Microplastic Pellets Research Articles

The promoting effects of soil microplastics on alien plant invasion depend on microplastic shape and concentration

Both alien plant invasions and soil microplastic pollution have become a concerning threat for terrestrial ecosystems, with consequences on the human well-being. However, our current knowledge of microplastic effects on the successful invasion of plants remains limited, despite numerous studies demonstrating the direct and indirect impacts of microplastics on plant performance. To address this knowledge gap, we conducted a greenhouse experiment involving the mixtures of soil and low-density polyethylene (LDPE) microplastic pellets and fragments at the concentrations of 0, 0.5 % and 2.0 %. Additionally, we included Solidago decurrens (native plant) and S. canadensis (alien invasive plant) as the target plants. Each pot contained an individual of either species, after six-month cultivation, plant biomass and antioxidant enzymes, as well as soil properties including soil moisture, pH, available nutrient, and microbial biomass were measured. Our results indicated that microplastic effects on soil properties and plant growth indices depended on the Solidago species, microplastic shapes and concentrations. For example, microplastics exerted positive effects on soil moisture of the soil with native species but negative effects with invasive species, which were impacted by microplastic shapes and concentrations, respectively. Microplastics significantly impacted catalase (P < 0.05) and superoxide dismutase (P < 0.01), aboveground biomass (P < 0.01), and belowground/aboveground biomass (P < 0.01) of the native species depending on microplastic shapes, but no significant effects on those of the invasive species. Furthermore, microplastics effects on soil properties, nutrient, nutrient ratio, and plant antioxidant enzyme activities contributed to plant biomass differently among these two species. These results suggested that the microplastics exerted a more pronounced impact on native Solidago plants than the invasive ones. This implies that the alien invasive species displays greater resistance to microplastic pollution, potentially promoting their invasion. Overall, our study contributes to a better understanding of the promoting effects of microplastic pollution on plant invasion.

Screening of organic chemicals associated to virgin low-density polyethylene microplastic pellets exposed to the Mediterranean Sea environment by combining gas chromatography and liquid chromatography coupled to quadrupole-time-of-flight mass spectrometry

In this work, organic chemicals associated with microplastics (MPs) exposed to a coastal anthropogenized environment for up to eight weeks have been screened for, in order to discern the (de)sorption dynamics of chemicals in the marine ecosystem. Low-density polyethylene (LDPE) pellets were studied since they represent primary MPs used by the plastic industry and a relevant input of MPs into the oceans. To maximize the coverage of chemicals that could be detected, both liquid and gas chromatography coupled to quadrupole-time-of-flight (GC-QTOF and LC-QTOF, respectively) were used. In the case of LC-QTOF, an electrospray ionization source was employed, and the compounds were investigated by combining suspect and non-target screening workflows. The GC-QTOF was equipped with an electron ionization source and compounds were screened in raw and derivatized (silylated) extracts by deconvolution and contrast to high- and low-resolution libraries. A total of 50 compounds of multifarious classes were tentatively identified. Among them, melamine and 2-ethylhexyl salicylate (EHS) were detected in the original MPs but were rapidly desorbed. Melamine was completely released into the marine environment, while EHS was partly released but a portion remained bound to the MPs. On the other hand, many other chemicals of both anthropogenic (e.g. phenanthrene or benzophenone) and natural origin (e.g. betaine and several fatty acids) accumulated onto MPs over time. Quantification of 12 unequivocally identified chemicals resulted into a total concentration of 810 μg/kg after MPs exposure for 8 weeks.

Seasonal variation and spatial distribution of microplastic pellets and their associated contaminants along the central east coast of India.

Microplastic pellets (MPPs) are one of the significant sources of plastic pollution on shorelines worldwide. In this study, for the first time, we have examined the occurrence of MPPs and their spatial and seasonal distributions, adsorbed contaminants, polymer composition, and ecological risks at eight renowned beaches of Andhra Pradesh, central east coast of India. A total of 3950 MPPs were collected from eight beaches along the central east coast of India during October 2020, representing pre-northeast monsoon (pNEM), and during January 2021, representing the northeast monsoon (NEM). The abundance of MPPs was higher during the NEM than those found in the pNEM. ATR-FTIR and SEM analyses were conducted to characterize the polymer types and weathering patterns of MPPs. Energy-Dispersive X-ray spectrometer (EDS) results show the MPP adsorbance of heavy metals such as Ni, Cr, Cu, Pb, and Zn. The degree of contamination and polymer hazard risks of MPPs were assessed using the pollution load index (PLI) and polymer hazard index (PHI). The conducive wind and currents during the NEM lead to higher MPP abundance than during the pNEM. However, the spatial variations of MPPs showed significant differences among the beaches. This study revealed that the presence of MPPs on the beaches along the central east coast of India might pose a considerable polymer hazard risk to the ecosystem. The substantial surface weathering features of MPPs would lead to more toxic nanoplastics in the future.

Comparison of learning models to predict LDPE, PET, and ABS concentrations in beach sediment based on spectral reflectance

Microplastic (MP) contamination on land has been estimated to be 32 times higher than in the oceans, and yet there is a distinct lack of research on soil MPs compared to marine MPs. Beaches are bridges between land and ocean and present equally understudied sites of microplastic pollution. Visible-near-infrared (vis–NIR) has been applied successfully for the measurement of reflectance and prediction of low-density polyethylene (LDPE), polyethylene terephthalate (PET), and polyvinyl chloride (PVC) concentrations in soil. The rapidity and precision associated with this method make vis–NIR promising. The present study explores PCA regression and machine learning approaches for developing learning models. First, using a spectroradiometer, the spectral reflectance data was measured from treated beach sediment spiked with virgin microplastic pellets [LDPE, PET, and acrylonitrile butadiene styrene (ABS)]. Using the recorded spectral data, predictive models were developed for each microplastic using both the approaches. Both approaches generated models of good accuracy with R2 values greater than 0.7, root mean squared error (RMSE) values less than 3 and mean absolute error (MAE) < 2.2. Therefore, using this study’s method, it is possible to rapidly develop accurate predictive models without the need of comprehensive sample preparation, using the low-cost option ASD HandHeld 2 VNIR Spectroradiometer.

Concentration-Dependent Impacts of Microplastics on Soil Nematode Community in Bulk Soils of Maize: Evidence From a Pot Experiment

Agricultural land soils have become a source and sink for microplastics. Due to the low recycling rate, long durability, and small size, microplastics pose a potential risk to soil fauna, which are critical for maintaining healthy soil. However, whether and how would microplastics affect soil biodiversity and ecological functioning is not well-understood. Soil nematodes are valuable indicators of the soil food web. In the present study, the abundance, diversity, community composition, maturity indices, soil food web indices, and metabolic footprints of soil nematodes in bulk soils of maize were utilized to indicate the potential impacts of polypropylene (PP) microplastic pollution on soil fauna using a soil-incubation experiment in a climate-controlled chamber with four concentration levels of microplastic pellets (0%, 0.5%, 1%, and 2%, w/w) added to loess soil collected from the Loess Plateau in China. Soil sampling was conducted at the fully ripe stage of maize. Twenty-nine genera of nematodes, including thirteen genera of plant-feeding nematodes, seven genera of bacterial-feeding nematodes, five genera of fungal-feeding nematodes, and four genera of omnivorous nematodes were recovered from soil samples. Microplastic concentration negatively affected the abundance, diversity (including genus richness, Margalef’s richness, Shannon–Wiener index, and Simpson’s dominance index), sigma maturity index (∑MI), structural index, and metabolic footprints. The abundances of plant parasites, bacterivores, fungivores, and omnivores in 2% soils were reduced by 90.16%, 76.06%, 82.35%, and 100%, respectively, in comparison with those of control. The major drivers of soil nematode communities in bulk soils of maize at a depth range of 0–20 cm were the soil pH, soil organic carbon content, C/N, and TP content. In conclusion, the addition of 200 μm-sized PP microplastic pellets negatively affected the soil nematode community and associated ecological functioning under greenhouse conditions.

Binding, recovery, and infectiousness of enveloped and non-enveloped viruses associated with plastic pollution in surface water

Microplastics in wastewater and surface water rapidly become colonised by microbial biofilm. Such ‘plastisphere’ communities are hypothesised to persist longer and be disseminated further in the environment and may act as a vector for human pathogens, particularly as microplastics entering wastewater treatment plants are exposed to high concentrations of pathogenic bacteria. However, the potential for human viral pathogens to become associated with the plastisphere has never before been quantified. Here, we have used rotavirus (RV) SA11 (a non-enveloped enteric virus) and the enveloped bacteriophage Phi6 as model viruses to quantify binding and recovery from biofilm-colonised microplastic pellets in three different water treatments (filtered and non-filtered surface water, and surface water with added nutrients). Viruses associated with biofilm-colonised pellets were more stable compared to those remaining in the water. While infectious particles and genome copies of RV remained stable over the 48 h sampling period, Phi6 stability was highly impacted, with a reduction ranging from 2.18 to 3.94 log10. Virus particles were protected against inactivation factors when associated with the biofilm on microplastic surfaces, and when there was a high concentration of particulate matter in the liquid phase. Although our results suggest that the presence of an envelope may limit virus interaction with the plastisphere, the ability to recover both enveloped and non-enveloped infectious viruses from colonised microplastic pellets highlights an additional potential public health risk of surface waters becoming contaminated with microplastics, and subsequent human exposure to microplastics in the environment.

Hydrometeorological assessments of the transport of microplastic pellets in the Eastern Mediterranean

Microplastic pellets were sampled in May and November 2018 during one-week surveys at 13 coastal beaches in Iskenderun Bay/Turkey. Pellet pollution index (PPI) was calculated for the beaches as a tool to assess beach pollution by microplastic pellets. Hydrometeorological conditions, including wind, current, wave, surface run-off, and precipitation, were examined during 2018 to reveal the effect on the transport of microplastic pellets within the study area. Sea-surface heights, including the astronomical tide and the storm surge and the wave runup heights, were also considered in the analysis to study the extent of hydrodynamic forcing on the beach. Hydrometeorological assessments indicated that the pellet concentrations in the coastal zone are mostly related to wind-induced transport. Three major river discharges are considered as the main source of microplastic pellets effluents. A Lagrangian particle transport model was conducted to reveal the possible beaching hotspots of microplastic pellets released from these river mouths. Average microplastic pellets were calculated as 126.04 ± 54.08 items/m2 for May 2018 and 70.22 ± 18.25 items/m2 for November 2018. An overall mean PPI for May 2018 was calculated as 1.13, indicating a moderate degree of pellet pollution, and 0.56 for November 2018, indicating a low degree of pellet pollution. The simulations showed that Orontes River effluents affected the inner Iskenderun Bay coasts more than the Seyhan and Ceyhan River.

Microalgae colonization of different microplastic polymers in experimental mesocosms across an environmental gradient.

A variety of organisms can colonize microplastic surfaces through biofouling processes. Heterotrophic bacteria tend to be the focus of plastisphere research; however, the presence of epiplastic microalgae within the biofilm has been repeatedly documented. Despite the relevance of biofouling in determining the fate and effects of microplastics in aquatic systems, data about this process are still scarce, especially for freshwater ecosystems. Here, our goal was to evaluate the biomass development and species composition of biofilms on different plastic polymers and to investigate whether plastic substrates exert a strong enough selection to drive species sorting, overcoming other niche‐defining factors. We added microplastic pellets of high‐density polyethylene (HDPE), polyethylene terephthalate (PET), and a mix of the two polymers in 15 lentic mesocosms in five different locations of the Iberian Peninsula, and after one month, we evaluated species composition and biomass of microalgae developed on plastic surfaces. Our results, based on 45 samples, showed that colonization of plastic surfaces occurred in a range of lentic ecosystems covering a wide geographical gradient and different environmental conditions (e.g., nutrient concentration, conductivity, macrophyte coverage). We highlighted that total biomass differed based on the polymer considered, with higher biomass developed on PET substrate compared to HDPE. Microplastics supported the growth of a rich and diversified community of microalgae (242 species), with some cosmopolite species. However, we did not observe species‐specificity in the colonization of the different plastic polymers. Local species pool and nutrient concentration rather than polymeric composition seemed to be the determinant factor defying the community diversity. Regardless of specific environmental conditions, we showed that many species could coexist on the surface of relatively small plastic items, highlighting how microplastics may have considerable carrying capacity, with possible consequences on the wider ecological context.

Comparison of primary microplastics from Cartagena Bay and their toxicological evaluation using "Caenorhabditis elegans" as a biological model

BACKGROUND AND AIM: Microplastic pollution in world oceans is an issue of great concern, since they cause damage to marine ecosystems. When ingested, they can exert toxicity, causing oxidative stress, cell damage and inflammation, compromising somatic processes such as fertility and reproduction among others, and affecting humans through the ingestion of marine contaminated food. METHODS: This research includes a statistical comparison and toxicity evaluation of black/tarred and degraded microplastic pellets present on Cartagena Bay beaches – Colombia, against industrial microplastics pellets. Samples of pellets were collected from Castillogrande and Bocagrande beaches, two urban beaches with a high presence of microplastic pollution coming from the nearby plastic industry. Sod-4, gpx-4, mtl- 2 fluorescent Caenorhabditis elegans strains were expose to microplastics pellets soxhlet extraction previously characterized by Gas Chromatography/Mass Spectrometry. Mortality and gene expression test were performed. Relationships were made considering the location and chemical composition of the collected pellets. The nematode was exposed during 24 h to whole black pellet extract solution and a 50% dilution extract. RESULTS:In terms of the lethality tests, a higher mortality of the nematode was obtained using the 50% dilution extract (45%) compared to the concentrated solution (20%). For the gene expression assay the genes with the highest exposure in all the dilutions were sod-4 and mtl-2 showing superoxide dismutase activity and metallothionein-2, respectively. The chemical characterization, showed a 30% of long-chain hydrocarbons, 14.8% of pesticides and 3.1% of hormones as the more relevant chemicals present in black pellets but not in industrial pellets. For degraded pellets, 45.5% of long-chain hydrocarbons, 10.9% of pesticides and 7.3% of acid anhydrides as relevant results. Significant differences were found, considering Dunnet analysis. CONCLUSIONS:The above results showed that microplastic pellets can adsorb contaminants present in water that can interfere with biological processes, contributing to the poor health of this touristic sector and nearby ecosystems. KEYWORDS: Microplastics, Toxicology, Chemical exposures

The sorption of persistent organic pollutants in microplastics from the coastal environment

Microplastic (MP) pellets were sampled from six sandy beaches around Taiwan in order to investigate the concentrations and compositions of POPs, including: PCDD/Fs, PBDD/Fs, PBDEs, PCBs, PBBs, and their congeners. The concentrations of PCDD/Fs on the surface (Cs) of MP pellets from the six sampling sites were from 1.9 to 14.6 pg∙g−1, while the overall concentrations within MPs (Ct) were from 95.0 to 1110.6 pg∙g−1. As PCDD/Fs were adsorbed into the inner part of MPs, a ratio of the total concentrations to surficial concentration of MPs (Ct/Cs) was as high as 355.2 times. The Ct/Cs of other POPs were also significant, such as PBDEs being found up to 8068 times, which could be attributed to artificial addition during manufacturing processes as flame-retardant substances. Primary compositions of PCDD/Fs, PBDD/Fs, and PBDEs on the MPs in our POP congener analysis were all found containing species with higher number of chlorine or bromine, which were adsorbed on the MP surface more easily due to their relative higher KOW.

Surface adsorption of metallic species onto microplastics with long-term exposure to the natural marine environment.

Microplastics are ubiquitous in most biomes and environments, representing one of the most pressing global environmental challenges. This study investigated the ability of pre-production microplastic pellets to accumulate metals from the marine environment. An accidental ocean discharge of poly(propylene) pellets occurred via a wastewater treatment centre at the coastal city of Warrnambool, Victoria - Australia. These pellets were collected routinely from Shelly Beach, adjacent to the ocean discharge site over a period of 16-months following the spill. This collection formed a unique time-series that accurately represented the degree to which metal ions in the coastal marine environment accumulate on plastic debris. Elemental analysis indicated an increase in concentration over time of rare earth elements and a selection of other metals supporting the hypothesis that microplastics selectively adsorb metals from the environment. A subset of the poly(propylene) pellets contained a surfactant coating which significantly increased the adsorption capacity. The surface properties in relation to adsorption were further explored with surface imaging and these results are also discussed. This study shows how microplastics act as nucleation points and carriers of trace metal ions in marine environments.

Protocol for microplastic pollution monitoring in freshwater ecosystems: Towards a high-throughput sample processing - MICROPLASTREAM

Robust and reproducible quantification of microplastic pollution in freshwater ecosystems requires the processing of a large amount of samples collected in varying environmental conditions. Such samples are characterized by a high amount of organic matter compared to microplastics and are highly variable in terms of the quantity and the composition of matrices, requiring a standardized analytical protocol for sample treatment and analysis. However, two important and time-consuming steps for microplastic recovery are the elimination of organic matter and microscopic inspection of samples. Here, we developed and validated a protocol, targeting particles with length ranging from 700 µm to 5 mm, that includes a double-step digestion of organic matter, consisting of incubation with potassium hydroxide followed by hydrogen peroxide solutions, and two stereomicroscopic analyses. In addition, we developed several technical improvements allowing reducing the time needed to process samples, such as the design of an adapted filter-cap to improve the content transfer. The absence of physical and chemical alterations in the investigated microplastic pellets and the average reduction of 65.8% (± 9.59 SD) of organic matter in real samples demonstrated that our protocol is fit for purpose. We recommend a second stereomicroscopic analysis to avoid underestimating microplastic concentration and particle size distribution biased towards larger particles. When used for a large-scale monitoring of microplastic pollution, this protocol resulted in an estimated time of 38 h for one person for the treatment of a batch of 24 samples, allowing a higher throughput sample processing and reproducible quantification.• Protocol customization towards high-throughput sample processing• Double step digestion to improve organic matter elimination• Importance of stereomicroscopic analysis for microplastic recovery

Predicting the Dispersal and Accumulation of Microplastic Pellets Within the Estuarine and Coastal Waters of South-Eastern Brazil Using Integrated Rainfall Data and Lagrangian Particle Tracking Models

Understanding how microplastic particles move and accumulate within estuarine and coastal waters requires consideration of the entry of primary inputs (e.g., raw materials from industrial zones) as well as secondary inputs resulting from fluvial processes (i.e., materials carried into coastal waters by rivers and streams). This study presents a novel approach to achieve this aim, by comparing the individual and combined ability of Particle Tracking Models (PTMs) and seasonal rainfall data, to explain observed inputs of microplastic pellets to the ocean beaches of Santos City (south-eastern Brazil). A Lagrangian (PTM) based on high-resolution hydrodynamic models was used to simulate seasonal patterns of pellet dispersal from five potential release points within the Santos Estuarine System (SES) and nearshore waters which are known contributors to the regions microplastic debris problem. Model outputs suggested that the debris field is likely to be small within the estuary (ranging from 3.6 to 8.1 km2), intermediate at the river mouth (mean 34 km2) and greatest for near- and offshore sites (ranging from 34 to 40 km2). The spatial footprints were strongly modulated by season (and rainfall), with simulations alone unable to reconcile daily inputs of pellets observed on the beaches of Santos Bay (ranging from 2 - 51 particles m2 ∙ d-1). Given this discrepancy, a Generalized Additive Modelling approach was employed to integrate the PTM outputs with rainfall data to improve predictions of beached particles. Results confirmed that fluvial processes, could indeed significantly improve the ability to predict rates of pellet accumulation (raising the explained deviance in observed inputs from 41% to 93%). Thus, the study highlights the potential to couple widely used dispersion models with metrics that describe fluvial forcing (rainfall and estuarine flushing) in order to better understand the spatio-temporal dynamics of microplastic debris transport and accumulation within dynamic coastal environments.

Rainfall and Tidal Cycle Regulate Seasonal Inputs of Microplastic Pellets to Sandy Beaches

Microplastic contamination of coastal environments is a global problem and pellets used in industrial processes are a persistent form of microplastic pollution. Regions that host port facilities and industries may be sources of plastic pellets to local and adjacent coastal areas. This study assessed pellet densities over regional and local scales to provide a greater understanding of the spatio-temporal variation in its inputs to sandy beaches. Pellets were used as a proxy to undertake a multi-scale assessment of the spatial (local vs. regional) and temporal (tides and weather) stranding of microplastics. Regional variation was driven by weather (i.e., rainfall) and distance from source. Local-scale variability was driven by distance from source (along shore), tidal cycle, and beach hydrodynamics. Our results address the large spatio-temporal variability in microplastic pollution and provide useful information for monitoring programs by pointing to the need to consider variability in inputs over both regional and local scales.

Exposure to a microplastic mixture is altering the life traits and is causing deformities in the non-biting midge Chironomus riparius Meigen (1804)

The effect of microplastics (MP) exposure on the chironomid species Chironomus riparius Meigen, 1804 was investigated using the OECD sediment and water toxicity test. Chironomid larvae were exposed to an environmentally relevant low microplastics concentration (LC), a high microplastics concentration (HC) and a control (C). The LC was 0.007 g m−2 on the water surface + 2 g m−3 in the water column + 8 g m−2 in the sediment, and the HC was 10 X higher than this for each exposure. The size of the majority of the manufactured microplastic pellets varied between 20 and 100 μm. The MP mixture consisted of: polyethylene-terephtalate (PET), polystyrene (PS), polyvinyl-chloride (PVC) and polyamide (PA) in a ratio of 45%: 15%: 20%: 20%, respectively, for the sediment exposure; 100% polyethylene for the water column exposure; and 50% polyethylene: 50% polypropylene for the water surface exposure. Different endpoints were monitored, including morphological changes in the mandibles and mentums of 4th instar larvae, morphological changes in the wings, mortality, emergence ratio, and developmental time. A geometric morphometric analysis showed a tendency toward widening of the wings, elongation of the mentums and changing the shape of the mandibles in specimens exposed to both concentrations of microplastics. The development time of C. riparius was significantly prolonged by the MP treatment: 13.8 ± 0.5; 14.4 ± 0.6; and 15.3 ± 0.4 days (mean ± SD) in the C, LC, and HC, respectively. This study indicates that even environmentally relevant concentrations of MP mixture have a negative influence on C. riparius, especially at the larval stage.

In vitro avian bioaccessibility of metals adsorbed to microplastic pellets

Microplastics are known to be associated with co-contaminants, but little is understood about the mechanisms by which these chemicals are transferred from ingested plastic to organisms. This study simulates marine avian gastric conditions in vitro to examine the bioaccessibility of authigenic metals (Fe, Mn) and trace metals (Co, Pb) that have been acquired by polyethylene microplastic pellets from their environment. Specifically, different categories of pellet were collected from beaches in Cornwall, southwest England, and exposed to an acidified saline solution of pepsin (pH ∼ 2.5) at 40 °C over a period of 168 h with extracted metal and residual metal (available to dilute aqua regia) analysed by ICP-MS. For Fe, Mn and Co, kinetic profiles consisted of a relatively rapid initial period of mobilisation followed by a more gradual approach to quasi-equilibrium, with data defined by a diffusion model and median rate constants ranging from about 0.0002 (μg L−1)−1 h−1 for Fe to about 7 (μg L−1)−1 h−1 for Co. Mobilisation of Pb was more complex, with evidence of secondary maxima and re-adsorption of the metal to the progressively modified pellet surface. At the end of the time-courses, maximum total concentrations were 38.9, 0.81, 0.014 and 0.10 μg g−1 for Fe, Mn, Co and Pb, respectively, with maximum respective percentage bioaccessibilities of around 60, 80, 50 and 80. When compared with toxicity reference values for seabirds, the significance of metals acquired by microplastics from the environment and exposed to avian digestive conditions is deemed to be low, but studies of a wider range of plastics and metal associations (e.g. as additives) are required for a more comprehensive risk assessment.

Organic contamination of beached plastic pellets in the South Atlantic: Risk assessments can benefit by considering spatial gradients

Microplastics are important vectors for the transport and accumulation of persistent organic contaminants in coastal and marine environments. We determined the concentration of polycyclic aromatic hydrocarbons (PAHs) and polychlorinated biphenyls (PCBs) associated with microplastic pellets collected along a 39-km stretch of Brazil's South Atlantic coastline to understand the spatial dynamics and potential risk posed by these contaminants. Total PAH concentrations ranged from 1,454 to 6,002 ng g−1 and regularly exceeded the threshold effect level (TEL) for sediments defined by the United States Environmental Protection Agency. Sampling stations, spaced evenly along the coastline (i.e., 3-km intervals) exhibited a general north-to-south decline in the concentrations of some PAHs, but this spatial gradient was complicated by small-scale differences in the concentrations and composition of associated contaminants. Similarly, analysis of individual isomer ratios revealed further complexity driven by differences in the contribution of petrogenic versus pyrolytic inputs which pose different levels of risk to marine organisms. PCB concentrations ranged from 0.8 to 104.6 ng g−1 and were dominated by low chlorinated congeners likely to have originated from major industrial areas to the north. Overall, this study highlights the challenge of directly linking microplastic pollution with the potential toxicological effects of organic contaminants in coastal waters. We recommend that monitoring programs should explicitly consider both the origin (i.e., pellet sources and dispersal pathways) and nature of organic contamination (i.e., concentration and composition) when assessing the risks for biota and human health.

Releases of brominated flame retardants (BFRs) from microplastics in aqueous medium: Kinetics and molecular-size dependence of diffusion

Microplastics (<5 mm) are increasingly detected in aquatic environment, and the high levels of brominated flame retardants (BFRs) contained in them can potentially impact water quality. This study characterized the release kinetics of polybrominated diphenyl ethers (PBDEs) and 1,2-bis(2,4,6-tribromophenoxy)ethane (BTBPE) from millimeter-sized microplastic pellets in water at environmentally relevant temperatures. Leaching rates of BFRs from the microplastic pellets made of acrylonitrile butadiene styrene (ABS) were found to be controlled by their diffusion within the plastic matrix, and their diffusion coefficients (D) in the plastic matrices ranged from 10−28.30 to 10−20.84 m2 s−1. The apparent activation energies of the BFRs’ diffusion coefficients were estimated to be in the range of 64.1–131.8 kJ mol−1 based on their temperature dependence and the Arrhenius equation. The diffusion coefficients of the BFRs decrease with their molecular diameters, while the activation energies for diffusion increase with the molecular diameters, which are indicative of significant steric hindrance for BFR diffusion within the plastic matrices. A semi-empirical linear relationship was observed between Log10D and the glass transition temperature (Tg) of plastics, which allows prediction of the diffusion coefficients of BFRs in other types of microplastics commonly found in marine environment. The half-lives of BFR leaching (i.e., 50% depletion) from the microplastic pellets would range from tens of thousands to hundreds of billions of years at ambient temperatures if their physical and chemical structures could remain intact. Although the release fluxes of BFRs from microplastics are extremely low under the model conditions, a range of physical and chemical processes in the natural environment and the digestive systems of organisms that ingested them could potentially accelerate their leaching by causing breakdown and swelling of the plastic matrices.

Biodegradation of polyethylene microplastics by the marine fungus Zalerion maritimum

Plastic yearly production has surpassed the 300milliontons mark and recycling has all but failed in constituting a viable solution for the disposal of plastic waste. As these materials continue to accumulate in the environment, namely, in rivers and oceans, in the form of macro-, meso-, micro- and nanoplastics, it becomes of the utmost urgency to find new ways to curtail this environmental threat. Multiple efforts have been made to identify and isolate microorganisms capable of utilizing synthetic polymers and recent results point towards the viability of a solution for this problem based on the biodegradation of plastics resorting to selected microbial strains.Herein, the response of the fungus Zalerion maritimum to different times of exposition to polyethylene (PE) pellets, in a minimum growth medium, was evaluated, based on the quantified mass differences in both the fungus and the microplastic pellets used. Additionally, molecular changes were assessed through attenuated total reflectance Fourier transform Infrared Spectroscopy (FTIR-ATR) and Nuclear Magnetic Resonance (NMR).Results showed that, under the tested conditions, Z. maritimum is capable of utilizing PE, resulting in the decrease, in both mass and size, of the pellets. These results indicate that this naturally occurring fungus may actively contribute to the biodegradation of microplastics, requiring minimum nutrients.

Characteristics, seasonal distribution and surface degradation features of microplastic pellets along the Goa coast, India

Microplastic pellets (MPPs) are ubiquitous contaminants, recognised as a serious threat to the biota in coastal, estuarine and marine environment. The distribution, abundance, weathering and chemical characteristics of MPPs on the beaches of Goa, and their transport to the coast during the southwest (SW) monsoon are discussed in this paper. MPP samples collected from six sandy beaches were categorised based on colour and polymer types using Stereoscope microscope and FTIR-ATR spectroscopy, respectively. White colour MPPs were the most abundant, and Polyethylene (PE) and Polypropylene (PP) were the dominant polymer types of MPPs deposited on all the beaches. Carbonyl index values showed that MPPs collected in June 2015 (representing SW monsoon) were ‘new’, whereas the MPPs collected in January 2015 were ‘aged’, showing that MPPs are arriving at Goa coast only during SW monsoon due to conducive hydrodynamic conditions. Characteristics of MPPs suggest that they could be originated primarily from ocean-based sources. The winds and surface currents during SW monsoon are the driving forces for the transportation and deposition of MPPs on the Goa beaches. The results of this study will be useful to the National ‘Clean India’ program for effective plastic debris removal management.