Field to laboratory comparison of metal accumulation on aged microplastics in coastal waters

Adsorption of metals on aged microplastics in intensive mariculture areas: Aggravating the potential ecological risks to marine organisms

Field determination of the metal adsorption capacity of microplastics (MPs) by using a passive sampler had been done in typical subtropical mariculture area in China. The adsorption of eight metals (Fe, Mn, Cu, Zn, As, Pb, Cr and Cd) by five types of MPs (low-density polyethylene, polypropylene, polystyrene, poly(ethylene terephthalate) and poly(vinyl chloride) (PVC) was compared, including metal types, mariculture types (cage and longline culture), metal residue content in ambient environment, polymer types and particle sizes of MPs. The results showed that Cu, Zn, As, Cd, Pb and Cr in the mariculture environment were contaminated compared with the quality criteria. The concentrations of these six metals adsorbed on five MPs increased linearly with those in seawater. More enriched Cu and As in MPs in marine cage culture than in longline culture, due to the obvious endogenous pollution emissions for the artificial diets, fish medicine and disinfectants. Aged PVC with more cracks and pores showed higher metal adsorption capacity than any other polymers. MPs with a smaller size range of 50-74 μm tended to accumulate higher amounts of metals than those with a larger size range of 74-178 μm, consisting with the surface characteristics of MPs. The significant positive relationship between the concentrations of nutrients in seawater and the adsorption amounts of Cu, Zn and As on MPs implies that the eutrophication would promote their pollution. Based on the ecological risk assessment, the occurrence of MPs could aggravate the potential risk of metals to marine organisms in intensive mariculture areas. This is the first time to reveal the impacts of the adsorption of metals on aged MPs on the potential ecological risks of metals to organisms under the realistic environmental condition.

A bibliometric perspective on the occurrence and migration of microplastics in soils amended with sewage sludge

The land application of sewage sludge from wastewater treatment plants has been recognized as a major source of microplastic contamination in soil. Nevertheless, the fate and behavior of microplastics in soil remain uncertain, particularly their distribution and transport, which are poorly understood. This study does a bibliometric analysis and visualization of relevant research publications using the CiteSpace software. It explores the limited research available on the topic, highlighting the potential for it to emerge as a research hotspot in the future. Chinese researchers and institutions are paying great attention to this field and are promoting close academic cooperation among international organizations. Current research hot topics mainly involve microplastic pollution caused by the land application of sewage sludge, as well as the detection, environmental fate, and removal of microplastics in soil. The presence of microplastics in sludge, typically ranging from tens of thousands to hundreds of thousands of particles (p)/kg, inevitably leads to their introduction into soil upon land application. In China, the estimated annual accumulation of microplastics in the soil due to sludge use is approximately 1.7 × 1013 p. In European countries, the accumulation ranges from 8.6 to 71 × 1013 p. Sludge application has significantly elevated soil microplastic concentrations, with higher application rates and frequencies resulting in up to several-fold increases. The primary forms of microplastics found in soils treated with sludge are fragments and fibers, primarily in white color. These microplastics consist primarily of components such as polyamide, polyethylene, and polypropylene. The vertical transport behavior of microplastics is influenced by factors such as tillage, wind, rainfall, bioturbation, microplastic characteristics (e.g., fraction, particle size, and shape), and soil physicochemical properties (e.g., organic matter, porosity, electrical conductivity, and pH). Research indicates that microplastics can penetrate up to 90 cm into the soil profile and persist for decades. Microplastics in sewage sludge-amended soils pose potential long-term threats to soil ecosystems and even human health. Future research should focus on expanding the theoretical understanding of microplastic behavior in these soils, enabling the development of comprehensive risk assessments and informed decision-making for sludge management practices. PRACTITIONER POINTS: Microplastics in sewage sludge range from tens to hundreds of thousands per kilogram. Sludge land application contributes significantly to soil microplastic pollution. The main forms of microplastics in sludge-amended soils are fragments and fibers. Microplastics are mainly composed of polyamide, polyethylene, and polypropylene. Microplastics can penetrate up to 90 cm into the soil profile and persist for decades.

Modifying luteolin's algicidal effect on Microcystis by virgin and diversely-aged polystyrene microplastics: Unveiling novel mechanisms through microalgal adaptive strategies

Luteolin has shown great potential in inhibiting Microcystis-dominated cyanobacterial blooms. However, widespread microplastics (MPs) in natural aquatic systems often serve as substrates for cyanobacterial growth, which could impact cyanobacterial resistance to external stresses and interfere with luteolin's algicidal effect. This study explored the influence of virgin and diversely-aged polystyrene microplastics (PS-MPs) on inhibitory effect of luteolin on Microcystis growth and its microcystins (MCs) production/release. Moreover, the underlying mechanisms were also revealed by jointly analyzing SEM image, antioxidant response, exopolymeric substances (EPSs) production, and functional gene expression. Results suggested that 0.5, 5, and 50 mg/L virgin and diversely-aged PS-MPs almost weakened growth inhibition and oxidative damage of two doses of luteolin against Microcystisby stimulating its EPSs production and inducing self-aggregation of Microcystis cells and/or hetero-aggregation between Microcystis cells and PS-MPs. Compared to virgin PS-MPs, photo-aged PS-MPs possessed rougher flaky surfaces, and hydrothermal-aged PS-MPs showed internal cracking. These characteristics led to greater stimulation of EPS production and exhibited more significant protective effects on Microcystis. Notably, PS-MPs also decreased MCs content in aqueous phase, likely because they adsorbed some MCs. Such toxigenic hetero-aggregates formed by MCs, MPs, and Microcystis cells would directly poison grazing organisms that consume them and create more pathways for MCs into food web, posing greater eco-risks. This is the first study to clarify the influence and mechanisms of virgin and diversely-aged MPs on allelopathic algicidal effects from the perspective of microalgal inherent adaptive strategies.

Insight into the adsorption behaviors and bioaccessibility of three altered microplastics through three types of advanced oxidation processes

Advanced oxidation processes (AOPs) can significantly alter the structural properties, environmental behaviors and human exposure level of microplastics in aquatic environments. Three typical microplastics (Polyethylene (PE), polypropylene (PP), and polystyrene (PS)) and three AOPs (Heat-K2S2O8 (PDS), UV-H2O2, UV-peracetic acid (PAA)) were adopted to simulate the process when microplastics exposed to the sewage disposal system. 2-Nitrofluorene (2-NFlu) adsorption experiments found the equilibrium time decreased to 24 hours and the capacity increased up to 610 μg g-1, which means the adsorption efficiency has been greatly improved. The fitting results indicate the adsorption mechanism shifted from the partition dominant on pristine microplastic to the physical adsorption (pore filling) dominant. The alteration of specific surface area (21 to 152 m2 g-1), pore volume (0.003 to 0.148 cm3 g-1) and the particle size (123 to 16 μm) of microplastics after AOPs are implying the improvement for pore filling. Besides, the investigation of bioaccessibility is more complex, AOPs alter microplastic with more oxygen-containing functional groups and lower hydrophobicity detected by XPS and water contact angle, those modifications have increased the sorption concentration, especially in the human intestinal tract. Therefore, this indicates the actual exposure of organic compounds loaded in microplastic may be higher than in the pristine microplastic. This study can help to assess the human health risk of microplastic pollution in actual environments.

Aging of plastics in aquatic environments: Pathways, environmental behavior, ecological impacts, analyses and quantifications

The ubiquity of plastics in our environment has brought about pressing concerns, with their aging processes, photo-oxidation, mechanical abrasion, and biodegradation, being at the forefront. Microplastics (MPs), whether originating from plastic degradation or direct anthropogenic sources, further complicate this landscape. This review delves into the intricate aging dynamics of plastics in aquatic environments under various influential factors. We discuss the physicochemical changes that occur in aged plastics and the release of oxidation products during their degradation. Particular attention is given to their evolving environmental interactions and the resulting ecotoxicological implications. A rigorous evaluation is also conducted for methodologies in the analysis and quantification of plastics aging, identifying their merits and limitations and suggesting potential avenues for future research. This comprehensive review is able to illuminate the complexities of plastics aging, charting a path for future research and aiding in the formulation of informed policy decisions.

The iron matters: Aged microplastics disrupted the iron homeostasis in the liver organoids

Plastic products undergo artificial and unintentional aging during daily use, causing the presence of aged microplastics (aMP). Humans are inevitably exposed to aMP. Liver is one of the critical target organs of MP through oral intake, however, limited research has focused on the hepatic toxicity of aMP compared to pristine MP (pMP). We utilized the human pluripotent stem cells-derived liver organoids (LOs) to compare the cytotoxicity of pristine polystyrene microplastics (pPS) (1 μm, carbonyl index 0.08) and aged polystyrene microplastics (aPS) (1 μm, carbonyl index 0.20) ranged from 20 to 200 ng/mL. Our findings indicate that aPS was more cytotoxic than pPS. We explored the disrupted iron homeostasis in terms of the [Fe2+] and [Fe3+] levels, iron storage and transport. A "vector-like effect" induced by aPS has been preliminarily suggested by the correlated change in total iron level and co-localization of PS and ferritin light chain (FTL) in the LOs following exposure to aPS and ferric ammonium citrate (FAC) individually and combinedly. In addition, we observed abnormal mitochondrial morphology, elevated lipid peroxidation, and declined GSH peroxidase activity, together with the declined expression of transferrin receptor (TFRC) and elevated expressions of SLC7A11, FTL. The gene handled iron transport and iron use were disrupted by aPS. Moreover, we employed FAC to introduce iron overload and Nacetylcysteine (NAC) to protect the lipid peroxidation. In aPS + FAC group, aggravated effects could be observed in aspects of [Fe2+] level, lipid peroxidation, and compromised expression levels of iron homeostasis-related markers, in contrast, in aPS + NAC group, most of changes recovered but the hepatocytoxicity remained. Specifically, a dimorphic change in elevated FTL and decreased ferritin heavy chain (FTH1) caused by 50 ng/mL aMP (57.33 ± 3.57 items/mL, equivalent to human intake level), indicated a specific response to low-dose aMP.

An accessible method to standardize polyethylene microsphere (<100 μm) concentrations for zooplankton ingestion experiments

The ubiquity of microplastics has caused alarm as to the impact of these materials on aquatic life, leading to experimental studies to understand these effects. In zooplankton bioassays, microspheres (Ms) are often used as a proxy to represent aquatic microplastic contamination due to their homogeneity and small sizes (<100 μm). The present study proposes an accessible protocol that does not require highly specialized equipment for the creation of Ms stock solutions and environmentally realistic experimental concentrations and describes some common issues. Adult females of the calanoid copepod Centropages furcatus underwent treatments of two Ms sizes at experimental concentrations of 10 Ms/mL. They consumed on average 0.9 ± 2.6 Ms/mL of 45-53 μm Ms, and 2.4 ± 1.1 Ms/mL of 38-45 μm Ms. The results are not directly comparable with other studies due to the wide variety of methods used but successfully demonstrate the reproducibility of the proposed protocol.

Selection of the optimal extraction protocol to investigate the interaction between trace elements and environmental plastic

The interaction between environmental plastic and trace elements is an issue of concern. Understanding their interaction mechanisms is key to evaluate the potential threats for the environment. To this regard, consolidating confidence in extraction protocols can help in understanding the amount of different species present on plastic surface, as well as the potential mobility of trace elements present inside the plastic matrix (e.g., additives). Here we tested the efficacy of different reagents to mimic the elemental phases bonded to meso- and microplastic in the environment, in relation to the grade of ageing and the polymer composition. Results showed that a relatively high portion of trace elements is bonded in a weak phase and that other phases abundant in other matrices (e.g., oxides and bonded to organic matter) are only present to a limited degree in the plastic samples. The comparison of different sample types highlighted the important role of plastic ageing in governing interactions with trace elements, while the polymer composition has a limited influence on this process. Finally, the future steps toward a tailored extraction scheme for environmental plastic are proposed.

Factors Affecting the Adsorption of Heavy Metals by Microplastics and Their Toxic Effects on Fish

Fish not only constitute an important trophic level in aquatic ecosystems but also serve as an important source of protein for human beings. The health of fish is related to the sustained and healthy development of their entire aquatic ecosystem. Due to the widespread use, mass production, high disposal frequency, and degradation resistance of plastics, these pollutants are released into aquatic environments on a large scale. They have become one of the fastest growing pollutants and have a substantial toxic effect on fish. Microplastics have intrinsic toxicity and can absorb heavy metals discharged into water. The adsorption of heavy metals onto microplastics in aquatic environments is affected by many factors and serves as a convenient way for heavy metals to migrate from the environment to organisms. Fish are exposed to both microplastics and heavy metals. In this paper, the toxic effects of heavy metal adsorption by microplastics on fish are reviewed, and the focus is on the toxic effects at the individual (survival, feeding activity and swimming, energy reserves and respiration, intestinal microorganisms, development and growth, and reproduction), cellular (cytotoxicity, oxidative damage, inflammatory response, neurotoxicity, and metabolism) and molecular (gene expression) levels. This facilitates an assessment of the pollutants' impact on ecotoxicity and contributes to the regulation of these pollutants in the environment.

Microplastics pollution in mud crab (Scylla sp.) aquaculture system: First investigation and evidence

Microplastics (MPs) occurrence in farmed aquatic organisms has already been the prime priority of researchers due to the food security concerns for human consumption. A number of commercially important aquaculture systems have already been investigated for MPs pollution but the mud crab (Scylla sp.) aquaculture system has not been investigated yet even though it is a highly demanded commercial species globally. This study reported the MPs pollution in the mud crab (Scylla sp.) aquaculture system for the first time. Three different stations of the selected aquafarm were sampled for water and sediment samples and MPs particles in the samples were isolated by the gravimetric analysis (0.9% w/v NaCl solution). MP abundance was visualized under a microscope along with their size, shape, and color. A subset of the isolated MPs was analyzed by scanning electron microscope (SEM), and Fourier transform infrared spectroscopy (FTIR) for the surface and chemical characterization respectively. The average MPs concentration was 47.5 ± 11.875 particles/g in sediment and 127.92 ± 14.99 particles/100 L in the water sample. Fibrous-shaped (72.17%) and transparent-colored (59.37%) MPs were dominant in all the collected samples. However, smaller MPs (>0.05-0.5 mm) were more common in the water samples (47.69%) and the larger (>1-5 mm) MPs were in the sediment samples (47.83%). SEM analysis found cracks and roughness on the surface of the MPs and nylon, polyethylene, polypropylene, and polystyrene MPs were identified by FTIR analysis. PLI value showed hazard level I in water and level II in sediment. The existence of deleterious MPs particles in the mud crab aquaculture system was well evident. The other commercial mud crab aquafarms must therefore be thoroughly investigated in order to include farmed mud crabs as an environmentally vulnerable food security concern.

Adsorption of heavy metals on biodegradable and conventional microplastics in the Pearl River Estuary, China

In recent years, microplastics (MPs) as emerging carriers for environmental pollutants have attracted increasing worldwide attention. However, the adsorption of heavy metals on MPs, especially for biodegradable MPs, has been still poorly understood in estuarine environments. In this study, we investigated the aging of biodegradable and conventional MPs in the Pearl River Estuary after long-term exposure and their impacts on the adsorption of heavy metals from seawater. The results showed that the changes in surface characteristics were more prominent on biodegradable MPs than on conventional MPs after aging. Both biodegradable and conventional MPs could adsorb heavy metals, and their adsorption capacities fluctuated greatly on different MPs and different exposure times. The adsorption capacities of Cu, Pb, and As on biodegradable MPs were higher than those on conventional MPs, whereas Mn, Cr, and Co had lower adsorption on biodegradable MPs after 9-12 months by inductively coupled plasma-mass spectrometry (ICP-MS). The aging characteristics (CI, O/C, and X_c) of MPs accounted for a contribution of 51.0% on heavy metal adsorption, while the environmental factors (temperature, salinity, pH, and heavy metal concentration) only contributed to 13.2%. Therefore, the present study can provide important evidence on the environmental behaviors and ecological risks of biodegradable and conventional MPs in estuarine systems.

A Systematic Review of Nano- and Microplastic (NMP) Influence on the Bioaccumulation of Environmental Contaminants: Part I-Soil Organisms

Nano- and microplastics (NMPs) are a group of contaminants that cause concern due to their abundance in the environment, high persistence, and interaction with other contaminants. This review aims to understand the role of NMP in the bioaccumulation of environmental contaminants. For that, a comprehensive literature search was conducted to identify publications that compared the uptake of contaminants in the presence and absence of NMP. In this part I, twenty-eight publications of the terrestrial compartment were analyzed. Two main taxonomic groups were studied, namely, earthworms and terrestrial plants. In earthworms, most studies observed an increase in the bioaccumulation of the contaminants, while in plants, most studies observed a decrease in the bioaccumulation. Changes in bioavailable fractions of contaminants due to NMP presence was the main reason pointed out by the authors for their outcomes. Moreover, biological aspects were also found to be important in defining how NMPs affect bioaccumulation. Dermal damage and changes in contaminant-degrading bacteria in the gut of earthworms caused an increase in bioaccumulation, and root pore blockage was a common reason for the decrease in the bioaccumulation of contaminants in plants. Nevertheless, such effects were mainly observed at high, unrealistic NMP concentrations. Finally, knowledge gaps were identified, and the limitations of this systematic review were presented.

Microplastics and plastics-associated contaminants in food and beverages; Global trends, concentrations, and human exposure

Microplastics has become a global concern due to their ubiquitous presence which poses unavoidable human exposure risks. Geographical distribution and yearly trends of research on microplastics, food, and beverages do not exist. Thus, no overall account is available regarding the presence of microplastics and plastics-associated contaminants in food and beverages. Hence, this attempt is to review the geographical distribution of studies through a brief bibliometric analysis and the plastics-associated contaminants including plasticizers and microplastics in food and beverages. Estimated microplastic consumption has been listed for the pool of publications reviewed here. Further, this review discusses the ingestion potency of micropollutants associated with microplastics, possible health impacts, and existing challenges. Global trend in research exponentially increased after 2018 and China is leading. Studies on microplastics were limited to a few beverages and food; milk, beer, tea, refreshing drinks, salt, sugar, honey, etc., whereas seafood and drinking water have been extensively studied. Publications on plastic-additives were reported in two ways; migration of plastic-additives from packaging by leaching and the presence of plastic-additives in food and beverages. Bisphenol A and bis(2-Ethylhexyl) phthalate were the most frequently reported both in food and beverages. Exposure of packaging material to high temperatures predominantly involves plastic-additive contamination in food and beverages. Microplastics-bound micropollutants can also be ingested through food and beverages; however, a lack of knowledge exists. The complex matrix of food or beverages and the absence of standard procedures for analysis of microplastics and micropollutants exist as challenges. More investigations on the presence of microplastics and plastic-additives in food and beverage are urgent needs to a better assessment of potential human exposure and human health risk.

A review on the effect of micro- and nano-plastics pollution on the emergence of antimicrobial resistance

The recent upsurge in the studies on micro/nano plastics and antimicrobial resistance genes has proven their deleterious effects on the environmental and human health. Till-date, there is a scarcity of studies on the interactions of these two factors and their combined influence. The interaction of microplastics has led to the formation of new plastics namely plastiglomerates, pyroplastics. and anthropoquinas. It has long been ignored that the occurrence of microplastics has become a breeding ground for the emergence of antimicrobial resistance genes. Evidently microplastics are also associated with the occurrence of other pollutants such as polyaromatic hydrocarbons and pesticides. The increased use of antibiotics (after Covid breakout) has further elevated the detrimental effects on human health. Therefore, this study highlights the relation of microplastics with antibiotic resistance generation. The factors such as uncontrolled use of antibiotics and negligent plastic consumption has been evaluated. Furthermore, the future research prospective was provided that can be helpful in correctly identifying the seriousness of the environmental occurrence of these pollutants.

Selective adsorption of antibiotics on aged microplastics originating from mariculture benefits the colonization of opportunistic pathogenic bacteria

Microplastics and antibiotics widely coexist in the aquatic environment, especially in mariculture regions. However, antibiotics adsorbed on microplastics and their role in the colonization of microorganisms on microplastics are poorly understood. Therefore, in-situ aging experiments were conducted to investigate the impact of antibiotics and microplastics co-occurrence on microorganisms and assess their potential risks to human health. Results showed that antibiotics were adsorbed selectively on microplastics, with 29 investigated antibiotics (n = 40) detected in surrounding water but only 6 investigated antibiotics were adsorbed on microplastics. The concentration of antibiotics accumulated on microplastics was controlled by microplastic types and environmental conditions. For example, aged polypropylene (PP) had more developed pore structures resulting in higher adsorption of antibiotics than other microplastic types. High-throughput sequencing showed higher diversity and distinct composition of microorganisms attached to the microplastics than the surrounding water. Opportunistic pathogenic bacteria such as Mycobacterium possessed positive relationships with tetracycline and doxycycline on aged microplastics, which showed adsorbed antibiotics on aged microplastics could benefit some specific pathogens colonized on the microplastics and spread into unaffected ecosystems, marine organisms even humans. The health risk quotient (HQ) implied the potential human health risk of consuming commercial seafood polluted by antibiotics and microplastic loaded with antibiotics. This study revealed the interaction of antibiotics and microorganisms with aged microplastics in aquaculture systems, providing a novel insight into their synergistic effects on ecological and human health.

Enhanced heavy metal adsorption on microplastics by incorporating flame retardant hexabromocyclododecanes: Mechanisms and potential migration risks

Microplastics (MPs) are known to act as carriers of heavy metals; however, little is known about the intrinsic chemical additives of MPs, such as hexabromocyclododecane (HBCD), in terms of the adsorption behaviors and migration risks of heavy metals on MPs. Here, we reported the potential mechanisms and risks of HBCD inherent in polystyrene (PS) MPs with Cu(II), Ni(II), and Zn(II) adsorption/desorption. A comparison of the adsorption capacity of the metals onto HBCD/PS composites (HBCD/PS) MPs (10.31-20.76 μmol/g), pure MPs (0-3.60 μmol/g), and natural minerals (0.11-13.88 μmol/g) showed that the addition of HBCD significantly promoted the metals adsorption onto the HBCD/PS MPs, and even exceeded that of natural particles. Isotherms and thermodynamic data suggested that the adsorption process of the metals onto the HBCD/PS MPs was spontaneous and endothermic, and that the adsorption was a mainly multi-ion process with an inclined direction. Furthermore, the results of SEM-EDS, FTIR, and XPS analyses, as well as density functional theory well explained that the metals were mainly adsorbed on the -O and -Br groups of the HBCD/PS MPs via electrostatic interactions and surface complexation. More importantly, by comparing the desorption activity with natural river water and seawater, HBCD inherent in MPs can enhance the long-range transfer of metals carried by the HBCD/PS MPs from contamination sources to potential sink like oceans. Thus, the HBCD/PS MPs with high loading of Cu(II), Ni(II), and Zn(II) could be potential secondary sources of these metals in seawater. Overall, these findings revealed the potential risks of flame retardant in MPs associated with metal migration, and advocated that flame retardant-related waste MPs should be included in coastal sustainable development.

Change in adsorption behavior of aquatic humic substances on microplastic through biotic and abiotic aging processes

Interactions between microplastics (MPs) and humic substances (HS) are inevitable in MP-contaminated aquatic environment because of the ubiquitous presence of HS. In this study, we explored the effects of abiotic and biotic aging processes on the adsorption behavior of aquatic HS on MPs. Aging experiments were conducted using polyethylene (PE) as a representative MP, in which UV irradiation and microbial incubation were applied for 15 to 18 days to mimic the natural abiotic and biotic aging processes. Surface modifications after the aging treatments were evidenced by the appearance of CO, CO, O-C=O, and -OH groups; the formation of grooves on UV-aged PE; and the formation of biofilms on the surface of bio-aged PE. The specific surface areas of both treated PE MPs increased with aging. Higher HS adsorption on PE surface was observed after the aging treatments, with a highest kinetic rate for UV-aged PE than that for bio-aged PE. The adsorption isotherm models revealed that the aging processes enhanced the HS adsorption tendency, as evidenced by the highest adsorption capacity for UV-aged PE (~187 μg C/m²), followed by bio-aged PE (~157 μg C/m²) and pristine PE (~87.5 μg C/m²) for a comparable extended aging period (15-18 days). The difference was more pronounced at a lower pH. The enhanced HS adsorption was mainly attributed to the formation of hydrogen bonds, whereas HS adsorption on pristine PE was dominated by hydrophobic interactions and weak van der Waals interactions. Among the two identified fluorescent components (terrestrial humic-like C1 and protein-like C2), C1 exhibited a higher affinity for adsorption onto PE irrespective of aging. Our findings provide insights into the substantial changes that occur in the interactions between MPs and aquatic organic matter with aging processes, which may alter the fate and environmental impacts of MPs in many aquatic systems.

Correlation of metals and degraded marine (micro)plastic litter in geologically similar coastal areas with different anthropogenic characteristics

The association and statistical correlation of anthropogenically important trace metals (TM) Cd, Cu, Pb, Zn and degraded marine microplastic (MP) extracted from the bulk debris samples at two locations from two marine systems, estuarine and coastal, in the Croatian Adriatic coastal area were assessed. The abundance of MP particles at both sites were primarily defined by local wave climate, with the open coastal site containing 9-fold more microplastic particles (>4 mm) as compared to the semi-closed estuarine, or twice as much considering bulk plastics. Generally, the higher abundance of adsorbed metal on MP were observed in the more anthropogenically influenced estuary than in the open coastal site and followed the order: polystyrene > polypropylene > low density polyethylene. The amounts of adsorbed zinc were the highest on all types of plastics at both sites, while the affinity of polystyrene for metals followed: Zn > Pb ≈ Cu > Cd.

A review on the remediation of microplastics using constructed wetlands: Bibliometric, co-occurrence, current trends, and future directions

Massive prevalence of microplastics (MPs) in the environment has become one of the world's most serious environmental concerns. Human dependence on plastics has created a constant flow of MPs from different sources into natural environment, which has raised public concern regarding consequences of MPs coming into contact with the natural environment. Deploying constructed wetlands (CWs) to reduce MPs pollution is considered a promising method, however there are still barriers for breakthroughs in this technology, particularly knowledge gaps in the mechanisms affect removal process. Recognising this, we provide a comprehensive summary of current advances and theories regarding the mechanisms of occurrence in this research area. In this work, the bibliometric methods were first used to identify annual publication trends and topical topics of research interest. The selected documents were then statistically analyzed using VOSviewer and the 'bibliometrix' package in R to derive the annual productivity of countries or organizations, the most relevant affiliations, the most relevant authors, the most relevant sources, textual analysis, co-occurrence analysis, and cluster analysis of keywords. Finally, detailed information concerning the removal of MPs by CWs was summarised, covering the most common operational and design parameters (i.e., structure types, wetland plants, substrate materials, and microbial communities), to reveal how these parameters can be adjusted for more efficient MPs removal rate. Challenges and future directions were additionally proposed. It is hoped that the review will help identify current research trends, provide insight into the mechanisms of the removal process, and contribute further to the development of this important area.

Wastewater treatment plants act as essential sources of microplastic formation in aquatic environments: A critical review

According to extensive in situ investigations, the microplastics (MPs) determined in current wastewater treatment plants (WWTPs) are mostly aged, with roughened surfaces and varied types of oxygen-containing functional groups (i.e., carbonyl and hydroxyl). However, the formation mechanism of aged MPs in WWTPs is still unclear. This paper systematically reviewed MP fragmentation and generation mechanisms in WWTPs at different treatment stages. The results highlight that MPs are prone to undergo physical abrasion, biofouling, and chemical oxidation-associated weathering in WWTPs at different treatment stages and can be further decomposed into smaller secondary MPs, including in nanoplastics (less than 1000 nm or 100 nm in size), suggesting that WWTPs can act as a formation source for MPs in aquatic environments. Sand associated mechanical crashes in the primary stage, microbes in active sewage sludge-related biodegradation in the secondary stage, and oxidant-relevant chemical oxidation processes (light photons, Cl₂, and O₃) in the tertiary stage are the dominant causes of MP formation in WWTPs. For MP formation mechanisms in WWTPs, external environmental forces (shear and stress forces, UV radiation, and biodegradation) can first induce plastic chain scission, destroy the plastic molecular arrangement, and create abundant pores and cracks on the MP surface. Then, the physicochemical properties (modulus of elasticity, tensile strength and elongation at break) of MPs shift consequently and finally breakdown into smaller secondary MPs or nanoscale plastics. Overall, this review provides new insights to better understand the formation mechanism, occurrence, fate, and adverse effects of aged microplastics/nanoplastics in current WWTPs.

Adsorption behavior of aged polybutylece terephthalate microplastics coexisting with Cd(II)-tetracycline

Microplastics (MPs) are one of the emerging classes of pollutants that can be infiltrated into any aqueous solutions from disposed toxic metals and antibiotics, further exacerbating the potential biotoxicity of MPs. However, the research on the interaction between MPs and various pollutants is limited. Therefore, in this study, the changes in toxicity of polybutylece terephthalate (PBT) MPs were assessed following adsorption of heavy metals and antibiotics. The adsorption behavior of Cd(II) and tetracycline (TC) on ultraviolet (UV) light-aged PBT was investigated. The results demonstrated that the Cd(II) adsorption behavior could be described by the pseudo-second-order kinetic and Langmuir isothermal models, while the TC adsorption behavior has well fitted using Elovich and Sips models. The whole adsorption process occurred via either external diffusion or internal diffusion. The interactions between aged PBT and pollutants were evaluated under different environmental conditions, such as solution pH and the concentrations of dissolved organic matter and cations. The amounts of Cd(II) and TC adsorbed were higher in the competitive systems than the single solution, which might attribute to the formation of Cd(II)-TC complexes and aged PBT functional group changes. The results of two-dimensional correlation spectroscopy (2D-COS) describes the sequence of functional group transformation during the uptake of Cd(II)-TC by aged PBT in binary systems. These findings identify a strong interaction between aged PBT and contaminants, establishing the potential fate of aged MPs under natural aquatic environment conditions.

Incubation habitats and aging treatments affect the formation of biofilms on polypropylene microplastics

Microbial colonization and biofilm formation associated with microplastics (MPs) have recently attracted wide attention. However, little is known about the effect of MP aging and different exposed habitats on biofilm formation and associated microbial community characteristics. To obtain a comprehensive understanding, virgin and aged polypropylene MPs were selected as attachment substrates and exposed to different aquatic habitats (marine, estuary, and river). The results showed that the aging process could destroy surface structure and increase oxygen-containing groups of MPs. The total biomass of the biofilms, attached-bacterial OTU numbers, and α diversities increased with exposure time. The biofilms biomass and α diversity of MPs in the river were significantly higher than those in the marine and estuary habitats, and temperature and salinity were primary factors affecting microbial colonization. Bacterial communities in MP-attached biofilms were significantly different from those in surrounding water. Microorganisms tend to adhere to aged MPs, and especially, genes related to human pathogens were significantly expressed on aged MPs, suggesting a potential ecological and health risk of aged MPs in aquatic ecosystems. Our results showed that aged MPs and different habitats have an important influence on microbial colonization, and the weathering process can accelerate biofilm formation on MPs.

Microplastics in the Gulf of Mexico: A Bird’s Eye View

Microplastic debris is a persistent, ubiquitous global pollutant in oceans, estuaries, and freshwater systems. Some of the highest reported concentrations of microplastics, globally, are in the Gulf of Mexico (GoM), which is home to the majority of plastic manufacturers in the United States. A comprehensive understanding of the risk microplastics pose to wildlife is critical to the development of scientifically sound mitigation and policy initiatives. In this review, we synthesize existing knowledge of microplastic debris in the Gulf of Mexico and its effects on birds and make recommendations for further research. The current state of knowledge suggests that microplastics are widespread in the marine environment, come from known sources, and have the potential to be a major ecotoxicological concern for wild birds, especially in areas of high concentration such as the GoM. However, data for GoM birds are currently lacking regarding typical microplastic ingestion rates uptake of chemicals associated with plastics by avian tissues; and physiological, behavioral, and fitness consequences of microplastic ingestion. Filling these knowledge gaps is essential to understand the hazard microplastics pose to wild birds, and to the creation of effective policy actions and widespread mitigation measures to curb this emerging threat to wildlife.

Occurrence, spatial distribution, and risk assessment of microplastics in surface water and sediments of Saint Martin Island in the Bay of Bengal

Microplastics (MPs) are emerging contaminants in aquatic and terrestrial ecosystems and have caused substantial concern worldwide. This study surveyed the presence of MPs in surface water and sediments across the coastal area of Saint Martin Island in the Bay of Bengal. MPs were collected following the standard protocol and identified as various types like expanded polystyrene, foam, filaments, fragments, lines, fibres, and paint flakes. Total MPs pollution in beach sediment was 317 particles/kg across 14 sampling sites, varied from 11 to 10589 particles/m² of dry sediment and 0.95 particles/m³, having ~2 to 19 particles/30 min trawl in coastal surface water samples. Most of the frequent MPs in beach sediments ranged from 1.0 to 2.0 mm, whereas the fragments were predominant in sediment and surface water samples. MPs distribution revealed that different shapes were dominant at different sites within the Island. The calculated pollution risk index due to the presence of MPs indicated that the sediment and surface water samples were under the low-risk category. However, polymeric risk assessment and contamination factors suggest that the coastline is significantly polluted, as high pollution load indices (PLI >1) were observed for sediments and coastal surface water samples. This work provides the detailed MPs data in the coastal environment of Saint Martin Island for the first time; hence it may be helpful to develop proper strategies to deal with environmental problems.

Weathering of geotextiles under ultraviolet exposure: A neglected source of microfibers from coastal reclamation

Geotextiles are a group of polymeric materials widely used in coastal reclamation projects. However, long-term exposure to solar illumination deteriorates the performance of geotextiles, resulting in physicochemical changes and high risks of releasing microfibers. This study investigated the photoaging behavior of geotextiles and evaluated the capacity of geotextiles to release microfibers in coastal reclamation areas through a combination of field research and laboratory experiments. A field survey in the coastal reclamation area of Yancheng (China) confirmed that many geotextiles made from polyethylene terephthalate (PET) existed on the beach, which was accompanied by a high value of carbonyl index of 0.70-0.93. The results from laboratory experiments revealed that ultraviolet exposure activated the photooxidative process and promoted the breakdown of PET geotextiles. Data of scanning electron microscope and laser particle analyzer showed that, initially, particles with the size of less than 1 μm were generated on the surface of geotextiles, followed by fragments with sizes of 1-100 μm falling off with the passage of time. The number of particles on the surface was calculated using Image-Pro Plus software and the maximum particle density was found to be around 2.52 million particles·mm^-2. In addition, based upon the conversion of irradiance between the simulated solar and natural solar, it was roughly estimated that the annual emissions of PET geotextile fibers in coastal reclamation areas were 0.24-0.79 million tons all over the world. It is inferred that polymer-made geotextile is a significant source of microplastic pollution in reclamation zones of coastal areas.