Spatial distribution and source identification of hydrophobic organic compounds (HOCs) on sedimentary microplastic in Hong Kong

A review on micro- and nanoplastics in humans: Implication for their translocation of barriers and potential health effects

As emerging contaminants, micro- and nanoplastics (MNPs) can absorb and leach various toxic chemicals and ultimately endanger the health of the ecological environment and humans. With extensive research on MNPs, knowledge about MNPs in humans, especially their translocation of barriers and potential health effects, is of utmost importance. In this review, we collected literature published from 2000 to 2023, focusing on MNPs on their occurrence in humans, penetrating characteristics in the placental, blood-brain, and blood-testis barriers, and exposure effects on mammalian health. The characteristics and distributions of MNPs in human samples were analyzed, and the results demonstrated that MNPs were ubiquitous in most human samples, except for kidneys and cerebrospinal fluid. In addition, the phenomenon of MNPs crossing barriers and their underlying mechanisms were discussed. We also summarized the potential factors that may affect the barrier crossing and health effects of MNPs, including characteristics of MNPs, exposure doses, administration routes, exposure durations, co-exposure to other pollutants, and genetic predisposition. Exposure to MNPs may cause cytotoxicity, neurotoxicity, and developmental and reproductive toxicity in mammals. People are encouraged to reduce their exposure to MNPs to prevent these adverse health effects. Finally, we discussed the shortcomings of current research on MNPs in humans, providing a valuable reference for understanding and evaluating the potential health risks from MNP exposure in mammals, including humans.

Interaction of microplastics with perfluoroalkyl and polyfluoroalkyl substances in water: A review of the fate, mechanisms and toxicity

It is well known that microplastics can act as vectors of pollutants in the environment and are widely spread in freshwater and marine environments. PFAS (perfluoroalkyl and polyfluoroalkyl substances) can remain in the aqueous environment for long periods due to their wide application and good stability. The coexistence of microplastics and PFAS in the aqueous environment creates conditions for their interaction and combined toxicity. Studies on adsorption experiments between them and combined toxicity have been documented in the literature but have not been critically summarized and reviewed. Therefore, in this review, we focused on the interaction mechanisms, influencing factors, and combined toxicity between microplastics and PFAS. It was found that surface complexation may be a new interaction mechanism between microplastics and PFAS. In addition, aged microplastics reduce the adsorption of PFAS due to the presence of oxygenated groups on the surface compared to virgin microplastics. Attached biofilms can increase the adsorption capacity and create conditions for biodegradation. And, the interaction of microplastics and PFAS affects their spatial and temporal distribution in the environment. This review can provide insights into the fate of microplastics and PFAS in the global aquatic environment, fill knowledge gaps on the interactions between microplastics and PFAS, and provide a basic reference for assessing their combined toxicity.

Microplastics and PAHs mixed contamination: An in-depth review on the sources, co-occurrence, and fate in marine ecosystems

Microplastics (MPs) and polycyclic aromatic hydrocarbons (PAHs) are toxic contaminants that have been found in marine ecosystems. This review aims to explore the sources and mechanisms of PAHs and MPs mixed contamination in marine environments. Understanding the released sources of PAHs and MPs is crucial for proposing appropriate regulations on the release of these contaminants. Additionally, the mechanisms of co-occurrence and the role of MPs in distributing PAHs in marine ecosystems were investigated in detail. Moreover, the chemical affinity between PAHs and MPs was proposed, highlighting the potential mechanisms that lead to their persistence in marine ecosystems. Moreover, we delve into the various factors influencing the co-occurrence, chemical affinity, and distribution of mixed contaminants in marine ecosystems. These factors, including environmental characteristics, MPs properties, PAHs molecular weight and hydrophobicity, and microbial interactions, were critically examined. The co-contamination raises concerns about the potential synergistic effects on their degradation and toxicity. Interesting, few studies have reported the enhanced photodegradation and biodegradation of contaminants under mixed contamination compared to their individual remediation. However, currently, the remediation strategies reported for PAHs and MPs mixed contamination are scarce and limited. While there have been some initiatives to remove PAHs and MPs individually, there is a lack of research specifically targeting the removal of mixed contaminants. This deficiency highlights the need for further investigation and the development of effective remediation approaches for the efficient remediation of PAHs and MPs from marine ecosystems.

Investigation of organic micropollutant pollution in İzmit Bay: a comparative study of passive sampling and instantaneous sampling techniques

In this study, we used a comprehensive array of sampling techniques to examine the pollution caused by organic micropollutants in İzmit Bay for the first time. Our methodology contains spot seawater sampling, semi-permeable membrane devices (SPMDs) passive samplers for time-weighted average (TWA), and sediment sampling for long-term pollution detection in İzmit Bay, together. Additionally, the analysis results obtained with these three sampling methods were compared in this study. Over the course of two seasons in 2020 and 2021, we deployed SPMDs for 21 days in the first season and for 30 days in the second season. This innovative approach allowed us to gather sea water samples and analyze them for the presence of polycyclic aromatic hydrocarbons (Σ15 PAHs), polychlorinated biphenyls (Σ7 PCBs), and organochlorine pesticides (Σ11 OCPs). Using SPMD-based passive sampling, we measured micropollutant concentrations: PAHs ranged from 1963 to 10342 pg/L in 2020 and 1338 to 6373 pg/L in 2021; PCBs from 17.46 to 61.90 pg/L in 2020 and 8.37 to 78.10 pg/L in 2021; and OCPs from 269.2 to 8868 pg/L in 2020 and 141.7 to 1662 pg/L in 2021. Our findings revealed parallels between the concentrations of PAHs, PCBs, and OCPs in both SPMDs and sediment samples, providing insights into the distribution patterns of these pollutants in the marine ecosystem. However, it is worth noting that due to limited data acquisition, the suitability of spot sampling in comparison to instantaneous sampling remains inconclusive, highlighting the need for further investigation and data collection.

Organic pollutants adsorbed on microplastics: Potential indicators for source appointment of microplastics

Pollution by microplastics (MPs) has caused potential threats to the environment. Understanding the sources of MPs in the environment can help control their emissions and reduce environmental risks. Source apportionment of MPs has been conducted according to the characteristics of MPs themselves (such as types of polymers and morphological characteristics). However, the specificity and resolution of the appointments of sources need to be improved. Organic pollutants adsorbed on MPs can be used as a novel and reliable indicator to identify the source of MPs in the environment. In the present work, the analytical methods of MPs and organic pollutants adsorbed on MPs were critically reviewed, and the occurrence of organic pollutants and factors influencing their adsorption on MPs were discussed. Furthermore, the potential applications of organic pollutants adsorbed on MPs as indicators for determining the sources of MPs were highlighted. The study would help recognize the sources of MPs, which will support efforts aimed at reducing their emissions and further pollution of the ecosystem.

Nanopolystyrene size effect and its combined acute toxicity with halogenated PAHs on Daphnia magna

Nanoplastics (NPs, diameter <1 μm) not only have toxicity but also change the toxicity of other pollutants in water. To date, the nanopolystyrene (nano-PS) size effect and its combined toxicity with halogenated polycyclic aromatic hydrocarbons (HPAHs) remain unclear. In this study, the single toxicity, combined toxicity, and mode of action of the binary mixture of polystyrene (PS) and HPAH were examined. At the same time, the nano-PS size effect on combined toxicity was also discussed. According to our results, the 48 h acute toxicity test results showed that 30 nm PS was highly toxic (EC50-48 h = 1.65 mg/L), 200 nm PS was moderately toxic (EC50-48 h = 17.8 mg/L), and 1 μm PS was lowly toxic (EC50-48 h = 189 mg/L). The NP toxicity decreased with increasing size. HPAHs were highly toxic substances to Daphnia magna (EC50-48 h = 0.12-0.22 mg/L). The mode of action of PS and HPAHs was antagonistic according to the toxicity unit method (TU), additive index method (AI), and mixture toxicity index method (MTI). The size effect of nano-PS operates via two mechanisms: the inherent toxicity of nano-PS and the sorption of pollutants by nano-PS. The former impacts the combined toxicity more than the latter. In the binary mixed system, the larger the particle size and the higher the proportion of NPs in the system, the less toxic the system was. Linear interpolation analysis can be used to predict the combined toxicity of a mixed system with any mixing ratio.

Micro (nano)plastics and phthalate esters drive endophytic bacteria alteration and inhibit wheat root growth

Endophytes play an important role in plant growth and stress tolerance, but limited information is available on the complex effects of micro (nano)plastics and phthalate esters (PAEs) on endophytes in terrestrial plants. To better elucidate the ecological response of endophytic bacteria on exogenous pollutants, a hydroponic experiment was conducted to examine the combined impact of polystyrene (PS) and PAEs on endophyte community structure, diversity, and wheat growth. The findings revealed that wheat roots were capable of absorbing and accumulating PS nanoparticles (PS-NPs, 0.1 μm), whereas PS microparticles (PS-MPs, 1 and 10 μm) merely adhered to the root surface. The addition of PAEs resulted in a stronger accumulation of fluorescent signal from PS-NPs in the roots. The dibutyl phthalate (DBP) and di(2-ethylhexyl) phthalate (DEHP) were identified in wheat roots, and they could be metabolized to form minobutyl phthalate and phthalic acid, and mono-(2-ethylhexyl) phthalate, respectively. Compared to single PAEs, the concentration of PAEs and their metabolites in the roots treated with PS-NPs showed a great increase, while they exhibited a significant decline in the presence of PS-MPs. Principal coordinate analysis and permutational multivariate analysis of variance demonstrated that PS size were the major factor that induced oxidative damage, and altered the endogenous homeostasis of wheat roots. The increase in PS size positively promoted the relative abundance of dominant endophytes. Specifically, Proteobacteria. Proteobacteria were the most important in the symbiosis survival, which had a great impact on the microbial community and diversity. Therefore, PS and PAEs could affect the endophytes directly and indirectly. Structural equation modeling further implied that these endophytic bacteria, along with antioxidant enzymes such as superoxide dismutase which were regulated by non-enzymatic mechanisms, promoted root biomass increase. These results indicated a synergistic resistance mechanism between antioxidant enzymes and endophytic bacteria in response to environmental stress.

Surface functional groups and biofilm formation on microplastics: Environmental implications

Microplastics (MPs) contamination is becoming a significant environmental issue, as the widespread omnipresence of MPs can cause many adverse consequences for both ecological systems and humans. Contrary to what is commonly thought, the toxicity-inducing MPs are not the original pristine plastics; rather, they are completely transformed through various surface functional groups and aggressive biofilm formation on MPs via aging or weathering processes. Therefore, understanding the impacts of MPs' surface functional groups and biofilm formation on biogeochemical processes, such as environmental fate, transport, and toxicity, is crucial. In this review, we present a comprehensive summary of the distinctive impact that surface functional groups and biofilm formation of MPs have on their significant biogeochemical behavior in various environmental media, as well as their toxicity and biological effects. We place emphasis on the role of surface functional groups and biofilm formation as a means of influencing the biogeochemical processes of MPs. This includes their effects on pollutant fate and element cycling, which in turn impacts the aggregation, transport, and toxicity of MPs. Ultimately, future research studies and tactics are needed to improve our understanding of the biogeochemical processes that are influenced by the surface functional groups and biofilm formation of MPs.

Voyaging of halogenated polycyclic aromatic hydrocarbons, an emerging group of pollutants, on micro-mesoplastics in the marine environment

The limited existing research on the accumulation of hazardous chlorinated and brominated polycyclic aromatic hydrocarbons (ClPAHs and BrPAHs) in micro-mesoplastics (mMPs) motivated this investigation. We collected mMPs from the coastal environments of Sri Lanka and Japan. Out of 75 target compounds analyzed, 61 were detected, with total parent PAH concentrations reaching 16,300 and 1770 ng/g plastic in Sri Lanka and Japan, respectively. The total parent PAH concentrations in mMPs from the southern Sri Lankan coastline were relatively higher than those from the eastern coastline. Phenanthrene and naphthalene were the dominant parent PAH congeners in most mMP samples. Chlorinated pyrenes and brominated naphthalene were predominant among halogenated PAHs. The estimated toxic equivalency quotient (TEQ) ranged from 0.67 to 1057 ng-TEQ/g plastic, with the highest levels observed in polystyrene (PS) particles from the southern Sri Lankan coast. Benzo[a]pyrene and dibenzo[a,h]anthracene exhibited elevated TEQ for parent PAHs, whereas dichloropyrene, and dibromopyrene represented the highest TEQs for ClPAHs and BrPAHs, respectively. The data evidenced that several HPAH congeners can increase the PAH-like toxicity (∼86%) in mMPs. This study provides insights into the accumulation of parent and halogenated PAHs in mMPs, highlighting their potential combined implications in marine and terrestrial ecosystems.

Selective enrichments for color microplastics loading of marine lipophilic phycotoxins

Microplastics (MPs) and marine lipophilic phycotoxins (MLPs) are two classes of emerging contaminants. Together, they may exacerbate the negative impacts on nearshore marine ecosystems. Herein, the loading of 14 representative MLPs, closely related to toxin-producing algae, on MPs and their relations with colorful MPs have been explored for the first time based on both field and lab data. The objectives of our study are to explore the roles of multiple factors (waterborne MLPs and MP characteristics) in the loading of MLPs by MPs with the applications of various statistical means, and to further explore the role of the color of MP in the loading of specific MLPs through lab simulation experiments. Our results demonstrated that MPs color determined the loading of some specific MLPs on MPs and green MPs can load much more than other colorful fractions (p < 0.05). These interesting phenomena illustrated that the color effects on the loading processes of MLPs on MPs are a dynamic process, and it can be well explained by the shading effect of MP color, which may affect the growth and metabolism of the attached toxic-producing algae on MPs and hence the production of specific MLPs. Furthermore, loading of MLPs on MPs can be considered as the comprehensive physicochemical and biological processes. Our results caution us that special attention should be paid to explore the real-time dynamic color shading effects on all kinds of bio-secreted contaminants loading on MPs, and highlight the necessary to comprehensive investigate the interaction between biota, organic contaminants and MPs.

Chromium (IV) transfer to Amusium pleuronectes by LDPE microplastics: An experimental study

An experiment was carried out to investigate the potential of virgin LDPE microplastics to transfer heavy metals. Desired shapes (fibres, fragments, and films) and sizes (< 5 mm) of virgin LDPE microplastics were immersed in a known concentration (30 µg/l) of chromium (IV). These Cr-coated microplastics were introduced into a culture tank containing edible scallops (Amusium pleuronectes). After the completion of the experiment (5 days), the sediments in the culture tank and edible tissues of A. pleuronectes were tested for the presence of Cr. In the sediments, a maximum concentration of 1.934 µg/g of Cr was accumulated at a rate of R2 = 0.979, while in the tissues, the maximum accumulation concentration was 0.733 µg/g of Cr at a rate of R2 = 0.807. Energy Dispersive X-ray Spectroscopy analysis also confirmed the presence of Cr (2.61 ± 0.44 mass % and 1.80 ± 0.30 atom%) in the tissues of A. pleuronectes, which was absent in the control tissues. The study showed that when exposed to contaminants such as heavy metals, LDPE microplastics can adhere and transfer them to biotic tissues. LDPE showed the potential to transfer adhered contaminants; however, the effects caused by these transferred contaminants on biota must be studied further. Risk assessment study showed that potential ecological risk of Cr is < 40 indicating low risk however, the combined effect of Cr and LDPE can compound its toxicity which needs to be studied further.

Microplastic-sorbed persistent organic pollutants in coastal Mediterranean Sea areas of Tunisia

Microplastics (MPs) are emerging pollutants of global concern due to their pervasiveness, high sorption ability for persistent organic pollutants (POPs) and direct and indirect toxicity to marine organisms, ecosystems, as well as humans. As one of the major coastal interfaces, beaches are considered among the most affected ecosystems by MPs pollution. The morphological characteristics of MPs (pellets and fragments) collected from four beaches along the Tunisian coast and sorbed POPs, including polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs), were investigated in this study. The results showed that the MPs varied greatly in color, polymer composition and degradation degree. The color varied from colored to transparent and the most prevalent polymer identified using Raman spectroscopy was polyethylene. Scanning electron microscope (SEM) images exhibited various surface degradation features including cavities, cracks, attached diatom remains, etc. The concentrations of Σ12PCBs over all beaches ranged from 14 to 632 ng g-1 and 26 to 112 ng g-1 in the pellets and fragments, respectively, with a notable presence and dominance of highly-chlorinated PCBs such as CB-153 and -138. Among the OCPs, γ-HCH is the only compound detected with concentrations ranging from 0.4 to 9.7 ng g-1 and 0.7 to 4.2 ng g-1 in the pellets and fragments, respectively. Our findings indicate that MPs found on the Tunisian coast may pose a chemical risk to marine organisms as the concentrations of PCBs and γ-HCH in most of the analysed samples exceeded the sediment-quality guidelines (SQG), especially the effects range medium (ERM) and the probable effects level (PEL). As the first report of its kind, the information gathered in this study can serve as the baseline and starting point for future monitoring work for Tunisia and neighbouring countries, as well as for stakeholders and coastal managers in decision-making processes.

Use of a Dual-Labeled Bioaccumulation Method to Quantify Microplastic Vector Effects for Hydrophobic Organic Contaminants in Soil

Although in vitro simulation and in vivo feeding experiments are commonly used to evaluate the carrier role of microplastics in the bioaccumulation of toxic chemicals, there is no direct method for quantitatively determining their vector effect. In this study, we propose a dual-labeled method based on spiking unlabeled hydrophobic organic contaminants (HOCs) into soils and spiking their respective isotope-labeled reference compounds into microplastic particles. The bioaccumulation of the unlabeled and isotope-labeled HOCs in Eisenia fetida earthworms was compared. Earthworms can assimilate both unlabeled and isotope-labeled HOCs via three routes: dermal uptake, soil ingestion, and microplastic ingestion. After 28 days of exposure, the relative fractions of bioaccumulated isotope-labeled HOCs in the soil treated with 1% microplastics ranged from 15.5 to 55.8%, which were 2.9-47.6 times higher than those in the soils treated with 0.1% microplastics. Polyethylene microplastics were observed to have higher relative fractions of bioaccumulated isotope-labeled HOCs, potentially because of their surface hydrophobicity and amorphous rubbery state. The general linear models suggested that the vector effects were mainly due to the microplastic concentration, followed by polymer properties and HOC hydrophobicity. This proposed method and the derived empirical formula contribute to a more comprehensive understanding of the vector effects of microplastics for HOC bioaccumulation.

Fate and environmental behaviors of microplastics through the lens of free radical

Microplastics (MPs), as plastics with a size of less than 5 mm, are ubiquitously present in the environment and become an increasing environmental concern. The fate and environmental behavior of MPs are significantly influenced by the presence of free radicals. Free radicals can cause surface breakage, chemical release, change in crystallinity and hydrophilicity, and aggregation of MPs. On the other hand, the generation of free radicals with a high concentration and oxidation potential can effectively degrade MPs. There is a limited review article to bridge the fate and environmental behaviors of MP with free radicals and their reactions. This paper reviews the sources, types, detection methods, generation mechanisms, and influencing factors of free radicals affecting the environmental processes of MPs, the environmental effects of MPs controlled by free radicals, and the degradation strategies of MPs based on free radical-associated technologies. Moreover, this review elaborates on the limitations of the current research and provides ideas for future research on the interactions between MPs and free radicals to better explain their environmental impacts and control their risks. This article aims to keep the reader abreast of the latest development in the fate and environmental behaviors of MP with free radicals and their reactions and to bridge free radical chemistry with MP control methodology.

Microplastics in aquatic environments: A comprehensive review of toxicity, removal, and remediation strategies

The occurrence of microplastics (MPs) in aquatic environments has been a global concern because they are toxic and persistent and may serve as a vector for many legacies and emerging pollutants. MPs are discharged to aquatic environments from different sources, especially from wastewater plants (WWPs), causing severe impacts on aquatic organisms. This study mainly aims to review the Toxicity of MPs along with plastic additives in aquatic organisms at various trophic compartments and available remediation methods/strategies for MPs in aquatic environments. Occurrences of oxidative stress, neurotoxicity, and alterations in enzyme activity, growth, and feeding performance were identical in fish due to MPs toxicity. On the other hand, growth inhibition and ROS formation were observed in most of the microalgae species. In zooplankton, potential impacts were acceleration of premature molting, growth retardation, mortality increase, feeding behaviour, lipid accumulation, and decreased reproduction activity. MPs togather with additive contaminants could also exert some toxicological impacts on polychaete, including neurotoxicity, destabilization of the cytoskeleton, reduced feeding rate, growth, survivability and burrowing ability, weight loss, and high rate of mRNA transcription. Among different chemical and biological treatments for MPs, high removal rates have been reported for coagulation and filtration (>86.5 %), electrocoagulation (>90 %), advanced oxidation process (AOPs) (30 % to 95 %), primary sedimentation/Grit chamber (16.5 % to 58.84 %), adsorption removal technique (>95 %), magnetic filtration (78 % to 93 %), oil film extraction (>95 %), and density separation (95 % to 100 %). However, desirable extraction methods are required for large-scale research in MPs removal from aquatic environments.

Sources, distribution, and environmental effects of microplastics: a systematic review

Microplastics (MPs) are receiving increasing attention from researchers. They are environmental pollutants that do not degrade easily, are retained for prolonged periods in environmental media such as water and sediments, and are known to accumulate in aquatic organisms. The aim of this review is to show and discuss the transport and effects of microplastics in the environment. We systematically and critically review 91 articles in the field of sources, distribution, and environmental behavior of microplastics. We conclude that the spread of plastic pollution is related to a myriad of processes and that both primary and secondary MPs are prevalent in the environment. Rivers have been indicated as major pathways for the transport of MPs from terrestrial areas into the ocean, and atmospheric circulation may be an important avenue for transporting MPs between environmental compartments. Additionally, the vector effect of MPs can change the original environmental behavior of other pollutants, leading to severe compound toxicity. Further in-depth studies on the distribution and chemical and biological interactions of MPs are highly suggested to improve our understanding of how MPs behave in the environment.

Microplastics as vectors of chemical contaminants and biological agents in freshwater ecosystems: Current knowledge status and future perspectives

Microplastics (MPs) are becoming ubiquitous, and their environmental fate is becoming an issue of concern. Our review aims to synthesize current knowledge status and provide future perspectives regarding the vector effect of MPs for chemical contaminants and biological agents. The evidence in the literature indicates that MPs are a vector for persistent organic pollutants (POPs), metals and pharmaceuticals. Concentrations of chemical contaminant in orders of six-fold higher on MPs surfaces than in the surrounding environmental waters have been reported. Chemical pollutants such as perfluoroalkyl substances (PAFSs), hexachlorocyclohexane (HCHs) and polycyclic aromatic hydrocarbons (PAHs), exhibiting polarities in the range of 3.3-9 are the commonest chemicals reported on MP surfaces. Regarding metals on MPs including chromium (Cr), lead (Pb), cobalt (Co), the presence of C-O and N-H in MPs promote a relatively high adsorption of these metals onto MP surfaces. Regarding pharmaceuticals, not much has been done, but a few studies indicate that commonly used drugs such as ibuprofen, ibuprofen, diclofenac, and naproxen have been associated with MPs. There is sufficient evidence supporting the claim that MPs can act as vectors for viruses, bacterial and antibiotic-resistant bacteria and genes, and MPs act to accelerate horizontal and vertical gene transfer. An area that deserves urgent attention is whether MPs can act as vectors for invertebrates and vertebrates, mainly non-native, invasive freshwater species. Despite the ecological significance of invasive biology, little research has been done in this regard. Overall, our review summarises the state of the current knowledge, identifies critical research gaps and provides perspectives for future research.

Organic Pollutants Associated with Plastic Debris in Marine Environment: A Systematic Review of Analytical Methods, Occurrence, and Characteristics

Plastic pollution has become one of the most serious environmental problems, and microplastics (MPs, particles < 5 mm size) may behave as a vehicle of organic pollutants, causing detrimental effects to the environment. Studies on MP-sorbed organic pollutants lack methodological standardization, resulting in a low comparability and replicability. In this work, we reviewed 40 field studies of MP-sorbed organic contaminants using PRISMA guidelines for acquiring information on sampling and analytical protocols. The papers were also scored for their reliability on the basis of 7 criteria, from 0 (minimum) to 21 (maximum). Our results showed a great heterogeneity of the methods used for the sample collection, MPs extraction, and instruments for chemicals' identification. Measures for cross-contamination control during MPs analysis were strictly applied only in 13% of the studies, indicating a need for quality control in MPs-related research. The most frequently detected MP-sorbed chemicals were polychlorinated biphenyls (PCBs), polycyclic aromatic hydrocarbons (PAHs), and organochlorine pesticides (OCPs). Most of the studies showed a good reliability (>75% of the total score), with 32 papers scoring 16 or higher. On the basis of the collected information, a standardizable protocol for the detection of MPs and MP-sorbed chemicals has been suggested for improving the reliability of MPs monitoring studies.

Potential risk of co-occurrence of microplastics and chlorinated persistent organic pollutants to coastal wetlands: Evidence from a case study

Microplastic (MP) pollution in coastal wetlands is of a global concern. Little attention has been paid to the co-occurrence and corresponding risk of MPs with pollutants, especially refractory chlorinated persistent organic pollutants (CPOPs). A case study of Zhejiang, China was conducted to investigate the occurrence of MPs and targeted CPOPs in coastal wetlands. MPs were 100% detected, but with the lowest abundance in coastal wetlands (average: 666.1 ± 159.1 items kg^-1), as compared to other 6 terrestrial ecosystems (average: 1293.9 ± 163.7 items kg^-1) including paddy field, upland, facility vegetable field, forestland, urban soil, and grassland. A total of 35 kinds CPOPs were also detected in all studied coastal wetlands, with their concentration almost under 10 μg kg^-1 (90.1%). Both enrichment of MPs and CPOPs was affected by sediment TOC, wetland vegetation and land use simultaneously. Interestingly, the occurrence of MPs was significantly correlated with polychlorinated biphenyls (PCBs) but not organochlorine pesticides (OCPs). Results of co-occurrence pollution assessment of MPs and CPOPs further indicated only Hangzhou Bay showed the ecological risk among all tested wetlands. This would suggest a potential risk of co-occurrence of MPs and modern CPOPs in coastal wetland in economic development area. Possible reason may lie on strong MP vector effect to CPOPs. More attention should thus be paid to other wetlands polluted by MPs and MP-carrying CPOPs in area with relatively great environmental pressure induced by human activity. This study may provide reference for a better understanding with respect to the risk level posed by co-occurrence of MPs and CPOPs to global coastal wetlands.

Seasonal variation of temperature affects HMW-PAH accumulation in fishery species by bacterially mediated LMW-PAH degradation

Currently, the specific mechanism generating seasonal variation in polycyclic aromatic hydrocarbons (PAHs) via bacterial biodegradation remains unclear, and whether this alteration affects PAH bioaccumulation is unknown. Therefore, we performed a study between 2015 and 2020 to investigate the effects of seasonal variation on bacterial communities and PAH bioaccumulation in the Pearl River Estuary. Significantly high PAH concentrations in both aquatic and fishery species were determined in dry seasons (the mean ∑₁₆PAH concentration: water, 37.24 ng/L (2015), 30.83 ng/L (2020); fish, 51.01 ng/L (2015) and 72.60 ng/L (2020)) compared to wet seasons (the mean ∑₁₆PAH concentration: water, 22.38 ng/L (2015), 19.40 ng/L(2020); fish, 25.28 ng/L (2015) and 32.59 ng/L (2020)). Distinct differences in taxonomic and functional composition of bacterial communities related to biodegradation of low molecular weight PAHs (LMW-PAHs) were observed between seasons, and the concentrations of PAHs were negatively correlated with seasonal variation in temperature. Temperature-related specific bacterial taxa (e.g., Stenotrophomonas) directly or indirectly participated in LMW-PAH degradation via encoding PAH degradation enzymes (e.g., protocatechuate 4,5-dioxygenase) that subsequently led to bioaccumulation of high molecular weight PAHs (HMW-PAHs) in wild and fishery species due to LMW-PAHs in the water. Based on this alteration, the ecological risk posed by PAHs decreased in wet seasons, and an unbalanced spatio-temporal distribution of PAHs was observed in this estuary. These results suggest that seasonal variation of temperature affects HMW-PAH accumulation in fishery species via bacterially mediated LMW-PAH biodegradation.

Microplastics contributed much less than organic matter to the burial of polycyclic aromatic hydrocarbons by sediments in the past decades: a case study from an urban lake

The role of microplastics in burying hydrophobic organic compounds remains largely unknown. Sediment cores collected from the center of a typical urban lake (Lake Qianhu) in China were chosen to explore the contribution of microplastics to the burial of polycyclic aromatic hydrocarbons (PAHs) by sediments, and to elucidate how this contribution changed with microplastic composition and the hydrophobicity of PAHs on a decade scale. Our results showed that the concentration of individual PAHs adsorbed by microplastics varied from detection limit (LOD) to 7.2 mg g^-1 MP, which was much higher than the LOD to 31.0 μg g^-1 TOC buried by total organic carbon. However, the amount of individual PAHs adsorbed by microplastics only contributed to 0-34.2% of that in sediments. Changes in the composition of microplastics, including the increased proportion of polyethylene and polypropylene : polyethylene polymer in sediments, resulted in the average microplastic sediment burial ratios (MSBRs) of most PAHs increasing by 0.13% to 2.7% in the period from 1997 to 2018 compared with those in the period from 1975 to 1996. The average MSBRs varied with the hydrophobicity of PAHs, which increased with log K_ow value if it varied from 3.45 to 5.20, but decreased with log K_ow if it was in the range of 5.30 to 6.50. Our study provides novel knowledge on the contribution of microplastics to the burial of PAHs by sediments.

Effects of microplastic sorption on microbial degradation of halogenated polycyclic aromatic hydrocarbons in water

Halogenated PAHs (HPAHs) are ubiquitous in the environment and have a toxicity similar to that of dioxin. Microplastics exist widely in the environment, and their sorption allows them to act as carriers of HPAHs, potentially changing the bioavailability of HPAHs. However, to the best of our knowledge related studies are limited. In this study, degrading bacteria of five HPAHs were cultivated from mangrove sediments. Among them, the Hyphomicrobium genus has good degradation ability on 9-BrAnt, 2-BrPhe and 2-ClPhe. The degradation process is in line with the first-order degradation kinetic characteristics. The kinetic equations of five kinds of HPAHs showed that the degradation half-lives are 0.65 days (2-BrFle), 0.79 days (9-ClPhe), 1.50 days (2-ClAnt), 5.94 days (9-BrPhe) and 14.1 days (9-BrAnt). The greater the number of benzene rings and the heavier the halogen substituents, the slower the degradation of HPAHs. The sorption of microplastics inhibited the biodegradation of HPAHs, and the degradation half-life of HPAHs will be extended from 0.65 to 14.1 days (the average is 4.59 days) to 1.71-9.93 days (average 5.40 days) for PA, 0.70-35.2 days (average 12.8 days) for PE, 6.02-28.2 (average 15.7 days) days for POM, and 4.60-24.0 (average 19.2 days) days for PP, which is mainly related to the partition coefficient between microplastics and water. This study provides a reference for reducing the uncertainty of the ecological risk assessment of HOCs in the aquatic environment.

Microplastics and associated organic pollutants in beach sediments from the Gulf of Guinea (SE Atlantic) coastal ecosystems

Microplastics (MPs) are emerging pollutants of global concern due to their pervasiveness, sorptive capacity for organic and inorganic pollutants, and direct and indirect toxicity to organisms and ecosystems. This study aimed to assess the concentration and the statistical difference in the concentration of microplastic-sorbed organic pollutants from two ecosystems, the marine and estuarine lagoon. Surface sediment from the estuarine lagoon and marine ecosystems were sampled for microplastics (1-5 mm). A total of 3680 MP particles were collected. The plastics were analyzed for polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs) and organochlorine pesticides (OCPs). ∑PAHs, ∑PCBs and ∑OCPs were between 0.00 and 0.32 mg/kg, 0.00-0.53 mg/kg and 0.04-2.02 mg/kg, respectively. The results showed a correlation of -0.2, 0.8 and 0.2 between the number of MPs and the concentration of PAHs, PCBs and OCPs, respectively, suggesting that the potential risk of accumulation of plastic-sorbed PCBs is higher than those of OCPs and PAHs. Mann Whitney U test (at 95% confidence level) indicated no statistical difference in the concentration of organic pollutants in lagoon and beach MPs. In addition, we found no significant difference in the accumulation of organic pollutants in MPs from beach drift and high waterlines. The result suggests that the concentration of microplastics-sorbed organic pollutants in both ecosystems is comparable and likely to pose similar potential risks. We recommend that plastic pollution in all ecosystems require attention.

Characteristics and source-pathway of microplastics in freshwater system of China: A review

China plays a key role in global plastic production, consumption and disposal, which arouses growing concern about microplastics (MPs) contamination in Chinese freshwater systems. However, few reviews have discussed the characteristics of MP pollution in whole freshwater systems at a national scale. In this review, we summarized the characteristics, sources and transport pathways of MPs in Chinese freshwater systems including surface water and sediment. Results showed that current research mainly focused on the middle and lower reaches of the Yangtze River and its tributaries, as well as lakes and reservoirs along the Yangtze River. Large-scale reservoirs, rivers and lakes located in densely populated areas usually showed higher abundances of MPs. The majority of MPs in Chinese surface water and sediment mainly consisted of polyethylene and polypropylene, and the most common morphologies were fibers and fragments. To identify the sources and pathways, we introduced the source-sink-pathway model, and found that sewage system, farmland and aquaculture area were the three most prevalent sinks in freshwater systems in China. The source-sink-pathway model will help to further identify the migration of MPs from sources to freshwater systems.

Microplastics: A review of analytical methods, occurrence and characteristics in food, and potential toxicities to biota

Microplastics (MPs) are ubiquitous in various environment compartments, including food. Here, we collected research reports of MPs in food published during 2010-2020, and summarized the analytical methods developed and utilized by researchers (e.g., digestion, separation and identification, as well as related QA/QC measures implemented), the occurrence, and the characteristics of MPs in six kinds of food. The potential effects on biota from exposure to MPs were also reviewed. The results showed that most researchers digested food samples using chemical solutions such as HNO₃, H₂O₂, KOH, or NaOH. FT-IR and Raman spectroscopy were the main technique for identifying MPs, and microscopes were used to count MP particles. The abundances MPs were in the ranges of 0-5860, 2.00-1100, 0-698, 4.00-18.7, 0-5.68 × 10⁴ and 900-3000 particles/kg in beverages, condiments, honey, meat, seafood and vegetables, respectively. The "maximum" annual human intake of MPs from these foods is approximately 1.42 × 10⁵-1.54 × 10⁵ particles/capita, equivalent to the consumption of 50 plastic bags (size: 0.04 mm × 250 mm × 400 mm, density: 0.98 g/cm³) each year. Blue-colored and fiber-shaped MP particles were the most commonly observed in food, predominated by PA, PE, PES, PET and PP types. Toxicity studies indicated that MPs, additives of MPs and adsorbents or microorganisms on the surfaces of MPs were all somewhat toxic to cells or biota. Exposure to MPs may induce oxidative stress, inflammation, neurotoxicity, and reproductive toxicity, and change the structure of intestinal microflora in cells or biota. Therefore, we call for more investigation into the residual, excretion and bioavailability of MPs or related absorbents/additives in biota and humans.

Biofilm-Developed Microplastics As Vectors of Pollutants in Aquatic Environments

Microplastics are a big and growing part of global pollution, which has aroused increasing concern in recent years because of their large amount, wide distribution, and adverse effects. Microplastics can sorb various pollutants from aquatic environments and act as vectors of pollutants. Most studies mainly focused on the virgin microplastics. However, microplastics in environments can be easily colonized by microorganisms, and form biofilm, which will influence the behaviors and potential risks of microplastics. The formation of biofilm on microplastics and its effects on their properties have been studied before, but their sorption and transport behaviors, and potential risks for pollutants' transfer have not been reviewed. In this paper, the role of biofilm-developed microplastics as vectors of pollutants was thoroughly analyzed and summarized. First, the formation of biofilm on microplastics, the compositions of microorganisms in biofilm, the influencing factors, and the property changes of microplastics after biofilm attachment are thoroughly reviewed. Second, the sorption of pollutants onto biofilm-developed microplastics is discussed. Third, the role of biofilm-developed microplastics as vector of pollutants are analyzed. We concluded that microplastics could provide unique substrates for microorganisms. Biofilm-developed microplastics can sorb more pollutants than the virgin ones, then act as vectors to introduce pollutants and attached microorganisms to aquatic environments and to organisms.

Measurement, quantification, and potential risk of microplastics in the mainstream of the Pearl River (Xijiang River) and its estuary, Southern China

The goals of this study were to investigate the distribution profiles, sources, and inventory of microplastics in the surface water of the mainstream of the Pearl River (Xijiang River) and its estuary, China, and to assess the potential ecological risks of the microplastics in this subtropical riverine habitat. The results showed that the microplastic abundances of the Humen (HUM, 16.33 ± 0.88 items/L), Zhaoqing (ZQ, 15.33 ± 0.67 items/L), and Hutiaomen (HTM, 14.67 ± 1.33 items/L) sites were significantly higher than those of the other sampling sites, indicating that the microplastics in Xijiang River and its estuary exhibited an unbalanced spatial distribution. The most common microplastic color was transparent and the major shape of the microplastics was fragments. Microplastics with a size of 0.01-0.1 mm were dominant throughout the 16 sampling sites. Polyolefin elastomer (POE, 33.33%), polyethylene terephthalate (PET, 23.81%), and polyurethane acrylate (PUA, 14.29%) were the dominant microplastic polymers. The microplastic abundance co-varied with most of the selected socio-economic indicators, including the population density, urban land area, gross domestic product (GDP), freshwater aquatic products, and freshwater cultivated area, but without significant differences, indicating that there are additional factors affecting the microplastic abundance. The potential risk (i.e., the potential ecological risk, RI; polymer risk index, H; and pollution load index, PLI) posed by the microplastics was higher in HUM, followed by ZQ and HTM, and it was lower for the other sites, suggesting that the main outlets and the biggest city on the Xijiang River contributed more to the high risks of microplastic pollution. Consistent with microplastic abundance distribution profiles, the average potential risk index values of the western river outlets were higher than those of the eastern river outlets and the Xijiang River, implying that the western river outlets had non-negligible potential ecological risks. Our findings deepen the understanding of the risks posed by microplastics and further contribute to microplastic risk management of riverine ecosystems.

Investigation of the Adsorption of Sulfamethoxazole by Degradable Microplastics Artificially Aged by Chemical Oxidation

In this study, three different types of microplastics were aged by the thermal activation K₂S₂O₈ method to investigate the adsorption behavior for sulfamethoxazole (SMX) in aqueous solution. The effects of pH, salinity and humic acid (HA) on adsorption behavior were also investigated. At the same time, the morphology and functional groups of microplastics before and after adsorption were characterized. As the aging time increased, the adsorption capacity of the microplastics also increased significantly. Whether it was pristine or aged, polylactic acid (PLA) had the highest adsorption capacity. The adsorption capacity of microplastics was the largest under acidic conditions, and its adsorption capacity decreased significantly in alkaline solutions. The presence of salinity inhibited the adsorption of SMX on polyethylene terephthalate (PET) and PP, but the adsorption capacity of PLA increases when salinity was above 10‰. The adsorption of SMX on microplastics was promoted by HA. When the concentration of HA was 20 mg/L, the adsorption capacity of PLA and PET decreased. Kinetic and isotherm fits were applied to the adsorption process. The increase in sorption capacity was related to the development of holes and cracks and the enhanced number of surface oxygen-containing functional groups. The adsorption kinetics to pristine microplastics conformed to a pseudo-first-order kinetic model, while the kinetics of the aged microplastics conformed to a pseudo-second-order kinetic model. It implies that the adsorption of SMX by aging microplastics involves multiple processes. The adsorption isothermal adsorption process of SMX by microplastics accorded with Freundlich model, belonging to multi-layer adsorption.

Sorption and desorption of petroleum hydrocarbons on biodegradable and nondegradable microplastics

Both biodegradable and nondegradable plastics are widely used. However, their interactions with petroleum hydrocarbons (PHs) have not been sufficiently studied. In this study, a type of biodegradable [polylactic acid (PLA)] and five types of nondegradable microplastics [polyamide (PA), polyethylene (PE), polyethylene terephthalate (PET), polystyrene (PS), and polyvinyl chloride (PVC)] were selected to investigate the sorption and desorption mechanisms of PHs. The sorption kinetics of the six types of microplastics followed a pseudo-second-order kinetics model (R² ranged from 0.956 to 0.999) and indicated that chemical sorption dominated the sorption process. The key rate-controlling steps of the sorption of PHs on microplastics were intraparticle diffusion and liquid film diffusion. The sorption capacity of PHs on microplastics followed the order of PA > PE > PS > PET > PLA > PVC. The difference in sorption capacity might be due to the crystallinity, and rubber or glass state of the microplastics. In addition, all types of microplastics exhibited reversible sorption without noticeable desorption hysteresis. No obvious differences were observed in the sorption and desorption of PHs between biodegradable and nondegradable microplastics. Both biodegradable and nondegradable microplastics could sorb/desorb PHs and serve as transportation vectors.

The nexus of macroplastic and microplastic research and plastic regulation policies in the Philippines marine coastal environments

The Philippines was reported as one of the top plastic polluters (macroplastics and microplastics (MPs)) to the marine coastal environment, which necessitated the development and enforcement of plastic regulation policies. However, the nexus between the growing research on macroplastic/MP and the plastic regulation policies in the country is unexplored. Current review suggests that macroplastic/MP research in the Philippines is still in its infancy owing to methodological and technological constraints to apportion the sources and fluxes, characterize macroplastics/MPs, and identify influencing socio-environmental factors. While government efforts are underway, it is also unclear if local researches on macroplastics/MPs were the basis in institutionalizing the existing plastic regulation policies. Therefore the nexus between the researches carried out on this problem and the policies enforced cannot be concluded. Overall, this review presents gaps on the macroplastic/MP research needing more work on the problem to establish a sound science plastic regulation policy.

Environmental source, fate, and toxicity of microplastics

Microplastics are small plastic pieces with sizes less than 5 mm. Due to their widespread distribution in different environmental compartments, food, and drinking water, microplastics have attracted increasing attention across the world. Previous reports have focused on the source, distribution, fate, and toxicity of microplastics. However, many of these studies and reviews are not quite comprehensive, and most of them have only focused on marine environments. Therefore, we comprehensively reviewed the available literature on the source, occurrence, and fate of microplastics in different environments, including air, freshwater, soil, and ocean, across the world. Our review suggests that the sources of microplastics are extensive and diverse and that their occurrence, transport, and fate in the environment are affected by a variety of natural factors as well as their own physicochemical properties. Studies on the toxicological effects of microplastics are also reviewed. We found that large research gaps exist in the quantitative analysis of different exposure routes of microplastics, and microplastic toxicity to organisms. Moreover, key suggestions for future research are presented, and we call for more efforts focusing on the occurrence and fate of microplastics in terrestrial environments, especially in the atmosphere and soil, and further investigations on the toxicity mechanisms of microplastics.

Bisphenol A and its analogues in sedimentary microplastics of Hong Kong

The occurrence and spatial distribution of bisphenol A (BPA) and analogues bisphenol B (BPB), bisphenol F (BPF) and bisphenol S (BPS) were investigated in microplastic on 11 beaches in Hong Kong. At 10 sites, BPA was the only detected chemical with concentrations ranged from 82.4-989 ng g^-1 microplastic. BPA, BPB and BPS co-occurred at only one site, where it is located close proximity to the outfall of a sewage treatment plant. There was no significant spatial difference of BPA concentrations in microplastic when all the sites were considered, indicating that some remote and presumably cleaner beaches have been contaminated. PE, PP and PS (represented >90% of total polymers) were the most dominated polymers, but there was no correlation between polymer types and BPA concentrations. No evidence was found that the BPA and its analogues accumulate on microplastic since the concentrations were comparable to those found in the sediment.

Sorption of chemical contaminants on degradable and non-degradable microplastics: Recent progress and research trends

Microplastics (<5 mm) are ubiquitous contaminants of growing concern. These have been found in multiple environmental compartments, including remote sites where anthropogenic activity is null. Once released, microplastics interact with multiple chemicals in the environment, many of which are classified as organic contaminants or heavy metals. Some contaminants have an affinity for microplastics, attributed to certain sorption mechanisms, and thus become vectors of hazardous chemicals. Here, we focused on the sorption behavior of degradable and non-degradable microplastics, including field and laboratory experiments. We reviewed the sorption mechanisms, namely hydrophobic interactions, electrostatic interactions, pore-filling, Van der Waals forces, hydrogen bonding, and π-π interactions, and the factors strengthening or weakening these mechanisms. Then, we analyzed the literature investigating the sorption behavior of a wide range of chemicals contaminants on microplastics, and the current knowledge regarding the occurrence of organic contaminants and heavy metals on microplastics extracted from the environment. The future perspectives and research priorities were discussed. It is apparent that degradable microplastics, such as polylactic acid or polybutylene succinate, have a greater affinity for hydrophobic contaminants than conventional synthetic non-degradable microplastics according to recent studies. However, studies assessing degradable microplastics are scarce and much research is required to further prove this point. We stated several knowledge gaps in this new line of research and suggest the future studies to follow an integrative approach, allowing to comprehend the multiple factors involved, such as ecotoxicity, bioaccumulation, and fate of the chemical contaminants.

Suspended particulate matter (SPM)-bound polycyclic aromatic hydrocarbons (PAHs) in lakes and reservoirs across a large geographical scale

Suspended particulate matter (SPM) plays a key role in the environmental fate of polycyclic aromatic hydrocarbons (PAHs) in lake environment. However, less is known about the occurrence, compositions and sources of SPM-bound PAHs as well as the correlations between SPM-bound PAHs and different suspended particulate organic matter (SPOM) on large geographical scale. In this study, we focused on the SPM-bound PAHs in 46 lakes and reservoirs across China to fill this gap. Our results showed that the concentrations of Σ₂₀ PAHs ranged from 334 to 38427 ng·g^-1 with a geometric mean (GM) of 3915 ng·g^-1. The occurrence of SPM-bound PAHs in this study was at a moderate level with large variations, which was associated with location and water depth according to linear discriminant analysis (LDA). Phenanthrene (Phe) was investigated as the overwhelming species with a GM of 1777 ng·g^-1, and was followed by fluoranthene (Fla), fluorene (Flu) and pyrene (Pyr) with GMs of 499 ng·g^-1, 276 ng·g^-1 and 184 ng·g^-1, respectively. The profiles of SPM-bound PAHs were primarily dominated by low-ring PAHs ranging from 56.0% to 97.1% (85.5% ± 7.7%, mean ± standard deviation). Four diagnostic ratios were applied for preliminary diagnoses, but inconsistent results were obtained in most samples. Ridge regression was applied to ascertain the potential influences of different SPOM on SPM-bound PAHs. The results revealed that the presence of SPM-bound PAHs was not only influenced by anthropogenic emissions, but also associated with biogenic organic matter. Our results provided a higher explanation than those just preliminarily estimated by total organic carbon (TOC). Nevertheless, there still exist over 50% of variance unexplained for most PAHs, and further study could focus more on the information of SPOM structures and potential local effects.

Microplastic's story

The problem of microplastic pollution is now the order of the day in front of everyone's eyes affecting the environment and the health of leaving creature. This work aims to retrace the history of microplastics in a critical way through a substantial bibliographic collection, defining the points still unresolved and those that can be resolved. Presence of marine litter in different environments is reviewed on a global scale, focusing in particular on micro and macro plastics definition, classification and characterization techniques.

Adsorption and Desorption of Triclosan on Biodegradable Polyhydroxybutyrate Microplastics

Biodegradable plastics have been increasingly used as a solution to the problem of plastic pollution in recent years. However, there are few studies on the negative effects of biodegradable microplastics. Triclosan, a widely used disinfectant, is a highly toxic substance. In the present study, the adsorption and desorption processes of triclosan on a type of biodegradable plastics, polyhydroxybutyrate (PHB), were investigated and also compared with one conventional plastic type, polyethylene. The adsorption equilibrium quantities of polyethylene and PHB were 3431.85 and 9442.27 μg/g, respectively. The adsorption rate and equilibrium adsorption capacity of triclosan on PHB are much higher than on polyethylene. Physical adsorption of triclosan on PHB and polyethylene microplastics may play a dominant role in this process. The desorption hysteresis indices are all less than zero; this indicates that triclosan is easily released from PHB and polyethylene microplastics under physiological conditions. Our results indicate that biodegradable PHB microplastics are stronger carriers for triclosan than the conventional polyethylene microplastics in the aquatic environment. Environ Toxicol Chem 2021;40:72-78. © 2020 SETAC.

Plastics Are an Insignificant Carrier of Riverine Organic Pollutants to the Coastal Oceans

Global rivers act as a dominant transport pathway for land-based plastic debris to the marine environment. Organic pollutants (OPs) affiliated with riverine plastics can also enter the global oceans, but their amounts remain unknown. Microplastic (MP) samples were collected in a one-year sampling event from the surface water of the eight main riverine outlets in the Pearl River Delta (PRD), China, and analyzed for OPs affiliated with MPs, including 16 polycyclic aromatic hydrocarbons (PAHs), eight polybrominated diphenyl ethers (PBDEs), and 14 polychlorinated biphenyls (PCBs). The mean concentrations of MP-affiliated ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB were 2010 (range: 25-40,100), 412 (range: 0.84-14,800), and 67.7 (range: 1.86-456) ng g^-1, respectively. Based on these and previous results, the annual riverine outflows of MP-affiliated OPs were 148, 83, and 8.03 g for ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB, respectively. Assuming that plastic debris of different sizes contained the same concentrations of the target pollutants as MPs, the mean riverine outflows of plastic-bound ∑₁₆PAH, ∑₈PBDE, and ∑₁₄PCB were 6.75, 3.77, and 0.37 kg year^-1, respectively, which were insignificant compared with the riverine outflows of OPs through riverine water discharge (up to hundred tons per year). Apparently, plastics are an insignificant carrier of riverine OPs to the coastal oceans.

Microextraction based on microplastic followed by SERS for on-site detection of hydrophobic organic contaminants, an indicator of seawater pollution

Microplastics (MPs) have been proven to concentrate hydrophobic organic contaminants (HOCs) from seawater as the sorbent phase, and the concentration of HOCs in aqueous solutions could be estimated from MPs preloaded with HOCs by equilibrium partition coefficient. This study firstly proposed to in situ quantify fluoranthene (a representative HOCs) pre-concentrated on MPs using surface enhance raman scattering (SERS) in combination with mathematical models, as an efficient monitoring tool for fluoranthene pollution in the aquatic environment. AgNPs-coated quartz (AgNPs@SiO2) substrate was fabricated. The SERS substrate was tested using fluoranthene standard solution with the minimal detectable concentration of 1 ng/mL achieved. Applying SERS for the detection of fluoranthene sorbed on MPs, the detection limit of fluoranthene on MPs was 3.3 ng/g, where the concentration in the corresponding equilibrium seawater was 0.97 ng/mL. Since more than one fluoranthene peak was observed, the quantitative detection was investigated by interval partial least square model. Eight characteristic peak ranges were selected to develop the model for predicting fluoranthene concentration, with R²c and R²v of 0.90 and 0.82, respectively. The study provides a promising solution to monitor trace level of contaminations in aquatic environment, using MPs as the passive sampler.

Microplastics in invertebrates on soft shores in Hong Kong: Influence of habitat, taxa and feeding mode

Microplastic (MP) pollution in the marine environment has gained much concern in recent years. This study investigated the occurrence of MPs in invertebrates collected on 18 mudflats and sandy beaches in Hong Kong and its relationships to biological taxon, feeding mode and habitat. In total 38 species of gastropods, bivalves and crabs were collected and the mean number of suspected microplastics ranged from 0 to 9.68 particles g^-1 wet weight or 0 to 18.4 particles individual^-1. Around 26% of the suspected microplastics were confirmed to be synthetic polymers, including CP (cellophane), PET (polyethylene terephthalate), and PA (polyamide). Microplastic fibres were the most abundant type of MPs, followed by pellets. Significantly higher abundance of suspected microplastics was found in gastropods. Since MP abundance might vary with taxon, it is recommended to include different taxonomic groups in any ecological assessment of the impact of MPs.

Organic pollutants in sedimentary microplastics from eastern Guangdong: Spatial distribution and source identification

Microplastics have a strong affinity for potentially toxic organic pollutants such as polycyclic aromatic hydrocarbons (PAHs) and organochlorine pesticides (OCPs). Since 2005, the International Pellet Watch used plastic pellets to monitor hydrophobic organic contaminants in marine environments. We examined the spatial distribution and sources of 16 PAHs and eight OCPs on microplastics (pellets, fragments, and foam) collected from eastern Guangdong beaches with the goal of evaluating the feasibility of exclusively using pellets in global monitoring of hydrophobic organic contaminants. The ∑PAH and ∑OCP concentrations ranged from 11.2 to 7710 ng g^-1 and 2.2-1970 ng g^-1, respectively. Although inter-site and regional differences were insignificant in fragments and foam, regional differences were observed in ∑OCP concentrations on pellets samples collected at the estuary mouth and the distributary (p < 0.05). No regional difference in ∑PAH concentration on microplastics was observed, except between fragments from the remote beach and those from the distributary (p = 0.015) and the estuary mouth (p = 0.015). The compositional profiles of PAHs revealed that PAHs with 2-4 rings were more dominant than those with >4 rings. Considering low molecular weight PAHs are less hydrophobic and more toxic; the results suggest low molecular weight PAHs may pose a significant risk to marine organisms. This study shows that the International Pellet Watch could offer critical data on source and transport of microplastic-associated OCPs but may overlook critical vehicles of PAHs in coastal environments such as foam.

Heavy metals contamination of sedimentary microplastics in Hong Kong

This is the first study of heavy metals (As, Zn, Cd, Ni, Fe, Mn, Cu) contamination of microplastics on sandy beaches in Hong Kong. Three study sites are located in the eastern waters (Pak Lap Wan, Stanley Bay, Tung Lung Chau) and the other three in the western waters (Tai Pai Tsui, Ha Pak Nai, Shui Hau Wan). The three most abundant types of microplastics were polyethylene (42.2%), polypropylene (23.3%) and polystyrene (19.5%). The median concentration of Fe (302 mg kg^-1) was the highest and followed by Zn (19.6 mg kg^-1) and Mn (18.6 mg kg^-1). Very low concentrations of Cu (0.89 mg kg^-1), Ni (0.15 mg kg^-1), As (<LOD) and Cd (<LOD) were measured. The western sites have significantly higher concentrations of Ni, Fe, Mn and Cu than the eastern sites, indicating that Pearl River was likely to be a major source of heavy metals on microplastics. In view of a continual increase in the abundance of microplastics in the marine environment and its potential impacts on marine organisms, immediate actions should be taken in establishing long term monitoring programs for heavy metals associated with microplastics. In-depth research on the mechanisms of adsorption and desorption processes between metals and microplastics will help assess the associated risks to both human health and the environment.

Adsorption behavior of three triazole fungicides on polystyrene microplastics

Environmental pollution caused by microplastics (MPs) and pesticides has become a global challenge, and increasing evidence shows that MPs can adsorb organic pollutants which may affect their distribution and bioavailability. As widely used pesticides, triazole fungicides with potential environmental and human safety risks often coexist with MPs in the environment. Understanding the adsorption behavior is the basis of risk assessment of co-exposure of MPs and triazole fungicides. In this study, the adsorption behavior of three commonly used triazole fungicides on polystyrene (PS) was studied using adsorption test. The influences of PS particle size and environmental factors on adsorption capacity were evaluated, and the adsorption mechanisms were discussed. Results suggested that the adsorption kinetics and isotherm conformed to the Pseudo-second-order and Freundlich model, respectively. The order of adsorption and desorption capacity was hexaconazole (HEX) > myclobutanil (MYC) > triadimenol (TRI), which was positively correlated with LogKow of pesticides. To a certain extent, the decrease in PS particle size and change in solution pH value and increase in salt ion strength all contribute to increasing adsorption capacity. The main mechanisms of adsorption were hydrophobic and electrostatic interactions. MPs can adsorb and may become the source and sink of triazole fungicides in aqueous environments. Our results demonstrate that more attention should be given to the combined water pollution risk of MPs and triazoles fungicides.