Orientation of reduced graphene oxide in composite coatings

Composite coatings containing reduced graphene oxide (rGO) and 3-(aminopropyl)triethoxysilane functionalised rGO (APTES-rGO) were prepared by sol-gel technology and deposited on Al 2024 T-3. Covalent functionalisation of GO by APTES occurred by formation of amide bonds, accompanied by GO reduction. The thin sheets were retained. The hydrophilicity of the coating increased when APTES-rGO was added. The opposite was observed when GO was added. A key finding is that the rGO flakes agglomerate and lie in a random orientation in the coating, whereas the APTES-rGO flakes are more evenly distributed in the matrix and appear to lie along the plane of the substrate.

Synthetic and natural rubber associated chemicals drive functional and structural changes as well as adaptations to antibiotics in in vitro marine microbiomes

The leaching of additives from plastics and elastomers (rubbers) has raised concerns due to their potential negative impacts on the environment and the development of antibiotic resistance. In this study, we investigated the effects of chemicals extracted from two types of rubber on microbiomes derived from a benthic sea urchin and two pelagic fish species. Additionally, we examined whether bacterial communities preconditioned with rubber-associated chemicals displayed adaptations to antibiotics. At the highest tested concentrations of chemicals, we observed reduced maximum growth rates and yields, prolonged lag phases, and increased alpha diversity. While the effects on alpha and beta diversity were not always conclusive, several bacterial genera were significantly influenced by chemicals from the two rubber sources. Subsequent exposure of sea urchin microbiomes preconditioned with rubber chemicals to the antibiotic ciprofloxacin resulted in decreased maximum growth rates. This indicates a more sensitive microbiome to ciprofloxacin when preconditioned with rubber chemicals. Although no significant interaction effects between rubber chemicals and ciprofloxacin exposure were observed in bacterial alpha and beta diversity, we observed log-fold changes in two bacterial genera in response to ciprofloxacin exposure. These findings highlight the structural and functional alterations in microbiomes originating from various marine species when exposed to rubber-associated chemicals and underscore the potential risks posed to marine life.

Polystyrene nanoplastics affected the nutritional quality of Chlamys farreri through disturbing the function of gills and physiological metabolism: Comparison with microplastics

Although microplastics (MPs) and nanoplastics (NPs) have become a global concern because of their possible hazards to marine organisms, few studies have investigated the effects of MPs/NPs on the nutritional quality of marine economic species, and the toxicity mechanisms remain unclear. We therefore investigated the effects of polystyrene MPs (PS-MPs, 5 μm) and NPs (PS-NPs, 100 nm) at an environmentally relevant concentration on adult scallops Chlamys farreri through the determination of nutritional composition, physiological metabolism, enzymatic response, and histopathology. Results showed that plastic particles significantly decreased the plumpness (by 33.32 % for PS-MPs and 36.69 % for PS-NPs) and protein content of the adductor muscle (by 4.88 % for PS-MPs and 8.77 % for PS-NPs) in scallops, with PS-NPs causing more notable impacts than PS-MPs. Based on the integrated biomarker response analysis, PS-NPs exhibited greater toxicity than PS-MPs, suggesting a size-dependent effect for plastic particle. Furthermore, PS-NPs significantly affected the physiological metabolism (e.g., filtration and ammonia excretion) than PS-MPs. Using gill transcriptomics analysis, the key toxicological mechanisms caused by NPs exposure included enrichment of the mitophagy pathway, responses to oxidative stress, and changes related to genes associated with nerves. This study provides new insights into the potential negative effects of MPs/NPs on the mariculture industry.

New insights into the impact of polystyrene micro/nanoplastics on the nutritional quality of marine jacopever (Sebastes schlegelii)

Microplastics (MPs) and nanoplastics (NPs) are ubiquitous in the marine environments due to the wide use and mismanagement of plastics. However, the effect of MPs/NPs on the nutrition quality of economic species is poorly understood, and their underlying mechanisms remained unclear. We therefore investigated the impacts of polystyrene MPs/NPs on the nutrition composition of marine jacopever Sebastes schlegelii from the perspective of assimilation and metabolism. Results showed that NPs reduced more nutrition quality than MPs. Despite no notable impact on intestinal microbiota function, MPs/NPs influenced the assimilation of fish through intestinal damage. Furthermore, NPs induced greater damage to hepatocyte metabolism than MPs, caused by hepatocyte uptake through membrane protein pumps/channels and clathrin/caveolin-mediated endocytosis for NPs, while through phagocytosis/pinocytosis for MPs. NPs triggered more cell apoptosis signals in Ferroptosis and FoxO signaling pathways than MPs, destroying mitochondria structure. Compared with MP treatments, a significant upregulation of genes (PRODH and SLC25A25A) associated with the electron transfer chain of mitochondria was detected in the NP treatments, influencing the tricarboxylic acid cycle and interfering with liver metabolism of proteins, fatty acid, glycerol phospholipids, and carbohydrates. This work provides new insights into the potential impacts of MPs/NPs on the quality and safety of seafood.

A recipe for plastic: Expert insights on plastic additives in the marine environment

The production and consumption of plastic products had been steadily increasing over the years, leading to more plastic waste entering the environment. Plastic pollution is ubiquitous and comes in many types and forms. To enhance or modify their properties, chemical additives are added to plastic items during manufacturing. The presence and leakage of these additives, from managed and mismanaged plastic waste, into the environment are of growing concern. In this study, we gauged, via an online questionnaire, expert knowledge on the use, characteristics, monitoring and risks of plastic additives to the marine environment. We analysed the survey results against actual data to identify and prioritise risks and gaps. Participants also highlighted key factors for future consideration, including gaining a deeper understanding of the use and types of plastic additives, how they leach throughout the entire lifecycle, their toxicity, and the safety of alternative options. More extensive chemical regulation and an evaluation of the essentiality of their use should also be considered.

Training the next generation of plastics pollution researchers: tools, skills and career perspectives in an interdisciplinary and transdisciplinary field

Plastics pollution research attracts scientists from diverse disciplines. Many Early Career Researchers (ECRs) are drawn to this field to investigate and subsequently mitigate the negative impacts of plastics. Solving the multi-faceted plastic problem will always require breakthroughs across all levels of science disciplinarity, which supports interdisciplinary discoveries and underpins transdisciplinary solutions. In this context, ECRs have the opportunity to work across scientific discipline boundaries and connect with different stakeholders, including industry, policymakers and the public. To fully realize their potential, ECRs need to develop strong communication and project management skills to be able to effectively interface with academic peers and non-academic stakeholders. At the end of their formal education, many ECRs will choose to leave academia and pursue a career in private industry, government, research institutes or non-governmental organizations (NGOs). Here we give perspectives on how ECRs can develop the skills to tackle the challenges and opportunities of this transdisciplinary research field and how these skills can be transferred to different working sectors. We also explore how advisors can support an ECRs' growth through inclusive leadership and coaching. We further consider the roles each party may play in developing ECRs into mature scientists by helping them build a strong foundation, while also critically assessing problems in an interdisciplinary and transdisciplinary context. We hope these concepts can be useful in fostering the development of the next generation of plastics pollution researchers so they can address this global challenge more effectively.

Graphical Abstract

Comprehensive Two-Dimensional Gas Chromatography with Peak Tracking for Screening of Constituent Biodegradation in Petroleum UVCB Substances

Petroleum substances, as archetypical UVCBs (substances of unknown or variable composition, complex reaction products, or biological substances), pose a challenge for chemical risk assessment as they contain hundreds to thousands of individual constituents. It is particularly challenging to determine the biodegradability of petroleum substances since each constituent behaves differently. Testing the whole substance provides an average biodegradation, but it would be effectively impossible to obtain all constituents and test them individually. To overcome this challenge, comprehensive two-dimensional gas chromatography (GC × GC) in combination with advanced data-handling algorithms was applied to track and calculate degradation half-times (DT50s) of individual constituents in two dispersed middle distillate gas oils in seawater. By tracking >1000 peaks (representing ∼53-54% of the total mass across the entire chromatographic area), known biodegradation patterns of oil constituents were confirmed and extended to include many hundreds not currently investigated by traditional one-dimensional GC methods. Approximately 95% of the total tracked peak mass biodegraded after 64 days. By tracking the microbial community evolution, a correlation between the presence of functional microbial communities and the observed progression of DT50s between chemical classes was demonstrated. This approach could be used to screen the persistence of GC × GC-amenable constituents of petroleum substance UVCBs.

Organic chemicals associated with rubber are more toxic to marine algae and bacteria than those of thermoplastics

The current study investigated the chemical complexity of fifty plastic (36) and elastomer/rubber (14) methanol extracts from consumer products, focusing on the association with toxicity in two screening assays (bacteria luminescence and marine microalgae). The chemical composition varied considerably between the products and polymers. The most complex sample (car tire rubber) contained 2456 chemical features and the least complex (disposable water bottle) only 39 features, with a median of 386 features across all products. Individual extract toxicity also varied significantly across the products and polymers, with the two toxicity assays showing comparable results in terms of defining low and high toxicity extracts, and correlation between medium toxicity extracts. Chemical complexity and abundance both correlated with toxicity in both assays. However, there were strong differences in toxicity between plastic and elastomer extracts. Overall, 86-93 % of the 14 elastomer extracts and only 33-36 % of other polymer extracts (n = 36) were more toxic than the median. A range of compounds were tentatively identified across the sample set, with several concerning compounds being identified, mostly in the elastomers. While the current focus on plastic chemicals is towards thermoplastics, we show that elastomers may be of more concern from an environmental and human health perspective.

Physicochemical characterization and quantification of nanoplastics: applicability, limitations and complementarity of batch and fractionation methods

A comprehensive physicochemical characterization of heterogeneous nanoplastic (NPL) samples remains an analytical challenge requiring a combination of orthogonal measurement techniques to improve the accuracy and robustness of the results. Here, batch methods, including dynamic light scattering (DLS), nanoparticle tracking analysis (NTA), tunable resistive pulse sensing (TRPS), transmission electron microscopy (TEM), and scanning electron microscopy (SEM), as well as separation/fractionation methods such as centrifugal liquid sedimentation (CLS) and field-flow fractionation (FFF)-multi-angle light scattering (MALS) combined with pyrolysis gas chromatography mass spectrometry (pyGC-MS) or Raman microspectroscopy (RM) were evaluated for NPL size, shape, and chemical composition measurements and for quantification. A set of representative/test particles of different chemical natures, including (i) polydisperse polyethylene (PE), (ii) (doped) polystyrene (PS) NPLs, (iii) titanium dioxide, and (iv) iron oxide nanoparticles (spherical and elongated), was used to assess the applicability and limitations of the selected methodologies. Particle sizes and number-based concentrations obtained by orthogonal batch methods (DLS, NTA, TRPS) were comparable for monodisperse spherical samples, while higher deviations were observed for polydisperse, agglomerated samples and for non-spherical particles, especially for light scattering methods. CLS and TRPS offer further insight with increased size resolution, while detailed morphological information can be derived by electron microscopy (EM)-based approaches. Combined techniques such as FFF coupled to MALS and RM can provide complementary information on physical and chemical properties by online measurements, while pyGC-MS analysis of FFF fractions can be used for the identification of polymer particles (vs. inorganic particles) and for their offline (semi)quantification. However, NPL analysis in complex samples will continue to present a serious challenge for the evaluated techniques without significant improvements in sample preparation.

Mechanism of nanoplastics capture by jellyfish mucin and its potential as a sustainable water treatment technology

The accumulation of nanoplastics (NPs) in the environment has raised concerns about their impact on human health and the biosphere. The main aim of this study is to understand the mechanism that governs the capture of NPs by jellyfish mucus extracted from the jellyfish Aurelia sp. (A.a.) and compare the capture/removal efficiency to that of conventional coagulants and mucus from other organisms. The efficacy of A.a mucus to capture polystyrene and acrylic NPs (∼100 nm) from spiked wastewater treatment plant (WWTP) effluent was evaluated. The mucus effect on capture kinetics and destabilization of NPs of different polymer compositions, sizes and concentrations was quantified by means of fluorescent NPs, dynamic light scattering and zeta potential measurements and visualized by scanning electron microscopy. A dosing of A.a. mucus equivalent to protein concentrations of ∼2-4 mg L^-1 led to a rapid change in zeta potential from a baseline of -30 mV to values close to 0 mV, indicating a marked change from a stable to a non-stable dispersion leading to a rapid (<10 min) and significant removal of NPs (60 %-90 %) from a stable suspension. The A.a. mucus outperformed all other mucus types (0-37 %) and coagulants (0 %-32 % for ferric chloride; 23-40 % for poly aluminum chlorohydrate), highlighting the potential for jellyfish mucus to be used as bio-flocculant. The results indicate a mucus-particle interaction consisting of adsorption-bridging and "mesh" filtration. Further insight is provided by carbohydrate composition and protein disruption analysis. Total protein disruption resulted in a complete loss of the A.a. mucus capacity to capture NPs, while the breaking of disulfide bonds and protein unfolding resulted in improved capture capacity. The study demonstrates that natural jellyfish mucin can capture and remove NPs in water and wastewater treatment systems more efficiently than conventional coagulants, highlighting the potential for development of a new type of bio-flocculant.

Generating environmental sampling and testing data for micro- and nanoplastics for use in life cycle impact assessment

Ongoing efforts focus on quantifying plastic pollution and describing and estimating the related magnitude of exposure and impacts on human and environmental health. Data gathered during such work usually follows a receptor perspective. However, Life Cycle Assessment (LCA) represents an emitter perspective. This study examines existing data gathering and reporting approaches for field and laboratory studies on micro- and nanoplastics (MNPs) exposure and effects relevant to LCA data inputs. The outcomes indicate that receptor perspective approaches do not typically provide suitable or sufficiently harmonised data. Improved design is needed in the sampling, testing and recording of results using harmonised, validated and comparable methods, with more comprehensive reporting of relevant data. We propose a three-level set of requirements for data recording and reporting to increase the potential for LCA studies and models to utilise data gathered in receptor-oriented studies. We show for which purpose such data can be used as inputs to LCA, particularly in life cycle impact assessment (LCIA) methods. Implementing these requirements will facilitate proper integration of the potential environmental impacts of plastic losses from human activity (e.g. litter) into LCA. Then, the impacts of plastic emissions can eventually be connected and compared with other environmental issues related to anthropogenic activities.

Assessing Fuzzy Cognitive Mapping as a participatory and interdisciplinary approach to explore marine microfiber pollution

Fuzzy Cognitive Mapping (FCM) is a participatory modelling tool used to explore complex systems by facilitating interdisciplinary cooperation and integrating a variety of knowledge systems. Here FCM was used to explore marine microfiber pollution. Through individual interviews with representatives from the research, industry, water and environmental sectors, five stakeholder FCMs were developed and used to produce an aggregated community FCM in a stakeholder workshop. Stakeholder FCMs and the revised community FCM were used to compute how the modelled system reacted to changes under two scenarios developed during the stakeholder workshop; (i) Green Shift and (ii) increased textile consumption and production. Significant differences were observed in scenario results from the stakeholder-based models and the community-based model. For societal challenges characterized by unknowns around the problem and potential solutions, inclusion of a variety of knowledge systems through FCM and deliberation processes contribute to a more holistic picture of the system and its uncertainties.

Microplastic in the coral reef environments of the Gulf of Mannar, India - Characteristics, distributions, sources and ecological risks

Microplastics (MPs; particles <5 mm) are widely distributed in various habitats from the land to the oceans. They have even reached the remotest of places, including the deep seas and Polar Regions. Although research on MPs pollution in the marine environment has received widespread attention in recent years, the distribution, sources and ecological risks of MPs in coastal areas remain unclear. This study assessed the abundance, characteristics, sources and ecological risk of MPs in surface waters and sediment of the mainland coast and four island groups comprising the coral reef environment of the Gulf of Mannar (GoM), southeast India. Mean MPs abundance across all 95 sampling sites ranged from 28.4 to 126.6 items L^-1 in water and from 31.4 to 137.6 items kg^-1 in sediment. MP fibers <2 mm dominated the water, while fragments >3 mm were predominant in sediments. Polyethylene (PE) and polypropylene (PP) were the most common polymers in both matrices. The major proportion of MPs in the GoM derived from land-based sources, with distance to the mainland, coastal population density and improper handling of solid waste being the main factors influencing the abundance of MPs. Polymer Hazard Index (PHI), Pollution Load Index (PLI) and Potential Ecological Risk Index (PERI) were used to assess current levels of MPs. While the GoM has high PHI values (>1000) resulting from MPs with high hazard scores (e.g. polyamide, polystyrene, polyvinyl chloride), the PLI values (1.46 and 1.51) indicate low MPs pollution levels in GoM waters and sediments, and the PERI values (31.7 and 24.4) indicate that this represents a minor ecological risk. The results from the current study enhance our understanding of the characteristics, sources, and associated environmental risks of MPs to marine ecosystems. This data may provide a baseline for future monitoring and the formulation of environmental policy.

Secondary PVC microplastics are more toxic than primary PVC microplastics to Oryzias melastigma embryos

Irregular-shaped and partially degraded secondary microplastics (SMP) account for the majority of MPs in marine environments, yet little is known about their effects on marine organisms. In this study, we investigated the embryotoxicity of polyvinyl chloride SMP and primary microplastics (PMP) to the marine medaka Oryzias melastigma. This study aimed to determine the physical impacts of MPs and, for the first time, elucidate the underlying mechanisms of physical toxicity. SMP shortened hatching time and induced higher teratogenic effects on larvae relative to PMP, indicating a higher toxicity from SMP. Physical damage from SMP to the chorion surface appears to be the main toxicity mechanism, caused by their irregular shape and reduced aggregation relative to PMP. In contrast, real-time changes in oxygen demonstrated that hypoxia caused by greater PMP adsorption to the chorion surface contributes to the toxicological responses of this material relative to SMP. Modulation of genes involved in hypoxia-response, cardiac development and hatching confirmed the toxicity mechanisms of PMP and SMP. The chemical contribution to observed toxicity was negligible, confirming impacts derived from physical toxicity. Our findings highlight the negative effects of environmentally relevant SMP on the marine ecosystems.

Fate, source and mass budget of sedimentary microplastics in the Bohai Sea and the Yellow Sea

As reservoirs for pollutants transported via the Yangtze and Yellow Rivers, the Bohai Sea (BS) and Yellow Sea (YS) play an important role in transporting microplastics (MPs) to the Pacific Ocean. The fate, sources and mass budget of MPs in the BS and the YS were investigated by Pearson correlation, principal component analysis-multilinear regression analysis (PCA-MRLA) and a mass balance model to sedimentary MPs data. Average MP abundances were 137 and 119 items kg^-1 in the Bohai and Yellow Seas, respectively. MPs <1000 μm exhibited similar distribution patterns to total organic carbon and fine-grained sediments, while MPs >1000 μm were confined in the BS and exhibited a strong positive correlation with chlorophyll-a and polyethylene terephthalate, suggesting that larger MPs might deposit faster due to biofouling or when comprised of high density polymers. PCA-MLRA analysis indicated land-based inputs (packing materials, textile material and daily commodities) were dominant in the BS, while maritime activities (fishing and mariculture) were the main source of MPs in the YS. The mass balance model revealed that the total MP input and output to the BS and the YS was 3396.92 t yr^-1 and 3814.81 t yr^-1, respectively. The major input pathway of MPs to the BS and the YS were river discharge and air deposition, respectively. Notably, 94% of MPs in the BS and the YS were deposited to sediments. This study revealed that BS and YS sediments play an important role in preventing MPs from being further transported to the Pacific Ocean, thus more attention should be paid to local ecological risk assessment.

Quantifying spatial variation in the uptake of microplastic by mussels using biodeposit traps: A field-based study

Spatial uptake patterns of microplastics (MP) by marine species are largely unexplored under field conditions. A novel "biodeposit trap" that measure uptake and egestion of MP by suspension-feeders through the analysis of their biodeposits, was designed and used to estimate the spatial variation of these processes by mussels in field conditions. Traps containing wild or farmed mussels or control empty shells were deployed at three sites characterised by different MP concentrations and water flow conditions. A different MP dimensional composition was observed between MP pools present in biodeposit and control traps, with the latter shifted towards higher dimensional range (0.05-5 mm). Conversely, mussels accumulated small MP (0.02-0.05 mm) into their biodeposits without any significant difference between wild and farmed specimens. MP uptake rates were on average 4-5 times higher at the site where MP contamination was expected to be highest and where water flow conditions were considered moderate.

Sources, distribution and effects of rare earth elements in the marine environment: Current knowledge and research gaps

Rare earth elements and yttrium (REY) are critical elements for a wide range of applications and consumer products. Their growing extraction and use can potentially lead to REY and anthropogenic-REY chemical complexes (ACC-REY) being released in the marine environment, causing concern regarding their potential effects on organisms and ecosystems. Here, we critically review the scientific knowledge on REY sources (geogenic and anthropogenic), factors affecting REY distribution and transfer in the marine environment, as well as accumulation in- and effects on marine biota. Further, we aim to draw the attention to research gaps that warrant further scientific attention to assess the potential risk posed by anthropogenic REY release. Geochemical processes affecting REY mobilisation from natural sources and factors affecting their distribution and transfer across marine compartments are well established, featuring a high variability dependent on local conditions. There is, however, a research gap with respect to evaluating the environmental distribution and fate of REY from anthropogenic sources, particularly regarding ACC-REY, which can have a high persistence in seawater. In addition, data on organismal uptake, accumulation, organ distribution and effects are scarce and at best fragmentary. Particularly, the effects of ACC-REY at organismal and community levels are, so far, not sufficiently studied. To assess the potential risks caused by anthropogenic REY release there is an urgent need to i) harmonise data reporting to promote comparability across studies and environmental matrices, ii) conduct research on transport, fate and behaviour of ACC-REY vs geogenic REY iii) deepen the knowledge on bioavailability, accumulation and effects of ACC-REY and REY mixtures at organismal and community level, which is essential for risk assessment of anthropogenic REY in marine ecosystems.

Moving forward in microplastic research: A Norwegian perspective

Given the increasing attention on the occurrence of microplastics in the environment, and the potential environmental threats they pose, there is a need for researchers to move quickly from basic understanding to applied science that supports decision makers in finding feasible mitigation measures and solutions. At the same time, they must provide sufficient, accurate and clear information to the media, public and other relevant groups (e.g., NGOs). Key requirements include systematic and coordinated research efforts to enable evidence-based decision making and to develop efficient policy measures on all scales (national, regional and global). To achieve this, collaboration between key actors is essential and should include researchers from multiple disciplines, policymakers, authorities, civil and industry organizations, and the public. This further requires clear and informative communication processes, and open and continuous dialogues between all actors. Cross-discipline dialogues between researchers should focus on scientific quality and harmonization, defining and accurately communicating the state of knowledge, and prioritization of topics that are critical for both research and policy, with the common goal to establish and update action plans for holistic benefit. In Norway, cross-sectoral collaboration has been fundamental in supporting the national strategy to address plastic pollution. Researchers, stakeholders and the environmental authorities have come together to exchange knowledge, identify knowledge gaps, and set targeted and feasible measures to tackle one of the most challenging aspects of plastic pollution: microplastic. In this article, we present a Norwegian perspective on the state of knowledge on microplastic research efforts. Norway's involvement in international efforts to combat plastic pollution aims at serving as an example of how key actors can collaborate synergistically to share knowledge, address shortcomings, and outline ways forward to address environmental challenges.

The sub-lethal impact of plastic and tire rubber leachates on the Mediterranean mussel Mytilus galloprovincialis

Ocean contamination by synthetic polymers can represent a risk for the fitness of marine species due to the leaching of chemical additives. This study evaluated the sub-lethal effects of plastic and rubber leachates on the mussel Mytilus galloprovincialis through a battery of biomarkers encompassing lysosomal endpoints, oxidative stress/detoxification parameters, and specific responses to metals/neurotoxicants. Mussels were exposed for 7 days to leachates from car tire rubber (CTR), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC), containing organic additives and metals in the ng-μg/L range. The leachate exposure affected general stress parameters, including the neutral lipid content (all leachates), the lysosomal membrane stability (PS, PP, PVC and CTR leachates) and lysosomal volume (PP, PVC and TR leachates). An increased content of the lipid peroxidation products malondialdehyde and lipofuscin was observed in mussels exposed to PET, PS and PP leachates, and PP, PVC and CTR leachates, respectively. PET and PP leachates increased the activity of the phase-II metabolism enzyme glutathione S-transferase, while a decreased acetylcholinesterase activity was induced by PVC leachates. Data were integrated in the mussel expert system (MES), which categorizes the organisms' health status based on biomarker responses. The MES assigned healthy status to mussels exposed to PET leachates, low stress to PS leachates, and moderate stress to PP, CTR and PVC leachates. This study shows that additives leached from selected plastic/rubber polymers cause sub-lethal effects in mussels and that the magnitude of these effects may be higher for CTR, PVC and PP due to a higher content and release of metals and organic compounds.

Factors influencing the occurrence and distribution of microplastics in coastal sediments: From source to sink

Microplastic (MP) pollution is attracting growing global attention, but little is known about the factors influencing MP occurrence and distributions in marine sediments. Here, MPs were sampled from the sediments of two semi-enclosed bays (Jinghai Bay and Laizhou Bay) and two coastal open zones (Lancelet Reserve and Solen grandis Reserve) in China. The order of MP abundance was Jinghai Bay > Laizhou Bay > Lancelet Reserve > Solen grandis Reserve. Average MP diversity indices for Laizhou Bay (1.84 ± 0.18), Lancelet Reserve (1.59 ± 0.43), S. grandis Reserve (1.58 ± 0.89), and Jinghai Bay (1.43 ± 0.14) revealed Laizhou Bay had the most complicated MP sources. A significant negative correlation between MP abundance and sediment grain size occurred in the semi-enclosed coastal zones (p = 0.004, r = -0.618) rather than in the open coastal zones (p = 0.051, r = -0.480), indicating small sediment particles can strongly enhance MP accumulation in semi-enclosed costal sediments. Although anthropogenic activities influence the MP distribution at source, the composition of regional and local sediments might impact MP occurrence in semi-enclosed coastal zones from the sink. These results help to improve our understanding of the fate and inventory of MPs in coastal sediments.

UV degradation of natural and synthetic microfibers causes fragmentation and release of polymer degradation products and chemical additives

A high proportion of the total microplastic (MP) load in the marine environment has been identified as microfibers (MFs), with polyester (PET) and polyamide (PA) typically found in the highest abundance. The potential for negative environmental impacts from MPs may be dependent on their degree of degradation in the environment, which is influenced by both intrinsic properties (polymer type, density, size, additive chemicals) and extrinsic environmental parameters. Most polymer products break down slowly through a combination of environmental processes, but UV degradation can be a significant source of degradation. The current study aimed to investigate the effect of UV irradiance on the degradation of natural (wool) and synthetic (PET and PA) MFs. Degradation of MFs was conducted in seawater under environmentally relevant accelerated exposure conditions using simulated sunlight. After 56 days of UV exposure, PA primarily exhibited changes in surface morphology with no significant fragmentation observed. PET and wool fibers exhibited both changes in surface morphology and fragmentation into smaller particles. A range of molecular degradation products were identified in seawater leachates after UV exposure, with increasing abundance over the duration of the experiment. Furthermore, a variety of additive chemicals were shown to leach from the MFs into seawater. While some of these chemicals were also susceptible to UV degradation and some are expected to biodegrade rapidly, others may be persistent and contribute to the overall load of chemical pollution in the marine environment.

Microplastic distributions in a domestic wastewater treatment plant: Removal efficiency, seasonal variation and influence of sampling technique

Wastewater treatment plants (WWTPs) serve as an important route of microplastics (MPs) to the environment. Therefore, more effective MPs sampling and detection methodologies, as well as a better understanding of their influence on MPs occurrence and distributions in WWTP effluents, are needed for better removal and control. In this work, the efficiency of a municipal WWTP to remove MPs was assessed by collecting samples from raw to tertiary effluent during a 12-month sampling campaign (season-based) using different sampling methods (containers, 24-h composite and large grab samples). MPs retrieved from different treatment units within the WWTP were identified and quantified using plastic/non-plastic staining followed by optical microscopy, SEM and μ-Raman microscopy. Overall, the mean removal efficiency of MPs in the WWTP was 97%, with most MPs removed by the secondary stage and a mean effluent concentration of 1.97 MPs L^-1 after sand filtration. The relative abundance of particles was lower than fibers in treated effluent compared with the raw wastewater, with MP fibers constituting 74% of the total MPs in raw wastewater and 91% in treated effluent. Taking seasonal variations into account is important as total MPs concentration in the effluent was notably higher in winter compared with the other seasons. Increasing the sampled volume using large samples or 24-h composite samples significantly reduced the variability between replicates. However, MPs concentration post the tertiary stage was significantly lower using morning sampling (9 am) by large grab sampling method (1.2 MPs L^-1) compared to 24-h composite sampling (3.2 MPs L^-1) possibly due to intra-daily changes. Using a finer mesh size (0.45 μm) to capture MPs beyond the size range typically studied (≥20 μm) effectively doubled the number of MPs detected in the tertiary effluent and highlights the importance of standardizing sampling procedures.

Microplastic fibres from synthetic textiles: Environmental degradation and additive chemical content

Microplastic fibres (MPFs) often make up the largest fraction of microplastic pollution in aquatic environments, yet little is known about their degradative fate and persistence. This study investigates the environmentally relevant photodegradation of common MPFs: polyester (PET), polyamide (PA) and polyacrylonitrile (PAN), their respective additive chemical profile, together with their potential for additive leaching. MPFs were subject to ultraviolet (UV) exposure in seawater and freshwater media over 10 months. PET and PA MPFs showed significant fragmentation and surface changes following UV exposure, additionally PA showed evidence of chemical changes. PAN did not undergo significant photodegradation in the same exposure period. Chemicals tentatively identified in MPFs and aqueous leachates via non-target gas chromatography-mass spectrometry include monomers, UV stabilisers and degradation products. Characterisation of several bisphenols (BPs) and benzophenones (BzPs) was performed via ultraperformance liquid chromatography tandem mass spectrometry. Bisphenol A, bisphenol S and benzophenone-3 were quantified in all MPFs and wool at concentrations between 4.3 and 501 ng/g, with wool displaying the highest sum concentration of BPs and BzPs at 863 and 27 ng/g, respectively.

Microplastic and heavy metal distributions in an Indian coral reef ecosystem

The current study focuses on the occurrence and characteristics of microplastics (MPs) and spatial distribution and pollution status of heavy metals in the water and sediments of the coral reef ecosystems associated with the Tuticorin and Vembar groups of islands in the Gulf of Mannar, southeast India. Mean abundance of MPs varies from 60 ± 54 to 126.6 ± 97 items/L in water and from 50 ± 29 to 103.8 ± 87 items/kg in sediment. Water and sediment samples from the Tuticorin islands contain higher MP concentrations than the Vembar islands. The highest MP were observed in the mainland samples, while MP distributions in the shoreward direction i.e. towards the islands closely reflect those of the mainland (p < 0.05). Polyethylene is the most common polymer, with fibers (1-3 mm) being the most abundant form in water and fragments (3-5 mm) being the most abundant in sediment. Pollution indices such as enrichment and contamination factors indicate moderate contamination of sediments by Zn, Hg, Cd, Pb and Ni. Heavy metal associated with MPs are greater than those in sediments, and this indicates that MP may be a source of metal pollution or that metals from the sediment preferentially partition to MPs. SEM analysis highlights the presence of cracks, protrusions and depositions on the surface of many MPs, indicating partial degradation. EDAX frequently showed the presence of Zn, Cd, Pb, Ni and Fe associated with MP surfaces. This study offers an insight into the level of MPs and associated elements that filter feeding corals in the region are exposed to current.

Wastewater-Aged Silver Nanoparticles in Single and Combined Exposures with Titanium Dioxide Affect the Early Development of the Marine Copepod Tisbe battagliai

In this study, the effects of aged Ag and TiO₂ nanoparticles (NPs), individually and as a mixture, in wastewater relative to their pristine counterparts on the development of the copepod nauplii (Tisbe battagliai) were investigated. NP behavior in synthetic wastewater and seawater was characterized during aging and exposure. A delayed development and subsequent mortality were observed after 6 days of exposure to aged Ag NPs, with a twofold decrease in EC₅₀ (316 μg/L) compared to pristine NPs (EC₅₀ 640 μg/L) despite the similar dissolved Ag concentrations measured for aged and pristine Ag NPs (441 and 378 μg/L, respectively). In coexposures with TiO₂ NPs, higher dissolved Ag levels were measured for aged NPs (238.3 μg/L) relative to pristine NPs (98.57 μg/L). Coexposure resulted in a slight decrease (15%) in the Ag NP EC₅₀ (270 μg/L) with a 1.9-fold increase in the Ag NP retained within the organisms after depuration (2.82% retention) compared to Ag NP single exposures as measured with sp-ICP-MS, suggesting that the particles are still bioavailable despite the heteroaggregation observed between Ag, Ti NPs, and wastewater components. This study shows that the presence of TiO₂ NPs can affect the stability and toxicity of Ag NPs in complex media that cannot be predicted solely based on ionic, total, or nanoparticulate concentrations, and the need for studying NP interactions in more complex matrices is highlighted.

Combined effects of exposure to engineered silver nanoparticles and the water-soluble fraction of crude oil in the marine copepod Calanus finmarchicus

While it is likely that ENPs may occur together with other contaminants in nature, the combined effects of exposure to both ENPs and environmental contaminants are not studied sufficiently. In this study, we investigated the acute and sublethal toxicity of PVP coated silver nanoparticles (AgNP) and ionic silver (Ag⁺; administered as AgNO₃) to the marine copepod Calanus finmarchicus. We further studied effects of single exposures to AgNPs (nominal concentrations: low 15 μg L^-1 NPL, high 150 μg L^-1 NPH) or Ag⁺ (60 μg L^-1), and effects of co-exposure to AgNPs, Ag⁺ and the water-soluble fraction (WSF; 100 μg L^-1) of a crude oil (AgNP + WSF; Ag⁺+WSF). The gene expression and the activity of antioxidant defense enzymes SOD, CAT and GST, as well as the gene expression of HSP90 and CYP330A1 were determined as sublethal endpoints. Results show that Ag⁺ was more acutely toxic compared to AgNPs, with 96 h LC₅₀ concentrations of 403 μg L^-1 for AgNPs, and 147 μg L^-1 for Ag⁺. Organismal uptake of Ag following exposure was similar for AgNP and Ag⁺, and was not significantly different when co-exposed to WSF. Exposure to AgNPs alone caused increases in gene expressions of GST and SOD, whereas WSF exposure caused an induction in SOD. Responses in enzyme activities were generally low, with significant effects observed only on SOD activity in NPL and WSF exposures and on GST activity in NPL and NPH exposures. Combined AgNP and WSF exposures caused slightly altered responses in expression of SOD, GST and CYP330A1 genes compared to the single exposures of either AgNPs or WSF. However, there was no clear pattern of cumulative effects caused by co-exposures of AgNPs and WSF. The present study indicates that the exposure to AgNPs, Ag⁺, and to a lesser degree WSF cause an oxidative stress response in C. finmarchicus, which was slightly, but mostly not significantly altered in combined exposures. This indicated that the combined effects between Ag and WSF are relatively limited, at least with regard to oxidative stress.

Reporting Guidelines to Increase the Reproducibility and Comparability of Research on Microplastics

The ubiquitous pollution of the environment with microplastics, a diverse suite of contaminants, is of growing concern for science and currently receives considerable public, political, and academic attention. The potential impact of microplastics in the environment has prompted a great deal of research in recent years. Many diverse methods have been developed to answer different questions about microplastic pollution, from sources, transport, and fate in the environment, and about effects on humans and wildlife. These methods are often insufficiently described, making studies neither comparable nor reproducible. The proliferation of new microplastic investigations and cross-study syntheses to answer larger scale questions are hampered. This diverse group of 23 researchers think these issues can begin to be overcome through the adoption of a set of reporting guidelines. This collaboration was created using an open science framework that we detail for future use. Here, we suggest harmonized reporting guidelines for microplastic studies in environmental and laboratory settings through all steps of a typical study, including best practices for reporting materials, quality assurance/quality control, data, field sampling, sample preparation, microplastic identification, microplastic categorization, microplastic quantification, and considerations for toxicology studies. We developed three easy to use documents, a detailed document, a checklist, and a mind map, that can be used to reference the reporting guidelines quickly. We intend that these reporting guidelines support the annotation, dissemination, interpretation, reviewing, and synthesis of microplastic research. Through open access licensing (CC BY 4.0), these documents aim to increase the validity, reproducibility, and comparability of studies in this field for the benefit of the global community.

Rainfall triggers more deep-seated landslides than Cascadia earthquakes in the Oregon Coast Range, USA

The coastal Pacific Northwest USA hosts thousands of deep-seated landslides. Historic landslides have primarily been triggered by rainfall, but the region is also prone to large earthquakes on the 1100-km-long Cascadia Subduction Zone megathrust. Little is known about the number of landslides triggered by these earthquakes because the last magnitude 9 rupture occurred in 1700 CE. Here, we map 9938 deep-seated bedrock landslides in the Oregon Coast Range and use surface roughness dating to estimate that past earthquakes triggered fewer than half of the landslides in the past 1000 years. We find landslide frequency increases with mean annual precipitation but not with modeled peak ground acceleration or proximity to the megathrust. Our results agree with findings about other recent subduction zone earthquakes where relatively few deep-seated landslides were mapped and suggest that despite proximity to the megathrust, most deep-seated landslides in the Oregon Coast Range were triggered by rainfall.

Microplastic dispersal behavior in a novel overhead stirring aqueous exposure system

Using nominal dose metrics to describe exposure conditions in laboratory-based microplastic uptake and effects studies may not adequately represent the true exposure to the organisms in the test system, making data interpretation challenging. In the current study, a novel overhead stirring method using flocculators was assessed for maintaining polystyrene (PS) microbeads (Ø10.4 μm; 1.05 g cm^-3) in suspension in seawater during 24 h and then compared with static and rotational exposure setups. Under optimized conditions, the system was able to maintain 59% of the initial PS microbeads in suspension after 24 h, compared to 6% using a static system and 100% using a rotating plankton wheel. Our findings document for the first time that overhead stirring as well as other, commonly used exposure systems (static) are unable to maintain constant microplastic exposure conditions in laboratory setups whereas rotation is very effective. This suggests toxicological studies employing either static or overhead stirring systems may be greatly overestimating the true microplastic exposure conditions.

Between source and sea: The role of wastewater treatment in reducing marine microplastics

Wastewater treatment plants (WWTPs) are a focal point for the removal of microplastic (MP) particles before they are discharged into aquatic environments. WWTPs are capable of removing substantial quantities of larger MP particles but are inefficient in removing particles with any one dimension of less than 100 μm, with influents and effluents tending to have similar quantities of these smaller particles. As a single WWTP may release >100 billion MP particles annually, collectively WWTPs are significant contributors to the problem of MP pollution of global surface waters. Currently, there are no policies or regulations requiring the removal of MPs during wastewater treatment, but as concern about MP pollution grows, the potential for wastewater technologies to capture particles before they reach surface waters has begun to attract attention. There are promising technologies in various stages of development that may improve the removal of MP particles from wastewater. Better incentivization could speed up the research, development and adoption of innovative practices. This paper describes the current state of knowledge regarding MPs, wastewater and relevant policies that could influence the development and deployment of new technologies within WWTPs. We review existing technologies for capturing very small MP particles and examine new developments that may have the potential to overcome the shortcomings of existing methods. The types of collaborations needed to encourage and incentivize innovation within the wastewater sector are also discussed, specifically strong partnerships among scientific and engineering researchers, industry stakeholders, and policy decision makers.

Monitoring and modelling of influent patterns, phase distribution and removal of 20 elements in two primary wastewater treatment plants in Norway

Many small- or medium-sized communities in Northern Europe employ only primary wastewater treatment plants (WWTPs) and effluent discharges can be a relevant source of pollution. The current study combines monitoring and modelling approaches to investigate concentrations, influent patterns, size distribution and removal of 20 elements for the two primary WWTPs (Ladehammeren, LARA; Høvringen, HØRA) serving Trondheim, the third largest city in Norway. Element concentrations were determined in raw influent wastewater, effluents and biosolids, and diurnal inflow patterns were assessed. The elemental distribution in particulate, colloidal and dissolved fractions of untreated wastewater was characterized using filtration separation and electron microscopy. An influent generator model and multivariate statistical analyses were used to determine release patterns and to predict the (co-)occurrence of selected elements. Raw influent wastewater concentrations for most elements were similar in the two WWTPs, with only Ca, Mn, Fe, Co and Ba being significantly higher (p < 0.05) in HØRA (which receives more household and hospital discharges). Removal efficiencies varied between elements, but in most cases reflected their association with particulates. Nanosized particles of several elements were detected, with Cu/Zn being most common. Measured concentrations of most elements followed typical diurnal wastewater discharge patterns and enrichment factors calculated for biosolids confirmed the importance of anthropogenic sources for P, Cu, Zn, Cd, As, Cr, Ni, Pb, V, Co and Fe. Elemental concentrations generally correlated well with total suspended solid (TSS) concentrations at HØRA, while this was less pronounced in LARA (possibly due to higher industrial contributions). In one of its first applications for WWTP influent pattern examination, principal component analysis was found to be instrumental for source identification of target elements, showing significant differences between LARA and HØRA influents. The combined experimental, statistical and modelling approaches used herein allowed for improved understanding of element sources, patterns of discharge and fate in primary WWTPs.

Do different habits affect microplastics contents in organisms? A trait-based analysis on salt marsh species

Salt marshes in urban watersheds are prone to microplastics (MP) pollution due to their hydrological characteristics and exposure to urban runoff, but little is known about MP distributions in species from these habitats. In the current study, MP occurrence was determined in six benthic invertebrate species from salt marshes along the North Adriatic lagoons (Italy) and the Schelde estuary (Netherlands). The species represented different feeding modes and sediment localisation. 96% of the analysed specimens (330) did not contain any MP, which was consistent across different regions and sites. Suspension and facultative deposit-feeding bivalves exhibited a lower MP occurrence (0.5-3%) relative to omnivores (95%) but contained a much more variable distribution of MP sizes, shapes and polymers. The study provides indications that MP physicochemical properties and species' ecological traits could all influence MP exposure, uptake and retention in benthic organisms inhabiting European salt marsh ecosystems.

Sorption of PAHs to microplastic and their bioavailability and toxicity to marine copepods under co-exposure conditions

Organic chemical pollutants associated with microplastic (MP) may represent an alternative exposure route for these chemicals to marine biota. However, the bioavailability of MP-sorbed organic pollutants under conditions where co-exposure occurs from the same compounds dissolved in the water phase has rarely been studied experimentally, especially where pollutant concentrations in the two phases are well characterized. Importantly, higher concentrations of organic pollutants on ingested MP may be less bioavailable to aquatic organisms than the same chemicals present in dissolved form in the surrounding water. In the current study, the sorption kinetics of two model polycyclic aromatic hydrocarbons (PAHs; fluoranthene and phenanthrene) to MP particles in natural seawater at 10 and 20 °C were studied and the bioavailability of MP-sorbed PAHs to marine copepods investigated. Polyethylene (PE) and polystyrene (PS) microbeads with mean diameters ranging from 10 to 200 μm were used to identify the role of MP polymer type and size on sorption mechanisms. Additionally, temperature dependence of sorption was investigated. Results indicated that adsorption dominated at lower temperatures and for smaller MP (10 μm), while absorption was the prevailing process for larger MP (100 μm). Monolayer sorption dominated at lower PAH concentrations, while multilayer sorption dominated at higher concentrations. PE particles representing ingestible (10 μm) and non-ingestible (100 μm) MP for the marine copepod species Acartia tonsa and Calanus finmarchicus were used to investigate the availability and toxicity of MP-sorbed PAHs. Studies were conducted under co-exposure conditions where the PAHs were also present in the dissolved phase (C_free), thereby representing more environmentally relevant exposure scenarios. C_free reduction through MP sorption was reflected in a corresponding reduction of lethality and bioaccumulation, with no difference observed between ingestible and non-ingestible MP. This indicates that only free dissolved PAHs are significantly bioavailable to copepods under co-exposure conditions with MP-sorbed PAHs.

Chemical composition and ecotoxicity of plastic and car tire rubber leachates to aquatic organisms

Synthetic polymer-based materials are ubiquitous in aquatic environments, where weathering processes lead to their progressive fragmentation and the leaching of additive chemicals. The current study assessed the chemical content of freshwater and marine leachates produced from car tire rubber (CTR), polypropylene (PP), polyethylene terephthalate (PET), polystyrene (PS) and polyvinyl chloride (PVC) microplastics, and their adverse effects on the microalgae Raphidocelis subcapitata (freshwater) and Skeletonema costatum (marine) and the Mediterranean mussel Mytilus galloprovincialis. A combination of non-target and target chemical analysis revealed a number of organic and metal compounds in the leachates, including representing plasticizers, antioxidants, antimicrobials, lubricants, and vulcanizers. CTR and PVC materials and their corresponding leachates had the highest content of tentatively identified organic additives, while PET had the lowest. The metal content varied both between polymer leachates and between freshwater and seawater. Notable additives identified in high concentrations were benzothiazole (CTR), phthalide (PVC), acetophenone (PP), cobalt (CTR, PET), zinc (CTR, PVC), lead (PP) and antimony (PET). All leachates, except PET, inhibited algal growth with EC₅₀ values ranging from 0.5% (CTR) and 64% (PP) of the total leachate concentration. Leachates also affected mussel endpoints, including the lysosomal membrane stability and early stages endpoints as gamete fertilization, embryonic development and larvae motility and survival. Embryonic development was the most sensitive parameter in mussels, with EC₅₀ values ranging from 0.8% (CTR) to 65% (PET) of the total leachate. The lowest impacts were induced on D-shell larvae survival, reflecting their ability to down-regulate motility and filtration in the presence of chemical stressors. This study provides evidence of the relationship between chemical composition and toxicity of plastic/rubber leachates. Consistent with increasing contamination by organic and inorganic additives, the leachates ranged from slightly to highly toxic to mussels and algae, highlighting the need for a better understanding of the overall impact of plastic-associated chemicals on aquatic ecosystems.

Establishing a link between composition and toxicity of offshore produced waters using comprehensive analysis techniques - A way forward for discharge monitoring?

Extracts of produced waters from five mature Norwegian Sea oil fields were examined as total organic extracts (TOEs) and after fractionation into operationally-defined 'polar' and 'apolar' fractions. The TOEs and fractions were examined by gas chromatography (GC), GC-mass spectrometry (GC-MS), two dimensional GC-MS (GC × GC-MS) and liquid chromatography with high-resolution spectrometry (LC-HRMS) techniques. Low molecular weight aromatics, phenols and other common petroleum-derived hydrocarbons were characterized and quantified in the TOEs and fractions. In addition, a range of more uncommon polar and apolar constituents, including those likely derived from production chemicals, such as trithiolane, imidazolines and quaternary amine compounds (so-called 'quats'), were tentatively identified, using GC × GC-MS and LC-HRMS. The acute toxicity of the TOEs and subfractions was investigated using early life stages of the marine copepod Acartia tonsa. Toxicity varied significantly for different PW TOEs and subfractions. For some PWs, the toxicity was attributed mainly to the 'polar' components, while that of other PWs was associated mainly with the 'apolar' components. Importantly, the observed toxicity could not be explained by the presence of the commonly reported compounds only. Although, due to the vast chemical complexity even of the sub-fractions of the PW extracts, specific compounds driving the observed toxicity could be not be elucidated in this study, the proposed approach may suggest a way forward for future revisions of monitoring regimes for PW discharges.

Profiling microplastics in the Indian edible oyster, Magallana bilineata collected from the Tuticorin coast, Gulf of Mannar, Southeastern India

The objective of this study is to quantify the extent of microplastic (MP) contamination in the Indian edible oyster (Magallana bilineata) and to understand how this relates to the MP contamination in its surrounding marine environment. Samples of water, sediment and oysters of different sizes were collected from three sites along Tuticorin coast in Gulf of Mannar in Southeast India. The mean abundance of MP in oysters was found to be 6.9 ± 3.84 items/individual and the mean concentration to be 0.81 ± 0.45 items/g of tissue. Polyethylene (PE) and polypropylene (PP) fibers were the dominant MP types in oysters (92% and 4%, respectively) and in seawater (75% and 25%, respectively), with PE fibers, ranging from 0.25 to 0.5 mm, being the most common. Both PE and PP are low-density polymers which are slow to sediment to the seafloor. This increases the potential of their availability in the environment and ingestion by the oysters. The largest oysters (14-16 cm) contained the highest abundance and concentrations of MP, suggesting a greater proportion of MP in the water column is ingested with increasing size. The calculated microplastic index (0.02 to 0.99) also indicates that MP bioavailability increases with increasing size of oysters. The distribution patterns of MP abundance, shape and size in oysters more closely resemble those in water than in sediment. The surface morphology of the MPs reveals the characteristic pits and cracks which result from partial degradation through the weathering processes. Energy-dispersive X-ray spectroscopy analysis shows the presence of Ni and Fe in association with MP, and this probably indicates the fly-ash pollution and the petroleum-related activities in the surrounding area. Being sessile animals the oysters are good candidates for use as sentinel organisms for monitoring MP in specific marine environments.

Microplastic in wild populations of the omnivorous crab Carcinus aestuarii: A review and a regional-scale test of extraction methods, including microfibres

Microplastic (MP) has become ubiquitous in the marine environment. Its threat to marine organisms has been demonstrated under laboratory conditions, yet studies on wild populations still face methodological difficulties. We reviewed the methods used to separate MP from soft animal tissues and highlighted a lack of standardised methodologies, particularly critical for synthetic microfibres. We further compared enzymatic and a potassium hydroxide (KOH)-based alkaline digestion protocols on wild crabs (Carcinus aestuarii) collected from three coastal lagoons in the north Adriatic Sea and on laboratory-prepared synthetic polyester (PES) of different colour and polypropylene (PP). We compared the cost-effectiveness of the two methods, together with the potential for adverse quantitative or qualitative effects on MP that could alter the capability of the polymers to be recognised via microscopic or spectroscopic techniques. Only 5.5% of the 180 examined crabs contained MP in their gastrointestinal tracts, with a notably high quantitative variability between individuals (from 1 to 117 particles per individual). All MP found was exclusively microfibres, mainly PES, with a mean length (±SE) of 0.5 ± 0.03 mm. The two digestion methods provided comparable estimates on wild crabs and did not cause any visible physical or chemical alterations on laboratory-prepared microfibres treated for up to 4 days. KOH solution was faster and cheaper compared to the enzymatic extraction, involving fewer procedural steps and therefore reducing the risk of airborne contamination. With digestion times longer than 4 days, KOH caused morphological alterations of some of the PES microfibres, which did not occur with the enzymatic digestion. This suggests that KOH is effective for the digestion of small marine invertebrates or biological samples for which shorter digestion time is required, while enzymatic extraction should be considered as alternative for larger organisms or sample sizes requiring longer digestion times.

Effects of Nylon Microplastic on Feeding, Lipid Accumulation, and Moulting in a Coldwater Copepod

Microplastic debris is a pervasive environmental contaminant that has the potential to impact the health of biota, although its modes of action remain somewhat unclear. The current study tested the hypothesis that exposure to fibrous and particulate microplastics would alter feeding, impacting on lipid accumulation, and normal development (e.g., growth, moulting) in an ecologically important coldwater copepod Calanus finmarchicus. Preadult copepods were incubated in seawater containing a mixed assemblage of cultured microalgae (control), with the addition of ∼50 microplastics mL^-1 of nylon microplastic granules (10-30 μm) or fibers (10 × 30 μm), which are similar in shape and size to the microalgal prey. The additive chemical profiles showed the presence of stabilizers, lubricants, monomer residues, and byproducts. Prey selectivity was significantly altered in copepods exposed to nylon fibers (ANOVA, P < 0.01) resulting in a nonsignificant 40% decrease in algal ingestion rates (ANOVA, P = 0.07), and copepods exposed to nylon granules showed nonsignificant lipid accumulation (ANOVA, P = 0.62). Both microplastics triggered premature moulting in juvenile copepods (Bernoulli GLM, P < 0.01). Our results emphasize that the shape and chemical profile of a microplastic can influence its bioavailability and toxicity, drawing attention to the importance of using environmentally relevant microplastics and chemically profiling plastics used in toxicity testing.

Marine microplastic: Preparation of relevant test materials for laboratory assessment of ecosystem impacts

Studies investigating the effects of plastic litter on marine biota have almost exclusively utilised pristine plastic materials that are homogeneous in polymer type, size, shape and chemical composition. This is particularly the case for microplastics (<5 mm), where collecting sufficient quantities from the marine environment for use in laboratory impacts studies is simply not feasible. Weathered plastics collected from the marine environment show considerable physical and chemical differences to pristine and post-production consumer plastics. For this study, macroplastic litter was collected on a Dutch beach and cryo-milled to create a microplastic mixture for environmental impact assessments. The sample composition followed proportions of marine plastic litter types observed in an earlier large beach clean-up. Polymer composition of the sample was assessed by infrared spectroscopy (ATR-FTIR) and differential scanning calorimetry analysis (DSC). The particle size distribution of the cryo-milled microplastics showed that particles 0.5-2.0 mm represented 68% of mass, but smaller sizes (<2 mm) strongly dominated numerically. Inductively coupled plasma spectroscopy (ICP-MS and ICP-OES) analysis of the microplastic mixture revealed a broad range of metals and other elements (e.g. Al, Cd, Cr, Fe, Mg, Pb, S and Zn), representing common inorganic additives used as colorants, fillers and stabilisers. GC-MS analysis identified a broad range of organic plasticisers, stabilisers, antioxidants and flame retardants. Comparison of different analytical approaches showed that creation of a homogeneous microplastic mixture is possible, representing a first step in closing the gap between laboratory studies with pristine materials and realistic scenarios with weathered microplastic.

Adhesion of mechanically and chemically dispersed crude oil droplets to eggs of Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus)

Crude oil accidentally spilled into the marine environment undergoes natural weathering processes that result in oil components being dissolved into the water column or present in particulate form as dispersed oil droplets. Oil components dissolved in seawater are typically considered as more bioavailable to pelagic marine organisms and the main driver of crude oil toxicity, however, recent studies indicate that oil droplets may also contribute. The adhesion of crude oil droplets onto the eggs of pelagic fish species may cause enhanced transfer of oil components via the egg surface causing toxicity during the sensitive embryonic developmental stage. In the current study, we utilized an oil droplet dispersion generator to generate defined oil droplets sizes/concentrations and exposed Atlantic cod (Gadus morhua) and haddock (Melanogrammus aeglefinus) to investigate if the potential for dispersed oil droplets to adhere onto the surface of eggs was species-dependent. The influence of a commercial chemical dispersant on the adhesion process was also studied. A key finding was that the adhesion of oil droplets was significantly higher for haddock than cod, highlighting key differences and exposure risks between the two species. Scanning electron microscopy indicates that the differences in oil droplet adhesion may be driven by the surface morphology of the eggs. Another important finding was that the adhesion capacity of oil droplets to fish eggs is significantly reduced (cod 37.3%, haddock 41.7%) in the presence of the chemical dispersant.

Occurrence, characterisation and fate of (nano)particulate Ti and Ag in two Norwegian wastewater treatment plants

Due to their widespread application in consumer products, elemental titanium (e.g., titanium dioxide, TiO₂) and silver (Ag), also in nanoparticulate form, are increasingly released from households and industrial facilities to urban wastewater treatment plants (WWTPs). A seven-day sampling campaign was conducted in two full-scale WWTPs in Trondheim (Norway) employing only primary treatment. We assessed the occurrence and elimination of Ti and Ag, and conducted size-based fractionation using sequential filtration of influent samples to separate particulate, colloidal and dissolved fractions. Eight-hour composite influent samples were collected to assess diurnal variations in total Ti and Ag influx. Measured influent Ti concentrations (up to 290 μg L^-1) were significantly higher than Ag (<0.15-2.1 μg L^-1), being mostly associated with suspended solids (>0.7 μm). Removal efficiencies ≥70% were observed for both elements, requiring for one WWTP to account for the high Ti content (∼2 g L^-1) in the flocculant. Nano- and micron-sized Ti particles were observed with scanning transmission electron microscopy (STEM) in influent, effluent and biosolids, while Ag nanoparticles were detected in biosolids only. Diurnal profiles of influent Ti were correlated to flow and pollutant concentration patterns (especially total suspended solids), with peaks during the morning and/or evening and minima at night, indicating household discharges as predominant source. Irregular profiles were exhibited by influent Ag, with periodic concentration spikes suggesting short-term discharges from one or few point sources (e.g., industry). Influent Ti and Ag dynamics were reproduced using a disturbance scenario generator model, and we estimated per capita loads of Ti (42-45 mg cap^-1 d^-1) and Ag (0.11 mg cap^-1 d^-1) from households as well as additional Ag load (14-22 g d^-1) from point discharge. This is the first study to experimentally and mathematically describe short-term release dynamics and dry-weather sources of emissions of Ti and Ag in municipal WWTPs and receiving environments.

Ecotoxicological Effects of Transformed Silver and Titanium Dioxide Nanoparticles in the Effluent from a Lab-Scale Wastewater Treatment System

In this study, a lab-scale wastewater treatment plant (WWTP), simulating biological treatment, received 10 μg/L Ag and 100 μg/L TiO₂ nanoparticles (NPs) for 5 weeks. NP partitioning was evaluated by size fractionation (>0.7 μm, 0.1-0.7 μm, 3 kDa-0.1 μm, < 3 kDa) using inductively coupled plasma mass spectrometry (ICP-MS), single particle ICP-MS and transmission electron microscopy. The ecotoxicological effects of the transformed NPs in the effluent were assessed using a battery of marine and freshwater bioassays (algae and crustaceans) and an in vitro gill cell line model (RTgill-W1). TiO₂ aggregates were detected in the effluent, whereas Ag NPs (0.1-0.22 μg/L) were associated with S, Cu, Zn. Fractionation showed that >80% of Ag and Ti were associated with the effluent solids. Increased toxicity was observed during weeks 2-3 and the effects were species-dependent; with marine epibenthic copepods and algae being the most sensitive. Increased reactive oxygen species formation was observed in vitro followed by an increase in epithelial permeability. The effluent affected the gill epithelium integrity in vitro and impacted defense pathways (upregulation of multixenobiotic resistance genes). To our knowledge, this is the first study to combine a lab-scale activated sludge WWTP with extensive characterization techniques and ecotoxicological assays to study the effects of transformed NPs in the effluent.

Biodegradability of Plastics: Challenges and Misconceptions

Plastics are one of the most widely used materials and, in most cases, they are designed to have long life times. Thus, plastics contain a complex blend of stabilizers that prevent them from degrading too quickly. Unfortunately, many of the most advantageous properties of plastics such as their chemical, physical and biological inertness and durability present challenges when plastic is released into the environment. Common plastics such as polyethylene (PE), polypropylene (PP), polystyrene (PS), and polyethylene terephthalate (PET) are extremely persistent in the environment, where they undergo very slow fragmentation (projected to take centuries) into small particles through photo-, physical, and biological degradation processes¹. The fragmentation of the material into increasingly smaller pieces is an unavoidable stage of the degradation process. Ultimately, plastic materials degrade to micron-sized particles (microplastics), which are persistent in the environment and present a potential source of harm for organisms.

Evaluation of methods to determine adsorption of polycyclic aromatic hydrocarbons to dispersed carbon nanotubes

A number of methods have been reported for determining hydrophobic organic compound adsorption to dispersed carbon nanotubes (CNTs), but their accuracy and reliability remain uncertain. We have evaluated three methods to investigate the adsorption of phenanthrene (a model polycyclic aromatic hydrocarbon, PAH) to CNTs with different physicochemical properties: dialysis tube (DT) protected negligible depletion solid phase microextraction (DT-nd-SPME), ultracentrifugation, and filtration using various types of filters. Dispersed CNTs adhered to the unprotected polydimethylsiloxane (PDMS)-coated fibers used in nd-SPME. Protection of the fibers from CNT adherence was investigated with hydrophilic DT, but high PAH sorption to the DT was observed. The efficiency of ultracentrifugation and filtration to separate CNTs from the water phase depended on CNT physicochemical properties. While non-functionalized CNTs were efficiently separated from the water phase using ultracentrifugation, incomplete separation of carboxyl functionalized CNTs was observed. Filtration efficiency varied with different filter types (composition and pore size), and non-functionalized CNTs were more easily separated from the water phase than functionalized CNTs. Sorption of phenanthrene was high (< 70%) for three of the filters tested, making them unsuitable for the assessment of phenanthrene adsorption to CNTs. Filtration using a hydrophilic polytetrafluoroethylene (PTFE) filter membrane (0.1 μm) was found to be a simple and precise technique for the determination of phenanthrene adsorption to a range of CNTs, efficiently separating all types of CNTs and exhibiting a good and highly reproducible recovery of phenanthrene (82%) over the concentration range tested (70-735 μg/L).

Biokinetics of Nanomaterials: the Role of Biopersistence

Nanotechnology risk management strategies and environmental regulations continue to rely on hazard and exposure assessment protocols developed for bulk materials, including larger size particles, while commercial application of nanomaterials (NMs) increases. In order to support and corroborate risk assessment of NMs for workers, consumers, and the environment it is crucial to establish the impact of biopersistence of NMs at realistic doses. In the future, such data will allow a more refined future categorization of NMs. Despite many experiments on NM characterization and numerous in vitro and in vivo studies, several questions remain unanswered including the influence of biopersistence on the toxicity of NMs. It is unclear which criteria to apply to characterize a NM as biopersistent. Detection and quantification of NMs, especially determination of their state, i.e., dissolution, aggregation, and agglomeration within biological matrices and other environments are still challenging tasks; moreover mechanisms of nanoparticle (NP) translocation and persistence remain critical gaps. This review summarizes the current understanding of NM biokinetics focusing on determinants of biopersistence. Thorough particle characterization in different exposure scenarios and biological matrices requires use of suitable analytical methods and is a prerequisite to understand biopersistence and for the development of appropriate dosimetry. Analytical tools that potentially can facilitate elucidation of key NM characteristics, such as ion beam microscopy (IBM) and time-of-flight secondary ion mass spectrometry (ToF-SIMS), are discussed in relation to their potential to advance the understanding of biopersistent NM kinetics. We conclude that a major requirement for future nanosafety research is the development and application of analytical tools to characterize NPs in different exposure scenarios and biological matrices.

Characterisation of fine-grained tailings from a marble processing plant and their acute effects on the copepod Calanus finmarchicus

Submarine tailing disposal (STD) of mining waste is practiced as an alternative to land fill disposal in several countries. Knowledge regarding the environmental implications of STD on fjord and other marine ecosystems, including the pelagic environment, is scarce. In this study, we characterised the particle shape, size and metal content of the fine-grained fraction of tailings (FGT) from a Norwegian marble processing plant and investigated their acute toxicity and impact on feeding rate in adult Calanus finmarchicus. Initial tailing dispersions with a concentration of 1 mg mL^-1 contained approximately 72 million particles, with 62% of particles between 0.6 and 1 μm in size. After a sedimentation time of 1 h, 69% of the particles between 0.6 and 5 μm remained dispersed, decreasing to 22% after 6 h. When subjected to low energy turbulence in exposure experiments, the formation of fragile agglomerates was observed. The FGT contained Al, Mn, Fe and Ni, with no detectable dissolution occurring during the 48 h exposure period. Acute exposure (up to 5 g L^-1) to FGT caused no mortality in C. finmarchicus. Similarly, feeding rates determined during a 40 h depuration period, were not significantly impacted. However, surface attachment and uptake of FGT into the digestive tract of the copepods was observed. This indicates that, whilst marble FGT are not acutely toxic to copepods, chronic effects such as impacts on organism's energy budgets could occur, highlighting the need for further research on potential sublethal effects in organisms exposed to fine inorganic particles.

Phenanthrene Bioavailability and Toxicity to Daphnia magna in the Presence of Carbon Nanotubes with Different Physicochemical Properties

Studies investigating the effect of carbon nanotubes (CNTs) on the bioavailability and toxicity of hydrophobic organic compounds in aquatic environments have generated contradictory results, and the influence of different CNT properties remains unknown. Here, the adsorption of the polycyclic aromatic hydrocarbon phenanthrene (70-735 μg/L) to five types of CNTs exhibiting different physical and chemical properties was studied. The CNTs were dispersed in the presence of natural organic matter (nominally 20 mg/L) in order to increase the environmental relevance of the study. Furthermore, the bioavailability and toxicity of phenanthrene to Daphnia magna in the absence and presence of dispersed CNTs was investigated. Both CNT dispersion and adsorption of phenanthrene appeared to be influenced by CNT physical properties (diameter and specific surface area). However, dispersion and phenanthrene adsorption was not influenced by CNT surface chemical properties (surface oxygen content), under the conditions tested. Based on nominal phenanthrene concentrations, a reduction in toxicity to D. magna was observed during coexposure to phenanthrene and two types of CNTs, while for the others, no influence on phenanthrene toxicity was observed. Based on freely dissolved concentrations, however, an increased toxicity was observed in the presence of all CNTs, indicating bioavailability of CNT-adsorbed phenanthrene to D. magna.

Uptake and toxicity of methylmethacrylate-based nanoplastic particles in aquatic organisms

The uptake and toxicity of 2 poly(methylmethacrylate)-based plastic nanoparticles (PNPs) with different surface chemistries (medium and hydrophobic) were assessed using aquatic organisms selected for their relevance based on the environmental behavior of the PNPs. Pure poly(methylmethacrylate) (medium; PMMA PNPs) and poly(methylmethacrylate-co-stearylmethacrylate) copolymer (hydrophobic; PMMA-PSMA PNPs) of 86 nm to 125 nm were synthesized using a miniemulsion polymerization method. Fluorescent analogs of each PNP were also synthesized using monomer 7-[4-(trifluoromethyl)coumarin]acrylamide and studied. Daphnia magna, Corophium volutator, and Vibrio fischeri were employed in a series of standard acute ecotoxicity tests, being exposed to the PNPs at 3 different environmentally realistic concentrations (0.01 mg/L, 0.1 mg/L, and 1.0 mg/L) and a high concentration 500 mg/L to 1000 mg/L. In addition, sublethal effects of PNPs in C. volutator were determined using a sediment reburial test, and the uptake and depuration of fluorescent PNPs was studied in D. magna. The PNPs and fluorescent PNPs did not exhibit any observable toxicity at concentrations up to 500 mg/L to 1000 mg/L in any of the tests except for PMMA-PSMA PNPs and fluorescent PNPs following 48-h exposure to D. magna (median lethal concentration values of 879 mg/L and 887 mg/L, respectively). No significant differences were observed between labeled and nonlabeled PNPs, indicating the suitability of using fluorescent labeling. Significant uptake and rapid excretion of the fluorescent PNPs was observed in D. magna. Environ Toxicol Chem 2016;35:1641-1649. © 2015 SETAC.

Carbon Nanotube Properties Influence Adsorption of Phenanthrene and Subsequent Bioavailability and Toxicity to Pseudokirchneriella subcapitata

The bioavailability of organic contaminants adsorbed to carbon nanotubes (CNTs) remains unclear, especially in complex natural freshwaters containing natural organic matter (NOM). Here, we report on the adsorption capacity (Q(0)) of five CNTs exhibiting different physicochemical properties, including a single-walled CNT (SWCNTs), multiwalled CNTs (MWCNT-15 and MWCNT-30), and functionalized MWCNTs (hydroxyl, -OH, and carboxyl, -COOH), for the model polycyclic aromatic hydrocarbon phenanthrene (3.1-800 μg/L). The influence of phenanthrene adsorption by the CNTs on bioavailability and toxicity was investigated using the freshwater algae Pseudokirchneriella subcapitata. CNTs were dispersed in algal growth media containing NOM (DOC, 8.77 mg/L; dispersed concentrations: 0.5, 1.3, 1.3, 3.3, and 6.1 mg/L for SWCNT, MWCNT-15, MWCNT-30, MWCNT-OH, and MWCNT-COOH, respectively). Adsorption isotherms of phenanthrene to the dispersed CNTs were fitted with the Dubinin-Ashtakhov model. Q(0) differed among the CNTs, increasing with increasing surface area and decreasing with surface functionalization. SWCNT and MWCNT-COOH exhibited the highest and lowest log Q(0) (8.891 and 7.636 μg/kg, respectively). The presence of SWCNTs reduced phenanthrene toxicity to algae (EC50; 528.4) compared to phenanthrene-only (EC50; 438.3), and the presence of MWCNTs had no significant effect on phenanthrene toxicity. However, phenanthrene adsorbed to NOM-dispersed CNTs proved to be bioavailable and contribute to exert toxicity to P. subcapitata.