In-situ and real-time nano/microplastic coatings and dynamics in water using nano-DIHM: A novel capability for the plastic life cycle research

Disentangling the retention preferences of estuarine suspended particulate matter for diverse microplastic types

As a major source of microplastics (MPs) for global oceans, estuarine MPs pose challenges for numerical modeling due to their particle diversity, while hydrodynamics and suspended particulate matter (SPM) further exacerbate transport prediction uncertainties. This study employs a categorization framework to pinpoint 16 representative MPs types, precisely simulating their transport processes in the Yangtze River estuary (YRE). Furthermore, spatial links between SPM concentrations and MP types at 1800+ simulated sites were examined using ArcGIS and bivariate Local Indicators of Spatial Association (BI-LISA). Results indicate that low-density (≤0.95 g/cm³), small-diameter (<500 μm) fiber MPs are more prone to hetero-aggregation with estuarine SPM flocs, while MPs with opposite characteristics may move depending on their intrinsic properties. High-high BI-LISA clusters were observed both in river branches and at the confluence with the sea, the latter closely associated with the turbidity maximum zone that promote MP hetero-aggregation. The interaction of these currents and Yangtze (Changjiang) diluted water forms MPs clusters between 122.0°E and 122.5°E at the confluence of the South Branch, averaging over 870 μg/m3. Examining the trapping preferences of estuarine SPMs for various MPs through this classification framework can help to determine the bioavailability of environmental MPs to aquatic organisms and map the MPs baseline values for health risk quantification.

Microplastics in ecosystems: Critical review of occurrence, distribution, toxicity, fate, transport, and advances in experimental and computational studies in surface and subsurface water

Microplastics (MPs), particles under 5 mm, pervade water, soil, sediment, and air due to increased plastic production and improper disposal, posing global environmental and health risks. Examining their distribution, quantities, fate, and transport is crucial for effective management. Several studies have explored MPs' sources, distribution, transport, and biological impacts, primarily focusing on the marine environment. However, there is a need for a comprehensive review of all environmental systems together for enhanced pollution control. This review critically examines the occurrence, distribution, fate, and transport of MPs in the following environments: freshwater, marine, and terrestrial ecosystems. The concentration of MPs is highly variable in the environment, ranging from negligible to significant amounts (0.003-519.223 items/liter in water and 0-18,000 items/kg dry weight sediment, respectively). Predominantly, these MPs manifest as fibers and fragments, with primary polymer types including polypropylene, polystyrene, polyethylene, and polyethylene terephthalate. A complex interplay of natural and anthropogenic actions, including wastewater treatment plant discharges, precipitation, stormwater runoff, inadequate plastic waste management, and biosolid applications, influences MPs' presence and distribution. Our critical synthesis of existing literature underscores the significance of factors such as wind, water flow rates, settling velocities, wave characteristics, plastic morphology, density, and size in determining MPs' transport dynamics in surface and subsurface waters. Furthermore, this review identifies research gaps, both in experimental and simulation, and outlines pivotal avenues for future exploration in the realm of MPs.

Review of microplastics and chemical risk posed by plastic packaging on the marine environment to inform the Global Plastics Treaty

Plastic overproduction and the resulting increase in consumption has made plastic pollution ubiquitous in all ecosystems. Recognizing this, the United Nations (UN) has started negotiations to establish a global treaty to end plastic pollution, especially in the marine environment. The basis of the treaty has been formulated in terms of turning off the tap, signaling the will to prevent plastic pollution at its source. Based on the distribution of plastic production by sector, the plastic packaging sector consumes the most plastic. The volume and variety of chemicals used in plastic packaging, most of which is single-use, is a major concern. Single-use plastics including packaging is one of the most dominant sources of plastic pollution. Plastic waste causes pollution in water, air and soil by releasing harmful chemicals into the environment and can also lead to exposure through contamination of food with micro- and nano-plastic particles and chemicals through packaging. Marine life and humans alike face risks from plastic uptake through bioaccumulation and biomagnification. While the contribution of plastics ingested to chemical pollution is relatively minor in comparison to other pathways of exposure, the effect of plastic waste on marine life and human consumption of seafood is beyond question. To reduce the long-term impact of plastic, it is crucial to establish a global legally binding instrument to ensure the implementation of upstream rather than downstream solutions. This will help to mitigate the impact of both chemicals and microplastics, including from packaging, on the environment.

Enhancing aggregation of microalgae on polystyrene microplastics by high light: Processes, drivers, and environmental risk assessment

Microplastics (MPs) are emerging pollutants, causing potential threats to aquatic ecosystems and serious concern in aggregating with microalgae (critical primary producers). When entering water bodies, MPs are expected to sink below the water surface and disperse into varying water compartments with different light intensities. However, how light influences the aggregation processes of algal cells onto MPs and the associated molecular coupling mechanisms and derivative risks remain poorly understood. Herein, we investigated the aggregation behavior between polystyrene microplastics (mPS, 10 µm) and Chlorella pyrenoidosa under low (LL, 15 μmol·m-2·s-1), normal (NL, 55 μmol·m-2·s-1), and high light (HL, 150 μmol·m-2·s-1) conditions from integrated in vivo and in silico assays. The results indicated that under LL, the mPS particles primarily existed independently, whereas under NL and HL, C. pyrenoidosa tightly bounded to mPS by secreting more protein-rich extracellular polymeric substances. Infrared spectroscopy analysis and density functional theory calculation revealed that the aggregation formation was driven by non-covalent interaction involving van der Waals force and hydrogen bond. These processes subsequently enhanced the deposition and adherence capacity of mPS and relieved its phytotoxicity. Overall, our findings advance the practical and theoretical understanding of the ecological impacts of MPs in complex aquatic environments.

Navigating the difference of riverine microplastic movement footprint into the sea: Particle properties influence

As a critical source of marine microplastics (MPs), estuarine MPs community varied in movement due to particle diversity, while tide and runoff further complicated their transport. In this study, a particle mass gradient that represents MPs in the surface layer of the Yangtze River estuary was established. This was done by calculating the masses of 16 particle types using the particle size probability density function (PDF), with typical shapes and polymers as classifiers. Further, Aschenbrenner shape factor and polymer density were embedded into drag coefficients to categorically trace MP movement footprints. Results revealed that the MPs in North Branch moved northward and the MPs in South Branch moved southeastward in a spiral oscillation until they left the model boundary under Changjiang Diluted Water front and the northward coastal currents. Low-density fibrous MPs are more likely to move into the open ocean and oscillate more than films, with a single PE fiber trajectory that reached a maximum oscillatory width of 16.7 km. Over 95 % of the PVC fiber particles settled in nearshore waters west of 122.5°E. Elucidating the aggregation and retention of different MPs types can provide more accurate environmental baseline reference for more precise MP exposure levels and risk dose of ingestion for marine organisms.

Nanoplastics in Water: Artificial Intelligence-Assisted 4D Physicochemical Characterization and Rapid In Situ Detection

For the first time, we present a much-needed technology for the in situ and real-time detection of nanoplastics in aquatic systems. We show an artificial intelligence-assisted nanodigital in-line holographic microscopy (AI-assisted nano-DIHM) that automatically classifies nano- and microplastics simultaneously from nonplastic particles within milliseconds in stationary and dynamic natural waters, without sample preparation. AI-assisted nano-DIHM identifies 2 and 1% of waterborne particles as nano/microplastics in Lake Ontario and the Saint Lawrence River, respectively. Nano-DIHM provides physicochemical properties of single particles or clusters of nano/microplastics, including size, shape, optical phase, perimeter, surface area, roughness, and edge gradient. It distinguishes nano/microplastics from mixtures of organics, inorganics, biological particles, and coated heterogeneous clusters. This technology allows 4D tracking and 3D structural and spatial study of waterborne nano/microplastics. Independent transmission electron microscopy, mass spectrometry, and nanoparticle tracking analysis validates nano-DIHM data. Complementary modeling demonstrates nano- and microplastics have significantly distinct distribution patterns in water, which affect their transport and fate, rendering nano-DIHM a powerful tool for accurate nano/microplastic life-cycle analysis and hotspot remediation.

Direct observation and identification of nanoplastics in ocean water

Millions of tons of plastics enter the oceans yearly, and they can be fragmented by ultraviolet and mechanical means into nanoplastics. Here, we report the direct observation of nanoplastics in global ocean water leveraging a unique shrinking surface bubble deposition (SSBD) technique. SSBD involves optically heating plasmonic nanoparticles to form a surface bubble and leveraging the Marangoni flow to concentrate suspended nanoplastics onto the surface, allowing direct visualization using electron microscopy. With the plasmonic nanoparticles co-deposited in SSBD, the surface-enhanced Raman spectroscopy effect is enabled for direct chemical identification of trace amounts of nanoplastics. In the water samples from two oceans, we observed nanoplastics made of nylon, polystyrene, and polyethylene terephthalate-all common in daily consumables. The plastic particles have diverse morphologies, such as nanofibers, nanoflakes, and ball-stick nanostructures. These nanoplastics may profoundly affect marine organisms, and our results can provide critical information for appropriately designing their toxicity studies.

Shape- and polymer-considered simulation to unravel the estuarine microplastics fate

Environmental microplastics (MPs) constitute various sizes, polymers, and shape components. In estuaries, such differences are related to the reliability of assessing the seaward fate of MPs, aggregation hotspots, and ecological risks. This study sets the MP particle mass gradient using the shape factor and size probability density function to categorically estimate the MP load in the surface layer of the Yangtze River Estuary (YRE), which is the largest contributor of plastics to the sea. During the high plastic input period in July, the optimized estimated MP load through the surface layer of the YRE was 9766 kg/month, which was overestimated by 821 kg/month based on the empirical average particle mass. While tracking MP transport classified by shape and polymer type, the resuspension of MPs that accumulate in the intertidal zone cannot be neglected. The average relative error of the simulation was as low as 19.6% after including the abovementioned factors. Finally, the simulation results of the sensitive regions were extracted to assess the new MP risk index, which considers shape, abundance, and polymer type. By introducing these essential tools, this study helps to understand the fate of riverine MPs entering estuaries, where valuable opportunities for removing MPs exist before they spread to the oceans.