Prevalence of microplastic fibers in the marginal sea water column off southeast China

Deciphering morphology patterns of environmental microfibers: Insights into source apportionment

Microfibers, a prevalent form of microplastics, undergo diverse environmental interactions resulting in varied morphological changes. These changes can offer insights into their environmental trajectories. Despite its importance, comprehensive studies on microfiber morphology are scarce. This study collected 233 microfibers from the East China Sea and South China Sea. Based on morphological features observed in microscopic images of microfibers, such as curvature, cross-sectional shapes, diameter variations, and crack shapes, we identified a general morphological pattern, classifying the environmental microfibers into three distinct morphological types. Our findings highlight noticeable differences in morphological metrics (e.g., length, diameter, and surface roughness) across three types, especially the diameter. Microfibers of Type I had an average diameter of 19.45 ± 4.93 μm, significantly smaller than Type II (263.00 ± 75.15 μm) and Type III (299.68 ± 85.62 μm). Within the three-dimensional (3D) space fully defined by these quantitative parameters, the clustering results of microfibers are also consistent with the proposed morphology pattern, with each category showing a potential correlation with specific chemical compositions. Type I microfibers correspond to synthetic cellulose, while 94.79 % of Types II and III are composed of polymers. Notably, we also validated the great applicability of the morphology categories to microfibers in diverse environmental compartments, including water and sediments in nearshore and offshore areas. This classification aids in the efficient determination of microfiber sources and the assessment of their ecological risks, marking a significant advancement in microfiber environmental studies.

Microplastics in Hong Kong's marine waters: Impact of rainfall and Pearl River discharge

This study provided a systematic investigation of microplastics in Hong Kong's surface marine waters during the pandemic from 2019 to 2021. Microplastics (2.07 ± 4.00 particles/m3) exhibited significant temporal variations with higher abundance in the wet season, without a consistent trend after the mandatory mask-wearing requirement was announced. The impact of pandemic restrictions on microplastic distribution was found to be relatively minor. However, significant correlations between microplastic abundances and rainfall highlighted the substantial contribution of local emissions through surface runoff. Notably, sites in closer proximity to the Pearl River Delta exhibited higher microplastic abundances, indicating their association with emission sources. The influence of rainfall and adverse weather on marine microplastic loads demonstrated different sensitivities among various locations but can generally last for one month. These results revealed the impact of seasonal rainfall on coastal microplastics and emphasized the need for efforts to reduce microplastic discharge from land-based sources.

Unveiling microplastic distribution and interactions in the benthic layer of the Yangtze River Estuary and East China Sea

Microplastics (MPs), recognized as an emerging global environmental concern, have been extensively detected worldwide, with specific attention directed towards the Yangtze River Estuary (YRE) and East China Sea (ECS) regions. Despite their critical research significance, there remains a knowledge gap concerning the distribution of MPs in the benthic layer within this area, particularly regarding interactions governing their occurrence. Here we illuminate the distribution of MPs within the benthic layer and unravel the intricate interplay between bottom water and sediment in the YRE and ECS. We find that MPs are notably more abundant in bottom water, ranging from 8 to 175 times higher than in surface water. These MPs predominantly consist of polyester fibers, exhibit a size range between 0.5 and 5.0 mm, and display distinct coloration. Co-occurrence network analysis and Principal Coordinate Analysis confirm a robust correlation between MPs in bottom water and sediment, signifying the pivotal role of bottom water in mediating the distribution and transportation of MPs within the benthic layer. Furthermore, a positive correlation between MPs in sediment and bottom water turbidity underscores the impact of surface sediment resuspension and upwelling on MPs distribution. This study clarifies the intricate interactions within the benthic layer and highlights the crucial role of bottom water as a mediator in the vertical distribution of MPs, advancing our understanding of the "source-to-sink" transport processes governing MPs within water-sediment systems.

Rapid Mass Conversion for Environmental Microplastics of Diverse Shapes

Rivers have been recognized as the primary conveyors of microplastics to the oceans, and seaward transport flux of riverine microplastics is an issue of global attention. However, there is a significant discrepancy in how microplastic concentration is expressed in field occurrence investigations (number concentration) and in mass flux (mass concentration). Of urgent need is to establish efficient conversion models to correlate these two important paradigms. Here, we first established an abundant environmental microplastic dataset and then employed a deep neural residual network (ResNet50) to successfully separate microplastics into fiber, fragment, and pellet shapes with 92.67% accuracy. We also used the circularity (C) parameter to represent the surface shape alteration of pellet-shaped microplastics, which always have a more uneven surface than other shapes. Furthermore, we added thickness information to two-dimensional images, which has been ignored by most prior research because labor-intensive processes were required. Eventually, a set of accurate models for microplastic mass conversion was developed, with absolute estimation errors of 7.1, 3.1, 0.2, and 0.9% for pellet (0.50 ≤ C < 0.75), pellet (0.75 ≤ C ≤ 1.00), fiber, and fragment microplastics, respectively; environmental samples have validated that this set is significantly faster (saves ∼2 h/100 MPs) and less biased (7-fold lower estimation errors) compared to previous empirical models.

The pollution characteristics and risk assessment of microplastics in mollusks collected from the Bohai Sea

Microplastics (MPs) pollution in the marine environment has become a global problem. In this study, a number of 21 mollusk species (n = 2006) with different feeding habits were collected from 11 sites along the Bohai Sea for MPs uptake analysis. The MPs in mollusk samples were isolated and identified by micro-Fourier Transform Infrared Spectroscopy (μ-FTIR), and an assessment of the health risks of MPs ingested by mollusk consumption is also conducted. Approximately 91.9 % of the individuals among all the collected species inhaled MPs, and there was an average abundance of 3.30 ± 2.04 items·individual-1 or 1.04 ± 0.74 items·g-1 of wet weight. The shape of MPs was mainly fiber, and a total number of 8 polymers were detected, of which rayon had the highest detection rate (58.3 %). The highest abundance, uptake rate and polymer composition of MPs was observed in creeping types, suggesting that they might ingest these MPs from their food. The gastropod Siphonalia subdilatata contains the highest levels of MPs, which may increase the risk of human exposure if consumed whole without removing the digestive gland. The polymer risk level of MPs in these mollusks was Level III (H = 299), presenting harmful MPs such as polyvinyl chloride. In terms of human exposure risk, the average risk of human exposure to MPs through consumption of Bohai mollusks is estimated to be 3399 items·(capita·year)-1 (424-9349 items·(capita·year)-1). Overall, this study provides a basis for the ecological and health Risk assessment of MPs in mollusks collected from the coastline of China.

Research progress on occurrence characteristics and source analysis of microfibers in the marine environment

Synthetic microfiber pollution is a growing concern in the marine environment. However, critical issues associated with microfiber origins in marine environments have not been resolved. Herein, the potential sources of marine microfibers are systematically reviewed. The obtained results indicate that surface runoffs are primary contributors that transport land-based microfibers to oceans, and the breakdown of larger fiber plastic waste due to weathering processes is also a notable secondary source of marine microfibers. Additionally, there are three main approaches for marine microplastic source apportionment, namely, anthropogenic source classification, statistical analysis, and numerical simulations based on the Lagrangian particle tracking method. These methods establish the connections between characteristics, transport pathways and sources of microplastics, which provides new insights to further conduct microfiber source apportionment. This study helps to better understand sources analysis and transport pathways of microfibers into oceans and presents a scientific basis to further control microfiber pollution in marine environments.

Statistical analysis, machine learning modeling, and text analytics of aggregation attachment efficiency: Mono and binary particle systems

The aggregation attachment efficiency (α) is the fraction of particle-particle collisions resulting in aggregation. Despite significant research, α predictions have not accounted for the full complexity of systems due to constraints imposed by particle types, dispersed matter, water chemistry, quantification methods, and modeling. Experimental α values are often case-specific, and simplified systems are used to rule out complexity. To address these challenges, statistical analysis was performed on α databases to identify gaps in current knowledge, and machine learning (ML) was used to predict α under various particle types and conditions. Moreover, text analytics was employed to support knowledge from statistics and ML, as well as gain insight into the ideas communicated by current literature. Most studies investigated α in mono-particle systems, but binary or higher systems require more investigation. Furthermore, our work highlights that numerous variables, interactions, and mechanisms influence α behavior, making its investigation complex and difficult for both experiments and modeling. Consequently, future research should incorporate more particle types, shapes, coatings, and surface heterogeneities, and aim to address overlooked variables and conditions. Therefore, building a comprehensive α database can enable the development of more accurate empirical models for prediction.

Seasonal distribution of microplastics in the surface waters of the Yellow Sea, China

Different studies are filling the gaps in the distribution map of global marine microplastics. However, the data on the seasonal variation is relatively limited, which may lead to overestimation or underestimation of the distribution level of microplastics. To understand baseline data and seasonal variations of the microplastics in the surface seawater of the Yellow Sea, a survey over four seasons was conducted during 2017-2018. Microplastics were collected using a 330 μm manta net. It was found that the abundance of microplastics was 0.63 ± 0.57 particles/m³. The seasonal abundance variation was spring > summer ≈ winter > autumn. The main categories were foam, line, and fragments, accounting for 32 %, 19 %, and 19 % of the total amount, respectively, and the dominant components were polypropylene, polyethylene, and polyethylene terephthalate, accounting for 38 %, 22 %, and 22 % of particles, respectively. The factors affecting the variation included wind-induced mixing, river input, and environmental topography.

Formation of microplastic fibers and fibrils during abrasion of a representative set of 12 polyester textiles

Microplastic fibers (MPFs) released from synthetic textiles have been found to be a major source of microplastic in the environment. There is increasing evidence available that MPFs released during washing were likely formed during the manufacturing stage. However, real-life use of textiles is often associated with textile-on-textile abrasion, and the first evidence is available that MPFs and finer microplastic fiber fragments (fibrils) are formed during abrasion. In this study, we characterized the formation of MPFs and fibrils from a representative set of 12 polyester textiles after abrasion tests conducted with a Martindale tester. We also investigated the influence of rub intensity and the extractability of MPFs and fibrils from the abraded fabrics. For all textiles, the MPFs extracted after abrasion showed the same diameter as the fibers in non-abraded textiles (10-20 μm), while the extracted fibrils were much thinner (3-5 μm). The variability in the structure of the different polyester textiles led to a broad range of MPF and fibrils extracted during the first wash after 5000 rubs. One gram of textile released between 4900 and 640,000 MPFs and between 0 and 350,000 fibrils with an average fibril/MPF ratio of 0.8. The total number of MPFs and fibrils formed during abrasion was positively correlated with the increase in the number of rubs up to 10,000 times. Visible pilling on the textile surface was an important indicator for the formation of MPFs and fibrils. Our study revealed that textile abrasion is a critical, realistic, and overlooked mechanism for the formation of MPFs and fibrils, as abraded textiles (after 5000 times rubs) can release more than ten times the number of MPFs and fibrils compared to washing only.

First Evidence of Microplastic Occurrence in the Marine and Freshwater Environments in a Remote Polar Region of the Kola Peninsula and a Correlation with Human Presence

Microplastics (MPs) have even been detected in remote environments, including high-latitude regions, where human activities are restricted or strongly limited. We investigated the surface water of the bays of the Barents Sea and the freshwater lakes that are located close to and several kilometers from a year-round resident field station in the remote tundra region of the Kola Peninsula. The microplastics' presence in aquatic environments in this region has not been indicated yet. Microplastics were detected in all samples collected from the Barents Sea (<4800 items·m^-3) and the lakes (<3900 items·m^-3). Fibers made from polyethylene terephthalate (PET)-the most common thermoplastic polymer of the polyester family-and semi-synthetic cellulosic rayon were the most dominant. This indicated that the source of fiber contamination may come from protective clothes, ropes, ship equipment, and fishing nets. Small microplastics can spread through current and atmospheric transport. The Norwegian Current is likely responsible for the lack of correlations found between MP contamination and the distance from the field station between the studied bays of the Barents Sea. On the contrary, a significant correlation with human presence was observed in the concentration of microfibers in the water of the tundra lakes. The number of MP fibers decreased with an increase in the distance from the field station. This is the first study, to the best of our knowledge, that reports such a correlation in a remote region. We also discuss implications for animals. Our results show that even the most isolated ecosystems are not free from microplastic pollution.

Synthetic microplastic abundance and composition along a longitudinal gradient traversing the subtropical gyre in the North Atlantic Ocean

Plastic pollution has been reported in the North Atlantic Ocean since the 1970s, yet limited data over subsequent decades pose challenges when assessing spatio-temporal trends in relation to global leakages and intervention strategies. This study quantified microplastics within the upper ocean along a longitudinal transect of the North Atlantic and its subtropical gyre. Microplastics were sampled from surface and subsurface (-25 m) water using a manta trawl and NIKSIN bottle respectively. The surface water polymer community varied significantly between geographic positions ('inshore', 'gyre', 'open ocean'), and was significantly influenced by fragment quantity. Compared to other positions, the North Atlantic gyre was associated with high concentrations of polyethylene, polypropylene, acrylic and polyamide fragments. Subsurface water was dominated by polyamide and polyester fibres. Backtracked 2-year Lagrangian simulations illustrated connectivity patterns. Continued monitoring of microplastics throughout the water column of the North Atlantic Ocean is required to address knowledge gaps and assess spatio-temporal trends.

Impacts of terrestrial input on the distribution characteristics of microplastics in the East China Sea characterized by chromophoric dissolved organic matter (CDOM) analysis

Large quantities of microplastics are found in the East China Sea (ECS), however, the impacts of complicated terrestrial input on the distribution characteristics of microplastics have not been studied. Hence, we aimed to characterize the microplastic distribution in the ECS combined with the fluorescence characteristics of chromophoric dissolved organic matter (CDOM), a sensitive technique to trace terrestrial substances in seawater. The average microplastic abundance in the surface seawater of ECS was 34.73 ± 4.05 items/m³ and sites in the north ECS had a higher microplastic abundance (55.90 ± 2.47 items/m³) than those in the southern region (11.22 ± 4.01 items/m³), due to its proximity to the Yangtze River estuary and Hangzhou Bay. Polyethylene (PE, 44.2 %) was the most abundant microplastic type in the northern region, whereas polyethylene terephthalate (PET, 28.4 %) had a higher proportion in the south ECS. Besides, sites in the north ECS had a higher diversity index of microplastics, suggesting various sources of microplastic pollution. Interestingly, a stronger correlation with the diversity index was found for protein-like component C3 (R² = 0.56) in northern regions compared to fulvic-like component C1 (R² = 0.32) and humic-like component C2 (R² = 0.28), suggesting the significant impact of anthropogenic discharge. Moreover, no correlation between fluorescence components and microplastic diversity index was found in the south ECS, indicating that CDOM can reflect the impact range of terrestrial input on the distribution characteristics of microplastics. This research might be useful in assessing and reducing the impact of terrestrial input on the distribution characteristics of microplastics in the ECS.

Antagonistic and synergistic effects of warming and microplastics on microalgae: Case study of the red tide species Prorocentrum donghaiense

Bibliometric network analysis has revealed that the widespread distribution of microplastics (MPs) has detrimental effects on marine organisms; however, the combined effects of MPs and climate change (e.g., warming) is not well understood. In this study, Prorocentrum donghaiense, a typical red tide species in the East China Sea, was exposed to different MP concentrations (0, 1, 5, and 10 mg L^-1) and temperatures (16, 22, and 28 °C) for 7 days to investigate the combined effects of MPs and simulated ocean warming by measuring different physiological parameters, such as cell growth, pigment contents (chlorophyll a and carotenoid), relative electron transfer rate (rETR), reactive oxygen species (ROS), superoxide dismutase (SOD), malondialdehyde (MDA), and adenosine triphosphate (ATP). The results demonstrated that MPs significantly decreased cell growth, pigment contents, and rETR_max, but increased the MDA, ROS, and SOD levels for all MP treatments at low temperature (16 °C). However, high temperatures (22 and 28 °C) increased the pigment contents and rETR_max, but decreased the SOD and MDA levels. Positive and negative effects of high temperatures (22 or 28 °C) were observed at low (1 and 5 mg L^-1) and high MP (10 mg L^-1) concentrations, respectively, indicating the antagonistic and synergistic effects of combined warming and MP pollution. These results imply that the effects of MPs on microalgae will likely not be substantial in future warming scenarios if MP concentrations are controlled at a certain level. These findings expand the current knowledge of microalgae in response to increasing MP pollution in future warming scenarios.

Microplastics can alter phytoplankton community composition

Microplastic pollution is a growing concern globally due to the risks they may pose to ecological communities. Phytoplankton are key ecological community in aquatic ecosystems providing both energy to food webs and have critical roles in ecosystem functions such as carbon cycling. To date studies on how microplastics effect phytoplankton have largely been limited to laboratory exposure studies using monocultures of algae. It remains unknown how the structure of phytoplankton communities will be influenced by growing microplastic pollution. The aim of this study was to determine how different concentrations microplastic fibers influence phytoplankton community structure. Two six-day microcosm studies were conducted testing the response of the phytoplankton community to low, medium, and high microplastics concentrations on the Georges River, Australia. The results showed the highest concentrations of microplastics significantly altered the structure phytoplankton community. These differences were largely driven by increased abundances of cyanobacteria taxa Aphanocapsa and Pseudanabaena, and to a lesser extent reduced abundances of taxa including Crucigenia and Chlamydmonas. There were no significant differences between controls and the low and medium treatments in either experiment. The high concentrations used in this experiment whilst likely rare in the environment are environmentally relevant and equivalent to some of more polluted ecosystems. The results highlight the potential risk to food webs and ecosystem functioning through altering the dynamics of primary production and provide evidence for further study examining the response of ecological communities to microplastics in the environment.