materials

2D Black Phosphorus Saturable Absorbers for Ultrafast Photonics

Can completely homogeneous nucleation occur? Large scale molecular dynamics simulations performed on a graphics-processing-unit rich supercomputer can shed light on this long-standing issue. Here, a billion-atom molecular dynamics simulation of homogeneous nucleation from an undercooled iron melt reveals that some satellite-like small grains surrounding previously formed large grains exist in the middle of the nucleation process, which are not distributed uniformly. At the same time, grains with a twin boundary are formed by heterogeneous nucleation from the surface of the previously formed grains. The local heterogeneity in the distribution of grains is caused by the local accumulation of the icosahedral structure in the undercooled melt near the previously formed grains. This insight is mainly attributable to the multi-graphics processing unit parallel computation combined with the rapid progress in high-performance computational environments.Nucleation is a fundamental physical process, however it is a long-standing issue whether completely homogeneous nucleation can occur. Here the authors reveal, via a billion-atom molecular dynamics simulation, that local heterogeneity exists during homogeneous nucleation in an undercooled iron melt.

/pdf/heterogeneity-in-homogeneous-nucleation-from-billion-atom-2thbquxnx8.pdf

Heterogeneity in homogeneous nucleation from billion-atom molecular dynamics simulation of solidification of pure metal

Grain growth kinetics in submicrometer-scale molecular dynamics simulation

Molecular dynamics simulations investigating consecutive nucleation, solidification and grain growth in a twelve-million-atom Fe-system

It is essential to control the microstructure of metals and alloys precisely during the production process since it affects physical and mechanical properties. Many practical metals and alloys undergo solidification and subsequent grain growth during their production.1) Therefore, it is important to understand a series of fundamental physics ranging from nucleation and solidification to grain growth comprehensively. Although a lot of efforts have been made over years to understand fundamental aspects of microstructure evolution,2) however, it is still challenging to control microstructures with a high degree of accuracy. One of the difficulties is to observe the evolution of threedimensional microstructure as it is during the production process. Although recent new methodologies such as synchrotron X-ray microtomography3) and serial sectioning technique4) achieve three-dimensional morphology of microstructure experimentally, most of observation and Grain Growth in Large-Scale Molecular Dynamics Simulation: Linkage between Atomic Configuration and von Neumann-Mullins Relation

Grain Growth in Large-Scale Molecular Dynamics Simulation: Linkage between Atomic Configuration and von Neumann-Mullins Relation

The scattering regolith during landing and take-off is one of the most important issues in planetary exploration because it affects not only spacecraft system such as optical component and thermal subsystem but also planetary protection. This issued is called Plume-Surface Interaction. However, there are very few numerical simulations to verify the microgravity experiments for planetary exploration. In this study, a coupled CFD and DEM analysis was conducted for a microgravity experiment using a drop tower. A coupled CFD-DEM analysis was performed to precisely simulate the behavior of sand scattered by air injected into a vacuum chamber. 

Shin Okita

Papers

Heterogeneity in homogeneous nucleation from billion-atom molecular dynamics simulation of solidification of pure metal

Grain growth kinetics in submicrometer-scale molecular dynamics simulation

Molecular dynamics simulations investigating consecutive nucleation, solidification and grain growth in a twelve-million-atom Fe-system

Grain Growth in Large-Scale Molecular Dynamics Simulation: Linkage between Atomic Configuration and von Neumann-Mullins Relation

Microgravity Experiment using Drop Tower and CFD-DEM Coupled Simulation about Plume-Surface Interaction