Environmental biodegradation of synthetic polymers I. Test methodologies and procedures

Biodegradation of Water-Soluble Polymers by Wastewater Microorganisms: Challenging Laboratory Testing Protocols

For water-soluble polymers (WSPs) that enter environmental systems at their end-of-life, biodegradability is a key functionality. For the development and regulation of biodegradable WSPs, testing methods that are both scientifically validated and economically practicable are needed. Here, we used respirometric laboratory tests to study the biodegradation of poly(amino acids), poly(ethylene glycol), and poly(vinyl alcohol), together with appropriate low-molecular-weight reference substrates. We varied key protocol steps of commonly used testing methods, which were originally established for small molecules and tested for effects on WSP biodegradation. We found that avoiding aeration of the wastewater inoculate prior to WSP addition, incubating WSP with filter-sterilized wastewater prior to biodegradation testing, and lowering the WSP concentration can increase biodegradation rates of WSPs. Combining the above-mentioned protocol variations substantially affected the results of the biodegradation testing for the two poly(amino acids) tested herein (i.e., poly(lysine) and poly(aspartic acid)). Our findings were consistent between microbial inocula derived from two municipal wastewater treatment plants. Our study presents promising biodegradation dynamics for poly(amino acids) and highlights the importance, strengths, and limitations of respirometric laboratory methods for WSP biodegradation testing.

Natural and Synthetic Polymers for Biomedical and Environmental Applications

Natural and synthetic polymers are a versatile platform for developing biomaterials in the biomedical and environmental fields. Natural polymers are organic compounds that are found in nature. The most common natural polymers include polysaccharides, such as alginate, hyaluronic acid, and starch, proteins, e.g., collagen, silk, and fibrin, and bacterial polyesters. Natural polymers have already been applied in numerous sectors, such as carriers for drug delivery, tissue engineering, stem cell morphogenesis, wound healing, regenerative medicine, food packaging, etc. Various synthetic polymers, including poly(lactic acid), poly(acrylic acid), poly(vinyl alcohol), polyethylene glycol, etc., are biocompatible and biodegradable; therefore, they are studied and applied in controlled drug release systems, nano-carriers, tissue engineering, dispersion of bacterial biofilms, gene delivery systems, bio-ink in 3D-printing, textiles in medicine, agriculture, heavy metals removal, and food packaging. In the following review, recent advancements in polymer chemistry, which enable the imparting of specific biomedical functions of polymers, will be discussed in detail, including antiviral, anticancer, and antimicrobial activities. This work contains the authors' experimental contributions to biomedical and environmental polymer applications. This review is a vast overview of natural and synthetic polymers used in biomedical and environmental fields, polymer synthesis, and isolation methods, critically assessessing their advantages, limitations, and prospects.

Assessing microbial plastic degradation requires robust methods

Plastics are versatile materials that have the potential to propel humanity towards circularity and ultimate societal sustainability. However, the escalating concern surrounding plastic pollution has garnered significant attention, leading to widespread negative perceptions of these materials. Here, we question the role microbes may play in plastic pollution bioremediation by (i) defining polymer biodegradability (i.e., recalcitrant, hydrolysable and biodegradable polymers) and (ii) reviewing best practices for evaluating microbial biodegradation of plastics. We establish recommendations to facilitate the implementation of rigorous methodologies in future studies on plastic biodegradation, aiming to push this field towards the use of isotopic labelling to confirm plastic biodegradation and further determine the molecular mechanisms involved.

Aging of plastics in aquatic environments: Pathways, environmental behavior, ecological impacts, analyses and quantifications

The ubiquity of plastics in our environment has brought about pressing concerns, with their aging processes, photo-oxidation, mechanical abrasion, and biodegradation, being at the forefront. Microplastics (MPs), whether originating from plastic degradation or direct anthropogenic sources, further complicate this landscape. This review delves into the intricate aging dynamics of plastics in aquatic environments under various influential factors. We discuss the physicochemical changes that occur in aged plastics and the release of oxidation products during their degradation. Particular attention is given to their evolving environmental interactions and the resulting ecotoxicological implications. A rigorous evaluation is also conducted for methodologies in the analysis and quantification of plastics aging, identifying their merits and limitations and suggesting potential avenues for future research. This comprehensive review is able to illuminate the complexities of plastics aging, charting a path for future research and aiding in the formulation of informed policy decisions.

Current studies on the degradation of microplastics in the terrestrial and aquatic ecosystem

Soil and water are two important basic ecosystems for the survival of different organisms. The excessive microplastic pollutants in soil have been directly discharged into the terrestrial ecosystems. Microplastic pollutants (MPs) constitute a ubiquitous global menace due to their durability, flexibility, and tough nature. MPs posed threat to the sustainability of the ecosystem due to their small size and easy transportation via ecological series resulting in the accumulation of MPs in aquatic and terrestrial ecosystems. After being emitted into the terrestrial ecosystem, the MPs might be aged by oxidative degeneration (photo/thermal), reprecipitation (bioturbation), and hetero-accumulation. The mechanism of adsorption, degradation, and breakdown of MPs into unaffected plastic debris is accomplished by using several biological, physical, and chemical strategies. This review presents the importance of ecosystems, occurrence and sources of MPs, its toxicity, and the alteration in the ecology of the ecosystems. The inhibitory impact of MPs on the ecosystems also documents to unveil the ecological hazards of MPs. Further research is required to study the immobilization and recovery efficiency of MPs on a larger scale.

Understanding the mechanism of enhanced anaerobic biodegradation of biodegradable plastics after alkaline pretreatment

Biodegradable plastics (BPs) tend to replace conventional plastics, which increases the amount of BP waste entering the environment. The anaerobic environment exists extensively in nature, and anaerobic digestion has become a widely used technique for organic waste treatment. Many kinds of BPs have low biodegradability (B_D) and biodegradation rates under anaerobic condition due to the limitation of hydrolysis, so they still have harmful environmental consequences in anaerobic environment. There is an urgent need to find an intervention method to improve the biodegradation of BPs. Therefore, this study aimed to investigate the effectiveness of alkaline pretreatment in accelerating the thermophilic anaerobic degradation of ten widely used BPs, such as poly (lactic acid) (PLA), poly (butylene adipate-co-terephthalate) (PBAT), thermoplastic starch (TPS), poly (butylene succinate-co-butylene adipate) (PBSA), cellulose diacetate (CDA), etc. The results showed that NaOH pretreatment significantly improved the solubility of PBSA, PLA, poly (propylene carbonate) (PPC), and TPS. Except for PBAT, pretreatment with an appropriate NaOH concentration could improve the B_D and degradation rate. The pretreatment also reduced the lag phase in the anaerobic degradation of BPs such as PLA, PPC, and TPS. Specifically, for CDA and PBSA, the B_D increased from 4.6 % and 30.5 % to 85.2 % and 88.7 %, with increments of 1752.2 % and 190.8 %, respectively. Microbial analysis indicated that NaOH pretreatment promoted the dissolution and hydrolysis of PBSA and PLA and the deacetylation of CDA, which contributed to rapid and complete degradation. This work not only provides a promising method for improving the degradation of BP waste but also lays the foundation for its large-scale application and safe disposal.

Fluorescence tracing the degradation process of biodegradable PBAT: Visualization and high sensitivity

Biodegradable plastics have emerged as a potential solution to the mounting plastic pollution crisis. However, current methods for evaluating the degradation of these plastics are limited in detecting structural changes rapidly and accurately, particularly for PBAT, which contains worrying benzene rings. Inspired by the fact that the aggregation of conjugated groups can endow polymers with intrinsic fluorescence, this work found that PBAT emits a bright blue-green fluoresces under UV irradiation. More importantly, we pioneered a degradation evaluation approach to track the degradation process of PBAT via fluorescence. A blue shift of fluorescence wavelength as the thickness and molecular weight of PBAT film decreased during degradation in an alkali solution was observed. Additionally, the fluorescence intensity of the degradation solution increased gradually as the degradation progressed, and was found to be exponentially correlated with the concentration of benzene ring-containing degradation products following filtration with the correlation coefficient is up to 0.999. This study proposes a promising new strategy for monitoring the degradation process with visualization and high sensitivity.

Environmental safety of second and third generation bioplastics in the context of the circular economy

Bioplastics derived from organic materials other than crude oil are often suggested as sustainable solutions for tackling end-of-life plastic waste, but little is known of their ecotoxicity to aquatic species. Here, we investigated the ecotoxicity of second and third generation bioplastics toward the freshwater zooplankton Daphnia magna. In acute toxicity tests (48 h), survival was impacted at high concentrations (g.L^-1 range), within the range of salinity-induced toxicity. Macroalgae-derived bioplastic induced hormetic responses under chronic exposure (21 d). Most biological traits were enhanced from 0.06 to 0.25 g.L^-1 (reproduction rate, body length, width, apical spine, protein concentration), while most of these traits returned to controls level at 0.5 g.L^-1. Phenol-oxidase activity, indicative of immune function, was enhanced only at the lowest concentration (0.06 g.L^-1). We hypothesise these suggested health benefits were due to assimilation of carbon derived from the macroalgae-based bioplastic as food. Polymer identity was confirmed by infra-red spectroscopy. Chemical analysis of each bioplastic revealed low metal abundance whilst non target exploration of organic compounds revealed trace amounts of phthalates and flame retardants. The macroalgae-bioplastic disintegrated completely in compost and biodegraded up to 86 % in aqueous medium. All bioplastics acidified the test medium. In conclusion, the tested bioplastics were classified as environmentally safe. Nonetheless, a reasonable end-of-life management of these safer-by-design materials is advised to ensure the absence of harmful effects at high concentrations, depending on the receiving environment.

The risks of marine micro/nano-plastics on seafood safety and human health

A considerable mass of plastics has been released into the marine environment annually through different human activities, including industrial, agriculture, medical, pharmaceutical and daily care products. These materials are decomposed into smaller particles such as microplastic (MP) and nanoplastic (NP). Hence, these particles can be transported and distributed in coastal and aquatic areas and are ingested by the majority of marine biotas, including seafood products, thus causing the contamination of the different parts of aquatic ecosystems. In fact, seafood involves a wide diversity of edible marine organisms, such as fish, crustaceans, molluscs, and echinoderms, which can ingest the micro/nanoplastics particles, and then transmit them to humans through dietary consumption. Consequently, these pollutants can cause several toxic and adverse impacts on human health and the marine ecosystem. Therefore, this chapter provides information on the potential risks of marine micro/nanoplastics on seafood safety and human health.

Degradation of polyvinyl chloride by a bacterial consortium enriched from the gut of Tenebrio molitor larvae

Polyvinyl chloride (PVC), a carbon backbone synthetic plastic containing chlorine element, is one of six widely used plastics accounting for 10% global plastics production. PVC wastes are recalcitrant to be broken down in the environment but release harmful chlorinated compounds, causing damage to the ecosystem. Although biodegradation represents a sustainable approach for PVC reduction, virtually no efficient bacterial degraders for additive-free PVC have been reported. In addition, PVC depolymerization by Tenebrio molitor larvae was suggested to be gut microbe-dependent, but to date no additive-free PVC degraders have been isolated from insect guts. In this study, a bacterial consortium designated EF1 was newly enriched from the gut of Tenebrio molitor larvae, which was capable of utilizing additive-free PVC for its growth with the PVC-mass reduction and dechlorination of PVC. PVC films inoculated with consortium EF1 for 30 d were analyzed by diverse polymer characterization methods including atomic force microscopy, scanning electron microscope, water contact angle, time-of-flight secondary ion mass spectrometry, Fourier transform infrared spectroscopy, differential scanning calorimetry, thermogravimetric analysis technique, and ion chromatography. It was found that bio-treated PVC films were covered with tight biofilms with increased -OH and -CC- groups and decreased chlorine contents, and erosions and cracks were present on their surfaces. Meanwhile, the hydrophilicity of bio-treated films increased, but their thermal stability declined. Furthermore, M_w, M_n and M_z values were reduced by 17.0%, 28.5% and 16.1% using gel permeation chromatography, respectively. In addition, three medium-chain aliphatic primary alcohols and their corresponding fatty acids were identified as PVC degradation intermediates by gas chromatography-mass spectrometry. Combing all above results, it is clear that consortium EF1 is capable of efficiently degrading PVC polymer, providing a unique example for PVC degradation by gut microbiota of insects and a feasibility for the removal of PVC wastes.

Exploitation of bacterial strains for microplastics (LDPE) biodegradation

Plastic waste (microplastics) is one of the primary sources of environmental pollutants, serving as a reservoir for them. In this study, previously isolated and screened polymer-degrading bacteria (B. subtilis V8, P. aminophilusB1 4-, P. putida C 2 5, P. aeruginosa V1, and A. calcoaceticus V4) were utilised to examine the biodegradation of LDPE (low-density polyethylene) microplastics. Response surface methodology (RSM) was used to optimize the physicochemical growth parameters (pH, temperature, and ammonium sulphate concentration). By using the polyphasic approach, including CO₂ estimation, weight loss analysis, scanning electron microscopy (SEM), fourier transform infrared (FT-IR) spectroscopy, and electrical conductivities examine the plastic biodegradability. After four months, all biodegradable plastic samples were evaluated. When compared to the other tested cultures, P. aeruginosa V1 showed the most significant degradation (CO₂evolution of 8.86 g.l^-l and percentage weight loss of 18.21 %) with increased electrical conductivity, followed by B. subtilis V8 (CO₂ evolution of 8.10 g.l^-l and percentage weight loss of 16.12 %), A. calcoaceticus V4 (CO₂ evolution of 7.21 g.l^-l and percentage weight loss of 15.44 %), P. putida C 2-5 (CO₂ evolution of 5.76 g.l^-l and percentage weight loss of 13.30 %), and P. aminophilus B1 4- (CO₂ evolution of 5.62 g.l^-l and percentage weight loss of 11.72 %). The deteriorated materials' exterior modifications (surface alteration) were also examined using SEM analysis, and the chemical bonding alterations (bond vibration-bending) were determined using FT-IR spectroscopy.

Plastic invasion tolling: First evaluation of microplastics in water and two crab species from the nature reserve lagoonary complex of Kune-Vain, Albania

Microplastic (MP) pollution is an emerging global challenge and actually has become a reality in aquatic ecosystems in Albania. According to the World Wildlife Fund (WWF) report of 2019, Albania, is one of the most problematic countries, with the highest percentage of untreated plastic waste, 73 %, and one of the top four countries with the highest norm of untreated plastic waste in the Mediterranean. This study evaluates and characterizes for the first time the MPs in water, sediment, and gastrointestinal tracts of two crab species, C. aestuarii and C. sapidus, common inhabitants of the lagoonary complex of Kune-Vain Nature Reserve, known for their important role in the lagoon ecosystem. The results showed that all sampled crabs had MPs in their gut in an average of 11.0 ± 1.85 items g^-1, while the total MPs content in water ranges from 370 to 750 MPs per L^-1. No significant difference in the content of MPs between the two crab species was found and a positive Pearson correlation, between microplastic abundance in the water and in the crabs regardless of species, was confirmed. The composition of microplastics showed consistency in crabs, sediment, and water, with fibers and pellets as the dominant types followed by microbeads, and fragments. Characterized MPs varied in size from <0.1 mm to 0.1-0.5 mm, showing variable colors of black, blue, and red domination. Fourier Transform Infrared Spectroscopy (FT-IR) analysis of the chemical composition of microplastics distinguished presence of the high-density polyethylene (HDPE), polypropylene (PP), polyethylene (PE), and low-density polyethylene (LDPE), which showed consistency in water, sediment, and crab samples. In conclusion, high levels of MPs pollution observed in the Kune-Vain complex represent a serious threat to the lagoon ecosystem and to the local inhabitants. Furthermore, studies on MPs' impact on biota and local population health are urgently required.

Synthesis, Characterization, and Soil Burial Degradation of Biobased Polyurethanes

There is an urgent need for developing degradable polymeric systems based on bio-derived and sustainable materials. In recent years, polyurethanes derived from castor oil have emerged due to the large availability and sustainable characteristics of castor oil. However, these polymers are normally prepared through tedious and/or energy-intensive procedures or using high volatile and/or toxic reagents such as volatile isocyanates or epoxides. Furthermore, poor investigation has been carried out to design castor oil derived polyurethanes with degradable characteristics or thorough specifically sustainable synthetic procedures. Herein, castor oil-derived polyurethane with more than 90% biomass-derived carbon content and enhanced degradable features was prepared through a simple, eco-friendly (E-factor: 0.2), and scalable procedure, employing a recently developed commercially available biomass-derived (61% bio-based carbon content) low-volatile polymeric isocyanate. The novel material was compared with a castor oil derived-polyurethane prepared with a commercially available fossil-based isocyanate counterpart. The different castor oil-derived polyurethanes were investigated by means of water uptake, soil burial degradation, and disintegration tests in compost. Characterization analyses, including thermogravimetric analysis (TGA), differential scanning calorimetry (DSC), attenuated total reflection Fourier transform infrared spectroscopy (ATR-FTIR) and scanning electron microscopy (SEM), were carried out both prior to and after degradation tests. The results suggest potential applications of the degradable castor oil-derived polyurethane in different fields, such as mulch films for agricultural purposes.

Partially hydrolyzed polyacrylamide: enhanced oil recovery applications, oil-field produced water pollution, and possible solutions

Polymers, such as partially hydrolyzed polyacrylamide (HPAM), are widely used in oil fields to enhance or improve the recovery of crude oil from the reservoirs. It works by increasing the viscosity of the injected water, thus improving its mobility and oil recovery. However, during such enhanced oil recovery (EOR) operations, it also produces a huge quantity of water alongside oil. Depending on the age and the stage of the oil reserve, the oil field produces ~ 7-10 times more water than oil. Such water contains various types of toxic components, such as traces of crude oil, heavy metals, and different types of chemicals (used during EOR operations such as HPAM). Thus, a huge quantity of HPAM containing produced water generated worldwide requires proper treatment and usage. The possible toxicity of HPAM is still ambiguous, but its natural decomposition product, acrylamide, threatens humans' health and ecological environments. Therefore, the main challenge is the removal or degradation of HPAM in an environmentally safe manner from the produced water before proper disposal. Several chemical and thermal techniques are employed for the removal of HPAM, but they are not so environmentally friendly and somewhat expensive. Among different types of treatments, biodegradation with the aid of individual or mixed microbes (as biofilms) is touted to be an efficient and environmentally friendly way to solve the problem without harmful side effects. Many researchers have explored and reported the potential of such bioremediation technology with a variable removal efficiency of HPAM from the oil field produced water, both in lab scale and field scale studies. The current review is in line with United Nations Sustainability Goals, related to water security-UNSDG 6. It highlights the scale of such HPAM-based EOR applications, the challenge of produced water treatment, current possible solutions, and future possibilities to reuse such treated water sources for other applications.

Biodegradation of Biodegradable Polymers in Mesophilic Aerobic Environments

Finding alternatives to diminish plastic pollution has become one of the main challenges of modern life. A few alternatives have gained potential for a shift toward a more circular and sustainable relationship with plastics. Biodegradable polymers derived from bio- and fossil-based sources have emerged as one feasible alternative to overcome inconveniences associated with the use and disposal of non-biodegradable polymers. The biodegradation process depends on the environment's factors, microorganisms and associated enzymes, and the polymer properties, resulting in a plethora of parameters that create a complex process whereby biodegradation times and rates can vary immensely. This review aims to provide a background and a comprehensive, systematic, and critical overview of this complex process with a special focus on the mesophilic range. Activity toward depolymerization by extracellular enzymes, biofilm effect on the dynamic of the degradation process, CO2 evolution evaluating the extent of biodegradation, and metabolic pathways are discussed. Remarks and perspectives for potential future research are provided with a focus on the current knowledge gaps if the goal is to minimize the persistence of plastics across environments. Innovative approaches such as the addition of specific compounds to trigger depolymerization under particular conditions, biostimulation, bioaugmentation, and the addition of natural and/or modified enzymes are state-of-the-art methods that need faster development. Furthermore, methods must be connected to standards and techniques that fully track the biodegradation process. More transdisciplinary research within areas of polymer chemistry/processing and microbiology/biochemistry is needed.

Biodegradation of poly(butylene succinate) in soil laboratory incubations assessed by stable carbon isotope labelling

Using biodegradable instead of conventional plastics in agricultural applications promises to help overcome plastic pollution of agricultural soils. However, analytical limitations impede our understanding of plastic biodegradation in soils. Utilizing stable carbon isotope (¹³C-)labelled poly(butylene succinate) (PBS), a synthetic polyester, we herein present an analytical approach to continuously quantify PBS mineralization to ¹³CO₂ during soil incubations and, thereafter, to determine non-mineralized PBS-derived ¹³C remaining in the soil. We demonstrate extensive PBS mineralization (65 % of added ¹³C) and a closed mass balance on PBS−¹³C over 425 days of incubation. Extraction of residual PBS from soils combined with kinetic modeling of the biodegradation data and results from monomer (i.e., butanediol and succinate) mineralization experiments suggest that PBS hydrolytic breakdown controlled the overall PBS biodegradation rate. Beyond PBS biodegradation in soil, the presented methodology is broadly applicable to investigate biodegradation of other biodegradable polymers in various receiving environments.

This study applies stable carbon isotope labelling to study polymer biodegradation in soils. This labelling enables accurate and precise tracking of polymer carbon during biodegradation and, thereby, provides a holistic picture of this process.

Classification and Regression Machine Learning Models for Predicting Aerobic Ready and Inherent Biodegradation of Organic Chemicals in Water

Machine learning (ML) is viewed as a promising tool for the prediction of aerobic biodegradation, one of the most important elimination pathways of organic chemicals from the environment. However, available models only have small datasets (<3200 records), make binary classification predictions, evaluate ready biodegradability, and do not incorporate experimental conditions (e.g., system setup and reaction time). This study addressed all these limitations by first compiling a large database of 12,750 records, considering both ready and inherent biodegradation under different conditions, and then developing regression and classification models using different chemical representations and ML algorithms. The best regression model (R² = 0.54 and root mean square error of 0.25) and classification model (the prediction accuracy from 85.1%) achieved very good performance. The model interpretation indicated that the models correctly captured the effects of chemical substructures, following the order of C═O > O═C-O > OH > CH₃ > halogen > branching > N > 6-member ring. The consideration of chemical speciation based on pK_a and α notations did not affect the regression model performance but significantly improved the classification model performance (the accuracy increased to 87.6%). The models also showed large applicability domains and provided reasonable predictions for more than 98% of over 850,000 environmentally relevant chemicals in the Distributed Structure-Searchable Toxicity database. These robust, trustable models were finally made widely accessible through two free online predictors with graphical user interface.

Influence of Calcium Carbonate Nanoparticles on the Soil Burial Degradation of Polybutyleneadipate-Co-Butylenetherephthalate Films

A polybutyleneadipate-co-butylenetherephthalate (PBAT) sample, commercially known as Ecoflex^®, was processed via melt extrusion with CaCO₃ nanoparticles coated with a hydrophobic coating. Blown films of PBAT and two composites with nanofiller (2% and 5%wt) were prepared and degradation tests in soil at 30 °C up to 180 days were carried out with weight loss measurements. Furthermore, biodegradation test according to ISO 14851 was carried out at 30 °C. The effect of CaCO₃ on soil burial degradation was assessed by surface wettability and SEM. ATR-FTIR and XPS analyses highlighted chemical modifications induced by soil degradation. CaCO₃ nanoparticles decreased surface wettability and discouraged the disintegration in soil. Interestingly, SEM images after soil degradation highlighted in the nanocomposite films selective zones of disintegration. XPS showed an increasing peak area C 1s ratio of C–O to C=O with degradation time. Moreover, after the soil burial test, carbonyl index determined by ATR-FTIR increased in both nanocomposites. In fact, the addition of CaCO₃ leads to a rise in the carbonyl zone due to the presence of the carbonate group. Remarkably, FTIR data after soil degradation showed an enrichment of the aromatic content, a preferential cleavage and erosion of the aliphatic moiety in PBAT films, amplified by the presence of the CaCO₃ nanofiller.

Closing the Carbon Loop in the Circular Plastics Economy

Today, plastics are ubiquitous in everyday life, problem solvers of modern technologies, and crucial for sustainable development. Yet the surge in global demand for plastics of the growing world population has triggered a tidal wave of plastic debris in the environment. Moving from a linear to a zero-waste and carbon-neutral circular plastic economy is vital for the future of the planet. Taming the plastic waste flood requires closing the carbon loop through plastic reuse, mechanical and molecular recycling, carbon capture, and use of the greenhouse gas carbon dioxide. In the quest for eco-friendly products, plastics do not need to be reinvented but tuned for reuse and recycling. Their full potential must be exploited regarding energy, resource, and eco efficiency, waste prevention, circular economy, climate change mitigation, and lowering environmental pollution. Biodegradation holds promise for composting and bio-feedstock recovery, but it is neither the Holy Grail of circular plastics economy nor a panacea for plastic littering. As an alternative to mechanical downcycling, molecular recycling enables both closed-loop recovery of virgin plastics and open-loop valorization, producing hydrogen, fuels, refinery feeds, lubricants, chemicals, and carbonaceous materials. Closing the carbon loop does not create a Perpetuum Mobile and requires renewable energy to achieve sustainability. This article is protected by copyright. All rights reserved.

Microplastics waste in environment: A perspective on recycling issues from PPE kits and face masks during the COVID-19 pandemic

During the COVID-19 pandemic, the extensive use of face masks and protective personal equipment (PPE) kits has led to increasing degree of microplastic pollution (MP) because they are typically discarded into the seas, rivers, streets, and other parts of the environment. Currently, microplastic (MP) pollution has a negative impact on the environment because of high-level fragmentation. Typically, MP pollution can be detected by various techniques, such as microscopic analysis, density separation, and Fourier transform infrared spectrometry. However, there are limited studies on disposable face masks and PPE kits. A wide range of marine species ingest MPs in the form of fibers and fragments, which directly affect the environment and human health; thus, more research and development are needed on the effect of MP pollution on human health. This article provides a perspective on the origin and distribution of MP pollution in waterbodies (e.g., rivers, ponds, lakes, and seas) and wastewater treatment plants, and reviews the possible remediation of MP pollution related to the excessive disposal of face masks and PPE kits to aquatic environments.

REVIEW OF EVALUATION METHODS FOR BIODEGRADABILITY OF POLYMERIC MATERIALS

Development and further use of biodegradable polymeric materials requires prior assessment the degree of their biodegradation. There are a large number of methods developed taking into account the specifics of the destruction of polymeric materials. The purpose of this review is to systematize scientific and technical information regarding methods for assessing the biodegradation of polymeric materials. Laboratory methods of researches, including the following: influence of abiotic factors (temperature, moisture, UV irradiation), impact of microorganisms (fungi, bacteria, yeast), respiratory methods (Sturm, Zahn-Wellness, etc.), conditions of composting, enzyme analysis methods, ecotoxicity tests are given. Test methods in both aqueous and solid media are also presented. The parameters of biodegradability, which determine the degree of destruction (mass, strain strength, molecular weight distribution, temperature characteristics, macro-and microstructure of samples, etc.) or the composition and properties of the biological system in which biodegradation takes place (acidity, respiratory activity, chemical and microbiological composition of soil or other biological environment, etc.) are considered as well. Advantages of laboratory methods for studying the biodegradation of polymeric materials could be realized in the given directions: varying of the experimental conditions (temperature, humidity, UV and IR radiation, the presence of aggressive media, etc.), biochemical compositions of the environment; study of the ability of individual strains of microorganisms to dispose of polymer composites and targeted selection of the most active microbial associations (in particular, for the manufacture of special biocomposts); utilize of simple and fast methodical approaches and modern devices for evaluation experiments. However, laboratory methods do not always allow modeling a set of endogenous and exogenous factors that define the process of biodegradation in the natural environment. Therefore, this review also considers methods for assessing biodegradation in the environment. So, the essence of the test regarding the samples’ burial in the ground is given. International standards governing methods for assessing the biodegradability of organic substances and polymeric materials are summarized. Applying different test methods, one can evaluate the whole process of biodegradation of polymeric materials, consisting of several stages, which occur regardless the type of microorganisms and accompanying abiotic factors, and can be represented as follows: adhesion → colonization → biodeterioration → biofragmentation → assimilation → mineralization. Thus, the adhesion and colonization of microorganisms can be estimated by visual, bioindicator and spectral methods. Abiotic degradation and biodeterioration are associated with physical tests (e.g., thermal and physico-mechanical). Biofragmentation is detected by identifying fragments of lower molecular weight (i.e. by chromatographic methods). In turn, assimilation is assessed by the amount of metabolites produced using, for example, respirometric methods or involving analysis of microbial biomass (e.g., macroscopic and microscopic observations). The most productive should be considered a comprehensive approach to the study of biodegradation of polymers. To determine the reliable kinetic parameters and link the mechanism of this process, it is necessary to carry out a comparative analysis of the results of physical, chemical, microbiological experiments, which are carried out in both laboratory and natural conditions.

A review of the cost and effectiveness of solutions to address plastic pollution

Plastic usage increases year by year, and the growing trend is projected to continue. However as of 2017, only 9% of the 9 billion tons of plastic ever produced had been recycled leaving large amounts of plastics to contaminate the environment, resulting in important negative health and economic impacts. Curbing this trend is a major challenge that requires urgent and multifaceted action. Based on scientific and gray literature mainly published during the last 10 years, this review summarizes key solutions currently in use globally that have the potential to address at scale the plastic and microplastic contaminations from source to sea. They include technologies to control plastics in solid wastes (i.e. mechanical and chemical plastic recycling or incineration), in-stream (i.e. booms and clean-up boats, trash racks, and sea bins), and microplastics (i.e. stormwater, municipal wastewater and drinking water treatment), as well as general policy measures (i.e. measures to support the informal sector, bans, enforcement of levies, voluntary measures, extended producer responsibility, measures to enhance recycling and guidelines, standards and protocols to guide activities and interventions) to reduce use, reuse, and recycle plastics and microplastics in support of the technological options. The review discusses the effectiveness, capital expenditure, and operation and maintenance costs of the different technologies, the cost of implementation of policy measures, and the suitability of each solution under various conditions. This guidance is expected to help policymakers and practitioners address, in a sustainable and cost-efficient way, the plastic and microplastic management problem using technologies and policy instruments suitable in their local context.

Biodegradation of polymers in managing plastic waste - A review

The modern economy that is fast-moving and convenience centric has led to excessive consumption of plastic. This has unwittingly led to egregious accumulation of plastic waste polluting the environment. Unfortunately, present means of plastic waste management have all been proven as less than adequate; namely recycling, landfill and incineration. Recent focus on plastic waste management has seen the confluence of the developments in biodegradable polymers and microbial engineering strategy for more expedient decomposition of plastic waste at composting facilities. This review paper is an assimilation of current developments in the areas of biodegradable polymer as well as microbial strategy towards management of polymer waste. Advents in biodegradable polymers have been promising, especially with aliphatic polyesters and starch in blends or co-polymers of these. Microbial strategies have been pursued for the identification of microbial strains and understanding of their enzymatic degradation process on polymers. New insights in these two areas have been focused in improving the rate of degradation of plastic waste at composting facilities. Recent alignment of testing and certification standards is outlined to give intimate insights into the mechanisms and factors influencing biodegradation. Despite recent milestones, economic viability of composting plastic waste in mainstream waste facilities is still a distance away. As it remains that a polymer that is biodegradable is functionally inferior to conventional polymers. Rather, it requires a shift in consumer behaviour to accept less durable biodegradable plastic products, this will then lower the threshold for biodegradable polymers to become a commercial reality.

Synthesis and Biodegradation Studies of Low-Dispersity Poly(Acrylic Acid)

Poly(acrylic acid) (PAA) is produced on an industrial scale and widely-used in applications such as personal care products and cleaning formulations that end up "down-the-drain." Relatively high molecular weight PAA is considered poorly biodegradable, but little is known about the biodegradability of low molecular weight PAA at the wastewater treatment plant according to current regulatory and industrial OECD standards. We report the synthesis, separation, and characterization of a series of ultralow dispersity PAA oligomers (i.e., Đ <1.10) in the molecular weight range M_n ∼ 350-1200 Da and the results of biodegradability testing. Miniaturized, high-throughput screening studies in a parallel respirometer revealed a strong trend towards lower biodegradation at higher molecular weight; these results were confirmed and expanded using standardized method OECD 301F. Biodegradability reached ∼40% at M_n = 380 Da, ∼26% at M_n = 770 Da, and ∼17% at M_n = 1190 Da for discrete polyacid oligomers. These data not only shed light on potential biodegradation mechanisms for linear PAA, but also may inspire the future design of biodegradable PAA-containing macromolecules. This article is protected by copyright. All rights reserved.

Biopackaging Potential Alternatives: Bioplastic Composites of Polyhydroxyalkanoates and Vegetal Fibers

Initiatives to reduce plastic waste are currently under development worldwide. As a part of it, the European Union and private and public organizations in several countries are designing and implementing regulations for single-use plastics. For example, by 2030, plastic packaging and food containers must be reusable or recyclable. In another approach, researchers are developing biopolymers using biodegradable thermoplastics, such as polyhydroxyalkanoates (PHAs), to replace fossil derivatives. However, their production capacity, high production costs, and poor mechanical properties hinder the usability of these biopolymers. To overcome these limitations, biomaterials reinforced with natural fibers are acquiring more relevance as the world of bioplastics production is increasing. This review presents an overview of PHA–vegetal fiber composites, the effects of the fiber type, and the production method’s impact on the mechanical, thermal, barrier properties, and biodegradability, all relevant for biopackaging. To acknowledge the behaviors and trends of the biomaterials reinforcement field, we searched for granted patents focusing on bio-packaging applications and gained insight into current industry developments and contributions.

Microbial biodegradation of plastics: Challenges, opportunities, and a critical perspective

The abundance of synthetic polymers has increased due to their uncontrolled utilization and disposal in the environment. The recalcitrant nature of plastics leads to accumulation and saturation in the environment, which is a matter of great concern. An exponential rise has been reported in plastic pollution during the corona pandemic because of PPE kits, gloves, and face masks made up of single-use plastics. The physicochemical methods have been employed to degrade synthetic polymers, but these methods have limited efficiency and cause the release of hazardous metabolites or by-products in the environment. Microbial species, isolated from landfills and dumpsites, have utilized plastics as the sole source of carbon, energy, and biomass production. The involvement of microbial strains in plastic degradation is evident as a substantial amount of mineralization has been observed. However, the complete removal of plastic could not be achieved, but it is still effective compared to the preexisting traditional methods. Therefore, microbial species and the enzymes involved in plastic waste degradation could be utilized as eco-friendly alternatives. Thus, microbial biodegradation approaches have a profound scope to cope with the plastic waste problem in a cost-effective and environmental-friendly manner. Further, microbial degradation can be optimized and combined with physicochemical methods to achieve substantial results. This review summarizes the different microbial species, their genes, biochemical pathways, and enzymes involved in plastic biodegradation.

Microplastics in Combined Sewer Overflows: An Experimental Study

One of the main sources of microplastics inside surface waters is represented by combined sewer overflows (CSOs), involving severe risks for the environment. The entry of microplastics into water bodies also depends on the characteristics of sewer diversion structures used as flow control devices. In this work, an experimental investigation was carried out to evaluate the outflow of microplastic particles, consisting of different types of nylon fibers, from a side weir located on a channel with a rectangular section. A specific methodology was developed for the fiber sampling and outflow assessment after the tests were performed. For the tested configurations, an increase in fibers discharged up to 196.15% was measured as the water flow rate increased by 62.75%, combined with an increase in the side weir length up to 40% and a decrease in the crest height up to 20%. The size and weight of the different fibers showed a low impact due to their low inertia, and their motion was governed by the water flow. An empirical equation to evaluate the fiber outflow as a function of water flow rate and side weir geometric characteristics was also proposed and calibrated for the experimentally tested ranges of the dimensionless lateral water outflow Q* = 0.51–0.83 and of the dimensionless geometric parameter S* = 0.114–0.200. These first experimental results make it possible to carry out a preliminary assessment of the impact of CSOs in terms of microplastics spilled into water bodies.

Assessment of the Decomposition of Oxo- and Biodegradable Packaging Using FTIR Spectroscopy

The strength and resistance of plastics at the end of their service life can hinder their degradation. The solution to this problem may be materials made of biodegradable and oxo-biodegradable plastics. The aim of this research was to determine the degree and nature of changes in the composition and structure of composted biodegradable and oxo-biodegradable bags. The research involved shopping bags and waste bags available on the Polish market. The composting of the samples was conducted in an industrial composting plant. As a result of the research, only some of the composted samples decomposed. After composting, all samples were analysed using FTIR (Fourier Transformation Infrared) spectroscopy. Carbonyl index and hierarchical cluster analysis method was used to detect similarities between the spectra of the new samples. The analysis of the obtained results showed that FTIR spectroscopy is a method that can be used to confirm the degradation and detect similarities in the structure of the analysed materials. The analysis of spectra obtained with the use of FTIR spectroscopy indicated the presence of compounds that may be a potential source of compost contamination. Plastics with certificates confirming their biodegradability and compostability should be completely biodegradable, i.e., each element used in their production should be biodegradable and safe for the environment.

Sewage sludge as a source of microplastics in the environment: A review of occurrence and fate during sludge treatment

Modern wastewater treatment plants (WWTPs) effectively remove microplastics (MPs) from wastewater and unsurprisingly concentrate them in sludge. Hence through its beneficial use and disposal, sludge causes secondary release pathways of an estimated average amount of 10⁶ to 10¹⁴ wastewater-based MPs to various environmental compartments yearly. Despite these numbers, studies investigating sludge are scarce. Currently, majority of the studies in the field focus on identifying the magnitude of the problem, whereas research investigating the fate and effects of MPs during sludge treatment are very rare. This review aims to bring together and critically evaluate the limited studies conducted about MPs in the sludge treatment line and bring out the key gaps and research needs in the area. Studies conducted so far indicate that depending on the type, size, and amount of MPs, their effects during anaerobic digestion differ, with some studies demonstrating serious negative impact on biogas production. Possible effect mechanisms are also suggested such as formation of reactive oxygen species (ROS) and leaching of toxic chemicals. Moreover, a potential for sludge treatment processes (thickening, dewatering, drying, stabilization, etc.) to change the characteristics and the number of MPs, which may increase surface area available for adsorption and desorption of pollutants, was observed. Review uncovers that, in the broad universe of MPs, some highly abundant ones in sludge such as polypropylene, polyurethane, polycarbonate, and acrylic are not yet investigated in sludge treatment. Future research should focus not only to investigate the fate/effects but to fully understand the mechanisms behind these, which is missing in many studies reviewed. Besides, new studies show that effect of MPs start from the floc formation stage during biological treatment, which in fact determine the final sludge behavior in thickening and dewatering. Therefore, holistic approaches starting from wastewater till sludge exits WWTP seem necessary. Substantiating from polymer chemistry and response of plastics to stress conditions, review suggests possibilities of deterioration during sludge treatment processes. It becomes evident that some totally uninvestigated aspects such as disintegration conducted before stabilization, can change the fate of MPs during sludge treatment and may bring new perspectives to the solution of the problem.

Biodegradation of bisphenol-A polycarbonate plastic by Pseudoxanthomonas sp. strain NyZ600

Bisphenol-A polycarbonate (PC) is a widely used engineering thermoplastic and its release has caused damage to the ecosystem. Microbial degradation of plastic represents a sustainable approach for PC reduction. In this study, a bacterial strain designated Pseudoxanthomonas sp. strain NyZ600 capable of degrading PC was isolated from activated sludge by using diphenyl carbonate as a surrogate substrate. Within a 30-day period of incubating with strain NyZ600, PC films were analyzed with atomic force microscopy, scanning electron microscope, water contact angle, X-ray photoelectron spectroscopy, fourier transform infrared spectroscopy, differential scan calorimeter and thermogravimetric analysis technique. The analyses results indicated that the treated PC films were bio-deteriorated and formed some "corrosion pits" on the PC film surface. In addition, strain NyZ600 performed broad depolymerization of PC indicated by the reduction of Mn from 23.55 to 16.75 kDa and Mw from 45.67 to 31.97 kDa and two degradation products bisphenol A and 4-cumylphenol (the two monomers of PC) were also found, which established that PC were biodegraded by strain NyZ600. Combing all above results, it is clear that the strain NyZ600 can degrade PC which provides a unique example for bacterial degradation of PC and a feasibility for the removal of PC waste.

Comparative assessment of marine weathering of ROP-derived biopolymers against conventional plastics

Bio-based plastics were designed to replace single-use plastics and to cause less post-consumer environmental damage. This paper assesses the weathering of four bio-based polymers created by ring opening polymerization (ROP) promoted by a previously reported Ti-based catalyst, to detect any problems before production was scaled up. Samples were aged in seawater to identify degradation products and monitor structural changes. Surfaces evidenced degradation and a range of leaching products was observed. Aside from compounds used in the preparation of the plastics (i.e. residual monomers and benzyl alcohol), the degradation products included carboxylic acids (often found in plastic leachate), oxacyclohexadecan-2-one (potentially toxic to aquatic life) and triphenylmethane (potential carcinogen). Overall, there were fewer structural changes in the fossil fuel based polymer (PS) and in the commercially available bio-based plastic studied for comparison purposes than the lab based bio-based polymers.

Bridging Three Gaps in Biodegradable Plastics: Misconceptions and Truths About Biodegradation

In the wake of plastic pollution increasing around the world, biodegradable plastics are one of the fastest-growing segments within the global plastics market. The biodegradation of these plastics depends on diverse factors including, but not limited to, the physicochemical structure of the materials, environmental conditions, and the microbial populations involved in the biodegradation. Although laboratory-based biodegradation tests simulate natural processes, they cannot precisely mimic the natural biodegradation of biodegradable plastics due to the disparity of several factors. In addition, the biodegradation levels claimed and/or reported by individuals and studies in different environments vary to a great extent. Biodegradable plastics are considered a sustainable alternative to non-biodegradable conventional plastics and are being promoted as an eco-friendlier choice for consumers. However, biodegradable plastics might not be as biodegradable as commonly believed, particularly in natural environments. This mini-review aims to bridge the following three gaps in biodegradable plastics by elucidating the common misconceptions and truths about biodegradation: i) the gaps among reported biodegradation level of biodegradable plastics; ii) the gaps between the biodegradation conditions in the controlled laboratory system and in the natural environment; and iii) the gaps between public perception and the actual environmental fate of biodegradable products. These gaps are critically reviewed with feasible solutions. This work will ease the assessment of biodegradable plastics and provide sound communication on corresponding claims–a prerequisite for successful market performance.

Source, distribution and emerging threat of micro- and nanoplastics to marine organism and human health: Socio-economic impact and management strategies

The nature of micro- and nanoplastics and their harmful consequences has drawn significant attention in recent years in the context of environmental protection. Therefore, this paper aims to provide an overview of the existing literature related to this evolving subject, focusing on the documented human health and marine environment impacts of micro- and nanoplastics and including a discussion of the economic challenges and strategies to mitigate this waste problem. The study highlights the micro- and nanoplastics distribution across various trophic levels of the food web, and in different organs in infected animals which is possible due to their reduced size and their lightweight, multi-coloured and abundant features. Consequently, micro- and nanoplastics pose significant risks to marine organisms and human health in the form of cytotoxicity, acute reactions, and undesirable immune responses. They affect several sectors including aquaculture, agriculture, fisheries, transportation, industrial sectors, power generation, tourism, and local authorities causing considerable economic losses. This can be minimised by identifying key sources of environmental plastic contamination and educating the public, thus reducing the transfer of micro- and nanoplastics into the environment. Furthermore, the exploitation of the potential of microorganisms, particularly those from marine origins that can degrade plastics, could offer an enhanced and environmentally sound approach to mitigate micro- and nanoplastics pollution.

The Effect of Poly (Ethylene glycol) Emulation on the Degradation of PLA/Starch Composites

As a hydrophilic renewable polymer, starch has been widely used in biocompatible plastics as a filler for more than two decades. The present study aimed at investigating the effects of polyethylene glycol (PEG), as a plasticizer, on the physicochemical properties of a hybrid composite-polylactic acid (PLA) and thermoplastic starch (TPS). A solvent evaporation process was adopted to gelatinize the starch and disparate PEG contents ranging from 3 to 15 wt.% (with respect to the sample weight) were examined. It was revealed that the increase in the PEG content was accompanied by an increment in the starch gelatinization degree. Referring to the microstructural analyses, the TPS/PLA mixture yielded a ductile hybrid composite with a fine morphology and a uniform phase. Nevertheless, two different solvents, including acetone and ethanol, were used to assess if they had any effect on the hybrid's morphology, tensile strength and thermal properties. It was found that ethanol culminated in a porous hybrid composite with a finer morphology and better starch distribution in the PLA structure than acetone. As the result of PEG addition to the composite, the crystallinity and tensile strength were decreased, whereas the elongation increased. The hydrolytic degradation of samples was assessed under different pH and thermal conditions. Moreover, the microbial degradation of the PLA/TPS hybrid composite containing different PEG molar fractions was investigated in the soil for 45 days. The rate of degradation in both hydrolytic and biodegradation increased in the samples with a higher amount of PEG with ethanol solvent.

Review on the Biological Degradation of Polymers in Various Environments

Biodegradable plastics can make an important contribution to the struggle against increasing environmental pollution through plastics. However, biodegradability is a material property that is influenced by many factors. This review provides an overview of the main environmental conditions in which biodegradation takes place and then presents the degradability of numerous polymers. Polylactide (PLA), which is already available on an industrial scale, and the polyhydroxyalkanoates polyhydroxybutyrate (PHB) and polyhydroxybutyrate-co-valerate (PHBV), which are among the few plastics that have been proven to degrade in seawater, will be discussed in detail, followed by a summary of the degradability of further petroleum-, cellulose-, starch-, protein- and CO₂-based biopolymers and some naturally occurring polymers.

Fragmentation of plastic objects in a laboratory seawater microcosm

We studied the fragmentation of conventional thermoplastic and compostable plastic items in a laboratory seawater microcosm. In the microcosm, polyurethane foams, cellulose acetate cigarette filters, and compostable polyester and polylactic acid items readily sank, whereas polyethylene air pouches, latex balloons, polystyrene foams and polypropylene cups remained afloat. Microbial biofilms dominated by Cyanobacteria, Proteobacteria, Planctomycetes and Bacteriodetes grew on the plastics, and caused some of the polyethylene items to sink to the bottom. Electrical resistances (ER) of plastic items decreased as function of time, an indication that seawater had penetrated into microscopic crevices in the plastic that had developed over time. Rate constants for ER decrease in polyethylene items in the microcosm were similar to tensile elongation decrease of polyethylene sheets floating in sea, measured previously by others. Weight loss of plastic items was ≤ 1% per year for polyethylene, polystyrene and polypropylene, 3-5% for latex, polyethylene terephthalate and polyurethane, 15% for cellulose acetate, and 7-27% for polyester and polylactic acid compostable bags. The formation of microplastics observed in the microcosm was responsible for at least part of the weight loss. This study emphasizes the need to obtain experimental data on plastic litter degradation under conditions that are realistic for marine environments.

Microplastic Contamination in Freshwater Environments: A Review, Focusing on Interactions with Sediments and Benthic Organisms

Plastic is one of the most commonly produced and used materials in the world due to its outstanding features. However, the worldwide use of plastics and poor waste management have led to negative impacts on ecosystems. Plastic degradation in the environment leads to the generation of plastic particles with a size of <5 mm, which are defined as microplastics (MPs). These represent a global concern due to their wide dispersion in water environments and unclear potential ecotoxicological effects. Different studies have been performed with the aim of evaluating the presence and impacts of MPs in the marine environment. However, the presence of MPs in freshwater systems is still poorly investigated, making data retrieval a difficult task. The purpose of this review is to identify the main aspects concerning MPs pollution sources in lakes and rivers, with a focus on freshwater sediments as a site of accumulation and as the habitat of benthic organisms, which are key components of food webs and play a fundamental role in energy/contaminant transfer processes, but are still poorly considered. Through this review, the sources and fate of MPs in freshwater are analysed, ecotoxicological studies focused on sediments and benthic fauna are exposed, the most frequently used sampling and analysis strategies are reported, and future trends of MPs analysis in this field are proposed.

Comparative Investigation on the Soil Burial Degradation Behaviour of Polymer Films for Agriculture before and after Photo-Oxidation

Polymer films based on biodegradable polymers, polyethylene (PE) and modified PE with oxo-degradable additive were prepared by film blowing. Carbon black (1%) was added to all the films. Commercial biodegradable Ecovio^® and Mater-Bi^® samples were used. Mechanical properties, soil burial degradation and surface wettability were investigated, before and after UV irradiation. Chemical modifications induced by UV and soil degradation, or a synergic effect, were highlighted by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR). Photo-oxidized film samples with an elongation at break equal to 50% and 0.5 the initial value were selected for the soil burial degradation test at 30 °C. Weight loss measurements were used to follow biodegradation in soil. Predictably, the degradation in soil was higher for biodegradable polymer-based films than for the PE-based ones. UV irradiation increased surface wettability and encouraged the disintegration in soil of all the samples. In fact, photo-oxidation produced a molar mass reduction and hydrophilic end groups, thus increasing surface erosion and weight loss. This paper not only supplies new criteria to evaluate the performance of biodegradable films in agriculture, before and after lifetime, but also provides a comparative analysis on the soil burial degradation behaviour with traditional ones.

Microplastic ingestion cause intestinal lesions in the intertidal fish Girella laevifrons

We exposed juvenile intertidal fish to different amounts of Poly(styrene-co-divinylbenzene) microplastics in their diet. We fed ten individuals with pellets containing 0.01 g, another ten fish with pellets containing 0.1 g of PS, and ten fish without plastic as control. After 45 days of treatment, the whole intestine was removed, and the histological evaluation started immediately. We evaluated inflammation due to leukocyte infiltration (Lk), circulatory disorders like Hypermeia (Hyp), and regressive changes in the intestinal tissue, assessing Crypt cell loss (Ccl) and Villi cell loss (Vcl). The severity of the lesions increased according to the microplastic concentration. In the fish group feeding on microplastics, we found that leukocyte infiltration and hyperemia were more severe in the higher exposure group compared to the lower exposure; and crypt cell loss and villi cell loss increased significantly due to Poly(styrene-co-divinylbenzene) microplastic physical abrasion.

Aerobic biodegradation in freshwater and marine environments of textile microfibers generated in clothes laundering: Effects of cellulose and polyester-based microfibers on the microbiome

The aerobic biodegradation of common textiles that shed microfibers during laundering was evaluated under the action of microbes found in the environment, such as lake and seawater, and activated sludge at a low concentration from a wastewater treatment plant (WWTP). Under these conditions, the biodegradation potential was the same in all the experiments: Microcrystalline Cellulose (MCC) > Cotton > Rayon > Polyester/Cotton ≫ Polyester. Nevertheless, for cotton and rayon yarns, >70% biodegradation was achieved with activated sludge at low concentration and lake water, whereas in seawater, about 50% degradation was reached. Polyester did not appreciably degrade. The biodegradation results herein indicate potential not absolutes in nature. The bacterial diversity analyses in the different biodegradation inoculums show that there are distinct bacterial communities related to the assimilation and mineralization of complex carbohydrates that were promoted with the cellulosic MCC, cotton, and rayon samples different than the polyester sample.

Quantification of Synthetic Polyesters from Biodegradable Mulch Films in Soils

Soil biodegradable mulch films composed of the polyester polybutylene adipate-co-terephthalate (PBAT) are being increasingly used in agriculture. Analytical methods to quantify PBAT in field soils are needed to assess its soil occurrence and fate. Here, we report an analytical method for PBAT in soils that couples Soxhlet extraction or accelerated solvent extraction (ASE) with quantitative protonnuclear magnetic resonance (q-¹H NMR) spectroscopy detection. The ¹H NMR peak areas of aromatic PBAT protons increased linearly with PBAT concentrations dissolved in deuterated chloroform (CDCl₃), demonstrating accurate quantitation of PBAT by q-¹H NMR. Spike-recovery experiments involving PBAT addition to model sorbents and soils showed increased PBAT extraction efficiencies into chloroform (CHCl₃) with methanol (MeOH) as cosolvent, consistent with MeOH competitively displacing PBAT from H-bond donating sites on mineral surfaces. Systematic variations in solvent composition and temperatures in ASE revealed quantitative PBAT extraction from soil with 90/10 volume % CHCl₃/MeOH at 110-120 °C. Both Soxhlet extraction and ASE resulted in the complete recovery of PBAT added to a total of seven agricultural soils covering a range of physicochemical properties, independent of whether PBAT was added to soils dissolved in CHCl₃, as film, or as particles. Recovery was also complete for PBAT added to soil in the form of a commercial soil biodegradable mulch film with coextractable polylactic acid (PLA). The presented analytical method enables accurate quantification and biodegradation monitoring of PBAT in agricultural field soils.

Photo-Oxidative and Soil Burial Degradation of Irrigation Tubes Based on Biodegradable Polymer Blends

Irrigation tubes based on biodegradable polymers were prepared via an extrusion-drawing process by Irritec and compared to conventional pipes made of high-density polyethylene (HDPE). A commercial polylactide/poly (butyleneadipate-co-butyleneterephthalate) (PLA/PBAT) blend (Bio-Flex^®) and Mater-Bi^® were used. The polymers were characterized from rheological and mechanical points of view. Irrigation pipes were subjected to photoaging with continued exposure to UV radiation up to 22 days. The degradability in the soil of irrigation tube samples was studied. The influence of temperature and UV irradiation on soil burial degradation was investigated. A soil burial degradation test was carried out at 30 °C and 50 °C for up to 70 days. The degree of degradation was evaluated from the weight loss percentage. The degradation rate of irrigation tube samples based on Mater-Bi^® was higher at 30 °C and was stimulated after 14 days of UV irradiation. Higher temperatures or UV aging encouraged the disintegration in soil of Bio-Flex^®-based irrigation tubes. Furthermore, tube samples, before and after UV and soil burial degradation, were analyzed by Attenuated Total Reflection-Fourier Transform Infra-Red (ATR-FTIR) spectroscopy.

Microfibers generated from the laundering of cotton, rayon and polyester based fabrics and their aquatic biodegradation

The effect of fiber type (cotton, polyester, and rayon), temperature, and use of detergent on the number of microfibers released during laundering of knitted fabrics were studied during accelerated laboratory washing (Launder-Ometer) and home laundering experiments. Polyester and cellulose-based fabrics all shed significant amounts of microfibers and shedding levels were increased with higher water temperature and detergent use. Cellulose-based fabrics released more microfibers (0.2-4 mg/g fabric) during accelerated laundering than polyester (0.1-1 mg/g fabric). Using well-controlled aquatic biodegradation experiments it was shown that cotton and rayon microfibers are expected to degrade in natural aquatic aerobic environments whereas polyester microfibers are expected to persist in the environment for long periods of time.