Vertical Differentiation of Microplastics Influenced by Thermal Stratification in a Deep Reservoir

Abstract

Microplastics (MPs) are an emerging environmental concern. However, vertical transport of MPs remains unclear, particularly in deep reservoirs with thermal stratification (TS). In this study, the vertical variation in MP organization, stability, migration, and the driving factors of the profile in a deep reservoir were comprehensively explored. This is the first observation that TS interfaces in a deep reservoir act as a buffer area to retard MP subsidence, especially at the interface between the epilimnion and the metalimnion. Interestingly, there was a size-selection phenomenon for MP sinking. In particular, the high accumulation of largesized MPs (LMPs; >300 μm) indicated that LMPs were more susceptible to dramatic changes in water density at the TS interfaces. Furthermore, simultaneous analysis of water parameters and MP surface characteristics showed that the drivers of MP deposition were biological to abiotic transitions during different layers, which were influenced by algae and metals. Specifically, scanning electron microscopy coupled with energy-dispersive X-ray spectroscopy and microscopic Fourier transform infrared analyses implied that the occurrence of metals on the MP surface can promote MP deposition in the hypolimnion. Our findings demonstrated that TS significantly influenced the MP fate in deep reservoirs, and the hotspot of MP exposure risk for vulnerable benthic organisms on the reservoir floor deserves more attention.

Human Exposure to Ambient Atmospheric Microplastics in a Megacity: Spatiotemporal Variation and Associated Microorganism-Related Health Risk

“…The chemical composition and morphological parameters of AMPs were identified and measured using a Micro-Fourier transform infrared spectrometer (μ-FTIR, Nicolet iN10 MX, Thermo Fisher, USA) equipped with a Deuterated Triglycine Sulfate detector. , The Particles Wizards in OMNIC Picta software was adopted to allow the automaticpinpointing of the exact location of particles on the silicon slice by background intensity . To improve the efficiency, a 20% subset of the total area was chosen for detection.…”

Shapes of Hyperspectral Imaged Microplastics

“…For instance, spherical polystyrene (PS) beads exhibited higher toxicity than irregular fragments and fibers on Daphnia magna . Particle shape also matters for physical behavior like settling velocities. , It was found that a shape-dependent approach outperformed in predicting terminal settling velocities compared to simply assuming all particles were spheres, and the aerodynamics of microplastics depends highly on shape . Biochemically, shape can affect the biofouling of microplastics and hereby their environmental fate, , as well as the adsorbed and leached chemicals. , …”