The dynamic sink: How settling-resuspension cycles drive offshore transport of high-density microplastics.

Modeling atmospheric microplastic cycle by GEOS-Chem: An optimized estimation by a global dataset suggests likely 50 times lower ocean emissions

Oil spills enhanced dispersion and transport of microplastics in sea water and sand at coastal beachheads

For advancing current knowledge on the transport of microplastics (MPs) in the environment, this study used a real-time pore-scale visualization and quantitative system to examine the motions and mobility of fibrous and fragmental MPs under various surfactant (AEO, CTAC, and AES) and electrolyte conditions. The videos showed that fibrous MPs formed tangles through entanglement, which moved in an axial direction aligned with the flow streamline. Both fibrous and fragmental MPs showed suspended movement as well as surface movement (e.g., sliding, rolling, and saltating) in the porous media. Some deposited fibrous MPs showed flexible deformation due to shear flow. Compared to fragmental MPs, fibrous MPs showed lower mobility due to the tendency to deposit and clog the porous media. The mobility of fragmental MPs was enhanced in the presence of AEO but remained relatively unchanged with AES. In the presence of CTAC, the mobility of fragmental MPs was slightly inhibited under low ionic strength (IS) conditions but remarkably enhanced under high IS conditions. However, the mobility of fibrous MPs was largely unaffected by the surfactants. Both the numerical model and FDLVO calculations effectively described the transport and deposition of MPs in porous media.

In this study, we conduct numerical simulations to investigate the transport and accumulation of microplastics (MPs) in the Gulf of Finland (eastern Baltic Sea). The transport of MPs is simulated using a Lagrangian particle tracking model, developed by the authors, which accounts for the physical transport and transformational processes specific to MPs, such as diffusion, beaching, resuspension, and biofouling.Positively and negatively buoyant particles were included to represent different types of MPs. High-resolution (250 m) 3D hydrodynamic and biogeochemical model data are used as input to the MPs model. Major rivers and wastewater treatment plants around the Gulf of Finland are the sources of MPs in the model.The main objectives of the study are 1) to perform a sensitivity analysis of four processes (beaching, mixing, resuspension, and biofouling) to investigate the importance of each process on the distribution of MPs in the Gulf of Finland; and 2) to execute a multi-year simulation using realistic MPs input to locate the main accumulation areas in sediments and beaches around the Gulf of Finland.Results of the initial sensitivity analysis indicate that the changes in the parametrization of beaching have a stronger effect on the horizontal distribution of MPs in off-shore sediments than the changes in the parametrization of resuspension. The maximum MPs concentration is observed near the sea surface; however, MPs have also spread into the water column.

Dispersion and transport of microplastics in three water-saturated coastal soils

Effects of co-present mineral colloids on the transport of microplastics in porous media: The key role of hydrochemical and hydrodynamic conditions.

Impact of bed morphology on microplastic transport at a confluence between a channel and a pipeline.

The transport of microplastics by ants cannot be neglected in the soil ecosystem

The factors influencing the vertical transport of microplastics in marine environment: A review

Effects of solution chemistry and humic acid on transport and deposition of aged microplastics in unsaturated porous media

<p>Microplastics (MPs) have been found ubiquitously in oceanic and terrestrial environments.  As the production and consumption of plastic polymers increases the amount of plastic evading accepted disposal pathways and entering natural systems is also expected to increase. To date the focus of plastic and MP research in particular has been on the ocean, there has recently been a rapid increase in interest in MP levels and distribution in terrestrial systems. However, the focus of existing studies has mostly been on the quantification and distribution of MP contamination in the sediment or on the water column of rivers and lakes. The aim of this project is to investigate the fundamental physical and biological influences on the transport of microplastics (MPs) in lake systems. In particular, we will focus on an understanding of the migration and distribution of MPs, and a systematic investigation on transport and sedimentation of MP in the lake water column. Lab and field experiments are planned to investigate the behavior of different MPs polymers, shapes and sizes under different conditions and determine how this influence the MP transport.</p><p>The settling velocity of MPs in stationary water was measured in the laboratory using particle image velocimetry (PIV) which was then compared to manual timing of the sinking velocity. The trajectories of the settling MPs have also been tracked during weak turbulences. In addition, the results were compared with theoretical calculations.</p><p>To investigate microbial colonization and biofilm formation on the surface of MPs, samples were exposed on a natural lake environment for varying time periods. The colonization of MP surfaces by microorganisms and their excretion of extracellular polymeric substances (EPS) were examined by laser microscopic techniques and subsequently the effect of the microbiological colonization of settling velocity was determined. In this work we show that the transport of MP is complex, as it is influenced by plastic type, shape, and biological colonization as well as the hydrodynamic conditions in the lake water column.</p>

Transport of polyethylene and polypropylene microplastics under the action of agricultural chemicals: Role of pesticide adjuvants and neonicotinoid active ingredients

High spatiotemporal resolution analysis on suspended sediment and microplastic transport of a lowland river

Pore-scale visualization and microscale barrier mechanisms of microplastics transport in bio-based hydrogel modified soils.

Benthic biofilms are known for their ability to stabilise and trap fine estuarine sediments and contaminants. Due to their presence on the sediment surface, benthic biofilms interact with emerging contaminants such as microplastics (MPs) that settle to the bed, potentially influencing MP transport dynamics from land to sea. This study explores the influence of benthic biofilm development on the capture and retention of MPs under flow and how other chemical stressors adsorbed to the MPs, such as heavy metals, may influence biofilm retention of MPs. We hypothesised that i) higher biofilm development would increase MP capture and retention under flow and ii) that heavy metals associated with MPs would negatively affect the biofilm community and its ability to retain MPs.Sieved sediment (500µm to remove large fauna) was added to small 250mL chambers and inoculated with 30mL of biofilm-rich surface sediment (control-absent, low and high biofilm biomass). Tidal simulation in an outdoor greenhouse promoted biofilm development in chambers over 21 days. High-density MPs (polyamide) MPs were added to the chambers at ‘high tide’ on day 14. These MPs were mechanically- and UV-aged then exposed to heavy metals (control (no metal), copper (Cu) and lead (Pb)) prior to their use. MPs were also fluorescently stained with a non-toxic dye to aid in MP erosion measurements. At the end of the incubation period, intact inner cores were gently removed, flushed and placed level with the bed of a small benchtop recirculating flume and exposed to incremental increases in flow velocity to erode the MPs. All experimental runs were filmed under UV light to fluoresce MPs and image analysis was used to determine the critical erosion threshold for MP motion from the video footage based on the loss of coverage across the core area. The remaining sediment from the chambers was extracted for biochemical analysis. Significantly higher critical shear stresses were required to remove MPs from the bed when biofilm was present, while Cu and Pb contamination had minimal effects on MP resuspension. This suggests that benthic biofilms have the potential to mediate MP resuspension dynamics and therefore MP transport from land-to-sea. Comparing our MP erosion thresholds (for PA particles only) against the bed shear stresses from a 2-D hydrodynamic model of the macrotidal Humber estuary, UK, it was found that MP erosion thresholds would be exceed in ~76% of the modelled cells during a 10-day simulation period covering a late-neap, spring, early-neap tidal cycle in the absence of biofilms. However, the presence of biofilm reduced the area of critical shear stress exceedance to ~36%. Without biofilms, MP erosion thresholds would be exceeded in 80% of the permanently inundated cells and 11.3% of the intertidal cells. Again, with biofilms present, MP erosion thresholds would be exceeded in 38% of the permanently inundated cells and just 3.8% of the intertidal cells. These findings can help improve our understanding of MP fluxes across the sediment-water interface in estuaries and provides evidence that the role of benthic biofilms should be included when parameterising MP transport models.