An exploratory ecotoxicity study of primary microplastics versus aged in natural waters and wastewaters

Photoaging Elevated the Genotoxicity of Polystyrene Microplastics to Marine Mussel Mytilus trossulus (Gould, 1850)

Micro-sized particles of synthetic polymers (microplastics) are found in all parts of marine ecosystems. This fact requires intensive study of the degree of danger of such particles to the life activity of hydrobionts and needs additional research. It is evident that hydrobionts in the marine environment are exposed to microplastics modified by biotic and abiotic degradation. To assess the toxic potential of aging microplastic, comparative studies were conducted on the response of cytochemical and genotoxic markers in hemocytes of the mussel Mytilus trossulus (Gould, 1850) after exposure to pristine and photodegraded (UV irradiation) polystyrene microparticles (µPS). The results of cytochemical tests showed that UV-irradiated µPS strongly reduced metabolism and destabilized lysosome membranes compared to pristine µPS. Using a Comet assay, it was shown that the nuclear DNA of mussel hemocytes showed high sensitivity to exposure to both types of plastics. However, the level of DNA damage was significantly higher in mussels exposed to aging µPS. It is suggested that the mechanism of increased toxicity of photo-oxidized µPS is based on free-radical reactions induced by the UV irradiation of polymers. The risks of toxic effects will be determined by the level of physicochemical degradation of the polymer, which can significantly affect the mechanisms of toxicity.

Phytoremediation: A promising approach to remove microplastics from the aquatic environment

Due to the increasing amount of microplastics (MPs) in the environment, various technologies for their removal have been investigated. One of the possible technologies are phytoremediation methods, but insufficient understanding of the interactions between MPs and aquatic macrophytes limits their further development. In this context, the aim of this study was to investigate the interactions between polyethylene MPs and the floating aquatic macrophyte Lemna minor in terms of the extent and time frame of MPs adhesion to the plant biomass, the stability of the interactions under water movement and understanding the nature of the adsorption process through the adsorption isotherm models. The results showed that the maximum number of adhered MPs was reached after 24 h. With increased amount of plant biomass the number of adhered MPs increased as well. Slow movement of water had no statistically significant effect on the adhesion of MPs. Among several adsorption models, the Freundlich adsorption isotherm model was the best fit to the experimental data, which assumes weak binding of MPs to plant biomass. Finally, 79% of MPs was removed during 15 cycles of phytoremediation (i.e., the biomass was removed and replaced with new biomass 15 times) and it was calculated that 53 cycles would be needed to remove all MPs from the water phase under test conditions.

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

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

Naturally aged polylactic acid microplastics stunted pakchoi (Brassica rapa subsp. chinensis) growth with cadmium in soil

Biodegradable microplastics (BMPs) and cadmium (Cd) are posing threats to agro-systems especially to plants and current studies mostly used virgin BMPs to explore their ecological effects. However, effects of naturally aged BMPs and their combined effects with Cd on pakchoi are yet to be unraveled. Therefore, this study incubated naturally aged polylactic acid (PLA) MPs through soil aging process and investigated the single and combined effects of Cd and PLA MPs (virgin and aged) on pakchoi (Brassica rapa subsp. chinensis) morphology, antioxidant systems and soil microbial activities. Our results found that after being deposited in soil for six months, aged PLA (PLAa) MPs formed with a fractured surface, demonstrating more detrimental effects on pakchoi than virgin ones. PLA/PLAa MPs and Cd stunted pakchoi growth, caused oxidative stress and altered the biophysical environment in soil, separately. Moreover, co-existence of PLA/PLAa MPs and Cd caused greater damages to pakchoi than applied alone. The co-presence of PLAa MPs and Cd inhibited pakchoi biomass accumulation rate by 92.2 % compared with the no-addition group. The results unraveled here emphasized BMPs, especially aged BMPs, could trigger negative effects on agro-systems with heavy metals. These findings will give reference to future holistic assessments of BMPs' ecological effects.

The concentration-dependent physiological damage, oxidative stress, and DNA lesions in Caenorhabditis elegans by subacute exposure to landfill leachate

The leakage of landfill leachate (LL) into environmental media would be happened even in the sanitary/controlled landfill, due to the deterioration of geomembrane and the blockage of drainage system after long-term operation. Considering the complex composition and high concentration of pollutants in LL, its toxicity assessment should be conducted as a whole liquid contaminant. Therefore, the impacts of LL on Caenorhabditis elegans (C. elegans) were investigated under the condition of different exposure time and exposure volume fraction (EVF). The stimulating effects on locomotion behavior and growth of C. elegans were observed after acute (24 h) exposure to LL, which were increased firstly and then decreased with the increase of EVF. Meanwhile, the intestinal barrier was not affected by LL, and levels of reactive oxygen species (ROS) and cell apoptosis significantly decreased. However, stimulation and inhibition effects on locomotion behavior and growth of C. elegans were observed when subacute (72 h) exposure to 0.25%-0.5% and 1%-4% of LL, respectively. The intestinal injury index and levels of ROS and cell apoptosis significantly increased when EVF were 2% and 4%. Although the acute exposure of LL had resulted in obviously biological adaptability and antioxidant defense in C. elegans, the protective mechanisms failed to be induced as the exposure time increased (subacute exposure). The toxic effects were confirmed by the down-regulation of genes associated with antioxidant defense and neurobehavior, accompanied by the up-regulation of intestinal injury and cell apoptosis related genes. Moreover, the disturbance of metabolic pathways that associated with locomotion behaviors, growth, and antioxidant defense provided good supplementary evidence for the confirmation of oxidative stress in C. elegans. The research results verified the potential of C. elegans as model organism to determine the complex toxic effects of LL.

Multigenerational effects of microplastic fragments derived from polyethylene terephthalate bottles on duckweed Lemna minor: Size-dependent effects of microplastics on photosynthesis

The 2019 global coronavirus disease pandemic has led to an increase in the demand for polyethylene terephthalate (PET) packaging. Although PET is one of the most recycled plastics, it is likely to enter the aquatic ecosystem. To date, the chronic effects of PET microplastics (MPs) on aquatic plants have not been fully understood. Therefore, this study aimed to investigate the adverse effects of PET MP fragments derived from PET bottles on the aquatic duckweed plant Lemna minor through a multigenerational study. We conducted acute (3-day exposure) and multigenerational (10 generations from P0 to F9) tests using different-sized PET fragments (PET_0-200, < 200 μm; PET_200-300, 200-300 μm; and PET_300-500, 300-500 μm). Different parameters, including frond number, growth rate based on the frond area, total root length, longest root length, and photosynthesis, were evaluated. The acute test revealed that photosynthesis in L. minor was negatively affected by exposure to small-sized PET fragments (PET_0-200). In contrast, the results of the multigenerational test revealed that large-sized PET fragments (PET_300-500) showed substantial negative effects on both the growth and photosynthetic activity of L. minor. Continuous exposure to PET MPs for 10 generations caused disturbances in chloroplast distribution and inhibition of plant photosynthetic activity and growth. The findings of this study may serve as a basis for future research on the generational effects of MPs from various PET products.

Monitoring of biofilm development and physico-chemical changes of floating microplastics at the air-water interface

Microplastics in the aquatic environment serve as a habitat for microbial life, on which they can form biofilms. However, how the development of the biofilm alters the properties of floating microplastics that are at the air-water interface and, therefore, not fully submerged, is not well understood. In this context, an aging experiment was conducted to monitor biofilm formation and changes in physico-chemical properties of low-density polyethylene (floating) microplastics over time. The growth of the biofilm followed the typical bacterial/biofilm growth phases and reached about 30% of the total mass of the microplastics, while the concentration of extracellular polymeric substances within the biofilm remained stable. Presence of chlorophyll a and urease activity indicated presence of photosynthetic microrganisms within the biofilm which was also confirmed by analysis of the biofilm composition. Chemical characterization by FTIR showed the formation of additional functional groups attributed to the formed biofilm, and SEM imaging showed cracks on the surface of the aged microplastics, indicating incipient degradation of the polyethylene. Moreover, the adsorption capacity of the aged particles for metals (Pb(II)) was 52% higher compared to the pristine ones. Aging increased the density and size of the particles; however, it did not lead to the submersion of the aged particles even after 12 weeks of aging, suggesting that additional environmental processes may influence the transport of microplastics from the air-water interface into the water body.

Biofilm formation strongly influences the vector transport of triclosan-loaded polyethylene microplastics

This study aimed at evaluating the influence of biofilm in the role of microplastics (MPs) as vectors of pollutants and their impact on Daphnia magna. To do this, virgin polyethylene MPs, (PE-MPs, 40-48 μm) were exposed for four weeks to wastewater (WW) from influent and effluent to promote biofouling. Then, the exposed PE-MPs were put in contact with triclosan. Finally, the toxicity of TCS-loaded and non-TCS loaded PE-MPs were tested on the survival of D. magna adults for 21 days. Results from metabarcoding analyses indicated that exposure to TCS induced shifts in the bacterial community, selecting potential TCS-degrading bacteria. Results also showed that PE-MPs were ingested by daphnids. The most toxic virgin PE-MPs were those biofouled in the WW effluent. The toxicity of TCS-loaded PE-MPs biofouled in the WW effluent was even higher, reporting mortality in all tested concentrations. These results indicate that biofouling of MPs may modulate the adsorption and subsequent desorption of co-occurring pollutants, hence affecting their potential toxicity towards aquatic organisms. Future studies on realistic environmental plastic impact should include the characterization of biofilms growing on plastic. Since inevitably plastic biofouling occurs over time in nature, it should be taken into account as it may modulate the sorption of co-occurring pollutants.

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

Microplastics found in the environment are often covered with a biofilm, which makes their analysis difficult. Therefore, the biofilm is usually removed before analysis, which may affect the microplastic particles or lead to their loss during the procedure. In this work, we used laser-based analytical techniques and evaluated their performance in detecting, characterizing, and classifying pristine and aged microplastics with a developed biofilm. Five types of microplastics from different polymers were selected (polyamide, polyethylene, polyethylene terephthalate, polypropylene, and polyvinyl chloride) and aged under controlled conditions in freshwater and wastewater. The development of biofilm and the changes in the properties of the microplastic were evaluated. The pristine and aged microplastics were characterized by standard methods (e.g., optical and scanning electron microscopy, and Raman spectroscopy), and then laser-induced breakdown spectroscopy (LIBS) and laser ablation inductively coupled plasma mass spectrometry (LA-ICP-MS) were used. The results show that LIBS could identify different types of plastics regardless of the ageing and major biotic elements of the biofilm layer. LA-ICP-MS showed a high sensitivity to metals, which can be used as markers for various plastics. In addition, LA-ICP-MS can be employed in studies to monitor the adsorption and desorption (leaching) of metals during the ageing of microplastics. The use of these laser-based analytical techniques was found to be beneficial in the study of environmentally relevant microplastics.

The Response of Duckweed Lemna minor to Microplastics and Its Potential Use as a Bioindicator of Microplastic Pollution

Biomonitoring has become an indispensable tool for detecting various environmental pollutants, but microplastics have been greatly neglected in this context. They are currently monitored using multistep physico-chemical methods that are time-consuming and expensive, making the search for new monitoring options of great interest. In this context, the aim of this study was to investigate the possibility of using an aquatic macrophyte as a bioindicator of microplastic pollution in freshwaters. Therefore, the effects and adhesion of three types of microplastics (polyethylene microbeads, tire wear particles, and polyethylene terephthalate fibers) and two types of natural particles (wood dust and cellulose particles) to duckweed Lemna minor were investigated. The results showed that fibers and natural particles had no effect on the specific growth rate, chlorophyll a content, and root length of duckweed, while a significant reduction in the latter was observed when duckweed was exposed to microbeads and tire wear particles. The percentage of adhered particles was ten times higher for polyethylene microbeads than for other microplastics and natural particles, suggesting that the adhesion of polyethylene microbeads to duckweed is specific. Because the majority of microplastics in freshwaters are made of polyethylene, the use of duckweed for their biomonitoring could provide important information on microplastic pollution in freshwaters.

Review on the ecotoxicological impacts of plastic pollution on the freshwater invertebrate Daphnia

The environmental impacts of plastic pollution have recently attracted universal attention, especially in the aquatic environment. However, research has mostly been focused on marine ecosystems, even though freshwater ecosystems are equally if not more polluted by plastics. In addition, the mechanism and extent to which plastic pollution affects aquatic biota and the rates of transfer to organisms through food webs eventually reaching humans are poorly understood, especially considering leaching hazardous chemicals. Several studies have demonstrated extreme toxicity in freshwater organisms such Daphnia. When such keystone species are affected by ambient pollution, entire food webs are destabilized and biodiversity is threatened. The unremitting increase in plastic contaminants in freshwater environments would cause impairments in ecosystem functions and structure, leading to various kinds of negative ecological consequences. As various studies have reported the effects on daphnids, a consolidation of this literature is critical to discuss the limitations and knowledge gaps and to evaluate the risk posed to the aquatic environment. This review was undertaken due to the evident need to evaluate this threat. The aims were to provide a meaningful overview of the literature relevant to the potential impact of plastic pollution and associated contaminants on freshwater daphnids as primary consumers. A critical evaluation of research gaps and perspectives is conducted to provide a comprehensive risk assessment of microplastic as a hazard to aquatic environments. We outlined the challenges and limitations to microplastic research in hampering better-focused investigations that could support the development of new plastic materials and/or establishment of new regulations.

Ecotoxicological and health implications of microplastic-associated biofilms: a recent review and prospect for turning the hazards into benefits

Microplastics (MPs), over the years, have been regarded as a severe environmental nuisance with adverse effects on our ecosystem as well as human health globally. In recent times, microplastics have been reported to support biofouling by genetically diverse organisms resulting in the formation of biofilms. Biofilms, however, could result in changes in the physicochemical properties of microplastics, such as their buoyancy and roughness. Many scholars perceived the microplastic-biofilm association as having more severe consequences, providing evidence of its effects on the environment, aquatic life, and nutrient cycles. Furthermore, other researchers have shown that microplastic-associated biofilms have severe consequences on human health as they serve as vectors of heavy metals, toxic chemicals, and antibiotic resistance genes. Despite what is already known about their adverse effects, other interesting avenues are yet to be fully explored or developed to turn the perceived negative microplastic-biofilm association to our advantage. The major inclusion criteria for relevant literature were that it must focus on microplastic association biofilms, while we excluded papers solely on biofilms or microplastics. A total of 242 scientific records were obtained. More than 90% focused on explaining the environmental and health impacts of microplastic-biofilm association, whereas only very few studies have reported the possibilities and opportunities in turning the microplastic biofilms association into benefits. In summary, this paper concisely reviews the current knowledge of microplastic-associated biofilms and their adverse consequences and further proposes some approaches that can be developed to turn the negative association into positive.

Effects of pristine or contaminated polyethylene microplastics on zebrafish development

The presence of microplastics in the aquatic ecosystem represents a major issue for the environment and human health. The capacity of organic pollutants to adsorb onto microplastic particles raises additional concerns, as it creates a new route for toxic compounds to enter the food web. Current knowledge on the impact of pristine and/or contaminated microplastics on aquatic organisms remains insufficient, and we provide here new insights by evaluating their biological effects in zebrafish (Danio rerio). Zebrafish larvae were raised in ZEB316 stand-alone housing systems and chronically exposed throughout their development to polyethylene particles of 20-27 μm, pristine (MP) or spiked with benzo[α]pyrene (MP-BaP), supplemented at 1% w/w in the fish diet. While they had no effect at 30 days post-fertilization (dpf), MP and MP-BaP affected growth parameters at 90 and 360 dpf. Relative fecundity, egg morphology, and yolk area were also impaired in zebrafish fed MP-BaP. Zebrafish exposed to experimental diets exhibited an increased incidence of skeletal deformities at 30 dpf as well as an impaired development of caudal fin/scales, and a decreased bone quality at 90 dpf. An intergenerational bone formation impairment was also observed in the offspring of parents exposed to MP or MP-BaP through a reduction of the opercular bone in 6 dpf larvae. Beside a clear effect on bone development, histological analysis of the gut revealed a reduced number of goblet cells in zebrafish fed MP-BaP diet, a sign of intestinal inflammation. Finally, exposure of larvae to MP-BaP up-regulated the expression of genes associated with the BaP response pathway, while negatively impacting the expression of genes involved in oxidative stress. Altogether, these data suggest that long-term exposure to pristine/contaminated microplastics not only jeopardizes fish growth, reproduction performance, and skeletal health, but also causes intergenerational effects.

Acute and multigenerational effects of petroleum- and cellulose-based microfibers on growth and photosynthetic capacity of Lemna minor

Comparative toxicological assessment studies on the effects of petroleum- and cellulose-based microfibers on aquatic plants are limited. Therefore, we evaluated the acute and 10-generational toxicological effects of two types of petroleum- and cellulose-based microfibers on the duckweed Lemna minor. Plant growth and photosynthesis parameters were monitored as bioindicators. The multigenerational test revealed the following ranking of the microfibers according to the severity of their effects on L. minor: polypropylene > lyocell > viscose > polyethylene terephthalate. The acute tests revealed a significant increase in the energy required to initiate photosynthesis, although the growth of L. minor was not adversely affected by any microfiber. Both petroleum- and cellulose-based microfibers induced adverse effects on the growth and photosynthesis of L. minor in multigenerational tests. The results of the generational tests contribute to the understanding of the long-term adverse effects of microfibers on aquatic plants.

Effects of virgin and weathered polystyrene and polypropylene microplastics on Raphidocelis subcapitata and embryos of Danio rerio under environmental concentrations

Microplastics are ubiquitous contaminants of freshwater ecosystems. However, few ecotoxicity assays have been conducted on freshwater organisms using environmentally relevant concentrations of virgin and weathered microplastics. This work assessed the adverse effects of virgin and artificially weathered fragments of polystyrene and polypropylene on the microalga Raphidocelis subcapitata (72 h growth inhibition assay) and on embryos of the fish Danio rerio (96 h fish embryo assay) under environmentally relevant concentrations (2000-200,000 MP L^-1) and high concentrations (12.5-100 mg L^-1). Sizes of microplastics were measured as tens (polystyrene) to hundreds (polypropylene) of micrometers, while aging was assessed by measuring the carbonyl index. In the microalga, the tested high concentrations promoted growth, while environmentally relevant concentration induced either growth inhibition or promotion. In zebrafish embryos, environmentally relevant concentrations decreased body length and heart rates. No relevant effects were observed in organisms exposed to high concentrations for mortality, malformations, hatching rates, and swimming bladder inflation. Virgin microplastics presented slightly higher toxicity but direct comparison was hindered by the lack of a linear dose-response curve. Despite the lack of a clear pattern, adverse effects were often observed in the lowest environmentally relevant concentrations, raising concerns over the impacts of microplastics on freshwater ecosystems.

Rethinking the relevance of microplastics as vector for anthropogenic contaminants: Adsorption of toxicants to microplastics during exposure in a highly polluted stream - Analytical quantification and assessment of toxic effects in zebrafish (Danio rerio)

Given the increasing amounts of plastic debris entering marine and freshwater ecosystems, there is a growing demand for environmentally relevant exposure scenarios to improve the risk assessment of microplastic particles (MPs) in aquatic environments. So far, data on adverse effects in aquatic organisms induced by naturally exposed MPs are scarce and controversially discussed. As a consequence, we investigated the potential role of MPs regarding the sorption and transfer of environmental contaminants under natural conditions. For this end, a mixture of four common polymer types (polyethylene, polypropylene, polystyrene, polyvinyl chloride) was exposed to natural surface water in a polluted stream for three weeks. Samples of water, MP mixture, sediment, and suspended matter were target-screened for the presence of pollutants using GC/LC-MS, resulting in up to 94 different compounds. Possible adverse effects were investigated using several biomarkers in early developmental stages of zebrafish (Danio rerio). Exposure to natural stream water samples significantly inhibited acetylcholinesterase activity, altered CYP450 induction and modified behavioral patterns of zebrafish. In contrast, effects by samples of both non-exposed MPs and exposed MPs in zebrafish were less prominent than effects by water samples. In fact, the analytical target screening documented only few compounds sorbed to natural particles and MPs. Regarding acute toxic effects, no clear differentiation between different MPs and natural particles could be made, suggesting that - upon exposure in natural water bodies - MPs seem to approximate the sorption behavior of natural particles, presumably to a large extent due to biofilm formation. Thus, if compared to natural inorganic particles, MPs most likely do not transfer elevated amounts of environmental pollutants to biota and, therefore, do not pose a specific additional threat to aquatic organisms.

Microplastic Fibers Increase Sublethal Effects of AgNP and AgNO3 in Daphnia magna by Changing Cellular Energy Allocation

The effects of combined exposure to microplastics and contaminants are still not completely understood. To fill this gap, we assessed the effects of polyethylene terephthalate microplastic fibers (100 mg/L; 360 µm average length) on the toxicity of silver nanoparticles (AgNPs; 32 nm) and silver nitrate (AgNO₃ ; 0.1-10 µg Ag/L) to Daphnia magna. Acute immobilization (median effect concentration [EC50]) and cellular energy allocation (CEA; ratio between available energy and energy consumption) were determined in neonates (<24 h old) and juveniles (7 d old), respectively. The 48-h EC50 for AgNP and AgNO₃ (2.6 and 0.67 µg Ag/L, respectively) was not affected by the presence of microplastic fibers (2.2 and 0.85 µg Ag/L, respectively). No decrease in the available energy was observed: lipid, carbohydrate, and protein contents were unaffected. However, a significant increase in energy consumption was observed in animals exposed to AgNO₃ (250% compared with control) and to the combination of microplastic fibers with AgNP (170%) and AgNO₃ (260%). The exposure to microplastic fibers alone or in combination with both Ag forms decreased the CEA (values were 55-75% of control values). Our results show that after short-term exposure (48 h), microplastic fibers increased Ag toxicity at a subcellular level (i.e., CEA), but not at the individual level (i.e., immobilization). These results highlight the importance of combining different levels of biological organization to fully assess the ecotoxicological effects of plastics in association with environmental contaminants. Environ Toxicol Chem 2022;41:896-904. © 2021 SETAC.

Aquatic Biofilms-Sink or Source of Microplastics? A Critical Reflection on Current Knowledge

The scientific understanding regarding sources, occurrence, and effects of microplastics in the aquatic environment has advanced rapidly, leaving some meaningful knowledge gaps virtually untouched. One of them is the interactions of microplastics and biofilms, microbial communities ubiquitous in aquatic ecosystems and fundamental for a range of ecosystem-level processes. It is evident that biofilms can quickly develop on the microplastic surface and consequently change particle properties and, as such, its fate and ecotoxicity. Moreover, microplastics interact with ubiquitous biofilms that are developed on any surfaces in aquatic ecosystems. Although the knowledge about these interactions is at best limited, it is expected that microplastics attach to the water-biofilm interface or penetrate the biofilm matrix. Microplastics can accumulate and ab- or adsorb to those biofilms where they are subjected to transformation processes such as fragmentation. Thus, biofilms may function as a sink. Changes in environmental conditions may, however, stress biofilms initiating their dieback and microplastic release, which could turn biofilms into a source of microplastics. We argue that the accumulation and release dynamics are a largely overlooked but potentially important piece to the puzzle that is a comprehensive understanding of microplastic fate in the environment and thus under the influence of multiple interacting factors. Environ Toxicol Chem 2022;41:838-843. © 2021 The Authors. Environmental Toxicology and Chemistry published by Wiley Periodicals LLC on behalf of SETAC.

Seeking for a perfect (non-spherical) microplastic particle - The most comprehensive review on microplastic laboratory research

In recent decades, much attention has been paid to microplastic pollution, and research on microplastics has begun to grow exponentially. However, microplastics research still suffers from the lack of standardized protocols and methods for investigation of microplastics under laboratory conditions. Therefore, in this review, we summarize and critically discuss the results of 715 laboratory studies published on microplastics in the last five years to provide recommendations for future laboratory research. Analysis of the data revealed that the majority of microplastic particles used in laboratory studies are manufactured spheres of polystyrene ranging in size from 1 to 50 µm, that half of the studies did not characterize the particles used, and that a minority of studies used aged particles, investigated leaching of chemicals from microplastics, or used natural particles as a control. There is a large discrepancy between microplastics used in laboratory research and those found in the environment, and many laboratory studies suffer from a lack of environmental relevance and provide incomplete information on the microplastics used. We have summarized and discussed these issues and provided recommendations for future laboratory research on microplastics focusing on (i) microplastic selection, (ii) microplastic characterization, and (iii) test design of laboratory research on microplastics.

Uptake, Elimination and Effects of Cosmetic Microbeads on the Freshwater Gastropod Biomphalaria glabrata

The presence of plastic cosmetic microbeads in the environment due to their extensive use in society and inevitable dispersal into wastewater is concerning. Therefore, it is vital to understand the processes of microplastic uptake and elimination by aquatic organisms, and to further assess their potential to cause harmful effects and wider impacts. We therefore investigated the short-term (48-h) and long-term (21-d) uptake, elimination, and effects of exposure to polyethylene microbeads (a mixture of fragments and spheres extracted from commercially available facial scrubs) on the freshwater snail, Biomphalaria glabrata. We found fast uptake in the short-term (75 μg/g/h) and the long-term (6.94 μg/g/h) in B. glabrata exposed to 800 particles/200-mL and 80 particles/200-mL, respectively. Irregular fragments were more easily ingested and egested compared to spheres (ANOVA, p < 0.05) in both 48-h and 21-d exposures. The mean size of the fragments in B. glabrata tissues (413 ± 16 μm) after 48-h exposure was significantly larger than that of the standard sample (369 ± 26 μm) (ANOVA, F_3,20 = 3.339, p = 0.033), suggesting that aggregation in the gut may occur. Floating feces containing microbeads were observed in the long-term exposure, which could alter the fate, behavior, and bioavailability of egested microbeads. No significant effects on survival and growth were shown within 48-h or 21-d exposure periods. Thus, further studies on the specific features of microplastics (e.g., their shape and size) influencing uptake and elimination, as well as toxic molecular mechanisms, should be explored in future ecotoxicological studies.

Environmental hazard of polypropylene microplastics from disposable medical masks: acute toxicity towards Daphnia magna and current knowledge on other polypropylene microplastics

The COVID-19 pandemic has increased the use of disposable plastics, including medical masks, which have become a necessity in our daily lives. As these are often improperly disposed of, they represent an important potential source of microplastics in the environment. We prepared microplastics from polypropylene medical masks and characterised their size, shape, organic chemical leaching, and acute toxicity to the planktonic crustacean Daphnia magna. The three layers of the masks were separately milled and characterised. Each of the inner frontal, middle filtering, and outer layers yielded different types of microplastics: fibres were obtained from the inner and outer layer, but irregular fragments from the middle layer. The shape of the obtained microplastics differed from the initial fibrous structure of the intact medical mask layers, which indicates that the material is deformed during cryo-milling. The chemical compositions of plastics-associated chemicals also varied between the different layers. Typically, the inner layer contained more chemicals related to antimicrobial function and flavouring. The other two layers also contained antioxidants and their degradation products, plasticisers, cross-linking agents, antistatic agents, lubricants, and non-ionic surfactants. An acute study with D. magna showed that these microplastics do not cause immobility but do physically interact with the daphnids. Further long-term studies with these microplastics are needed using a suite of test organisms. Indeed, studies with other polypropylene microplastics have shown numerous adverse effects on other organisms at concentrations that have already been reported in the environment. Further efforts should be made to investigate the environmental hazards of polypropylene microplastics from medical masks and how to handle this new source of environmental burden.

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The online version contains supplementary material available at 10.1186/s43591-021-00020-0.

Ecological risks in a 'plastic' world: A threat to biological diversity?

Microplastics pollution is predicted to increase in the coming decades, raising concerns about its effects on living organisms. Although the effects of microplastics on individual organisms have been extensively studied, the effects on communities, biological diversity, and ecosystems remain underexplored. This paper reviews the published literature concerning how microplastics affect communities, biological diversity, and ecosystem processes. Microplastics increase the abundance of some taxa but decrease the abundance of some other taxa, indicating trade-offs among taxa and altered microbial community composition in both the natural environment and animals' gut. The alteration of community composition by microplastics is highly conserved across taxonomic ranks, while the alpha diversity of microbiota is often reduced or increased, depending on the microplastics dose and environmental conditions, suggesting potential threats to biodiversity. Biogeochemical cycles, greenhouse gas fluxes, and atmospheric chemistry, can also be altered by microplastics pollution. These findings suggest that microplastics may impact the U.N. Sustainability Development Goals (SDGs) to improve atmospheric, soil, and water quality and sustaining biodiversity.

Ecotoxicological effects of microplastics on aquatic organisms: a review

Microplastics   ( <5 mm), which are classified based on primary or secondary sources, are widely distributed in the environment and exert significant effects on aquatic life forms; however, evidence regarding the ecotoxicological effects of microplastics on aquatic organisms is still limited. This research aims at filling a knowledge gap regarding generation sources, distribution, physicochemical properties, and biological behavior of microplastics (MP) in aquatic environments and their interaction with aquatic organisms. The literature indicates that concentrations of MPs observed in such environments are higher than the threshold for safe concentration (6650 buoyant particles/m³). MPs having large specific surface area, low polarity, and hydrophobic properties have been shown to absorb dichlorodiphenyltrichloroethane (DDT), polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbon (PAHs), bisphenol A (BPA), polyfluoroalkyl substances (PFAS), antibiotics, and heavy metals. MPs adsorb large amounts of toxic organic chemicals (18,700 ng/g PCBs; 24,000 ng/g PAHs) and heavy metals (0.21-430 μg/g Cr; 0.0029-930 μg/g Cd; 0.35-2.89 μg/g As; 0.26-698,000 μg/g Pb). MPs originating from polystyrene (PS), polypropylene (PP), and polyvinylchloride (PVC) show greater toxicity toward aquatic organisms, with effects on the immune system, reproductive system, nervous system, and endocrine system. Thus, elucidating the cumulative toxic expression of MPs in different polluted environments is critical.

An extensive characterization of various environmentally relevant microplastics - Material properties, leaching and ecotoxicity testing

Microplastics in the environment occur in different sizes and shapes and are made of various polymers. Therefore, they also considerably differ in their properties and ecotoxicity. However, the majority of microplastics research uses pre-made spherical microplastics, which practically do not exist in the environment. Our work focused on a comprehensive study of six different types of microplastic that were prepared to simulate common microplastics found in the environment. All types of microplastics where chemically and physically characterized using Fourier-transform infrared spectroscopy, thermal analysis, field-emission scanning electron microscopy, optical microscopy and laser diffraction analysis. The specific surface area was determined using the BET method. Furthermore, effects of microplastics and microplastic leachates on a common duckweed (Lemna minor) were evaluated. All tested microplastics did not affect specific growth rate and chlorophyll a content in duckweed, while microplastics with a rough surface and sharp edges caused a significant reduction of duckweed root length. Microplastics made of Bakelite also showed an intensive leaching, which increased their ecotoxicity potential. Natural particles used as a control did not have any negative effect on duckweed. Overall, microplastic particles have significantly different ecotoxicity profiles depending on their physico-chemical properties. Therefore, the testing of environmentally relevant particles and their proper characterization, as well as the testing of microplastic leaching properties, is crucial for understanding of microplastics ecotoxicological potential.

Weathering Plastics as a Planetary Boundary Threat: Exposure, Fate, and Hazards

We described in 2017 how weathering plastic litter in the marine environment fulfils two of three criteria to impose a planetary boundary threat related to "chemical pollution and the release of novel entities": (1) planetary-scale exposure, which (2) is not readily reversible. Whether marine plastics meet the third criterion, (3) eliciting a disruptive impact on vital earth system processes, was uncertain. Since then, several important discoveries have been made to motivate a re-evaluation. A key issue is if weathering macroplastics, microplastics, nanoplastics, and their leachates have an inherently higher potential to elicit adverse effects than natural particles of the same size. We summarize novel findings related to weathering plastic in the context of the planetary boundary threat criteria that demonstrate (1) increasing exposure, (2) fate processes leading to poorly reversible pollution, and (3) (eco)toxicological hazards and their thresholds. We provide evidence that the third criterion could be fulfilled for weathering plastics in sensitive environments and therefore conclude that weathering plastics pose a planetary boundary threat. We suggest future research priorities to better understand (eco)toxicological hazards modulated by increasing exposure and continuous weathering processes, to better parametrize the planetary boundary threshold for plastic pollution.

Review of the artificially-accelerated aging technology and ecological risk of microplastics

After being discarded into the environment, the microplastics (MPs) will undergo weathering effects. However, the low degradation rate of MPs in natural processes greatly limits the understanding of long-term aging behavior. By critically reviewing 82 articles in Web of Science from 2015 to 2020, the paper summarized different laboratory technologies including light irradiation, chemical oxidation, heat treatment and γ-ray irradiation to simulate and accelerate the aging of MPs, and evaluated the feasibility by comparison with natural processes. The advantages of laboratory technologies are that aging conditions can be artificially controlled and that the labor and time costs can be saved, whereas the laboratory system is too simple to simulate complex aging processes in the environment. We further reviewed the potential impacts of aging process on the risks of MPs (i.e. physical injury, combined toxicity with external pollutants and chemical risk of additives and low-molecular products). The overall risks are seemingly enhanced by aging process due to the high ingestion by organisms, the strong interaction with pollutants and the release of MP-derived organic compounds. Further studies on the aging behavior of MPs should be focused on the laboratory techniques that can simulate multiple processes of natural aging, the long-term fragmentation behavior of MPs, the effect of aging on growth rate of biofilm in MPs and ingestion property by organisms, and the relationship between aging property of MPs and release rate of chemicals in leachates.

A Critical Review on the Impacts of Nanoplastics and Microplastics on Aquatic and Terrestrial Photosynthetic Organisms

Microplastic and nanoplastic contamination is widespread and affects aquatic and terrestrial ecosystems. Photosynthetic organisms are present in both media, they are primary producers, sink for CO₂ , and they represent a major point of entry in the food chain. Here, the current knowledge on the fate and impacts of microplastics and nanoplastics in interaction with these organisms is reviewed. As a general trend, plastic characteristics (smaller size and positive charge) play a crucial role in their toxicity toward photosynthetic organisms. Plastic leachates (containing additives) also represent a major source of toxicity, and some harmful compounds such as phthalate esters are shown to accumulate in plants and generate a risk for the consumers. Adsorption of plastic particles is evidenced for each type of photosynthetic organism, and uptake and translocation in terrestrial plants is evidenced for nanoplastics, leading to concerns for trophic chain contamination. The available techniques for the detection of microplastics and nanoplastics and their secondary products in biological samples and media are also listed. Finally, the current gaps of knowledge, specific challenges, and future research directions are also discussed.

Incubation in Wastewater Reduces the Multigenerational Effects of Microplastics in Daphnia magna

The aging of microplastics in the environment changes their physicochemical properties. While this may affect their toxicity, comparative data on the effects of aged compared to pristine microplastics are scarce. One of those aging processes is the sorption of chemicals, which has mainly been studied for individual pollutants present in marine ecosystems. To investigate how the sorption of a complex mixture of freshwater pollutants affects the toxicity of microplastics, we incubated irregular polystyrene particles (≤63 μm) in either wastewater or ultrapure water. We exposed Daphnia magna to these aged microplastics and their pristine counterparts (80, 400, 2000, and 10,000 particles mL^-1) over four generations using food limitation as an additional, environmentally realistic stressor. Both particle types affect the survival, reproduction, adult and neonate body lengths, and growth. An exposure to pristine microplastics results in the extinction of the third generation of daphnids. In contrast, wastewater-incubated particles induced a lower mortality. The incubation with wastewater does not change the microplastics' size, surface charge, and structure. Consistent with the literature, we assume that the adsorption of dissolved organic matter is a key aging process reducing the toxicity of microplastics. Consequently, toxicity testing using pristine microplastics may overestimate the effects of plastic particles in nature.

Environmental fate and impacts of microplastics in aquatic ecosystems: a review

Wide usage of plastic products leads to the global occurrence of microplastics (MPs) in the aquatic environment. Due to the small size, they can be bio-ingested, which may cause certain health effects. The present review starts with summarizing the main sources of various types of MPs and their occurrences in the aquatic environment, as well as their transportation and degradation pathways. The analysis of migration of MPs in water environments shows that the ultimate fate of most MPs in water environments is cracked into small fragments and sinking into the bottom of the ocean. The advantages and disadvantages of existing methods for detection and analysis of MPs are summarized. In addition, based on recent researches, the present review discusses MPs as carriers of organic pollutants and microorganisms, and explores the specific effects of MPs on aquatic organisms in the case of single and combined pollutants. Finally, by analysing the causes and influencing factors of their trophic transfer, the impact of MPs on high-level trophic organisms is explored.

The sources, fate and impacts of microplastics in aquatic ecosystems.

Ecotoxicological Assessment of Microplastics in Freshwater Sources—A Review

High living standards and a comfortable modern way of life are related to an increased usage of various plastic products, yielding eventually the generation of an increased amount of plastic debris in the environment. A special concern is on microplastics (MPs), recently classified as contaminants of emerging concern (CECs). This review focuses on MPs’ adverse effects on the environment based on their bioactivity. Hence, the main topic covered is MPs’ ecotoxicity on various aquatic (micro)organisms such as bacteria, algae, daphnids, and fish. The cumulative toxic effects caused by MPs and adsorbed organic/inorganic pollutants are presented and critically discussed. Since MPs’ bioactivity, including ecotoxicity, is strongly influenced by their properties (e.g., types, size, shapes), the most common classification of MPs types present in freshwater are provided, along with their main characteristics. The review includes also the sources of MPs discharge in the environment and the currently available characterization methods for monitoring MPs, including identification and quantification, to obtain a broader insight into the complex problem caused by the presence of MPs in the environment.

Combined effects of mulch film-derived microplastics and atrazine on oxidative stress and gene expression in earthworm (Eisenia fetida)

With the wide use of mulch film and pesticides, mulch film-derived microplastics are very likely to produce combined effects with pesticides in agricultural soil. However, little is known about their combined toxicity on terrestrial organisms. This study aimed to investigate the combined toxicity of unused or farmland residual transparent low-density polyethylene mulch film-derived microplastics (MPs and MPs-aged, respectively) (550-1000 μm) and atrazine (ATZ; 0.02 and 2.0 mg/kg) on the earthworm (Eisenia fetida). After single and combined exposure to ATZ and microplastics for 28 d, the results showed an accumulation of reactive oxygen species, a decrease in superoxide dismutase, catalase, and glutathione-S-transferase activities, an increase in the malondialdehyde and 8-hydroxydeoxyguanosine levels, and abnormal expression of annetocin, heat shock protein 70, translationally controlled tumor protein and calreticulin genes. Integrated biological response (IBR) values calculated at the biochemical level indicated that the combined exposure to ATZ and microplastics, particularly to high concentrations of ATZ, induced greater oxidative stress in E. fetida compared with that of exposure to ATZ or microplastics alone. In addition, the IBR values calculated at the gene level did not show regular changes after combined exposure to ATZ and microplastics compared with those of a single exposure. The oxidative stress and abnormal expression of genes in E. fetida induced by MPs-aged were higher than those induced by MPs; a similar trend was observed for oxidative stress induced by MPs/MPs-aged + ATZ2.0, whereas an opposite trend was observed for the abnormal expression of genes in E. fetida induced by MPs/MPs-aged + ATZ0.02/ATZ2.0. Our results suggest that mulch film-derived microplastics have the potential to enhance the toxicity of ATZ within the soil environment.

Photo-Oxidative Degradation Mitigated the Developmental Toxicity of Polyamide Microplastics to Zebrafish Larvae by Modulating Macrophage-Triggered Proinflammatory Responses and Apoptosis

Microplastics (MPs) are ubiquitous in the environment and pose substantial threats to the water ecosystem. However, the impact of natural aging of MPs on their toxicity has rarely been considered. This study found that visible light irradiation with hydrogen peroxide at environmentally relevant concentration for 90 days significantly altered the physicochemical properties and mitigated the toxicity of polyamide (PA) fragments to infantile zebrafish. The size of PA particles was reduced from ∼8.13 to ∼6.37 μm, and nanoparticles were produced with a maximum yield of 5.03%. The end amino groups were volatilized, and abundant oxygen-containing groups (e.g., hydroxyl and carboxyl) and carbon-centered free radicals were generated, improving the hydrophilicity and colloidal stability of degraded MPs. Compared with pristine PA, the depuration of degraded MPs mediated by multixenobiotics resistance was much quicker, leading to markedly lower bioaccumulation in fish and weaker inhibition on musculoskeletal development. By integrating transcriptomics and transgenic zebrafish [Tg(lyz:EGFP)] tests, differences in macrophages-triggered proinflammatory effects, apoptosis via IL-17 signaling pathway, and antioxidant damages were identified as the underlying mechanisms for the attenuated toxicity of degraded MPs. This work highlights the importance of natural degradation on the toxicity of MPs, which has great implications for risk assessment of MPs.

Wastewater treatment, reuse, and disposal-associated effects on environment and health

This paper presents the review of the literature published in the year 2019 related to treatment and reuse of wastewater and effects on the environment and human health. The scientific review on the treatment and reuse of wastewaters is divided into various sections in the paper. The review sections cover wastewater management, reuse, removal of microorganisms, and chemical constituents. Besides, the review also covers research focused on wastewater treatment plants, disposal, and the management of wastewater sludge as well as biosolids in the environment. PRACTITIONER POINTS: This paper highlights the review of scientific literature published in the year 2019.Review provide issues related to health risks associated with human and the general environment on the reuse of wastewater, treatment as well as disposal.The literature review covers selected papers relevant to the topic.

Zebrafish: An emerging model to study microplastic and nanoplastic toxicity

Microplastics (MPs) and nanoplastics (NPs) have received global concern due to its widespread contamination, ingestion in aquatic organisms and the ability to cross the biological barrier. However, our understanding of its bioaccumulation, toxicity, and interaction with other environmental pollutants is limited. Zebrafish is increasingly used to study the bioaccumulation and toxicity of environmental contaminants because of their small size, ease of breed, short life cycle and inexpensive maintenance. The transparent nature of zebrafish embryo and larvae provides excellent experimental advantages over other model organisms in studying the localization of fluorescent-labeled MPs/NPs particles. Zebrafish outplays the traditional rodent models with the availability of transgenic lines, high-throughput sequencing and genetic similarities to humans. All these characteristics provide an unprecedented opportunity to investigate the toxicity of MPs/NPs and associated contaminants. This review summarizes the existing literature on MPs/NPs research in zebrafish and suggests a path forward for future research.

Iced block method: An efficient method for preparation of micro-sized expanded polystyrene foams

Recently, numerous studies concerning dye-labeled microplastic beads have reported on the end-of-life, environmental effects of microplastics because of their ubiquitous commercial usage. Less is understood about the toxicity and bioaccumulation of plastics other than microplastic beads, which can also harm the environment (e.g., fragments, fibers, foams, and films). Expanded polystyrene (EPS) is widespread in the environment owing to its many uses, however, limited research has been conducted on EPS foams. This study focuses on developing an efficient method for the preparation of micro-sized EPS foams for research purposes and compares it with previous microplastics preparation methods reported in 68 previous studies. It was demonstrated that the iced EPS block method (iced EPS block + water) generated larger quantities of smaller-sized EPS foams (20-200 and 200-500 μm) compared to the EPS + ice + water and EPS + water methods. The optimal protocol includes 1) iced EPS block preparation, 2) grinding and sieving, and 3) collecting. Additionally, it was confirmed that the iced EPS block method requires less money, labor, and time compared to previously reported methods in the literature. The method proposed in this research can assist future investigations into the environmental effects of EPS foams.

Microplastics in Honey, Beer, Milk and Refreshments in Ecuador as Emerging Contaminants

According to the latest research, marine products have the greatest potential for microplastic (MPs) contamination. Therefore, their presence in terrestrial food has not managed to attract much attention—despite the fact that in the future they may represent a serious environmental risk. Research conducted in Europe and the US has indicated the presence of MPs in tap water, bottled water, table salt, honey, beer and snails for human consumption. The presence of MPs in food has not yet been evaluated in Latin America. This work focused on evaluating two widely consumed beverages: milk and soft drinks. Furthermore, honey and beer samples were analyzed and compared to findings in the literature. All products were sourced in Ecuador. In order to determine correlations with the intensity of anthropogenic activity, samples of both industrially processed and craft products were studied. For the analysis, an improvement of previous techniques used to determine MPs in honey was applied. This technique uses microfiltration followed by degradation of organic matter with hydrogen peroxide—and finally, continuous rinsing with deionized water. Size ranges were established between 0.8–200 mm. The number of microplastics found was between 10 and 100 MPs/L, with an average of around 40 MPs/L. The sizes of the particles found in the study are in the range of 13.45 and 6742.48 μm for the fibers, and between 2.48 and 247.54 μm for the fragments. From the composition analysis carried out with FTIR, we were able to confirm the presence of 12% of microplastic. The results generally showed a greater presence of MPs compared to those registered in Europe, probably due to processing methods rather than environmental pollution. Regarding composition, the main microplastics found were polyethylene, polypropylene and polyacrylamide.

Aquatic vascular plants - A forgotten piece of nature in microplastic research

Research on the interaction of microplastics and aquatic organisms has been mainly focused on the evaluation of various impacts on animals while aquatic vascular plants have been so far understudied. In this commentary, we summarized knowledge about interactions of microplastics with aquatic vascular plants and highlighted potential ecological implications. Based on recent research, microplastics have minimal impacts on plants. However, they are strongly attracted to plant tissues, adsorbed, and accumulated by plants. Several mechanisms drive microplastics adsorption and accumulation; the most possibly electrostatic forces, leaf morphology, and presence of periphyton belong among the most important ones. Adsorbed microplastics on plant tissues are easily ingested by herbivores. Plants can thus represent a viable pathway for microplastics to enter aquatic food webs. On the other hand, the strong interactions of microplastics with plants could be used for their phytostabilization and final removal from the environment. Aquatic vascular plants have thus an important role in the behavior and fate of microplastics in aquatic ecosystems, and therefore, they should also be included in the future microplastic research.

Microplastics provide new microbial niches in aquatic environments

Microplastics in the biosphere are currently of great environmental concern because of their potential toxicity for aquatic biota and human health and association with pathogenic microbiota. Microplastics can occur in high abundance in all aquatic environments, including oceans, rivers and lakes. Recent findings have highlighted the role of microplastics as important vectors for microorganisms, which can form fully developed biofilms on this artificial substrate. Microplastics therefore provide new microbial niches in the aquatic environment, and the developing biofilms may significantly differ in microbial composition compared to natural free-living or particle-associated microbial populations in the surrounding water. In this article, we discuss the composition and ecological function of the microbial communities found in microplastic biofilms. The potential factors that influence the richness and diversity of such microbial microplastic communities are also evaluated. Microbe-microbe and microbe-substrate interactions in microplastic biofilms have been little studied and are not well understood. Multiomics tools together with morphological, physiological and biochemical analyses should be combined to provide a more comprehensive overview on the ecological role of microplastic biofilms. These new microbial niches have so far unknown consequences for microbial ecology and environmental processes in aquatic ecosystems. More knowledge is required on the microbial community composition of microplastic biofilms and their ecological functions in order to better evaluate consequences for the environment and animal health, including humans, especially since the worldwide abundance of microplastics is predicted to dramatically increase.

Key Points • Bacteria are mainly studied in community analyses: fungi are neglected. • Microbial colonization of microplastics depends on substrate, location and time. • Community ecology is a promising approach to investigate microbial colonization. • Biodegradable plastics, and ecological roles of microplastic biofilms, need analysis.

An environmental concentration of aged microplastics with adsorbed silver significantly affects aquatic organisms

Microplastics are very complex pollutants; they can be made of many polymer types and exist in various shapes and sizes. When they enter the environment they are affected by biotic and abiotic factors that cause their properties to change. In this context, the aim of our study was to evaluate the extent to which biofouling affects the properties and toxicity of microplastics. Cosmetic polyethylene microbeads were incubated in stream water for four weeks resulting in biofouling and aging. Subsequently, the changes in properties (sinking, particle size, adsorption, and leaching of model metal - silver) and the microplastics toxicity to daphnids Daphnia magna and duckweed Lemna minor were evaluated. Pristine microplastics did not affect daphnids but they significantly affected the root growth of duckweed. On the other hand, reference natural particles (beech sawdust) did not show any negative effects. We observed significant differences in the properties of aged versus pristine microplastics. When compared to pristine microplastics, aged microplastics adsorbed more silver and the subsequent leaching of silver was more intensive, especially in the medium with an acidic pH. Microplastics with adsorbed silver had a high ecotoxicological potential and at environmentally relevant concentrations affected both daphnids and duckweed. This study suggests that biofouling is an important parameter that affects microplastics properties, pollutant adsorption and release into the environment, and toxicity. Overall, there are significant alterations of the microplastics properties, behaviour, and fate in the environment.

Evaluation of partial nitrification efficiency as a response to cadmium concentration and microplastic polyvinylchloride abundance during landfill leachate treatment

The partial nitrification efficiency response to the presence of cadmium (Cd²⁺) and microplastics was investigated. Microplastics polyvinylchloride (PVC) abundance was 0-10,000 particles/L, and Cd²⁺ concentration was 0-10 mg/L. Cd-only inhibited the NH₄⁺-N oxidation rate 1.21, 1.23, and 1.18 times with concentrations at 1, 5, and 10 mg/L, respectively. PVC-only inhibited NH₄⁺-N oxidation rate 1.01, 1.21 and 1.05 times with PVC abundance at 1000, 5000 and 10,000 particles/L, respectively. The ammonia oxidation rate was improved with the co-existence of PVC and Cd²⁺ at the conditions PVC1000 and PVC5000, which could be attributed to the PVC. PVC at 1000 particles/L could act as carrier and mitigate the negative effect of Cd²⁺ to the partial nitrification process. Moreover, the partial nitrification process was largely inhibited with PVC abundance at 10,000 particles/L. First-order kinetic models could simulate the NH₄⁺-N, NO₂^-N, and NO₃^--N changes in the partial nitrification process.

Is the development of Daphnia magna neonates affected by short-term exposure to polyethylene microplastics?

The study presents responses of D. magna newborns exposed during 96 h to polyethylene microplastics (MP) of size 40-48 μm in the concentrations of 20; 40; 80; 160 and 320 mg/L. The experimental design consisted of two exposure scenarios: the first group was fed at the beginning and after 48 h (3x10^-5 cells/mL of Raphidocelis subcaptata and fermented solution) and the second group was not fed as an additional stressor. The mobility of the organisms was not significantly affected in the presence of microplastics for both exposure groups. Nevertheless, the qualitative analysis showed that neonates promptly ingested microplastics in the first 24 h of the test, independently of the treatment. Polyethylene microplastics did not influence the molting process, however, significant differences were observed between the number of molts of the exposure without feed and with feed in 24 h (p = 0.0007), 48 h (p = 2.4 x 10^-10), 72 h (p = 3.6 x 10^-10) and 96 h (p = 0.003). The final body length of D. magna also showed that the food administration model in the tests contributes to the differentiation in responses.