Plastics in biosolids from 1950 to 2016: A function of global plastic production and consumption

A review of the ecotoxicological status of microplastic pollution in African freshwater systems

Microplastics (MPs) have found extensive application globally due to their low cost, flexibility and light weight. Microplastic pollution is a growing environmental concern that poses significant threats to aquatic ecosystems worldwide, including African freshwater systems. Nevertheless, although Africa houses some of the deepest and largest freshwater rivers and lakes in the world such as Lake Tanganyika and Victoria, River Congo and the Nile, there is limited information available regarding the presence of MPs in these inland waters. Selected published data on MPs in African freshwater systems, including sediments, biota, rivers, and lakes, were incorporated in this review. The study discovered that the sampling technique employed has a major impact on the morphological characteristics and abundance of MPs in African freshwater systems. Fibers and fragments were the most common shapes; black, white, and transparent were the most prevalent colors; and polyethene terephthalate, polystyrene, and polypropylene were the frequently dominant polymers. As the distance between the sampling sites increased geographically, the polymer similarities declined. MPs have been found to translocate into body cells and tissues where they are capable of causing genetic mutations, cytotoxicity, oxidative stress and neurotoxicity. In Africa, MPs are poorly managed and monitored, and there has been insufficient research done on the possibility that they could be present in drinking water. Considering the fact that humans in the continent are exposed to freshwater and aquatic organisms, the risk assessment routes are currently unvalidated, therefore it was recommended that African nations should strengthen their capacity for plastic management and environmental monitoring. This review provides up to date information on the occurrence, prevalence, ecotoxicity and management of MPs across African freshwater systems.

Looking beyond the obvious: The ecotoxicological impact of the leachate from fishing nets and cables in the marine mussel Mytilus galloprovincialis

Once in the marine environment, fishing nets and cables undergo weathering, breaking down into micro and nano-size particles and leaching plastic additives, which negatively affect marine biota. This study aims to unravel the ecotoxicological impact of different concentrations of leachate obtained from abandoned or lost fishing nets and cables in the mussel Mytilus galloprovincialis under long-term exposure (28 days). Biochemical biomarkers linked to antioxidant defense system, xenobiotic biotransformation, oxidative damage, genotoxicity, and neurotoxicity were evaluated in different mussel tissues. The chemical nature of the fishing nets and cables and the chemical composition of the leachate were assessed and metals, plasticizers, UV stabilizers, flame retardants, antioxidants, dyes, flavoring agents, preservatives, intermediates and photo initiators were detected. The leachate severely affected the antioxidant and biotransformation systems in mussels' tissues. Following exposure to 1 mg·L-1 of leachate, mussels' defense system was enhanced to prevent oxidative damage. In contrast, in mussels exposed to 10 and 100 mg·L-1 of leachate, defenses failed to overcome pro-oxidant molecules, resulting in genotoxicity and oxidative damage. Principal component analysis (PCA) and Weight of Evidence (WOE) evaluation confirmed that mussels were significantly affected by the leachate being the hazard of the leachate concentrations of 10 mg·L-1 ranked as major, while 1 and 100 mg·L-1 was moderate. These results highlighted that the leachate from fishing nets and cables can be a threat to the heath of the mussel M. galloprovincialis.

Microplastics in multi-environmental compartments: Research advances, media, and global management scenarios

During the past decades, microplastics (MPs) have become an emerging concern due to their persistence and potential environmental threat. MP pollution has become so drastic that it has been found in the human food chain, breast milk, polar regions, and even the Himalayan basin, lake, etc. Inflammation, pulmonary hypertension, vascular occlusions, increased coagulability and blood cell cytotoxicity, disruption of immune function, neurotoxicity, and neurodegenerative diseases can all be brought on by severe microplastic exposure. Although many MPs studies have been performed on single environmental compartments, MPs in multi-environmental compartments have yet to be explored fully. This review aims to summarize the muti-environmental media, detection tools, and global management scenarios of MPs. The study revealed that MPs could significantly alter C flow through the soil-plant system, the structure and metabolic status of the microbial community, soil pH value, biomass of plant shoots and roots, chlorophyll, leaf C and N contents, and root N contents. This review reveals that MPs may negatively affect many C-dependent soil functions. Different methods have been developed to detect the MPs from these various environmental sources, including microscopic observation, density separation, Raman, and FT-IR analysis. Several articles have focused on MPs in individual environmental sources with a developed evaluation technique. This review revealed the extensive impacts of MPs on soil-plant systems, microbial communities, and soil functions, especially on water, suggesting possible disturbances to vital ecological processes. Furthermore, the broad range of detection methods explored emphasizes the significance of reliable analytical techniques in precisely evaluating levels of MP contamination in various environmental media. This paper critically discusses MPs' sources, occurrences, and global management scenarios in all possible environmental media and ecological health impacts. Future research opportunities and required sustainable strategies have also been suggested from Bangladesh and international perspectives based on challenges faced due to MP's pollution.

Toxicity assessment of animal manure composts containing environmental microplastics by using earthworms Eisenia andrei

Nowadays, animal manure composting constitutes a sustainable alternative for farmers to enhance the level of nutrients within soils and achieve a good productivity. However, pollutants may be present in manures. This study focuses on the detection of environmental microplastics (EMPs) into composts, as well as on the assessment of their potential toxicity on the earthworm Eisenia andrei. To these aims, animals were exposed to two types of compost, namely bovine (cow) and ovine (sheep) manure, besides to their mixture, for 7 and 14 days. The presence and characterization of EMPs was evaluated in all the tested composts, as well as in tissues of the exposed earthworms. The impact of the tested composts was assessed by a multi-biomarker approach including cytotoxic (lysosomal membrane stability, LMS), genotoxic (micronuclei frequency, MNi), biochemical (activity of catalase, CAT, and glutathione-S-transferase, GST; content of malondialdehyde, MDA), and neurotoxic (activity of acetylcholinesterase, AChE) responses in earthworms. Results indicated the presence of high levels of EMPs in all the tested composts, especially in the sheep manure (2273.14 ± 200.89 items/kg) in comparison to the cow manure (1628.82 ± 175.23 items/kg), with the size <1.22 μm as the most abundant EMPs. A time-dependent decrease in LMS and AChE was noted in exposed earthworms, as well as a concomitant increase in DNA damages (MNi) after 7 and 14 days of exposure. Also, a severe oxidative stress was recorded in animals treated with the different types of compost through an increase in CAT and GST activities, and LPO levels, especially after 14 days of exposure. Therefore, it is necessary to carefully consider these findings for agricultural good practices in terms of plastic mitigation in compost usage, in order to prevent any risk for environment health.

Analysis of microplastics in commercial vegetable edible oils from Italy and Spain

In this work, assessment of microplastics (MPs) in commercial vegetable edible oils from Italy and Spain, including extra-virgin olive oil, olive oil, sunflower oil, and mixed seed oil, has been conducted for the first time. The method was based on sample dilution with ethanol:n-hexane (1:3, v/v), homogenization, vacuum filtration on macroporous silicon filters with 5 μm pore diameter to collect MPs, and automatic µ-FTIR spectroscopy for MPs detection and characterization. In the analysis of oil samples, a mean MPs abundance of 1140 ± 350 MPs/L was found. Observed MPs were characterized, being most of them fragments (81.2 %), with particle sizes < 100 µm (77.5 %), and mainly composed of polyethylene (50.3 %) and polypropylene (28.7 %), among others. Statistical analysis revealed that there were not significant differences (p-value > 0.05) in the abundance of MPs between oil samples or types.

Predictive modelling reveals Australian continental risk hotspots for marine debris interactions with key threatened species

Anthropogenic debris is a global threat that impacts threatened species through various lethal and sub-lethal consequences, as well as overall ecosystem health. This study used a database of over 24,000 beach surveys of marine debris collated by the Australian Marine Debris Initiative from 2012 to 2021, with two key objectives: (1) identify variables that most influence the occurrence of debris hotspots on a continental scale and (2) use these findings to identify likely hotspots of interaction between threatened species and marine debris. The number of particles found in each beach survey was modelled alongside fifteen biological, social, and physical spatial variables including land use, physical oceanography, population, rainfall, distance to waste facilities, ports, and mangroves to identify the significant drivers of debris deposition. The model of best fit for predicting debris particle abundance was calculated using a generalized additive model. Overall, debris was more abundant at sites near catchments with high annual rainfall (mm), intensive land use (km2), and that were nearer to ports (km) and mangroves (km). These results support previous studies which state that mangroves are a significant sink for marine debris, and that large ports and urbanized catchments are significant sources for marine debris. We illustrate the applicability of these models by quantifying significant overlap between debris hotspots and the distributions for four internationally listed threatened species that exhibit debris interactions; green turtle (26,868 km2), dugong (16,164 km2), Australian sea lion (2903 km2) and Flesh-footed Shearwater (2413 km2). This equates to less than 1% (Flesh-footed Shearwater, Australian sea lion), over 2% (green sea turtle) and over 5% (dugong) of their habitat being identified as areas of high risk for marine debris interactions. The results of this study hold practical value, informing decision-making processes, managing debris pollution at continental scales, as well as identifying gaps in species monitoring.

Microplastic Human Dietary Uptake from 1990 to 2018 Grew across 109 Major Developing and Industrialized Countries but Can Be Halved by Plastic Debris Removal

Microplastics (MPs), plastic particles smaller than 5 mm, are now a growing environmental and public health issue, as they are detected pervasively in freshwater and marine environments, ingested by organisms, and then enter the human body. Industrial development drives this environmental burden caused by MP formation and human uptake by elevating plastic pollution levels and shaping the domestic dietary structure. We map the MP human uptake across 109 global countries on five continents from 1990 to 2018, focusing on the world's major coastlines that are affected by plastic pollution that affects the United Nations' Sustainable Development Goals (SDGs): SDG 6 (Clean Water and Sanitation), SDG 14 (Life Below Water), and SDG 15 (Life on Land). Amid rapid industrial growth, Indonesia tops the global per capita MP dietary intake at 15 g monthly. In Asian, African, and American countries, including China and the United States, airborne and dietary MP uptake increased over 6-fold from 1990 to 2018. Eradicating 90% of global aquatic plastic debris can help decrease MP uptake by more than 48% in Southeast Asian countries that peak MP uptake. To reduce MP uptake and potential public health risks, governments in developing and industrialized countries in Asia, Europe, Africa, and North and South America should incentivize the removal of free plastic debris from freshwater and saltwater environments through advanced water treatment and effective solid waste management practices.

Mass quantification of nanoplastics at wastewater treatment plants by pyrolysis-gas chromatography-mass spectrometry

Municipal wastewater treatment plants (WWTPs) play a crucial role in the collection and redistribution of plastic particles from both households and industries, contributing to their presence in the environment. Previous studies investigating the levels of plastics in WWTPs, and their removal rates have primarily focused on polymer type, size, shape, colour, and particle count, while comprehensive understanding of the mass concentration of plastic particles, particularly those <1 µm (nanoplastics), remains unclear and lacking. In this study, pyrolysis gas chromatography-mass spectrometry was used to simultaneously determine the mass concentration of nine selected polymers (i.e., polyethylene (PE), polypropylene (PP), polystyrene (PS), poly(ethylene terephthalate) (PET), nylon 6, nylon 66, polyvinylchloride (PVC), poly(methyl methacrylate) (PMMA) and polycarbonate (PC)) below 1 µm in size across the treatment processes or stages of three WWTPs in Australia. All the targeted nanoplastics were detected at concentrations between 0.04 and 7.3 µg/L. Nylon 66 (0.2-7.3 µg/L), PE (0.1-6.6 µg/L), PP (0.1-4.5 µg/L), Nylon 6 (0.1-3.6 µg/L) and PET (0.1-2.2 µg/L), were the predominant polymers in the samples. The mass concentration of the total nanoplastics decreased from 27.7, 18 and 9.1 µg/L in the influent to 1, 1.4 and 0.8 µg/L in the effluent, with approximate removal rates of 96 %, 92 % and 91 % in plants A, B and C, respectively. Based on annual wastewater effluent discharge, it is estimated that approximately 24, 2 and 0.7 kg of nanoplastics are released into the environment per year for WWTPs A, B and C, respectively. This study investigated the mass concentrations and removal rates of nanoplastics with a size range of 0.01-1 µm in wastewater, providing important insight into the pollution levels and distribution patterns of nanoplastics in Australian WWTPs.

Effects of COVID-19 on coastal and marine environments: Aggravated microplastic pollution, improved air quality, and future perspective

The COVID-19 pandemic during 2020-2023 has wrought adverse impacts on coastal and marine environments. This study conducts a comprehensive review of the collateral effects of COVID-19 on these ecosystems through literature review and bibliometric analysis. According to the output and citation analysis of these publications, researchers from the coastal countries in Asia, Europe, and America payed more attentions to this environmental issue than other continents. Specifically, India, China, and USA were the top three countries in the publications, with the proportion of 19.55%, 18.99%, and 12.01%, respectively. The COVID-19 pandemic significantly aggravated the plastic and microplastic pollution in coastal and marine environments by explosive production and unproper management of personal protective equipment (PPE). During the pandemic, the estimated mismanaged PPE waste ranged from 16.50 t/yr in Sweden to 250,371.39 t/yr in Indonesia. In addition, the PPE density ranged from 1.13 × 10-5 item/m2 to 2.79 item/m2 in the coastal regions worldwide, showing significant geographical variations. Besides, the emerging contaminants released from PPE into the coastal and marine environments cannot be neglected. The positive influence was that the COVID-19 lockdown worldwide reduced the release of air pollutants (e.g., fine particulate matter, NO2, CO, and SO2) and improved the air quality. The study also analyzed the relationships between sustainable development goals (SDGs) and the publications and revealed the dynamic changes of SDGs in different periods the COVID-19 pandemic. In conclusion, the air was cleaner due to the lockdown, but the coastal and marine contamination of plastic, microplastic, and emerging contaminants got worse during the COVID-19 pandemic. Last but not least, the study proposed four strategies to deal with the coastal and marine pollution caused by COVID-19, which were regular marine monitoring, performance of risk assessment, effective regulation of plastic wastes, and close international cooperation.

Occurrence, spatiotemporal trends, fate, and treatment technologies for microplastics and organic contaminants in biosolids: A review

This review provides a comprehensive overview of the occurrence, fate, treatment and multi-criteria analysis of microplastics (MPs) and organic contaminants (OCs) in biosolids. A meta-analysis was complementarily analysed through the literature to map out the occurrence and fate of MPs and 10 different groups of OCs. The data demonstrate that MPs (54.7% occurrence rate) and linear alkylbenzene sulfonate surfactants (44.2% occurrence rate) account for the highest prevalence of contaminants in biosolids. In turn, dioxin, polychlorinated biphenyls (PCBs) and phosphorus flame retardants (PFRs) have the lowest rates (<0.01%). The occurrence of several OCs (e.g., dioxin, per- and polyfluoroalkyl substances, polycyclic aromatic hydrocarbons, pharmaceutical and personal care products, ultraviolet filters, phosphate flame retardants) in Europe appear at higher rates than in Asia and the Americas. However, MP concentrations in biosolids from Australia are reported to be 10 times higher than in America and Europe, which required more measurement data for in-depth analysis. Amongst the OC groups, brominated flame retardants exhibited exceptional sorption to biosolids with partitioning coefficients (log Kd) higher than 4. To remove these contaminants from biosolids, a wide range of technologies have been developed. Our multicriteria analysis shows that anaerobic digestion is the most mature and practical. Thermal treatment is a viable option; however, it still requires additional improvements in infrastructure, legislation, and public acceptance.

Tracing the origins of plastics in biosolids: The role of sewerage pipe materials and trade waste

Plastics are ubiquitous in virtually every environment on earth. While the specific sources of plastics entering wastewater are not well known, growing evidence suggests sewage sludge (biosolids) can be a sink for plastics. One potential source could be the sewerage pipe materials used to transport sewage between premises and wastewater treatment plants (WWTPs). To evaluate the significance of sewerage piping as a source of biosolids plastics concentrations, we compared the proportion of the total network (by length and surface area) of polyethylene (PE), polyvinylchloride (PVC), and polypropylene (PP) pipes from 10 WWTPs against their biosolids mass concentrations (mg plastic/g biosolid). Among the 10 catchments, the percentage of the network consisting of PP piping ranged from 0 to 1 %, with 0.8-21 % for PE, and 8-73 % for PVC. Biosolids plastics concentrations ranged from 0.09 to 8.62 mg/g (mg plastic/g biosolid) for PP and PE, respectively. For all three plastics, there was no significant Pearson correlation (r < 0.4) between the biosolids concentration (dry weight mg/g) and the proportion of the network material of the sewerage piping as plastic (either length or surface area). A comparison of trade waste entering a subset of 6 WWTP showed the highest biosolid principal components analysis (PCA) associations between loads of plastics (g/day) and automotive wash bays, general manufacturing, hospitals, laboratories, food manufacturing, laundry and dry cleaning, and cooling towers. A stepwise regression analysis indicated pipe length and surface area, as well as automotive wash bays and food manufacturing may be significant. While our data gave mixed results on the attribution of the sources of plastics entering WWTPs, it suggests that sewerage infrastructure and trade waste may play some role. Future studies should investigate the leachability of sewerage infrastructure and contributions from specific trade waste categories to determine their significance in plastics entering WWTPs.

Quantitative analysis of nanoplastics in environmental and potable waters by pyrolysis-gas chromatography-mass spectrometry

Nanoplastics are emerging environmental contaminants, but their presence in environmental and potable water remains largely understudied due to the absence of quantitative analytical methods. In this study, we developed and validated a pretreatment method that combines hydrogen peroxide digestion and Amicon® Stirred Cell ultrafiltration (at 100 kDa, approximately 10 nm) with subsequent detection by pyrolysis gas chromatography-mass spectrometry (Pyr-GC/MS). This method allows for the simultaneous identification and quantification of nine selected nanoplastic types, including poly(ethylene terephthalate) (PET), polyethylene (PE), polycarbonate (PC), polypropylene (PP), poly(methyl methacrylate) (PMMA), polystyrene (PS), polyvinylchloride (PVC), nylon 6, and nylon 66, in environmental and potable water samples based on polymer-specific mass concentration. Limits of quantification ranged from 0.01 to 0.44 µg/L, demonstrating the method's ability to quantitatively detect nanoplastics in environmental and potable water samples. Most of the selected nanoplastics were detected at concentrations of between 0.04 and 1.17 µg/L, except for PC, which was consistently below the limit of detection (<0.44 µg/L). The prevalent polymer components in the samples were PE (0.10 - 1.17 µg/L), PET (0.06 - 0.91 µg/L), PP (0.04 - 0.79 µg/L), and PS (0.06 - 0.53 µg/L) nanoplastics. The presented analytical method offers an accurate means to identify, quantify, and monitor nanoplastics in complex environmental and potable water samples. It fills gaps in our understanding of nanoplastic pollution levels, providing a valuable methodology and crucial reference data for future studies.

Biodegradable composite films based on mucilage from Opuntia ficus-indica (Cactaceae): Microstructural, functional and thermal properties

This study evaluated the feasibility of using cactus mucilage (CM) to elaborate biobased composite films blended with styrene-butadiene rubber latex (SBL). The CM was extracted and precipitated with ethanol (CMET) and isopropanol (CMIS). Mucilage-based films were formulated using three levels of mucilage (4, 6, and 8 wt%). The microstructure, thickness, moisture content, density, water contact angle, water vapor permeability, film solubility, thermal stability, and toughness of mucilage films blended with SBL (SBL/CMET and SBL/CMIS) were measured. The properties of mucilage-based films varied systematically, depending on the concentration of mucilage. The addition of SBL to CM film produces compatible, hydrophobic, flexible, and stiffer films with low moisture contents and good barrier properties. The mucilage film incorporated with 6 wt% CMET and CMIS reached the highest Young's modulus of 1512 ± 21 and 1988 ± 55 MPa, respectively. The DSC of produced films reveals that the Tg of SBL/CMIS is lower than that of SBL/CMIS. The synthesized films were structurally stable at high temperatures. The biodegradability of the composite films buried in the ground shows that the produced films are 100 % biodegradable after 40 days. Thus, CM blended with SBL can benefit specific applications, especially food packaging.

Recent Biotechnological Applications of Polyhydroxyalkanoates (PHA) in the Biomedical Sector-A Review

Petroleum-derived plastics are materials of great importance for the contemporary lifestyle, and are widely used commercially because they are low cost, resistant, malleable, and weightless, in addition to their hydrophobic character. However, some factors that confer the qualities of these materials also cause problems, mainly environmental, associated with their use. The COVID-19 pandemic aggravated these impacts due to the high demand for personal protective equipment and the packaging sector. In this scenario, bioplastics are environmentally positive alternatives to these plastics due to their applicability in several areas ranging from packaging, to biomedicine, to agriculture. Polyhydroxyalkanoates (PHAs) are biodegradable biopolymers usually produced by microorganisms as an energy reserve. Their structural variability provides a wide range of applications, making them a viable option to replace polluting materials. PHAs can be applied in various biotechnology sectors, such as producing drug carriers and scaffolds for tissue engineering. This review aimed to survey works published in the last five years on the study and biotechnological application of PHAs in the biomedical sector, exploring the versatility and advantages of their use and helping to understand how to enhance their application.

Microplastics and phthalate esters release from teabags into tea drink: occurrence, human exposure, and health risks

Tea, the most common infusion worldwide, is usually sold in teabags due to the ease of usage. The increase in the use of plastic materials in the food packaging industry has led to an increase in released contaminants, such as microplastics (MPs) and phthalates (PAEs), in various food products including teabags. In this research, the abundance and features of MPs as well as PAEs concentration were investigated in 45 teabag samples of different Persian and German brands. The abundance of MPs in the Persian and German teabag samples was averagely 412.32 and 147.28 items/single teabag, respectively. Also, average PAEs levels in the Persian and German teabag samples were 2.87 and 2.37 mg/g, respectively. The predominant size category of MPs was related to 100-250 μm. Fibers and transparent were the dominant shape and color of detected MPs in teabags, respectively. Polyethylene (PE) and nylon were the most common MP polymer types. The most prominent PAEs congeners in teabag samples were diethylhexyl phthalate (DEHP) and diisobutyl phthalate (DiBP). Furthermore, MP exposure hazard through tea ingestion was analyzed for children and adults. DEHP showed the cancer risk (CR) for children and adults. The findings of this research indicated that high MPs and PAEs levels are released from teabags into tea drinks. Considering a daily drinking of a volume of 150 and 250 mL tea by children and adults, 486 and 810 MPs may enter their bodies, respectively. Thus, tea prepared with teabag-packed herbs may pose a significant health risk for consumers.

Microplastics in Seabird Feces from Coastal Areas of Central Chile

Pollution from plastic waste thrown into the ocean affects all levels of the food chain. Marine species of birds are affected by plastic particles of different sizes, especially the mesoplastics (1 to 10 mm) found in their digestive tract, which mainly cause obstructions. In the case of microplastics (1.000 µm to 1 mm), their presence in the digestive tract of these species has been widely reported. We studied fecal samples of the Dominican gull (Larus dominicanus) (n = 14), Magellanic penguins (Spheniscus magellanicus) (n = 8), and Humboldt penguin (Spheniscus humboldti) (n = 1) obtained from the Wildlife Rehabilitation Center of the Biobío region, Chile. Microfibers of various colors were present in the feces of Dominican gulls and Magellanic penguins, corresponding mainly in composition to polypropylene (PP) (83%) and rayon (77%). These results demonstrate that microplastic particles occur in the coastal environments of central Chile and suggest that they are probably circulating in the food chain.

How many microplastic particles are present in Canadian biosolids?

Application of treated sewage sludge (biosolids) from wastewater treatment plants (WWTPs) to farmlands is an important pathway through which microplastic particles (MPs) enter terrestrial ecosystems. Yet, microplastic concentrations in Canadian biosolids have only been estimated in samples from four WWTPs previously. We aimed to fill this knowledge gap by quantifying microplastics in biosolids from 22 WWTPs located in nine provinces and two commercial fertilizer producers in Canada. All samples had substantial microplastic concentrations ranging from 228 to 1353 particles per gram dry weight (median = 636 particles), which are orders of magnitude greater than MPs reported from earlier investigations of biosolids from other countries. Fibers (median: 86%) were the most common type of MPs observed, followed by fragments (median: 13%). There were no statistically significant differences in the amount of microplastics observed in the biosolids from different geographical regions, WWTP types, and sludge treatment processes. This suggests that diverse combinations of local sewershed characteristics, site-specific treatment approaches, and daily flow at WWTPs may be influencing concentrations of microplastics in biosolids. Our results indicate that microplastic concentrations in biosolids are substantially higher than they are in other environmental matrices, and this has important implications to managing microplastic pollution in terrestrial ecosystems.

A novel flow-through dual-system electro-Fenton for boosting PAEs removal efficiency in natural waters

In a conventional electro-Fenton system with a single cathode, it is difficult to attain both high H2O2 generation by oxygen reduction reaction (ORR) and efficient iron reduction reaction (FRR). For this study, a flow-through dual-system electro-Fenton (FT-DEF) reactor was designed to overcome this shortcoming and promote mass transfer to effectively remove dimethyl phthalate (DMP) from water. By comparing the ORR and FRR performances of four different commercial carbon electrodes, the graphite felt with the highest amount of H2O2 generation was selected as the cathode of the ORR system, and the activated carbon fiber with the best Fe (III) reduction effect was selected as another cathode of the FRR system. The ORR system and FRR system operate simultaneously to form the DEF system. The FT-DEF system displayed many advantages compared with the conventional electro-Fenton (CI-ORR), presenting an improved efficiency and low energy consumption in phthalates removal. Under optimal reaction conditions, the FT-DEF system is capable to degrade 100% DMP in 20 min, which is 25% higher than the CI-ORR, while the reaction rate constant (0.271 min-1) is 16 times that of CI-ORR system (0.017min-1). In addition, the TOC removal of FT-DEF achieving 72.3% within 2 h with energy consumption of 2.35 kW h·m-3 is much better than CI-ORR that only achieves 18.3% TOC removal within 2 h with energy consumption of 8.13 kW h·m-3. Furthermore, control parameters and mechanism of FT-DEF were investigated in detail. The main intermediate products of DMP were analyzed by UPLC-ESI-HRMS, and the possible degradation path of DMP was speculated. In addition, application of FT-DEF in three types of natural water demonstrated its universal applicability of the system.

Persistence of algal toxicity induced by polystyrene nanoplastics at environmentally relevant concentrations

Polystyrene (PS) often found in the ocean is one of the most commonly used plastic polymers in the world and can exist in different particle sizes. In particular, PS degrades relatively faster and widely accumulates at the nanoscale. Therefore, the penetration is strong and it is easy to enter the body and cause adverse effects. However, the persistence or recovery of their toxicity remains largely unclear. Here, we designed two subexperiments (exposure and recovery experiments) and investigated the persistence of the toxicity of polystyrene (PS) NPs at a wide concentration range (0.01-10 mg/L) to diatoms (Phaeodactylum tricornutum). PS-NPs significantly inhibited algal growth and clearly wrinkled the surfaces of cells, membrane permeability was significantly increased, and the steady-state state of cell redox and mitochondrial membrane potential was disturbed. However, in the recovery experiment, the increased membrane permeability was observed to persist, but the induced oxidative damage was reversible, and the absorbed NPs could be excreted. Integrated omics techniques (metabolomics and transcriptomics) revealed that PS-NPs significantly disrupts cell metabolism, including disturbances in fatty acid biosynthesis and enhanced biosynthesis of phenylalanine, tyrosine, and tryptophan. Inhibition of fatty acid, amino acid, energy and carbohydrate metabolism and disturbance of the antioxidant system contribute to the persistence of toxicity. These findings highlight the phenomena and mechanisms of the persistence of phytotoxicity and are critical to the accurate assessment of NPs.

First insight into microplastic groundwater pollution in Latin America: the case of a coastal aquifer in Northwest Mexico

Microplastics have been studied on biota and other environmental domains, such as soils. Despite the importance of groundwater as a resource for millions of people worldwide as drinking water and personal hygiene, domestic, agricultural, mining, and industrial purposes, there are very few studies concerning microplastics in this domain around the world. We present the first study in Latin America addressing this topic. Six capped boreholes were analyzed in terms of abundance, concentration, and chemical characterization, at three different depths, from a coastal aquifer in Northwest Mexico. This aquifer is highly permeable and affected by anthropogenic activities. A total of 330 microplastics were found in the eighteen samples. In terms of concentration, the interval ranged from 10 to 34 particles/L, with an average of 18.3 particles/L. Four synthetic polymers were identified: isotactic polypropylene (iPP), hydroxyethylcellulose (HEC), carboxylated polyvinyl chloride (PVC), and low-density polyethylene (LDPE); with iPP being the most abundant (55.8%) in each borehole. Agriculture activities and septic outflows are considered the potential regional sources of these contaminants into the aquifer. Three possible transport pathways to the aquifer are suggested: (1) marine intrusion, (2) marsh intrusion, and (3) infiltration through the soil. More research about the occurrence, concentration, and distribution of the different kinds of microplastics in groundwater is needed to have a better understanding of the behavior and health risks to organisms, including human beings.

Darwin's paradise contaminated by marine debris. Understanding their sources and accumulation dynamics.☆

Plastic pollution is a global environmental threat. Remote and pristine islands are not safe from this threat. Here, we estimated beach macro- (>25 mm), meso- (5-25 mm) and microdebris (<5 mm) levels in Galapagos and studied the role of environmental variables determining their accumulation. The vast majority of beach macro- and mesodebris were plastic, while most microdebris were cellulosic. The levels of beach macro-, meso- and microplastics were notably high and comparable with exceptional levels reported in contaminated areas. Oceanic currents and the anthropic pressure of use of the beach were the main factors that determined the level of macro- and mesoplastics, as well as the diversity of items, with more types of items in the beaches facing the predominant current. Microplastic levels were mainly driven by the slope and, to some extent, the grain size of the sediment in the beach. The absence of relationship between the levels of large size debris and the level of microplastics suggests that secondary microplastics that accumulated in the beaches were previously fragmented before arriving to the beach. This differential influence of environmental factors in the accumulation of marine debris according to their size should be taken into account when developing strategies to mitigate plastic pollution. Additionally, this study reports high levels of marine debris reported in a remote and protected area such as Galapagos, which are comparable to areas with direct sources of marine debris. This is especially worrying for Galapagos since the sampled beaches are cleaned at least annually. This fact highlights the global dimension of this environmental threat that demands further extensive international commitment to conserve some of the last paradises on Earth.

Land use-based characterization and source apportionment of microplastics in urban storm runoffs in a tropical region

Urban stormwater runoff has been suggested as one important land-based pathway of microplastics (MPs) entering the oceans, in which the abundance and characteristics of MPs may be influenced by urban land use types. However, little information has been reported regarding this, especially in the tropical monsoon region. This study first reports the MPs in urban stormwater runoffs in a tropical monsoon region that were collected from four typical urban land use types, including industrial, highways, commercial, and residential areas. The average MP particle count and mass concentration were measured as 4.7 ± 3.5 particles/L and 3.8 ± 2.9 mg/L, respectively. MP abundances showed clear urban land use gradients following the order of industrial > transportation > commercial > residential area. In terms of the seasonal variation in MP abundances, a slightly increasing particle count in the dry season was noted for the residential site. Source apportionment of MPs in stormwater runoffs was demonstrated based on the land use type, particle morphology, and chemical compositions. With the simple apportionment approach, approximately 85% of the MP sources were able to be identified in the industrial, transportation, and residential sites. However, the commercial site showed high variability in terms of the morphology and polymer type of MPs. Furthermore, significantly positive correlations between MP abundance and runoff turbidity, TSS, COD, and rainfall intensity were identified, while, no significant correlation was found between MP characteristics and selected water quality/meteorological parameters.

Assessment of Nonalcoholic Fatty Liver Disease Symptoms and Gut-Liver Axis Status in Zebrafish after Exposure to Polystyrene Microplastics and Oxytetracycline, Alone and in Combination

BACKGROUND

Environmental pollution may give rise to the incidence and progression of nonalcoholic fatty liver disease (NAFLD), the most common cause for chronic severe liver lesions. Although knowledge of NAFLD pathogenesis is particularly important for the development of effective prevention, the relationship between NAFLD occurrence and exposure to emerging pollutants, such as microplastics (MPs) and antibiotic residues, awaits assessment.

OBJECTIVES

This study aimed to evaluate the toxicity of MPs and antibiotic residues related to NAFLD occurrence using the zebrafish model species.

METHODS

Taking common polystyrene MPs and oxytetracycline (OTC) as representatives, typical NAFLD symptoms, including lipid accumulation, liver inflammation, and hepatic oxidative stress, were screened after 28-d exposure to environmentally realistic concentrations of MPs (0.69mg/L) and antibiotic residue (3.00μg/L). The impacts of MPs and OTC on gut health, the gut-liver axis, and hepatic lipid metabolism were also investigated to reveal potential affecting mechanisms underpinning the NAFLD symptoms observed.

RESULTS

Compared with the control fish, zebrafish exposed to MPs and OTC exhibited significantly higher levels of lipid accumulation, triglycerides, and cholesterol contents, as well as inflammation, in conjunction with oxidative stress in their livers. In addition, a markedly smaller proportion of Proteobacteria and higher ratios of Firmicutes/Bacteroidetes were detected by microbiome analysis of gut contents in treated samples. After the exposures, the zebrafish also experienced intestinal oxidative injury and yielded significantly fewer numbers of goblet cells. Markedly higher levels of the intestinal bacteria-sourced endotoxin lipopolysaccharide (LPS) were also detected in serum. Animals treated with MPs and OTC exhibited higher expression levels of LPS binding receptor (LBP) and downstream inflammation-related genes while also exhibiting lower activity and gene expression of lipase. Furthermore, MP-OTC coexposure generally exerted more severe effects compared with single MP or OTC exposure.

DISCUSSION

Our results suggested that exposure to MPs and OTC may disrupt the gut-liver axis and be associated with NAFLD occurrence. https://doi.org/10.1289/EHP11600.

Investigation of Microplastics (≥10 μm) in Meconium by Fourier Transform Infrared Microspectroscopy

Microplastics are prevalent emerging pollutants with widespread distribution in air, land and water. They have been detected in human stool, blood, lungs, and placentas. However, human fetal microplastic exposure remains largely under-studied. To assess fetal microplastic exposure, we investigated microplastics using 16 meconium samples. We used hydrogen peroxide (H₂O₂), nitric acid (HNO₃) and a combination of Fenton's reagent and HNO₃ pretreatment methods respectively to digest the meconium sample. We analyzed 16 pretreated meconium samples with an ultra-depth three-dimensional microscope and Fourier transform infrared microspectroscopy. The result showed that H₂O₂, HNO₃ and Fenton's reagent combined with HNO₃ pretreatment methods could not digest our meconium samples completely. Alternatively, we developed a novel approach with high digestion efficiency using petroleum ether and alcohol (4:1, v/v), HNO₃ and H₂O₂. This pretreatment method had good recovery and non-destructive advantages. We found no microplastics (≥10 μm) in our meconium samples, indicating that microplastic pollution levels in the fetal living environment are miniscule. Different results between previous studies' and ours underscore that comprehensive and strict quality control are necessary for further studies on microplastic exposure using human bio-samples.

Microplastics in polystyrene-made food containers from China: abundance, shape, size, and human intake

Polystyrene-made food containers (PMFCs) have been widely used as takeout containers in China. However, the pollution of microplastics (MPs) in PMFCs used in Chinese restaurants remains not well known. For the first time, this study analyzed MPs in PMFC samples (n = 354) collected from different restaurants in 28 Chinese cities. MPs were detected in all PMFC samples, with an abundance of 5-173 items/container. PMFC samples from Taiyuan (mean of 86 items/container) contained the highest mean abundance of MPs. A relatively lower abundance of MPs was found in PMFCs from Urumqi (mean of 19 items/container) and Fuzhou (18 items/container). Fiber was the predominant shape of MPs in most of the PMFC samples. The abundance of MPs in PMFCs was positively correlated with the proportion of fiber. The major polymer composition of MPs was polystyrene, accounting for a mean of 45-90% of total polymers for MPs in PMFCs from different cities. The abundance of MPs in PMFC samples was negatively correlated with the proportion of polystyrene. The mean estimated oral exposure of MPs for the general population in different Chinese cities was 0.24-1.4 items/kg bw/day. Such data is important for human MP exposure risk assessment and also for elucidating the sources of human exposure to MPs.

Microplastics in different fish and shellfish species in the mangrove estuary of Bangladesh and evaluation of human exposure

The water bodies in Bangladesh thrive from plastic pollution. Estuaries are pools of environmental contaminants, and the world's largest mangrove forest, Sundarbans' estuary, is no exception. Thus, for the first time, we investigate MPs abundance in the muscle and gastrointestinal tract (GIT) of twenty estuarine species of fish and shellfish of the Sundarbans, as well as the human health risk. MPs abundance was evident in all the samples ranging from 5.37 ± 1.07 to 54.30 ± 16.53 MP items/g wet body weight (dw) in muscle samples and 7.33 ± 1.89 to 205.61 ± 136.88 MP items/g (dw) in GIT samples. The estimated health risk from MPs is substantial, where the average human intake will be 85,710.08 items of MPs per year per capita for the population of Bangladesh. The dominant polymer types observed using ATR-FTIR are PP and PE (17.5 %), PA (17.5 %) in the muscle tissues, and PP and PE (11.11 %), and EVA (11.11 %) in the GITs. Bottom-feeding species, such as demersal and benthic species, are more contaminated. However, the level of MPs in the species shows a negative correlation with the length and weight of the species. This study reveals that MP pollution is widespread and concerning in Bangladesh's Sundarban mangrove estuarine zone.

Mass quantification of microplastic at wastewater treatment plants by pyrolysis-gas chromatography-mass spectrometry

Municipal wastewater treatment plants (WWTPs) are a central point of collection of plastic particles from households and industry and for their re-distribution into the environment. Existing studies evaluating levels of plastics in WWTPs, and their removal rates have reported and used data on polymer type, size, shape, colour, and number of plastic particles, while the total mass concentration of plastic particles (especially >1 μm) remains unclear and unknown. To address this knowledge gap, raw influent, effluent, and reference water samples from three WWTPs in Australia were collected to analyse the mass concentrations and removal rates of seven common plastics (>1 μm in size) across the treatment schemes. Quantitative analysis was performed by pressurized liquid extraction followed by pyrolysis coupled to gas chromatography mass spectrometry. Results showed that the total plastic content in the WWTPs raw influent samples was between 840 and 3116 μg/L, resulting in an inflow of between about 2.1 and 196.4 kg/day of the total measured plastics. Overall, >99 % by mass of the plastics entering the three WWTPs from the raw influent was removed during the pre-treatment stages, presumably ending up in the sewage sludge, which means emissions (via treated effluent) from the treatment plants are low. Compared with the raw influent, the plastic mass concentrations in the treated effluents (i.e., Class C, A, and final effluent) from the three WWTPs, as well as the reference water samples within their catchments were below the limits of reporting. Of the five quantified plastic types, polyethylene (PE, 76.4 %), and polyvinylchloride (PVC, 21 %) dominated by mass, while polyethylene terephthalate (PET, 1.9 %), polypropylene (PP, 0.4 %) and polymethyl methacrylate (PMMA, 0.3 %) accounted for a small proportion of the total. Overall, this study investigated the mass concentrations of plastic particles above 1 μm in wastewater and their removal, which provided valuable information regarding the pollution level and distribution characteristics of plastic polymers in Australian WWTPs.

Tyre additive chemicals, tyre road wear particles and high production polymers in surface water at 5 urban centres in Queensland, Australia

Plastics pollution is a global issue impacting every part of our environment. Tyre road wear particle (TRWP) plastics pollution is thought to be one of the largest pollution sources in urban environments. These plastics are also of concern due to the presence of additive chemicals, incorporated during manufacture, that can be released into the surrounding environment. This study aimed to provide information on concentrations of a range of anthropogenic plastics related pollutants in the Australian environment through a scoping study of surface water in 5 key urban centres around Queensland, Australia. Samples were analysed for a suite of 15 common tyre additive chemicals, TRWPs and 6 common high production polymers, and included the new transformation product of concern 6PPD-quinone which has recent reports of causing mass mortality events in certain aquatic species. The additives were ubiquitously detected (2.9-1440 ng/L) with 6PPD-quinone concentrations lower than in previous studies (<0.05-24 ng/L) and TRWPs detected at 18 of the 21 sites ( Collapse

Key Words

• 6PPD-quinone
• Microplastics
• Surface water pollution
• Tyre tread

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MESH Headings

• Australia
• Environmental Monitoring
• Environmental Pollutants
• Plastics
• Polyethylenes
• Polymers
• Polypropylenes
• Queensland
• Water
• Water Pollutants, Chemical
• Phenylenediamines
• Benzoquinones

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Affiliation(s)

Cassandra Rauert Queensland Alliance for Environmental Health Sciences (QAEHS), The University of Queensland, 20 Cornwall Street, Woolloongabba, 4102, QLD, Australia.
Suzanne Vardy Water Quality and Investigation, Water Ecosystem Sciences, Science Division, Department of Environment and Science, Queensland Government, Dutton Park, QLD 4102, Australia
Benjamin Daniell Townsville City Council, Townsville, Australia
Nathan Charlton Queensland Alliance for Environmental Health Sciences (QAEHS), The University of Queensland, 20 Cornwall Street, Woolloongabba, 4102, QLD, Australia
Kevin V Thomas Queensland Alliance for Environmental Health Sciences (QAEHS), The University of Queensland, 20 Cornwall Street, Woolloongabba, 4102, QLD, Australia

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Occurrence and characteristics of atmospheric microplastics in Mexico City

While atmospheric microplastics have attracted scientific attention as a significant source of microplastic contamination in the environment, studies in large population centers remain sparse. Here we present the first report on the occurrence and distribution of atmospheric microplastics in Mexico City (Latin America's second most densely populated city), collected using PM₁₀ and PM_2.5 active samplers at seven monitoring stations (urban, residential, and industrial) during the dry and wet seasons of 2020. The results showed that microplastics were detected in all of the samples examined, with mean microplastic concentrations (items m^-3) of 0.205 ± 0.061 and 0.110 ± 0.055 in PM₁₀ and PM_2.5, respectively. The spatial distribution of microplastics showed seasonal variation, with greater abundances in locations closer to industrial and urban centers. There was also a significant difference in microplastic concentrations in PM₁₀ and PM_2.5 between the dry and wet seasons. The mean PM_2.5/PM₁₀ ratio was 0.576, implying that microplastics were partitioned more towards PM_2.5 than PM₁₀ in Mexico City. Fibers were the most prominent shape (>75 %), and blue was the most common color (>60 %). The size characteristics indicated microplastics of varying lengths, ranging from 39 to 5000 μm, with 66 % being <500 μm. Metal contaminants such as aluminum, iron, and titanium were detected using SEM-EDX on randomly selected microplastics. The microplastics were identified as cellophane, polyethylene, polyethylene terephthalate, polyamide, and cellulose (rayon) using ATR-FTIR spectral analysis. Our findings unravel the extent and characteristics of atmospheric microplastics in the Mexico City metropolitan area, which will aid future research to better understand their fate, transport, and potential health risks, demanding more investigations and close monitoring.

Microplastics distribution characteristics in typical inflow rivers of Taihu lake: Linking to nitrous oxide emission and microbial analysis

The microplastics in nature water are important for the environmental fate of nitrous oxide (N₂O). This study investigated the influence and microbial mechanism of microplastic abundance to the N₂O flux in typical inflow rivers of Taihu lake. The microplastic abundance were in a range of 160-700 particles/m³ surface water, and 514-3018 particles/kg dry sediment. The highest percentage of microplastic color was transparent, significantly higher than other color (p<0.0001) in both surface water and sediment. The dominant microplastic size was 500-5000 μm in surface water, while size lower than 1000 μm was dominant in sediment. The microplastic abundance in sediment was negatively correlated with the concentration of suspended sediments (SPS) (p<0.05), Chl-a (p<0.05), NH₄⁺-N (p<0.05) and TP (p<0.01) in inflow river surface water. The dissolved N₂O concentration were 45.71-132.42 nmol/L, and the N₂O fluxes were 29.85-276.60 μmol/m²/d. The dissolved N₂O concentration was significantly correlated with the nirK abundance and nirK/nosZI ratio negatively (p<0.05), revealed that sediment nirK-type denitrification was the main driver of dissolved N₂O. Meanwhile, the N₂O flux (water-air interface) was significantly correlated with nosZI, napA, narG and nirS negatively, implied that nitrification and denitrification interaction in sediment is the main influence factor. The denitrification process in sediment was the main driven factor of N₂O releasing. Mantel-test shows that microplastic abundance in surface water was significantly correlated with nitrification (p = 0.001∼0.01) and denitrification (p = 0.01∼0.05) genera in water. The dominant denitrification microorganism was Dechloromonas in sediment and Flavobacterium in surface water. These results provided new insight into the fact that plastisphere which comprises microbial community on microplastic could affect the N₂O emission in aquatic system.

Microplastics in aquatic systems, a comprehensive review: origination, accumulation, impact, and removal technologies

Although the discovery of plastic in the last century has brought enormous benefits to daily activities, it must be said that its use produces countless environmental problems that are difficult to solve. The indiscriminate use and the increase in industrial production of cleaning, cosmetic, packaging, fertilizer, automotive, construction and pharmaceutical products have introduced tons of plastics and microplastics into the environment. The latter are of greatest concern due to their size and their omnipresence in the various environmental sectors. Today, they represent a contaminant of increasing ecotoxicological interest especially in aquatic environments due to their high stability and diffusion. In this regard, this critical review aims to describe the different sources of microplastics, emphasizing their effects in aquatic ecosystems and the danger to the health of living beings, while examining, at the same time, those few modelling studies conducted to estimate the future impact of plastic towards the marine ecosystem. Furthermore, this review summarizes the latest scientific advances related to removal techniques, evaluating their advantages and disadvantages. The final purpose is to highlight the great environmental problem that we are going to face in the coming decades, and the need to develop appropriate strategies to invert the current scenario as well as better performing removal techniques to minimize the environmental impacts of microplastics.

Identification and Quantification of Micro-Bioplastics in Environmental Samples by Pyrolysis-Gas Chromatography-Mass Spectrometry

Bioplastics are materials that are biobased and/or biodegradable, but not necessarily both. Concerns about environmental plastic pollution are constantly growing with increasing demand for substituting fossil-based plastics with those made using renewable resource feedstocks. For many conventional bioplastics to completely decompose/degrade, they require specific environmental conditions that are rarely met in natural ecosystems, leading to rapid formation of micro-bioplastics. As global bioplastic production and consumption/use continue to increase, there is growing concern regarding the potential for environmental pollution from micro-bioplastics. However, the actual extent of their environmental occurrence and potential impacts remains unclear, and there is insufficient mass concentration-based quantitative data due to the lack of quantitative analytical methods. This study developed and validated an analytical method coupling pressurized liquid extraction and pyrolysis-gas chromatography-mass spectrometry combined with thermochemolysis to simultaneously identify and quantify five targeted micro-bioplastics (i.e., polylactic acid (PLA), polyhydroxyalkanoate, polybutylene succinate, polycaprolactone, and polybutylene adipate terephthalate (PBAT)) in environmental samples on a polymer-specific mass-based concentration. The recovery of spiked micro-bioplastics in environmental samples (biosolids) ranged from 74 to 116%. The limits of quantification for the target micro-bioplastics were between 0.02 and 0.05 mg/g. PLA and PBAT were commonly detected in wastewater, biosolids, and sediment samples at concentrations between 0.07 and 0.18 mg/g. The presented analytical method enables the accurate identification, quantification, and monitoring of micro-bioplastics in environmental samples. This study quantified five micro-bioplastic types in complex environmental samples for the first time, filling in gaps in our knowledge about bioplastic pollution and providing a useful methodology and important reference data for future research.

Insights into N2O turnovers under polyethylene terephthalate microplastics stress in mainstream biological nitrogen removal process

The ubiquitous microplastics in wastewater have raised growing concerns due to their unintended effects on microbial activities. However, whether and how microplastics affect nitrous oxide (N₂O) (a potent greenhouse gas) turnovers in mainstream biological nitrogen removal (BNR) process remain unclear. This work therefore aimed to fill such knowledge gap by conducting both long-term and batch tests. After over 100 days of feeding with wastewater containing polyethylene terephthalate (PET) microplastics (0-500 μg/L), the long-term results showed that both production and reduction of N₂O during denitrification were reduced, as well as the N₂O production during nitrification. Accordingly, 60% reduction in N₂O accumulation and 70% reduction in N₂O production were observed in the denitrification and nitrification batch tests, respectively. Nevertheless, the long-term N₂O emission factors under PET microplastics stress were comparable to that in the control reactor, mainly because PET microplastics led to more nitrite accumulation in anoxic period. With the aid of online N₂O sensors and site-preference analysis, it was demonstrated that the heterotrophic bacteria pathway and ammonia oxidizing bacteria denitrification pathway for N₂O production were negatively affected by PET microplastics, whereas a clear increase in the contribution of hydroxylamine pathway (+ 22.9%) was observed. Further investigation revealed that PET microplastics even at environmental level (i.e. 10 μg/L) significantly reshaped the BNR sludge characteristics (e.g. much larger particle size) and microbial communities (e.g. Thauera, Rhodobacte and Nitrospira) as well as the nitrogen metabolism pathways, which were chiefly responsible for the changes of N₂O turnovers and N₂O production pathways under the PET microplastics stress.

Widespread occurrence of microplastics in marine bays with diverse drivers and environmental risk

Microplastic contamination in the sediment of marine bays has attracted widespread attention, whereas the distribution, sedimentation, morphology and risk of microplastics at regional scale remain poorly understood. By introducing a data mining framework into microplastic research, we compiled a microplastic dataset of 649 samples from 24 bays to enhance the understanding of geographical difference and drivers, transfer, composition profile and environmental risk of sedimental microplastics. Microplastic abundance varied from 0.72 to 1963.96 items/kg dry weight, with higher concentrations mainly occurring in East Asian bays. The spatial pattern in abundance was driven by the river plastic emissions, aquaculture production and hydrodynamic condition. A significantly positive correlation between microplastic abundance in water and sediment was found, and microplastic sedimentation was related to polymer density, hydrodynamic conditions and sediment properties. The dominant shape and polymer of sedimental microplastics were fiber and polypropylene, respectively, and the similarity of microplastic composition decreased with increasing geographical distance. The environmental risks of microplastics were partitioned into three classes (Rank II-Rank IV) with a two-dimensional assessment system considering the bioavailability and toxicity of microplastics, and Asian bays were identified as potential high-risk areas. To reduce the environmental risk of sedimental microplastics in bays, priority should be given to the removal of microfibers, and control measures depend on the risk classes and dominant polymers. Microplastic abundance and composition were significantly affected by methodological choices regarding sampling, pretreatment and identification, suggesting a unified methodology is essential to further enhance our knowledge on the distribution and risk of microplastics in marine bays.

Dual drive acute lethal toxicity of methylene blue to Daphnia magna by polystyrene microplastics and light

Microplastics (MPs) can adsorb and influence the toxicity of traditional pollutants significantly. Although the complex toxicity of MPs and molecular pollutants were frequently reported, rare work has been done on the influence of MPs on the phototoxicity of photosensitive pollutants under light illumination condition. Herein, polystyrene microplastics (PS) (~1 μm in diameter, 5.0 mg/L) was used as a model MP to investigate its influence on the phototoxicity of a soluble blue dye, methylene blue (MB) using Daphnia magna as a model organism. The results indicate that PS could adsorb MB effectively and quickly, thus led to concentrated MB on PS/water interface. D. magna ingested MB-adsorbed PS very quickly within tens of minutes. Although MB or PS alone led to negligible lethal phototoxicity to D. magna, PS significantly enhanced the lethal phototoxicity of MB (0.25 mg/L) to D. magna after light illumination (10 h) with the survival rate decreased by 63.3 % compared with the control in the dark. Further, the phototoxicity of MB was found positively consistent with PS concentration from 0.50 mg/L to 7.50 mg/L. The singlet oxygen fluorescence assay indicates that the presence of PS did not increase the total amount of singlet oxygen in the aquatic environment but increased the local concentration in the gut area via non-selective ingestion of D. magna. High level singlet oxygen generated in the gut might possibly be the main reason that led to the massive death of D. magna. Surface adsorption of photosensitive pollutants may transform inert MPs into persistent solid sources of singlet oxygen production and become a new potential lethal threat to aquatic small organisms and ecological equilibrium. This kind of MPs and light dual drive phototoxicity of photosensitive pollutants needs to paid more attention in understanding the uncertain ecological risk of MPs.

Polyhydroxybutyrate Rice Hull and Torrefied Rice Hull Biocomposites

Raw and torrefied rice hulls (RRH and TRH) were incorporated into polyhydroxybutyrate (PHB) as fillers using extrusion and injection molding to produce biomass-polymer composites. Filler and composite materials were characterized by particle size analysis, thermomechanical analysis, thermogravimetric analysis, differential scanning calorimetry, FTIR analysis, CHNSO analysis, and mechanical testing. Heat distortion temperature of the RRH composites were 16–22 °C higher than TRH composites. The RRH composite samples showed a 50–60% increase in flexural modulus and 5% increase in stress at yield compared to PHB, while TRH composite samples showed nearly equal flexural modulus and a 24% decrease in stress at yield. The improved mechanical properties of the RRH composites in comparison to TRH composites were due to better particle-matrix adhesion. FTIR analysis showed RRH particles contained more surface functional groups containing oxygen than TRH particles, indicating that RRHs should be more compatible with the polar PHB plastic. SEM images showed space between filler and plastic in TRH composites and better wetted filler particles in the RRH composites.

A case study of distribution and characteristics of microplastics in surface water and sediments of the seas around Shenzhen, southern coastal area of China

Microplastics (MPs), known to cause environmental pollution, is attracting a growing attention worldwide owing to their extensive existence and potential risks to biota. The marginal sea areas are suspected to be especially susceptible to MPs pollution. Unfortunately, data on MPs in the surface water and sediments ecosystems are still limited, particularly in the southern coastal areas of China. The study was successfully utilized to explore the distribution and characteristics of MPs below 5 mm collected from 14 sites in the seas around Shenzhen, a typical special economic zone of China. MPs were detected in both surface water and sediments with concentrations ranging from 3.8 to 7.8 items per liter and 2.6 × 10³ to 10.0 × 10³ items per kilogram, respectively. The highest abundance of MPs appeared in S5/S9 and S14 in surface water and sediments, respectively. Fiber and film with small particle size (<0.5 mm) were identified as typical and abundant MPs type among all samples. In addition, polyethylene (PE) was considered as dominant forms of MPs in surface water and sediment samples. Results from this study indicated a positive correlation with abundance of MPs and urbanization rate, which also showed an evident difference of MPs in different urban functional areas. Based on the types and quantity of detected MPs, we assessed the risk of MPs pollution in this study area, and the ecological risk category of MPs was at a high level. Importantly, our work might be employed as a potential information so as to better understand MPs pollution, source tracing and ecological risk assessment, which enhances the possibility of achieving effective control and supervision of MPs pollution in southern coastal aera of China.

Is there tea complemented with the appealing flavor of microplastics? A pioneering study on plastic pollution in commercially available tea bags in Bangladesh

Microplastic pollution is a global concern, mainly due to its adverse effects on organisms and ecosystems. However, our knowledge of its impact on humans, in particular, is still very limited. Thus, while we have not gathered definitive information on their consequences, studies that aim to identify the MP's sources constitute subsidies to better understand the various exposure pathways to these pollutants. Thus, we investigated the possible presence of MP-like particles in teabag samples (of different brands) obtained in Dhaka, Bangladesh. Surprisingly, all analyzed samples (five brands) were contaminated with MPs. Fragments and fibers were identified in a higher percentage, and a wide variety of colors was identified, with a predominance of brown, blue, and red colors. Scanning electron microscope images of teabags exhibited net-like structures of fiber particles with a smooth surface. Furthermore, we observed irregularly shaped MPs and rougher surfaces and fragments in the process of detachment from the main fiber, oxidation flakes, and fracture-like. The average size of these pollutants was between 200.6 and 220.7 μm, and the polymer types identified via Fourier-transform infrared spectroscopy (FT-IR) were polytetrafluoroethylene, high-density polyethylene, polycarbonate, nylon, polyvinyl chloride, polytetrafluoroethylene, ethylene-vinyl acetate, cellulose acetate, and acrylonitrile butadiene styrene, the last three being the most frequent in the analyzed samples. Finally, we noticed that MPs from tea bags in Dhaka could cause an average emission of 10.9 million grams of MPs/year. Although the teabags analyzed in our study are not "complemented with the appealing flavor of MPs", it is very likely that tea ingestion in Dhaka is accompanied by the concomitant ingestion of plastic particles making teabags an important route of human exposure to these micropollutants.

Mechanisms of polystyrene microplastic degradation by the microbially driven Fenton reaction

Natural hydroxyl radical (·OH) production, which partially occurs through the microbially driven Fenton reaction, can enhance the degradation of polystyrene microplastics (PS-MPs). However, ·OH causes damage to microorganisms, which might in turn restrain the microbially driven Fenton reaction. Thus, whether PS-MPs can be continuously degraded by the microbially driven Fenton reaction and how they are degraded are still unknown. A pure-culture system using Shewanella putrefaciens 200 was set up to explore the effect and mechanism of microbially driven Fenton reaction on PS-MP degradation. In a 14-day operation, ·OH produced by the microbially driven Fenton reaction could degrade PS-MPs with a weight loss of 6.1 ± 0.6% and an O/C ratio of 0.6 (v.s. 0.6 ± 0.1% and 0.1, respectively, in the ·OH quenched group). Benzene ring derivatives such as 2-isopropyl-5-methyl-1-heptanol and nonahexacontanoic acid were the main soluble products of PS-MP degradation. The ·OH-induced oxidative damage on microorganisms did not affect ·OH production significantly when there was timely replenishment of organic carbon sources to promote reproduction of microorganisms. Thus, PS-MPs can be continuously degraded by microbially driven Fenton reactions in natural alternating anaerobic-aerobic environments. This study also provides a new microbial technique for MP degradation that is different from previous technologies based on microbial plastic-degrading enzymes.

Are there plastic particles in my sugar? A pioneering study on the characterization of microplastics in commercial sugars and risk assessment

Although several studies are confirming the ubiquity of microplastics (MPs) in environments, our knowledge about their effects on human health is still very limited. Therefore, while we have not gathered definitive information on their consequences, studies that aim to identify the MPs sources constitute subsidies to better understand the various exposure pathways to these pollutants. Thus, we investigated the possible presence of MP-like particles in five brands of commercial sugars and two unpacked, unbranded, and unlabeled sugars (hereinafter referred to as "non-branded"), obtained from different supermarkets in Dhaka (Bangladesh). Surprisingly, MPs-like particles were identified in all analyzed samples and taken together, our data demonstrated similar variations (between branded and non-branded samples) in terms of number, size, shape, color, and polymer composition. The number of plastic particles/kg sugar was, on average, 343.7 ± 32.08 (mean ± SEM), having been observed a tendency for a higher frequency of MPs < 300 μm. Overall, microfibers and spherules were the most and the predominant colors of MPs (in general) were black, pink, blue, and brown. The FT-IR analysis confirmed the chemical nature of MPs (in branded and non-branded), having identified nine polymeric types (ABS, PCV, PET, EVA, CA, PTFE, HDPE, PC, and nylon), being ABS and PVC the most frequent. Furthermore, we estimate that sugar consumption in Dhaka City can cause the ingestion of millions of tons of MPs annually (2.4 to 25.6 tons) (with an average of 10.2 tons). Our study is the most comprehensive report on the MP's occurrence in sugar, confirming that the ingestion of this food constitutes an important route of human exposure to these micropollutants and, therefore, serves as a baseline for future assessments and useful for generating efficient strategies to control MPs.

Adsorption of Tannic Acid and Macromolecular Humic/Fulvic Acid onto Polystyrene Microplastics: A Comparison Study

Dissolved organic matter (DOM) has been widely reported to influence the environmental behavior of microplastics (MPs), but little is known about the properties and mechanisms of interaction between specific DOM components and MPs. Here, we studied the adsorption of three representative DOM components (humic acid, HA; fulvic acid, FA; and tannic acid, TA) on polystyrene (PS) MPs in batch adsorption experiments. Results revealed that HA/FA adsorption was greater under acidic conditions, while higher TA adsorption on PS was found at pH 4 and 6. The divalent cation (Ca2+) exerted a more prominent role in enhancing HA, FA, and TA adsorption on PS than did monovalent ones (K+ and Na+). The adsorption process fitted well with the Freundlich isotherm model and the pseudo-second-order kinetics model. The adsorption site heterogeneity was evaluated using the site energy distribution analysis based on the Freundlich model. The greater binding ability of HA on the PS surface caused a more negatively charged surface than FA/TA, as reflected by Zeta potential values. The findings of this study not only provide valuable information about the adsorption behavior and interaction processes of various DOM components on PS MPs, but also aid our efforts to evaluate the environmental behaviors of MPs.

Microplastic Extraction from Agricultural Soils Using Canola Oil and Unsaturated Sodium Chloride Solution and Evaluation by Incineration Method

Environmental pollution by microplastics (MPs) has become a global problem, but little is known about MPs in soils. This is because MP extraction methods from soils have not yet been standardized. In this study, we tried to establish a simple and economical method to extract soil MPs using the buoyancy of canola oil and the density separation process using sodium chloride (NaCl). In addition, the incineration method was adapted to evaluate the effectiveness of extraction methods precisely. First, the ability and suitability of seven different oils to extract MP from soil were investigated and canola oil was selected. Then, the spiking and recovery test was performed with canola oil and NaCl solution for low-density polyethylene (LDPE), polypropylene (PP), and polyvinylchloride (PVC) as follows: (1) soil and MP mixtures were prepared, (2) 5 g L−1 NaCl and canola oil were added and shaken thoroughly, (3) the oil phase containing MPs were separated after sedimentation, (4) the extracted MPs were rinsed with 99.5% ethanol, and (5) the organic adherents to the extracted MPs were digested with hydrogen peroxide. After drying and incineration, the substantial recovery rates were calculated. In the spiking and recovery test for MP particles (<1 mm) from five typical Japanese agricultural soils, the recoveries of LDPE, PP, and PVC were 95.2–98.3%, 95.2–98.7%, and 76.0–80.5%, respectively, higher than those obtained by the density separation using saturated NaCl solution. In conclusion, the method is effective for extracting MPs, especially LDPE and PP, from soils and is less sensitive to soil type, texture, and physicochemical properties.

Photocatalytic degradation of (micro)plastics using TiO2-based and other catalysts: Properties, influencing factor, and mechanism

(Micro)plastics pollution has raised global concern because of its potential threat to the biota. The review on recent developments of photocatalytic degradation of (micro)plastics is still insufficient. In this study, we have discussed various bare and composites photocatalysts involved in the photocatalytic degradation of (micro)plastics. The photocatalytic mechanisms and factors affecting the degradation were also discussed. To improve the performance of photocatalysts, their surface is modified with metal or non-metal dopants. These doped photocatalysts are then compounded with a variety of environmentally friendly and nontoxic polymers to prepare multifunctional composites. The generation of reactive oxygen species (ROS) plays an important role in the photocatalytic degradation of (micro)plastics, and superoxide ions (O₂^-) and hydroxyl radicals (OH) participate in the photocatalytic degradation, leading to the breaking of the polymer chain and the production of some intermediates. Although satisfactory progress has been achieved in the photodegradation of (micro)plastics, most photocatalytic degradation technologies investigated to date cannot realize the complete mineralization of (micro)plastics. Furthermore, based on the current challenges of the existing photocatalytic degradation technologies, perspectives for future research directions have been proposed. This review presents a systematic summary of the progress made in the photocatalytic degradation of (micro)plastics and offers a comprehensive reference for future research on improving the (micro)plastics photocatalytic degradation efficiency.

Electro-peroxone with solid polymer electrolytes: A novel system for degradation of plasticizers in natural effluents

Electro-peroxone (EP) reaction has been considered as a promising process for real effluent treatments. However, the use of the technology in natural water conditions is limited by low electrical conductivity and high operating costs. Herein, a novel electrochemical system was designed to overcome this constrain by coupling EP with a solid polymer electrolyte (EP-SPE). Performances of EP-SPE system were thoroughly evaluated by comparing the decomposition and energy efficiencies of various plasticizers in different systems. The EP-SPE system achieved 50% of pollutants mineralization in only 10 min with the electrolysis energy consumption of 1.0kWh·m^-3, While the conventional EP system (not) adding salt compounds (CEP-(N) AS) need 30 (60) min to reach 50% of pollutants mineralization with 3.8(26.6)kWh·m^-3. Kinetics and mechanisms of EP-SPE were investigated in detail, while electronic paramagnetic resonance (EPR) detection and kinetic model revealed the occurrence, transient concentration and degradation contribution of reactive oxidizing species (ROS). Furthermore, tests of variety of SPEs and natural waters demonstrated universal applicability of EP-SPE. Additionally, EP-SPE did not show any performance deterioration after 15 runs. Therefore, this work provides a feasible technology for plasticizer purification in natural water.

A comprehensive review of the circulation of microplastics in aquatic ecosystem using scientometric method

Nowadays, the extensive application of microplastics (MPs) has led to the gradual accumulation of toxicity in aquatic environment and caused potential harm to aquatic organisms and human life, which has become a hot issue of worldwide concern. Although MPs show inert or sublethal toxicity in many cases, its long-term existence can still cause harmful ecological effects. However, to our knowledge, there is a lack of comprehensive literature on the current research hotspots, circulation process, and future development trend of MPs in aquatic ecosystem. This study aims to comprehend the current research hotspots and future development trend in the field of the MPs in aquatic ecosystem using scientometric method. And the circulation process of MPs in aquatic ecosystem is also investigated. The results indicate the most of the current publications on MPs in aquatic ecosystems focus on the formation and harmful properties of MPs. The current research hotspots mainly include the causes of the formation of MPs, the extent of contamination, deposition phenomena, and the toxicity and harm caused to aquatic organisms and humans after ingestion. And the future trends in the researches related to MPs mainly include the study of microplastic cycling processes in aquatic and terrestrial ecosystems, as well as the effective collection of microplastics and their conversion into valuable carbon sources. This review has filled in the knowledge gap in the field of MPs research in aquatic ecosystem to some extent and plays a guiding role in the future researches.

Does size matter? Quantification of plastics associated with size fractionated biosolids

This study investigated the occurrence and contribution of plastic particles associated with size fractionated biosolids to the total concentration in biosolids (treated sewage sludge) samples collected from 20 wastewater treatment plants (WWTP) across Australia. This was achieved through sequential size fractionation of biosolids samples to quantify the mass concentration of 7 common plastics across a range of biosolids size fractions, including below 25 μm which has not been assessed in many previous studies. Quantitative analysis was performed by pressurized liquid extraction followed by pyrolysis coupled to gas chromatography - mass spectrometry. Of the total quantified plastics (Σ₇plastics), the greatest proportion (27%) of the total mass were identified in the nominal <25 μm sized biosolids fraction. Polyethylene dominated the polymer mass in every size fraction, even though profiles varied between WWTPs. When comparing the sum of all sites for each sized biosolids fraction, the plurality of the polyethylene, polyvinyl-chloride, polystyrene, polypropylene, polycarbonate, and polyethylene-terephthalate concentrations were associated with the smallest size fraction (<25 μm). We confirm for the first time the presence of plastic particles in biosolids below a size fraction that is not captured by many methods. This is important, because of the potential greater significance of plastics in the low sizes to environmental and human health.

Soil microplastic pollution under different land uses in tropics, southwestern China

Terrestrial ecosystems encounter emerging risks of microplastic (MP) pollution. However, the distribution characteristics of soil MPs across different land uses in tropical areas have remain largely unknown. We sampled soils from two natural ecosystems (primary and secondary forests) and two artificial ecosystems (rubber and banana plantations) in tropical region of southwestern China. We aimed to evaluate the overall characteristics of soil MPs and analyze the distribution and source of MPs in different soil layers and land uses. We found that the dominant size of soil MPs were <1 mm and the major shapes were fragments and fibres, with colours blue, yellow, and green-blue. Most MPs were polyethylene (PE, 59.6%), rayon (RY, 12.0%), and polypropylene (PP, 10.9%). In artificial ecosystems, the abundance of MPs in the top soil (0-10 cm) was approximately 2.5 times that of in deep soil (10-20 cm), whereas it was only 50% in the natural ecosystems. The abundance of MPs in banana plantations reached as high as 10975.0 ± 261.0 particles kg^-1 (p kg^-1), which was about 10 times that of in rubber plantations (1112.5 ± 151.6 p kg^-1) and 18 times of those in secondary and primary forests (612.5 ± 119.2 p kg^-1 and 637.5 ± 181.6 p kg^-1). Anthropogenic and atmospheric transport may be the major sources of soil MPs for artificial ecosystems to natural ecosystems, respectively. Our results revealed the widespread presence of soil MPs in tropical areas, from artificial ecosystems to natural ecosystems, in both the top and deep soil layers. MP pollution in artificial ecosystems is considerably serious than that in natural ecosystems. Our study provides important support for further research on ecosystem risks pertaining to MPs in the context of land use changes, and promotes the development of effective measures and policies to control MP pollution in tropical areas.