Laser-based techniques: Novel tools for the identification and characterization of aged microplastics with developed biofilm

Capabilities of simultaneous 193 nm - LIBS/LA-ICP-MS imaging for microplastics characterization

Microplastics (MPs) are currently one of the major environmental challenges within our society. With the awareness of the impact of MPs on the environment increasing over the last years, the need for increased monitoring as well as comprehensive analysis to better understand the fate and impact of MPs has become more and more important. A major aspect of MP characterization is the assignment of the polymer type of individual particles. Here, per- and poly-fluoroalkyl substances (PFAS), originating from fluor-containing polymers, have gained a lot of attention due to the severe environmental impact. Additionally, quantitative analysis of the metal content is of great interest in the field, since MPs are prone to either leaching (in)organic additives into the environment or taking up and accumulating hazardous components (e.g., heavy metals). In this work we demonstrate the capabilities of a simultaneous LIBS/LA-ICP-MS setup for the analysis of MPs. In the first part, we demonstrate the potential of targeted LIBS analysis for the imaging of fluor-containing polymers. Using a laser spot size of 5 μm combined with highly sensitive ICCD detection enables analysis of particles in the low μm range. In the second part we combine the polymer-identification capabilities of LIBS with the high sensitivity of ICP-MS to perform matrix-matched quantification of the metal content of individual MPs. In this case we use a spot size of 50 μm facilitating polymer classification with a broadband spectrometer, resulting in detection limits of 0.72 μg/g for Pb and 9.5 μg/g for Sn simultaneously measured using ICP-MS.

Recognition and detection technology for microplastic, its source and health effects

Microplastic (MP) is ubiquitous in the environment which appeared as an immense intimidation to human and animal health. The plastic fragments significantly polluted the ocean, fresh water, food chain, and other food items. Inadequate maintenance, less knowledge of adverse influence along with inappropriate usage in addition throwing away of plastics items revolves present planet in to plastics planet. The present study aims to focus on the recognition and advance detection technologies for MPs and the adverse effects of micro- and nanoplastics on human health. MPs have rigorous adverse effect on human health that leads to condensed growth rates, lessened reproductive capability, ulcer, scrape, and oxidative nervous anxiety, in addition, also disturb circulatory and respiratory mechanism. The detection of MP particles has also placed emphasis on identification technologies such as scanning electron microscopy, Raman spectroscopy, optical detection, Fourier transform infrared spectroscopy, thermo-analytical techniques, flow cytometry, holography, and hyperspectral imaging. It suggests that further research should be explored to understand the source, distribution, and health impacts and evaluate numerous detection methodologies for the MPs along with purification techniques.

The bioadhesion and effects of microplastics and natural particles on growth, cell viability, physiology, and elemental content of an aquatic macrophyte Elodea canadensis

Microplastics in the aquatic environment can interact with aquatic plants, but the consequences of these interactions are poorly understood. Therefore, the aim of this study was to investigate the effects of microplastics commonly found in the environment, namely polyethylene (PE) fragments, polyacrylonitrile (PAN) fibres, tire wear (TW) particles under a relevant environmental concentration (5000 particles/L) on the growth, cell viability, physiology, and elemental content of the aquatic macrophyte Elodea canadensis. The effects of microplastics were compared to those of natural wood particles. The results showed that all types of microplastics adhered to plant tissues, but the effect on leaves (leaf damage area) was greatest at PE > PAN > TW, while the effect of natural particles was comparable to that of the control. None of the microplastics studied affected plant growth, lipid, carbohydrate, or protein content. Electron transport system activity was significantly higher in plants exposed to PAN fibres and PE fragments, but also when exposed to natural particles, while chlorophyll a content was negatively affected only by PE fragments and TW particles. Elemental analysis of plant tissue showed that in some cases PAN fibres and TW particles caused increased metal content. The results of this study indicated that aquatic macrophytes may respond differently to exposure to microplastics than to natural particles, likely through the combined effects of mechanical damage and chemical stress.

Ethanol, not water, should be used as the dispersant when measuring microplastic particle size distribution by laser diffraction

Size distribution is a crucial characteristic of microplastics (MPs). A typical method for measuring this property is wet laser diffraction. However, when measuring size distributions of MPs, despite it being a poor dispersant for many MPs, water is commonly selected, potentially limiting the reliability of reported measurements. To evaluate dispersant suitability, different aqueous concentrations of ethanol (0, 10, 20, 30, 40, 50, 75, 100 wt%) and aqueous solutions of 0.001 wt% Triton X-100 and a mixture comprising 10 wt% sodium pyrophosphate and 10 wt% methanol were used as dispersants in a laser granulometer (Mastersizer 2000) to determine particle size distributions (PSDs) of granular polyethylene MP35, MP125 and MP500 particles (nominally <35, <125 and, < 500 μm in size). The reliability of the PSDs depended on the dispersant used and size of primary MPs. With increasing ethanol concentrations, PSD curves of MP35 particles shifted from multi-modal to mono-modal distributions. The measured size distribution reduced from 1588.7 to 4.5 μm in water to 39.9 to 0.1 μm in 100 wt% ethanol. Generally, as ethanol concentration increased, uncertainty associated with the PSD parameters decreased. Although Triton X-100 and the mixed solution also showed better dispersion than water, measured particle sizes and coefficient of variation (COV, %) were notably larger than those for 100 wt% ethanol. Similar trends were observed for larger-sized MP125 and MP500 particles, but differences in PSD curves, PSD parameters, and COV (%) among dispersants were less pronounced. In all dispersants, the volume weighted mean diameters (VWMD) in 100 wt% ethanol (MP35: 14.1 μm, MP125: 102.5 μm, MP500: 300.0 μm) were smallest and close to diameters determined from microscope observations (MP35: 14.6 μm, MP125: 109.0 μm, MP500: 310.6 μm). Therefore, for accurate determinations of the PSDs of MP by wet laser diffraction, ethanol rather than water should be used as the dispersant.

Determining weathering-induced heterogeneous oxidation profiles of polyethylene, polypropylene and polystyrene using laser-induced breakdown spectroscopy

Weathering-induced polymer degradation is typically heterogeneous which plays an integral part in fragmentation. Despite that, the current selection of techniques to investigate such heterogeneities, especially beneath the sample surface, is sparse. We introduce Laser-induced Breakdown Spectroscopy (LIBS) as an analytical tool and evaluate its performance for depth profiling. Three types of polymers were selected (polyethylene, polypropylene, and polystyrene) that were aged under controlled conditions. We demonstrate that LIBS can detect heterogeneous oxidation on the surface and inside the samples. The results reveal that different oxidation behaviors are linked to the sample's lattice structure and the subsequent formation of microcracks. This implies that LIBS is beneficial to give additional insights into the weathering and degradation behavior of environmentally relevant plastics.

Selection of the optimal extraction protocol to investigate the interaction between trace elements and environmental plastic

The interaction between environmental plastic and trace elements is an issue of concern. Understanding their interaction mechanisms is key to evaluate the potential threats for the environment. To this regard, consolidating confidence in extraction protocols can help in understanding the amount of different species present on plastic surface, as well as the potential mobility of trace elements present inside the plastic matrix (e.g., additives). Here we tested the efficacy of different reagents to mimic the elemental phases bonded to meso- and microplastic in the environment, in relation to the grade of ageing and the polymer composition. Results showed that a relatively high portion of trace elements is bonded in a weak phase and that other phases abundant in other matrices (e.g., oxides and bonded to organic matter) are only present to a limited degree in the plastic samples. The comparison of different sample types highlighted the important role of plastic ageing in governing interactions with trace elements, while the polymer composition has a limited influence on this process. Finally, the future steps toward a tailored extraction scheme for environmental plastic are proposed.