Spatial distribution of microplastics in the tropical Indian Ocean based on laser direct infrared imaging and microwave-assisted matrix digestion

Nile red staining for rapid screening of plastic-suspect particles in edible seafood tissues

Concerns regarding microplastic (MP) contamination in aquatic ecosystems and its impact on seafood require a better understanding of human dietary MP exposure including extensive monitoring. While conventional techniques for MP analysis like infrared or Raman microspectroscopy provide detailed particle information, they are limited by low sample throughput, particularly when dealing with high particle numbers in seafood due to matrix-related residues. Consequently, more rapid techniques need to be developed to meet the requirements of large-scale monitoring. This study focused on semi-automated fluorescence imaging analysis after Nile red staining for rapid MP screening in seafood. By implementing RGB-based fluorescence threshold values, the need for high operator expertise to prevent misclassification was addressed. Food-relevant MP was identified with over 95% probability and differentiated from natural polymers with a 1% error rate. Comparison with laser direct infrared imaging (LDIR), a state-of-the-art method for rapid MP analysis, showed similar particle counts, indicating plausible results. However, highly variable recovery rates attributed to inhomogeneous particle spiking experiments highlight the need for future development of certified reference material including sample preparation. The proposed method demonstrated suitability of high throughput analysis for seafood samples, requiring 0.02-0.06 h/cm2 filter surface compared to 4.5-14.7 h/cm with LDIR analysis. Overall, the method holds promise as a screening tool for more accurate yet resource-intensive MP analysis methods such as spectroscopic or thermoanalytical techniques.

Characteristics, distribution patterns and sources of atmospheric microplastics in the Bohai and Yellow Seas, China

Although the prevalence of microplastics in the atmosphere has recently received considerable attention, there is little information available regarding the distribution of atmospheric microplastics over oceanic regions. In this study, during the summer and autumn months of 2022, we investigated atmospheric microplastics in four marine regions off the eastern coast of mainland China, namely, the southern, middle, and northern regions of the Yellow Sea, and the Bohai Sea. The abundance of atmospheric microplastics in these regions ranged from 1.65 to 16.80 items/100 m3 during summer and from 0.38 to 14.58 items/100 m3 during autumn, although we detected no significant differences in abundance among these regions. Polyamide, chlorinated polyethylene, and polyethylene terephthalate were identified as the main types of plastic polymer. On the basis of meteorological data and backward trajectory model analyses, we established that the atmospheric microplastics detected during summer were mainly derived from the adjacent marine atmosphere and that over the continental landmass in the vicinity of the sampling area, whereas microplastics detected during autumn appear to have originated mainly from the northeast of China. By influencing the settlement and migration of microplastics, meteorological factors, such as relative humidity and wind speed, were identified as potential factors determining the distribution and characteristics of the detected microplastics. Our findings in this study, revealing the origin and fate of marine atmospheric microplastics, make an important contribution to our current understanding of the distribution and transmission of microplastics within the surveyed region and potentially worldwide.

An analytical strategy for challenging members of the microplastic family: Particles from anti-corrosion coatings

Potentially hazardous particles from paints and functional coatings are an overlooked fraction of microplastic (MP) pollution since their accurate identification and quantification in environmental samples remains difficult. We have applied the most relevant techniques from the field of microplastic analysis for their suitability to chemically characterize anti-corrosion coatings containing a variety of polymer binders (LDIR, Raman and FTIR spectroscopy, Py-GC/MS) and inorganic additives (ICP-MS/MS). We present the basis of a possible toolbox to study the release and fate of coating particles in the (marine) environment. Our results indicate that, due to material properties, spectroscopic methods alone appear to be unsuitable for quantification of coating/paint particles and underestimate their environmental abundance. ICP-MS/MS and an optimized Py-GC/MS approach in combination with multivariate statistics enables a straightforward comparison of the multi-elemental and organic additive fingerprints of paint particles. The approach can improve the identification of unknown particles in environmental samples by an assignment to different typically used coating types. In future, this approach may facilitate allocation of emission sources of different environmental paint/coating particles. Indeed, future work will be required to tackle various remaining analytical challenges, such as optimized particle extraction/separation of environmental coating particles.

Analysing micro- and nanoplastics with cutting-edge infrared spectroscopy techniques: a critical review

The escalating prominence of micro- and nanoplastics (MNPs) as emerging anthropogenic pollutants has sparked widespread scientific and public interest. These minuscule particles pervade the global environment, permeating drinking water and food sources, prompting concerns regarding their environmental impacts and potential risks to human health. In recent years, the field of MNP research has witnessed the development and application of cutting-edge infrared (IR) spectroscopic instruments. This review focuses on the recent application of advanced IR spectroscopic techniques and relevant instrumentation to analyse MNPs. A comprehensive literature search was conducted, encompassing articles published within the past three years. The findings revealed that Fourier transform infrared (FTIR) spectroscopy stands as the most used technique, with focal plane array FTIR (FPA-FTIR) representing the cutting edge in FTIR spectroscopy. The second most popular technique is quantum cascade laser infrared (QCL-IR) spectroscopy, which has facilitated rapid analysis of plastic particles. Following closely is optical photothermal infrared (O-PTIR) spectroscopy, which can furnish submicron spatial resolution. Subsequently, there is atomic force microscopy-based infrared (AFM-IR) spectroscopy, which has made it feasible to analyse MNPs at the nanoscale level. The most advanced IR instruments identified in articles covered in this review were compared. Comparison metrics encompass substrates/filters, data quality, spatial resolution, data acquisition speed, data processing and cost. The limitations of these IR instruments were identified, and recommendations to address these limitations were proposed. The findings of this review offer valuable guidance to MNP researchers in selecting suitable instrumentation for their research experiments, thereby facilitating advancements in research aimed at enhancing our understanding of the environmental and human health risks associated with MNPs.

Microplastic in clams: An extensive spatial assessment in south Brazil

Microplastic pollution is becoming a continuously growing environmental concern, while bivalve mollusks are particularly vulnerable due to their sessile habits and feeding through water filtration processes. Microplastic incidence in soft tissues of the clam Amarilladesma mactroides was assessed along unconsolidated substrates distributed in extensive coastal regions of southern Brazil. Influence of urbanization levels, distance to rivers and local hydrodynamics on microplastic accumulation by the clam was tested. The average concentration of microplastics was high (3.09 ± 2.11 particles.g-1), considering 16 sampled sites. Particles were mainly composed by polyamide, polyethylene and polyethylene terephthalate, while were mainly smaller, fibrous and colorless. High urbanization and closer proximity to rivers insured higher contamination, which is a trend observed globally. No influence of coastal hydrodynamics was seen. Considering obtained findings, A. mactroides presents good potential to be used as a valuable tool to assess microplastic contamination in unconsolidated substrates of beach areas.

New Evidence of Microplastics in the Lower Respiratory Tract: Inhalation through Smoking

To investigate the relation of smoking and microplastic inhalation, we conducted a prospective study combining population-based and experimental work. Bronchoalveolar lavage fluid (BALF) samples from 17 smokers and 15 nonsmokers were collected in Zhuhai City, China. We simulated an active smoking model to explore the contribution of smoking to inhaled microplastics. The characteristics of microplastics in BALF samples and cigarette smoke were determined using laser direct infrared spectroscopy. We compared the differences between smokers and nonsmokers as well as between cigarette smoke and control groups. Microplastics were identified positive in all BALF samples. Smokers had higher concentrations of total microplastics (25.86 particles/g), polyurethane (11.34 particles/g), and silicone (1.15 particles/g) than nonsmokers. In the cigarette smoking simulation model, higher concentrations of total microplastics (9.99 particles/L), polyurethane (4.66 particles/L), and silicone (2.78 particles/L) were present in the cigarette smoke than those in the control group. We confirmed and extended the evidence on the presence of microplastics in the lower respiratory tract. These findings also provide new evidence on the relation between cigarette smoking and microplastic inhalation.

Oysters and mussels as equivalent sentinels of microplastics and natural particles in coastal environments

Filter-feeder organisms such as oyster and mussels are exposed to particles like microplastics (MPs). Although widely used to monitor MPs contamination, little is known about their performance as sentinels, which are biological monitors accumulating contaminants without significant adverse effects. This study comparatively evaluated the quantitative and qualitative accumulation of MPs by oysters (Crassostrea brasiliana) and mussels (Perna perna) along a gradient of contamination in a highly urbanized estuarine system of Brazil. In the most contaminated site, both species presented the worst status of nutrition and health, and also one of the highest MPs levels reported for molluscs to date (up to 44.1 particles·g^-1). Despite some inter-specific differences, oysters and mussels were suitable and showed an equivalent performance as sentinels, reflecting the gradient condition demonstrated for other contaminants in the region. The similarity in MPs accumulation was also observed for qualitative aspects (polymer composition, sizes, shapes and colors). Particles were mostly <1000 μm, fibrous, colorless and composed by cellulose and polymethyl methacrylate (PMMA). Thus, despite small variations, the usage of C. brasiliana and P. perna is recommended and provides reliable information for environmental levels of microplastics.

Quantification and characterization of microplastics in surface water samples from the Northeast Atlantic Ocean using laser direct infrared imaging

15 filtration samples were collected at eight locations onboard the RV Sonne (cruise SO279 in 2020) from 6 m water depth using a fractionated stainless-steel filtration unit. The size fraction > 300 μm was visually examined and potential microplastic particles were analyzed by ATR-FTIR spectroscopy. The treatment of size class 20 μm < d < 300 μm was based on enzymatic-oxidative microwave-assisted "one-pot" matrix digestion in conjunction with analysis of the microplastics by time-efficient LDIR imaging. Total number concentrations ranged from 47 to 2154 microplastic particles per m³ (average for all stations: 500 ± 700 microplastic particles m^-3 (1 SD; n = 8)). In total, 20 polymer types were identified. The most common polymer types were polyethylene terephthalate (20 %) and acrylates/polyurethane/varnish (15 %). 93 % of the detected microplastics were smaller than 100 μm in length. Analysis of sample replicates indicates high spatio-temporal variations in microplastic pollution within the investigated region.

Laser microdissection pressure catapulting (LMPC): a new technique to handle single microplastic particles for number-based validation strategies

This study examines laser microdissection pressure catapulting (LMPC) as an innovative method for microplastic research. Laser pressure catapulting as part of commercially available LMPC microscopes enables the precise handling of microplastic particles without any mechanical contact. In fact, individual particles with sizes between several micrometers and several hundred micrometers can be transported over centimeter-wide distances into a collection vial. Therefore, the technology enables the exact handling of defined numbers of small microplastics (or even individual ones) with the greatest precision. Herewith, it allows the production of particle number-based spike suspensions for method validation. Proof-of-principle LMPC experiments with polyethylene and polyethylene terephthalate model particles in the size range from 20 to 63 µm and polystyrene microspheres (10 µm diameter) demonstrated precise particle handling without fragmentation. Furthermore, the ablated particles showed no evidence of chemical alteration as seen in the particles' IR spectra acquired via laser direct infrared analysis. We propose LMPC as a promising new tool to produce future microplastic reference materials such as particle-number spiked suspensions, since LMPC circumvents the uncertainties resulting from the potentially heterogeneous behavior or inappropriate sampling from microplastic suspensions. Furthermore, LMPC could be advantageous for the generation of very accurate calibration series of spherical particles for microplastic analysis via pyrolysis-gas chromatography-mass spectrometry (down to 0.54 ng), as it omits the dissolution of bulk polymers.

Impact of coastal wastewater treatment plants on microplastic pollution in surface seawater and ecological risk assessment

This study aims to understand the influence of wastewater treatment plant discharge on the microplastic status in the surface seawater of Istanbul. For this purpose, for the first time, the distribution, composition, and ecological risk of microplastics at nine sampling stations on the southern coast of Istanbul, Marmara, were investigated at monthly intervals over a one-year period. The results showed that the microplastic abundance ranged from 0 to over 1000 particles per liter. Fibers were the dominant form at all stations. Microplastics 249-100 μm were the dominant size, and transparency was the color most found at all stations. Polyethylene and ethylene-vinyl acetate were the major types of microplastics, accounting for 50% overall. The pollution load index revealed that over 70% of sampling stations were at hazard level I. However, the hazardous index was categorized as level III with a value of 662.3 due to the presence of the most hazardous polymer named polyurethane. Further investigations into the risk assessment of MP can reveal crucial knowledge for understanding the microplastic cycle.

A high-throughput, automated technique for microplastics detection, quantification, and characterization in surface waters using laser direct infrared spectroscopy

A high-throughput approach to detecting, quantifying, and characterizing microplastics (MPs) by shape, size, and polymer type using laser direct infrared (LDIR) spectroscopy in surface water samples is demonstrated. Three urban creeks were sampled for their MP content near Cincinnati, OH. A simple Fenton reaction was used to oxidize the surface water samples, and the water samples were filtered onto a gold-coated polyester membrane. Infrared (IR) analysis for polymer identification was conducted, with recoveries of 88.3% ± 1.2%. This method was able to quantify MPs down to a diameter of 20 µm, a size comparable to that of MPs quantified by other techniques such as Fourier transform infrared spectroscopy (FTIR) and Raman spectroscopy. A shape-classifying algorithm was designed using the aspect ratio values of particles to categorize MPs as fibers, fibrous fragments, fragments, spherical fragments, or spheres. Cut-off values were identified from measurements of known sphere, fragment, and fibrous particles. About half of all environmental samples were classified as fragments while the other shapes accounted for the other half. A cut-off hit quality index (HQI) value of 0.7 was used to classify known and unidentified particles based on spectral matches to a reference library. Center for Marine Debris Research Polymer Kit 1.0 standards were analyzed by LDIR and compared to the given FTIR spectra by HQI, showing that LDIR obtains similar identifications as FTIR analysis. The simplicity and automation of the LDIR allows for quick, reproducible particle analysis, making LDIR attractive for high-throughput analysis of MPs.