Quantification of poly(ethylene terephthalate) micro- and nanoparticle contaminants in marine sediments and other environmental matrices

A plasmonic gold nano-surface functionalized with the estrogen receptor for fast and highly sensitive detection of nanoplastics

Nanoplastics are a global emerging environmental problem whose effects might pose potential threats to the human's health. Despite the relevance of the issue, fast, reliable and quantitative in situ analytical approaches to determine nanoplastics are not yet available. The aim of this work was to devise an optical sensor with the goal of direct detecting and quantifying nanoplastics in seawater without sample pre-treatments. To this purpose, a nano-plasmonic biosensor was developed by exploiting an Estrogen Receptor (ER) recognition element grafted onto a polymer-based gold nanograting (GNG) plasmonic platform. The ER-GNG biosensor required just minute sample volumes (2 μL), allowed rapid detection (3 min) and enabled to determine nanoplastics in simulated seawater with a linear dynamic concentrations range of 1-100 ng/mL, thus encompassing the expected environmental loads. The nanostructured grating (GNG) provided remarkable performance enhancements, extending the measurement range across five orders of magnitude, thanks to the both the SPR and the localized SPR phenomena occurring at the GNG chip. At last, the ER-GNG biosensor was tested on real seawater samples collected in the Naples area and the results (∼30 ng/mL) were verified by a conventional approach (filtration and evaporation), confirming the ER-GNG sensor offers a straightforward and highly sensitive method for the direct in-field nanoplastics monitoring.

Marine sponges as bioindicators of pollution by synthetic microfibers in Antarctica

Different marine sponge species from Tethys Bay, Antarctica, were analyzed for contamination by polyester and polyamide microplastics (MPs). The PISA (Polymer Identification and Specific Analysis) procedure was adopted as it provides, through depolymerization and HPLC analysis, highly sensitive mass-based quantitative data. The study focused on three analytes resulting from the hydrolytic depolymerization of polyesters and polyamides: terephthalic acid (TPA), 6-aminohexanoic acid (AHA), and 1-6-hexanediamine (HMDA). TPA is a comonomer found in the polyesters poly(ethylene terephthalate) (PET) and poly(butylene adipate co terephthalate) (PBAT), and in polyamides such as poly(1,4-p-phenylene terephthalamide) (Kevlar™ and Twaron™ fibers) and poly(hexamethylene terephthalamide) (nylon 6 T). AHA is the monomer of nylon 6. HMDA is a comonomer of the aliphatic nylon 6,6 (HMDA-co-adipic acid) and of semi-aromatic polyamides such as, again, nylon 6 T (HMDA-co-TPA). Except for the biodegradable PBAT, these polymers exhibit high to extreme mechanical, thermal and chemical resistance. Indeed, they are used as technofibers in protective clothing able to withstand extreme conditions as those typical of Antarctica. Of the two amine monomers, only HMDA was found above the limit of quantification, and only in specimens of Haliclona (Rhizoniera) scotti, at a concentration equivalent to 27 μg/kg of nylon 6,6 in the fresh sponge. Comparatively higher concentrations, corresponding to 2.5-4.1 mg/kg of either PBAT or PPTA, were calculated from the concentration of TPA detected in all sponge species. Unexpectedly, TPA did not originate from PET (the most common textile fiber) as it was detected in the acid hydrolysate, whereas the PISA procedure results in effective PET depolymerization only under alkaline conditions. The obtained results showed that sponges, by capturing and concentrating MPs from large volumes of filtered marine waters, may be considered as effective indicators of the level and type of pollution by MPs and provide early warnings of increasing levels of pollution even in remote areas.

Remediation plan of nano/microplastic toxicity in food

Microplastic pollution is causing a stir globally due to its persistent and ubiquitous nature. The scientific collaboration is diligently working on improved, effective, sustainable, and cleaner measures to control the nano/microplastic load in the environment especially wrecking the aquatic habitat. This chapter discusses the challenges encountered in nano/microplastic control and improved technologies like density separation, continuous flow centrifugation, oil extraction protocol, electrostatic separation to extract and quantify the same. Although it is still in the early stages of research, biobased control measures, like meal worms and microbes to degrade microplastics in the environment have been proven effective. Besides the control measures, practical alternatives to microplastics can be developed like core-shell powder, mineral powder, and biobased food packaging systems like edible films and coatings developed using various nanotechnological tools. Lastly, the existing and ideal stage of global regulations is compared, and key research areas are pinpointed. This holistic coverage would enable manufacturers and consumers to reconsider their production and purchase decisions for sustainable development goals.

The fate of microplastics in estuary: A quantitative simulation approach

Microplastics pollution is an emerging environmental concern. However, there are almost no MPs numerical simulation studies in the Yangtze Estuary which is considered as the largest plastic export in the world and quantitative simulation is not carried out in the existing models. Therefore, completing quantitative simulation and exploring different patterns of MPs transport are the main objectives of this study. In addition, the concentration distribution and risk of MPs are also analyzed. Mass-Number method is proposed to quantitatively simulate microplastics concentration in Feb. and May with errors of less than 18%. Compared with sediment flocculation and settling transport, independent floating transport is more susceptible to surface currents resulting in increased beaching and more inhomogeneous concentration distribution. Meanwhile, under the influence of current, local topography and salt wedge, the MPs perform linear motion and clockwise spiral motion inside and outside the estuary and rapidly form a "hot spot" on the southeastern part of Chongming Island and 57% to 90% of MPs are beached or settled inside the estuary, especially on the north shore. Therefore, MPs risk in some sensitive targets should be concerned according to risk assessment results. Our results break the space-time limit and explore the fate of MPs in the Yangtze Estuary and provide new idea and concern of MPs numerical simulation.

Coral-inspired environmental durability aerogels for micron-size plastic particles removal in the aquatic environment

Removing microplastics (MPs) from water has been a huge challenge due to their inherent features including small size and high stability. In this research, inspired by the active adsorption and passive adhesion mechanisms of corals to MPs, a new strategy to fabricate polydopamine enhanced magnetic chitosan (PDA-MCS) aerogels was developed with a target to match the surface properties of MPs, achieving high MPs removal efficiency. PDA-MCS aerogels were highly efficient in adsorbing polyethylene terephthalate (PET) microplastics in water at pH values of 6-9, with a removal efficiency of up to 91.6%. Even after three recycles, PDA-MCS aerogels still displayed comparatively high removal efficiency (83.4%). Kinetic and isothermal experiments showed that the adsorption process was the result of electrostatic interactions and physical adhesion between aerogels and microplastics. Moreover, PDA-MCS aerogels maintained high removal efficiency under simulated environmental conditions, and the removal efficiency of PET, polyethylene (PE) and polystyrene (PS) microplastics in waters reached 97.3%, 94.6%, and 92.3%, respectively. Therefore, high-efficiency environmentally durable aerogels adsorbent materials have the potential for the removal of MPs from the aquatic environment.

Oil extraction following digestion to separate microplastics from mussels

Mussels are often used as biological indicators for monitoring marine microplastic pollution. The crucial procedure during monitoring is the separation of microplastics from mussel samples. We investigated the separation efficiencies of six combinations of two digestion solutions (10% KOH and 30% H₂O₂) and three extraction solutions (NaCl, oil in H₂O, and oil in NaCl) for mussels with low- and high-density microplastics. After KOH digestion, no polyethylene terephthalate (PET) could be extracted using the three extraction solutions, which might be due to the degradation of PET. After H₂O₂ digestion, the total extraction recovery rates of polypropylene, polyvinyl chloride, and PET for oil in H₂O and oil in NaCl solution ranged from 95.6% ± 5.09%-100%, which were higher than those of the saturated NaCl solution (51.1% ± 17.1%-67.8% ± 13.9%). The first extraction recovery rates of oil in NaCl solution for PP, PET, and PVC were higher than those of oil in H₂O. In this study, extraction by oil in NaCl solution after 30% H₂O₂ digestion was suggested to separate microplastics from mussels. This method is conducive to promoting the standardization of microplastic monitoring in mussels and might be suitable for large-scale monitoring of marine microplastic pollution.

Quantification of polyethylene terephthalate microplastics and nanoplastics in sands, indoor dust and sludge using a simplified in-matrix depolymerization method

An effective 3-step method for the quantification of mass of polyethylene terephthalate microplastics and nanoplastics (PET MNPs) in complex environmental matrices was developed based on a simplified in-matrix depolymerization. Liquid chromatography (LC) coupled with ultraviolet (UV) detection was used for detection and quantification. Recoveries for PET-spiked sand samples were 99 ± 2% (1 mg/L) and 93 ± 7% (30 mg/L). The limit of quantification (LOQ) for PET was 0.4 μg/g for sand, 1 mg/g for indoor dust and 0.2 μg/g for wet sludge. This method was applied to seven beach sand samples, 20 indoor dust samples and one sewage sludge sample. PET MNPs levels in sand samples were all below the limit of detection (LOD) of LC-UV (0.1 μg/g). The concentrations of PET MNPs in indoor dust samples ranged from 1.2 to 305 mg/g and the PET MNPs in liquid sludge was 1.5 mg/L.

Microplastics in the environment: Sampling, pretreatment, analysis and occurrence based on current and newly-exploited chromatographic approaches

The omnipresent character of microplastics (MPs) in environmental matrices, organisms and products has recently posed the need of their qualitative as well as quantitative analysis imperative, in order to provide data about their abundance and specification of polymer types in several substrates. In this framework, current and emerging approaches based on the chromatographic separation are of increased relevance in the field of MPs analysis and possess a large number of merits, since most of them are applicable in various complex matrices, sensitive and ideal for the detection of small-sized particles, whereas the common absence of any special pre-treatment step before analysis should also be highlighted. Αnalytical pyrolysis coupled with gas chromatography mass spectrometry (GC-MS) has recently gained ground as a powerful means to deliver information on MPs composition and degradation after their release into environment. Several instrumentations and trends in the area of analytical pyrolysis are thoroughly described within this review, while newly-exploited chromatographic methods in the field of MPs analysis, including Liquid Chromatography (LC) and Gel Permeation Chromatography (GPC) in this line are also investigated. The present review fills the gap of standardization concerning sampling, pre-treatment and chromatographic approaches and gathers all the available methodologies applied inside this area in accordance with the studied substrate, with the most examined environmental matrices being the solid one. After investigating the various works, some development options arise and it appears that chromatographic approaches should focus on improved extraction processes in terms of MPs isolation, since it is a crucial part in plastic items monitoring and is commonly depended on the polymer type and matrix. Special attention is given on the potential of chromatographic techniques for microplastics identification as well as quantification by confirming the current research status and knowledge gaps and highlighting some of the recent trends in this field.

Searching Nanoplastics: From Sampling to Sample Processing

Nanoplastics (NPs) are considered emerging pollutants, namely unregulated contaminants whose toxic effect on humans and the environment has been demonstrated or suspected. They are the result of the physical fragmentation of the plastics that over time reach smaller dimensions (<100 nm). The issues related to the characterization and quantification of NPs in the environmental matrices are mainly related to the infinitepsimal size, to the fact that they are found in bulk, and to the different physico-chemical forms in which the same polymer can evolve over time by degradation. To deal with the study of a new class of pollutants it is necessary to assess the entire analytical method, carefully considering every single step (sampling, cleanup, qualitative, and quantitative analysis) starting from the validation method in the laboratory. This paper reviews the analytical method steps, focusing on the first ones, which the current literature often underestimates: laboratory tests, sampling, and sample processing; in fact, most errors and the quality of the analyses often depend on them. In addition, all newly introduced sample processing methods were examined.

Extraction of microplastics from sediment matrices: Experimental comparative analysis

Microplastics are small (<5 mm) fragments of plastic debris that are ubiquitous in oceans and terrestrial ecosystems. Studies on microplastics in sediment and soil matrices are particularly challenging because of the need to separate the plastics from the sediments. We investigated the efficiencies of 18 combinations of six extracting solutions (ESs) (oil, water, oil-in-water, NaCl, oil-in-NaCl, and NaI) and three isolation methods (IMs) (hand stirring, centrifugation, and aeration) for fine and coarse sediments, with low and high density polymers. IMs did not affect the extraction efficiency. Except in case of oil, all ESs enabled good extraction (84 ± 17%) of light polymers (PE and PE-ABS). NaI presented the best extraction efficiency (71 ± 17%) for the densest polymers (PET, PES, and PA). For these ESs, fibers were extracted at a lower efficiency than pellets and fragments, and sediment gran size did not affect the extraction. For other ESs, mean extraction rates ranged from 5% to 48%. Overall, the extraction efficiencies were lower than those found in the literature, despite repeating the separation process three times. The collection of floating materials remained a problem, as plastics tended to adhere to the glass wall. Our work will help the comparability between previous and future monitoring results and the selection of the most suitable protocols for future studies. This work clearly demonstrates also that there is no robust protocol for extracting all types and forms of microplastics from fine sediments and that research efforts to arrive at a reliable method remain by taking account the interaction of MPs with other particles as well as the electrostatic properties of MP.

Chemical Analysis of Microplastics and Nanoplastics: Challenges, Advanced Methods, and Perspectives

Microplastics and nanoplastics have become emerging particulate anthropogenic pollutants and rapidly turned into a field of growing scientific and public interest. These tiny plastic particles are found in the environment all around the globe as well as in drinking water and food, raising concerns about their impacts on the environment and human health. To adequately address these issues, reliable information on the ambient concentrations of microplastics and nanoplastics is needed. However, micro- and nanoplastic particles are extremely complex and diverse in terms of their size, shape, density, polymer type, surface properties, etc. While the particle concentrations in different media can vary by up to 10 orders of magnitude, analysis of such complex samples may resemble searching for a needle in a haystack. This highlights the critical importance of appropriate methods for the chemical identification, quantification, and characterization of microplastics and nanoplastics. The present article reviews advanced methods for the representative mass-based and particle-based analysis of microplastics, with a focus on the sensitivity and lower-size limit for detection. The advantages and limitations of the methods, and their complementarity for the comprehensive characterization of microplastics are discussed. A special attention is paid to the approaches for reliable analysis of nanoplastics. Finally, an outlook for establishing harmonized and standardized methods to analyze these challenging contaminants is presented, and perspectives within and beyond this research field are discussed.

The extraction of microplastics from sediments: An overview of existing methods and the proposal of a new and green alternative

Microplastics (MPs) contamination is an existing and concerning environmental issue. Plastic particles have been observed worldwide in every natural matrix, with water environments being the final sink of dispersed MPs. Microplastic distribution in water ecosystems varies as a function of multiple factors, including polymer properties (e.g., density and wettability) and environmental conditions (e.g., water currents and temperature). Because of the tendency of MPs to settle, sediment is known to be one of the most impacted environmental matrices. Despite the increasing awareness of their diffusion in sediments, a proper quantification of dispersed particles is still difficult, due to the lack of standard protocols, which avoid a proper comparison of different sites. This hampers the current knowledge on environmental implications and toxicological effects of MPs in sediments. In this work, we examined 49 studies carried out from 2004 to 2020 to describe the different extraction methods applied, and to highlight pros and cons, with the aim of evaluating the more promising protocols. Therefore, we evaluated each proposed method by considering precision, reproducibility, economic viability and greenness (in term of used reagents). Finally, we proposed a valid alternative procedure in term of reliability and costs, which can attract increasing interest for future studies.

New methodologies for the detection, identification, and quantification of microplastics and their environmental degradation by-products

Sampling, separation, detection, and characterization of microplastics (MPs) dispersed in natural water bodies and ecosystems is a challenging and critical issue for a better understanding of the hazards for the environment posed by such nearly ubiquitous and still largely unknown form of pollution. There is still the need for exhaustive, reliable, accurate, reasonably fast, and cost-efficient analytical protocols allowing the quantification not only of MPs but also of nanoplastics (NPs) and of the harmful molecular pollutants that may result from degrading plastics. Here a set of newly developed analytical protocols, integrated with specialized techniques such as pyrolysis-gas chromatography-mass spectrometry (Py-GC/MS), for the accurate and selective determination of the polymers most commonly found as MPs polluting marine and freshwater sediments are presented. In addition, the results of an investigation on the low molecular weight volatile organic compounds (VOCs) released upon photo-oxidative degradation of microplastics highlight the important role of photoinduced fragmentation at a molecular level both as a potential source of hazardous chemicals and as accelerators of the overall degradation of floating or stranded plastic debris.

Microplastics in soil: A review on methods, occurrence, sources, and potential risk

Microplastic is an emerging contaminant of concern in soil globally due to its widespread and potential risks on the ecological system. Some basic issues such as the occurrence, source, and potential risks of microplastics in the soil are still open questions. These problems arise due to the lack of systematic and comprehensive analysis of microplastic in soils. Therefore, we comprehensively reviewed the current status of knowledge on microplastics in soil on detection, occurrence, characterization, source, and potential risk. Our review suggests that microplastics are ubiquitous in soil matrices globally. However, the research progress of microplastics in the soil is restricted by inherent technological inconsistencies and difficulties in analyzing particles in complex matrices, and studies on the occurrence and distribution of microplastics in soil environments remain very scarce, especially in Africa, South America, and Oceania. The consistency of the characteristics and composition of the microplastics in the aquatic environment and soil demonstrate they may share sources and exchange microplastics. Wide and varied sources of microplastic are constantly filling the soil, which causes the accumulation of microplastics in the soil. Studies on the effects and potential risks of microplastics in soil ecosystems are also reviewed. Limited research has shown that the combination and interaction of microplastics with contaminants they absorbed may affect soil health and function, and even migration along the food chain. The occurrence and impact of microplastic on the soil depend on the morphology, chemical components, and natural factors. We conclude that large research gaps exist in the quantification and estimation of regional emissions of microplastics in soil, factors affecting the concentration of microplastics, and microplastic disguising as soil carbon storage, which need more effort.

A Systematic Study on the Degradation Products Generated from Artificially Aged Microplastics

Most of the analytical studies focused on microplastics (MPs) are based on the detection and identification of the polymers constituting the particles. On the other hand, plastic debris in the environment undergoes chemical and physical degradation processes leading not only to mechanical but also to molecular fragmentation quickly resulting in the formation of leachable, soluble and/or volatile degradation products that are released in the environment. We performed the analysis of reference MPs–polymer micropowders obtained by grinding a set of five polymer types down to final size in the 857–509 μm range, namely high- and low-density polyethylene, polystyrene (PS), polypropylene (PP), and polyethylene terephthalate (PET). The reference MPs were artificially aged in a solar-box to investigate their degradation processes by characterizing the aged (photo-oxidized) MPs and their low molecular weight and/or highly oxidized fraction. For this purpose, the artificially aged MPs were subjected to extraction in polar organic solvents, targeting selective recovery of the low molecular weight fractions generated during the artificial aging. Analysis of the extractable fractions and of the residues was carried out by a multi-technique approach combining evolved gas analysis–mass spectrometry (EGA–MS), pyrolysis–gas chromatography–mass spectrometry (Py–GC–MS), and size exclusion chromatography (SEC). The results provided information on the degradation products formed during accelerated aging. Up to 18 wt% of extractable, low molecular weight fraction was recovered from the photo-aged MPs, depending on the polymer type. The photo-degradation products of polyolefins (PE and PP) included a wide range of long chain alcohols, aldehydes, ketones, carboxylic acids, and hydroxy acids, as detected in the soluble fractions of aged samples. SEC analyses also showed a marked decrease in the average molecular weight of PP polymer chains, whereas cross-linking was observed in the case of PS. The most abundant low molecular weight photo-degradation products of PS were benzoic acid and 1,4-benzenedicarboxylic acid, while PET had the highest stability towards aging, as indicated by the modest generation of low molecular weight species.

Methods for separating microplastics from complex solid matrices: Comparative analysis

Microplastics (MPs) are widely found in complex solid matrices such as soil, sediments and sludge. The separation procedure is crucial for effective analysis of MPs, but existing methods varied among studies. Here, we systematically summarize and compare separation methods including density, oil, electrostatic, magnetic, and solvent extraction separation. Density separation is the most commonly used approach, but time-consuming and discharging hazardous materials dependent on extraction solutions. In contrast, oil, electrostatic, magnetic separation and solvent extraction separation are emerging approaches with advantages of low-cost, quick, or environmentally-friendly, but with high request of instruments. Despite variation among these approaches, the separation efficiency is closely related to characteristics of MPs including polymer types, sizes and shapes. The treatment of digestion and fluorescence staining can facilitate the detection of MPs. This analysis suggests that further optimization and improvement of existing approaches can facilitate the development of new separation technology for assaying MPs in complex environmental matrices.

Plastic breeze: Volatile organic compounds (VOCs) emitted by degrading macro- and microplastics analyzed by selected ion flow-tube mass spectrometry

Pollution from microplastics (MPs) has become one of the most relevant topics in environmental chemistry. The risks related to MPs include their capability to adsorb toxic and harmful molecular species, and to release additives and degradation products into ecosystems. Their role as a primary source of a broad range of harmful volatile organic compounds (VOCs) has also been recently reported. In this work, we applied a non-destructive approach based on selected-ion flow tube mass spectrometry (SIFT-MS) for the characterization of VOCs released from a set of plastic debris collected from a sandy beach in northern Tuscany. The interpretation of the individual SIFT-MS spectra, aided by principal component data analysis, allowed us to relate the aged polymeric materials that make up the plastic debris (polyethylene, polypropylene, and polyethylene terephthalate) to their VOC emission profile, degradation level, and sampling site. The study proves the potential of SIFT-MS application in the field, as a major advance to obtain fast and reliable information on the VOCs emitted from microplastics. The possibility to obtain qualitative and quantitative data on plastic debris in less than 2 min also makes SIFT-MS a useful and innovative tool for future monitoring campaigns involving statistically significant sets of environmental samples.

An Overview of the Sorption Studies of Contaminants on Poly(Ethylene Terephthalate) Microplastics in the Marine Environment

Marine pollution is one of the biggest environmental problems, mainly due to single-use or disposable plastic waste fragmenting into microplastics (MPs) and nanoplastics (NPs) and entering oceans from the coasts together with human-made MPs. A rapidly growing worry concerning environmental and human safety has stimulated research interest in the potential risks induced by the chemicals associated with MPs/NPs. In this framework, the present review analyzes the recent advances in adsorption and desorption studies of different contaminants species, both organic and metallic, on MPs made of Poly(Ethylene terephthalate). The choice of PET is motivated by its great diffusion among plastic items and, unfortunately, also in marine plastic pollution. Due to the ubiquitous presence of PET MPS/NPs, the interest in its role as a vector of contaminants has abruptly increased in the last three years, as demonstrated by the very high number of recent papers on sorption studies in different environments. The present review relies on a chemical engineering approach aimed at providing a deeper overview of both the sorption mechanisms of organic and metal contaminants to PET MPs/NPs and the most used adsorption kinetic models to predict the mass transfer process from the liquid phase to the solid adsorbent.

Nylon 6 and nylon 6,6 micro- and nanoplastics: A first example of their accurate quantification, along with polyester (PET), in wastewater treatment plant sludges

A novel procedure for nylon 6 and nylon 6,6 polyamide (PAs) microplastics (MPs) quantification is described for the first time. The overall procedure, including quantification of poly(ethylene terephthalate) (PET), was tested on wastewater treatment plant (WWTP) sludges. The three polymers account for the largest global share of synthetic textile microfibers, being possibly the most common MPs released upon laundering in urban wastewaters. Therefore, measuring their content in WWTP sludges may provide an accurate picture of the potential risks associated with both the inflow of these MPs in natural water bodies and the practice of using WWTP sludges as agricultural soil amendment. The novel procedure involves PAs depolymerization by acid hydrolysis followed by derivatization of the monomers 6-aminohexanoic acid (AHA) and hexamethylene diamine (HMDA) with a fluorophore. Reversed-phase HPLC analysis with fluorescence detection results in high sensitivities for both AHA (LOD = 8.85·10^-4 mg/L, LOQ = 3.73·10^-3 mg/L) and HMDA (LOD = 2.12·10^-4, LOQ = 7.04·10^-4 mg/L). PET quantification involves depolymerization, in this case by alkaline hydrolysis, followed by HPLC analysis of its comonomer terephthalic acid. Eight sludge samples from four WWTPs in Italy showed contamination in the 29.3-215.3 ppm and 10.6-134.6 ppm range for nylon 6 and nylon 6,6, respectively, and in the 520-1470 ppm range for PET.

Polymer Identification and Specific Analysis (PISA) of Microplastic Total Mass in Sediments of the Protected Marine Area of the Meloria Shoals

Microplastics (MPs) quantification in benthic marine sediments is typically performed by time-consuming and moderately accurate mechanical separation and microscopy detection. In this paper, we describe the results of our innovative Polymer Identification and Specific Analysis (PISA) of microplastic total mass, previously tested on either less complex sandy beach sediment or less demanding (because of the high MPs content) wastewater treatment plant sludges, applied to the analysis of benthic sediments from a sublittoral area north-west of Leghorn (Tuscany, Italy). Samples were collected from two shallow sites characterized by coarse debris in a mixed seabed of Posidonia oceanica, and by a very fine silty-organogenic sediment, respectively. After sieving at <2 mm the sediment was sequentially extracted with selective organic solvents and the two polymer classes polystyrene (PS) and polyolefins (PE and PP) were quantified by pyrolysis-gas chromatography-mass spectrometry (Pyr-GC/MS). A contamination in the 8-65 ppm range by PS could be accurately detected. Acid hydrolysis on the extracted residue to achieve total depolymerization of all natural and synthetic polyamides, tagging of all aminated species in the hydrolysate with a fluorophore, and reversed-phase high performance liquid chromatography (HPLC) (RP-HPLC) analysis, allowed the quantification within the 137-1523 ppm range of the individual mass of contaminating nylon 6 and nylon 6,6, based on the detected amounts of the respective monomeric amines 6-aminohexanoic acid (AHA) and hexamethylenediamine (HMDA). Finally, alkaline hydrolysis of the residue from acid hydrolysis followed by RP-HPLC analysis of the purified hydrolysate showed contamination by polyethylene terephthalate (PET) in the 12.1-2.7 ppm range, based on the content of its comonomer, terephthalic acid.

Microplastics in freshwater sediment: A review on methods, occurrence, and sources

There is a rising concern regarding the accumulation of microplastics in the aquatic ecosystems. However, compared to the marine environment, the occurrence, transport, and diffusion of microplastics in freshwater sediment are still open questions. This paper summarizes and compares the methods used in previous studies and provides suggestions for sampling and analysis of microplastics in freshwater sediment. This paper also reviews the findings on microplastics in freshwater sediment, including abundance, morphological characteristics, polymer types, sources, and factors affecting the abundance of microplastics in freshwater sediment. The results show that microplastics are ubiquitous in the investigated sediment of rivers, lakes, and reservoirs, with an abundance of 2-5 orders of magnitude across different regions. Low microplastics concentration was observed in the Ciwalengke River with an average abundance of 30.3 ± 15.9 items/kg. In particular, an extremely high abundance of microplastics was recorded in the urban recipient in Norway reaching 12,000-200,000 items/kg. Fibers with particle size less than 1 mm are the dominant shape for microplastics in freshwater sediment. In addition, the most frequently recorded colors and types are white/transparent, and PE/PS, respectively. Finally, we conclude that the consistency of morphological characteristics and components of microplastics between the beach or marine sediments and freshwater sediments may be an indicator of these interlinkages and source-pathways. Microplastics in freshwater sediment need further research and exploration to identify its spatial and temporal variations and driving force through further field sampling and implementation of standard and uniform analytical methodologies.

A review of microplastics aggregation in aquatic environment: Influence factors, analytical methods, and environmental implications

A large amount of plastic waste released into natural waters and their demonstrated toxicity have made the transformation of microplastics (MPs; < 5 mm) and nanoplastics (NPs; < 100 nm) an emerging environmental concern. Aggregation is one of the most important environmental behaviors of MPs, especially in aquatic environments, which determines the mobility, distribution and bioavailability of MPs. In this paper, the sources and inputs of MPs in aquatic environments were first summarized followed by the analytical methods for investigating MP aggregation, including the sampling, visualization, and quantification procedures of MP' particle sizes. We critically evaluated the sampling methods that still remains a methodological gap. Identification and quantification of MPs were mostly carried out by visual, spectroscopic and spectrometric techniques, and modeling analysis. Important factors affecting MP aggregation in natural waters and environmental implications of the aggregation process were also reviewed. Finally, recommendations for future research were discussed, including (1) conducting more field studies; (2) using MPs in laboratory works representing those in the environment; and (3) standardizing methods of identification and quantification. The review gives a comprehensive overview of current knowledge for MP aggregation in natural waters, identifies knowledge gaps, and provides suggestions for future research.

Identification and characterization of micro-plastics in the marine environment: A mini review

Micro-plastics (MPs) are an environmental threat that has been gaining importance lately with an increasing number of studies demonstrating that they are a larger threat than previously thought. Scientists around the world have used a wide number of methods in their studies and they have adapted changes in response to the specific nature of the research undertaken. This article provides an account of the historical development of the MP menace, development of methods and tools used in MP research and also describes the challenges that are faced to further advancement to take place. The article is categorized into various sections that include history, sources, isolation, extraction, and characterization of MPs. Among the thermal characterization techniques, direct pyrolysis mass spectrometry and secondary ion mass spectrometry, which are widely used to characterize the plastics, but not utilised so far in this field are also highlighted for future direction.

Microplastics in fish meal: Contamination level analyzed by polymer type, including polyester (PET), polyolefins, and polystyrene

Fish meal (FM) is an industrial product, mainly obtained from whole wild-caught fish, that is used as a high protein feedstuff component in aquaculture and intensive animal farming. Contamination of FM by microplastics (MPs), the synthetic polymer particles known to be nearly ubiquitous in the marine environment, is a likely consequence of their ingestion by zooplankton and other small marine animals that through the food chain end up in the fish commercialized not only for direct human consumption but also for the industrial production of FM. Unfortunately, analytical tools for quantifying contamination of FM by synthetic polymers are not available. A newly developed procedure described here allows quantification of the total amounts of polyolefins (including ethene and propene homo- and copolymers), polystyrene (PS), and poly(ethylene terephthalate) (PET), respectively, in FM. The multi-step procedure involves a sequence of solvent extractions, hydrolytic treatments to remove the biogenic matrix mainly consisting of proteins and some lipids, and selective depolymerization for PET. The gravimetric and SEC-UV techniques employed for the quantification of polyolefins and PS, respectively, only allowed to estimate their concentration in FM at around or below 100 mg/kg each, a more accurate quantification being prevented by the interference from the organic matrix and, in the case of polyolefins, by the limited sensitivity of the quantification by gravimetry. On the other hand, the contamination by PET MPs could accurately be quantified at 12.9 mg/kg based on the dry FM mass. Ways to overcome the sensitivity limitations for PS and polyolefins by using e.g. pyrolysis-GC/MS are highlighted.

Thorough Multianalytical Characterization and Quantification of Micro- and Nanoplastics from Bracciano Lake’s Sediments

Lake basins can behave as accumulators of microplastics released in wastewaters as such or resulting from degradation of larger items before and/or during their journey toward the marine environment as a final sink. A novel multianalytical approach was adopted for the detection and quantification of microplastics with size < 2 mm in the sediments of the volcanic lake of Bracciano, Italy. Simple analytical techniques such as solvent extraction/fractionation (for polyolefins and polystyrene) or depolymerization (for polyethylene terephthalate, PET), along with chromatographic detection (SEC and HPLC), allowed quantitative and qualitative determination of the main synthetic polymer contaminants. In particular, PET microplastic concentrations of 0.8–36 ppm were found, with variability related to the sampling site (exposure to incoming winds and wave action). Proton Nuclear Magnetic Resonance (1H-NMR) and Attenuated Total Reflectance Fourier Transformed InfraRed (ATR-FTIR spectroscopic investigations supported the identification and chemical characterization of plastic fragments and polymer extracts. The average molecular weight of solvent extractable polymers was evaluated from 2D 1H-NMR diffusion ordered spectroscopy (DOSY) experiments. The proposed, easily accessible multianalytical approach can be considered as a useful tool for improving our knowledge on the nature and the concentration of microplastics in sediments, giving insights on the impact of human activities on the health status of aquatic ecosystems.