Can "Risk-Sharing" Mechanisms Help Clonal Aquatic Plants Mitigate the Stress of Nanoplastics?

Most aquatic plants applied to ecological restoration have demonstrated a clonal growth pattern. The risk-spreading strategy plays a crucial role in facilitating clonal plant growth under external environmental stresses via clonal integration. However, the effects of different concentrations of nanoplastics (NPs) on the growth traits of clonal aquatic plants are not well understood. Therefore, this study aimed to investigate the impact of NPs exposure on seedlings of parent plants and connected offspring ramets. A dose response experiment (0.1, 1, and 10 mg L-1) showed that the growth of Eichhornia crassipes (water hyacinth) was affected by 100 nm polystyrene nanoplastics after 28 days of exposure. Tracer analysis revealed that NPs are accumulated by parent plants and transferred to offspring ramets through stolon. Quantification analysis showed that when the parent plant was exposed to 10 mg L-1 NPs alone for 28 days, the offspring ramets contained approximately 13 ± 2 µg/g NPs. In the case of connected offspring ramets, leaf and root biomass decreased by 24%-51% and 32%-51%, respectively, when exposed to NP concentrations ranging from 0.1 to 10 mg L-1. Excessive enrichment of NPs had a detrimental effect on the photosynthetic system, decreasing the chlorophyll content and nonphotochemical quenching. An imbalance in the antioxidant defense systems, which were unable to cope with the oxidative stress caused by NP concentrations, further damaged various organs. The root system can take up NPs and then transfer them to the offspring through the stolon. Interference effects of NPs were observed in terms of root activity, metabolism, biofilm composition, and the plant's ability to purify water. However, the risk-spreading strategy employed by parent plants (interconnected offspring ramets) offered some relief from NP-induced stress, as it increased their relative growth rate by 1 to 1.38 times compared to individual plants. These findings provide substantial evidence of the high NP enrichment capacity of E. crassipes for ecological remediation. Nevertheless, we must also remain aware of the environmental risk associated with the spread of NPs within the clonal system of E. crassipes, and contaminated cloned individuals need to be precisely removed in a timely manner to maintain normal functions.

Microplastics in aquatic ecosystems of Africa: A comprehensive review and meta-analysis.

Microplastic pollution is a global issue of great public concern. Africa is flagged to host some of the most polluted water bodies globally, but there is no enough information on the extent of microplastic contamination and the potential risks of microplastic pollution in African aquatic ecosystems. This meta-analysis has integrated data from published articles about microplastic pollution in African aquatic ecosystems. The data on the microplastic distribution and morphological characteristics in water, sediments and biota from African rivers, lakes, oceans and seas were extracted from 75 selected studies. Multivariate statistics were used to critically analyze the effects of sampling and detection methods, ecological risks, spatial distribution and similarity of microplastics in relation to the geographical distance between sampling sites. This study found that sampling methods have significant effect on abundance and morphological characteristics of microplastics and that African aquatic ecosystems are highly contaminated with microplastics compared to global data. The most prevalent colors were white, transparent and black, the most prevalent shapes were fibres and fragments, and the most available polymers were polypropylene (PP), polystyrene (PS) and polyethene terephthalate (PET). Microplastic polymers similarity decreased with an increase in geographical distance between sites. Risk levels of microplastics in African aquatic ecosystems were comparatively high, and more than 40 % of water and sediments showed highest level of ecological risk. This review provides recent information on the prevalence, distribution and risks of microplastics in African aquatic ecosystems.

Engineering of Stable Anionic/Neutral MOFs with Zinc-Adeninate Building Units for Efficient C2H2/CO2 Separation.

Using adenine and metal ions to form secondary building units (SBUs), further connected by a highly symmetrical multicarboxylic linker to construct an amino-modified porous framework with high porosity, is an effective strategy. By regulating the deprotonation and hydrolysis capacity of the synthesized solvent, it is possible to obtain different charged frameworks. In this work, two stable anionic/neutral MOFs, (Et2NH2)[Zn3(TCPE)(adenine)2CH3COO]·DEF·3H2O (1) and [Zn3.5(adenine)(TCPE)1.5(DMA)(H2O)0.5]·2DMA·2H2O (2), have been synthesized based on zinc-adeninate building units and symmetric tetrakis(4-carboxyphenyl)ethylene (H4TCPE) in N,N-diethylformamide (DEF) and N,N-dimethylacetamide (DMA) reaction systems, respectively. 1 is an anionic framework based on 1D rod zinc-adeninate SBU, containing 1D rectangular (14.3 × 6.3 Å2) and square (14.3 × 14.3 Å2) channels. While 2 is a neutral framework built from isolated zinc-adeninate SBU, it contains hexagonal cages with a dimension of 5.5 Å in the structure. Both of them have high porosity (61.6% for 1 and 46.3% for 2) and high stability in a wide range of pH. 1 and 2 show high C2H2 adsorption capacity at 298 K (48.1 and 70.1 cm3 g-1, respectively) and selective capacity for C2H2/CO2 mixtures, which was confirmed by the breakthrough experiments. Furthermore, the interaction between the frameworks and gas molecules has also been explained by theoretical calculation. This work provides a good example of the design and regulation of porous structures for adsorption and separation functions.

Occurrence and risk assessment of microplastics in the Lhasa River-a remote plateau river on the Qinghai-Tibet Plateau, China.

Microplastics (MPs) are ubiquitous in the aquatic environment and have received widespread attention worldwide as emerging pollutants. Urbanization and anthropogenic activities are the main sources of MPs in rivers; however, the MPs in plateau rivers with less human activities are not well understood. In this study, the pollution of MPs in the surface water and shore sediment of the Lhasa River from the Qinghai-Tibet Plateau was investigated, and a risk assessment was conducted. The abundance of MPs in the surface water and shore sediment of Lhasa River were 0.63 n/L and 0.37 n/g, respectively. MPs in surface water were mainly dominated by films (43.23%) and fibers (31.12%) in shape, transparent (54.25%) in color, and 0-0.5 mm (75.83%) in size, while MPs in the shore sediment were mainly fibers (43.69%) and fragments (36.53%), transparent (71.91%), and 0-0.5 mm (60.18%). PP and PE were the predominant polymer types, accounting for 44.55% and 30.79% respectively in the surface water and 32.51% and 36.01% respectively in the shore sediment. More notably, the polymer pollution index (H) of MPs in the Lhasa River was at hazard level III due to the high risk caused by PVC, but the pollution load index (PLI) was low at hazard level I. This study reveals that the remote river in the Qinghai-Tibet Plateau are polluted by MPs, and their potential risks to the vulnerable ecosystem deserve attention.

Uniqueness and Dependence of Bacterial Communities on Microplastics: Comparison with Water, Sediment, and Soil.

Revealing the dependence and uniqueness of microbial communities on microplastics could help us better understand the assembly of the microplastic microbial community in river ecosystems. In this study, we investigated the composition and ecological functions of the bacterial community on microplastics from the Three Gorges Reservoir area compared with those in water, sediment, and soil at species-level via full-length 16S rRNA gene sequencing. The results showed that the full-length 16S rRNA sequencing provided more detail and accurate taxa resolution of the bacterial community in microplastics (100%), water (99.90%), sediment (99.95%), and soil (100%). Betaproteobacteriales were the most abundant bacteria in microplastics (14.1%), water (32.3%), sediments (27.2%), and soil (21.0%). Unexpectedly, oligotrophic SAR11 clade was the third abundant bacteria (8.51%) and dominated the ecological functions of the bacterial community in water, but it was less observed on microplastics, with a relative abundance of 2.73×10-5. However, four opportunistic pathogens identified at the species level were selectively enriched on microplastics. Stenotrophomonas maltophilia was the main opportunistic pathogen on microplastics (0.29%). Sediment rather than soil and water may be contributed mostly to pathogens on microplastics. Moreover, some bacteria species with the biodegradation function of microplastics were enriched on microplastics, such as bacteria Rhodobacter sp., and endemic bacteria Luteimonas sp. The distinct bacteria composition on microplastics enhanced several ecological functions, such as xenobiotics biodegradation, which allows screening the bacteria with the biodegradation function of microplastics through long-term exposure.

Hexagonal Cages and Lewis Acid-Base Sites in a Metal-Organic Framework for Synergistic CO2 Capture and Conversion under Mild Conditions.

The cycloaddition reaction of carbon dioxide (CO2) is a highly economic solution to becoming carbon-neutral. Herein, we have designed and synthesized a robust zinc(II)-organic framework (Zn-Ade-TCPE) by a function-directed strategy. Zn-Ade-TCPE possesses uncommon hexagonal cages with Lewis acid-base bifunctional sites and displays a high adsorption capacity for CO2. At room temperature and atmospheric pressure, Zn-Ade-TCPE exhibits outstanding activity, selectivity, and recyclability in the cycloaddition reaction of epoxides with CO2 because of the synergistic effect of multiple active sites and confined cavities.

Uptake, translocation, and biological impacts of micro(nano)plastics in terrestrial plants: Progress and prospects.

Micro(nano)plastics are emerging environmental contaminants of concern. The prevalence of micro(nano)plastics in soils has aroused increasing interest regarding their potential effects on soil biota including terrestrial plants. With the rapid increase in published studies on plant uptake and impacts of micro(nano)plastics, a review summarizing the current research progress and highlighting future needs is warranted. A growing body of evidence indicates that many terrestrial plants can potentially take up micro(nano)plastics via roots and translocate them to aboveground portions via the vascular system, primarily driven by the transpiration stream. Exposure to micro(nano)plastics can cause a variety of effects on the biometrical, biochemical, and physiological parameters of terrestrial plants, but the specific effects vary considerably as a function of plastic properties, plant species, and experimental conditions. The presence of micro(nano)plastics can also affect the bioavailability of other associated toxicants to terrestrial plants. Based on analysis of the available literature, this review identifies current knowledge gaps and suggests prospective lines for further research.

Environmental adaptation is stronger for abundant rather than rare microorganisms in wetland soils from the Qinghai-Tibet Plateau.

Disentangling the biogeographic patterns of rare and abundant microbes is essential in order to understand the generation and maintenance of microbial diversity with respect to the functions they provide. However, little is known about ecological assembly processes and environmental adaptation of rare and abundant microbes across large spatial-scale wetlands. Using Illumina sequencing and multiple statistical analyses, we characterized the taxonomic and phylogenetic diversity of rare and abundant bacteria and fungi in Qinghai-Tibet Plateau wetland soils. Abundant microbial taxa exhibited broader environmental thresholds and stronger phylogenetic signals for ecological traits than rare ones. By contrast, rare taxa showed higher sensitivity to environmental changes and closer phylogenetic clustering than abundant ones. The null model analysis revealed that dispersal limitation belonging to stochastic process dominated community assemblies of abundant bacteria, and rare and abundant fungi, while variable selection belonging to deterministic process governed community assembly of rare bacteria. Neutral model analysis and variation partitioning analysis further confirmed that abundant microbes were less environmentally constrained. Soil ammonia nitrogen was the crucial factor in mediating the balance between stochasticity and determinism of both rare and abundant microbes. Abundant microbes may have better environmental adaptation potential and are less dispersed by environmental changes than rare ones. Our findings extend knowledge of the adaptation of rare and abundant microbes to ongoing environmental change and could facilitate prediction of biodiversity loss caused probably by climate change and human activity in the Qinghai-Tibet Plateau wetlands.

New Perspective on the Nanoplastics Disrupting the Reproduction of an Endangered Fern in Artificial Freshwater.

The potential risks of micro/nanoplastics on the ecological environment, particularly aquatic fauna, have been realized in recent years. However, information about its potential effects on aquatic plants is scarce. In this study, a four-week exposure experiment was conducted to investigate the effects of varying polystyrene nanoplastics concentration (PS-NPs, 0-100 µg/mL) on the early development of an endangered aquatic plant, Ceratopteris pteridoides. Fluorescent observations demonstrated that PS-NPs were adsorbed and accumulated on the spore surface of C. pteridoides rapidly and massively with increasing exposure concentration and time. The adsorption and accumulation of PS-NPs on the spore surface posed a negative effect on spore imbibition, causing 2.3-22.4% reduction in final spore size. Spore germination and gametophyte sex differentiation were both negatively affected by PS-NP exposure, resulting in 10.4-88.0% inhibition in germination ratio and 2.9-53.4% reduction in hermaphroditic gametophyte ratio. Additionally, PS-NPs were observed to penetrate into the roots of gametophytes. Higher concentration of PS-NPs (100 µg/mL) can even induce pathological changes on gametophytes, although with a low incidence (4.9%). The results above indicated that exposure to PS-NPs caused a series of disruptions from the spore imbibition to germination and gametophyte stages, and are likely to pose an eco-physiological risk on the reproductive success of endangered ferns.

Microplastic abundance, distribution and composition in water, sediments, and wild fish from Poyang Lake, China.

Microplastic pollution in global aquatic environments has aroused increasing concern in recent years. In this study, the occurrence of microplastics in multiple environmental compartments was investigated in Poyang Lake, the largest freshwater lake of China. The abundance of microplastics was respectively 5-34 items/L for surface waters, 54-506 items/kg for sediments, and 0-18 items per individual for wild crucians (Carassius auratus). The distribution of microplastics in Poyang Lake varied heterogeneously in space, with the highest abundance being observed in the middle region of the lake for surface waters and in the northern region for sediments. Anthropogenic and topographic factors were speculated to be the major factors affecting the abundance and distribution of microplastics. The majority of the detected microplastics were found with a size of < 0.5 mm, with fibrous and coloured being the predominant characteristics. Polypropylene (PP) and polyethylene (PE) were the major polymer types of the selected plastic particles, indicating that domestic sewage and fishing activities might be the main sources of microplastics in the lake. No significant correlation was observed between microplastic abundance in surface water and sediment samples. Our results demonstrated the wide occurrence of microplastics in water, sediment and biota of the Poyang Lake, which may assist in extending our knowledge regarding microplastics pollution in inland freshwater systems.

Single-cell transcriptomics reveals the pulmonary inflammation induced by inhalation of subway fine particles.

People generally take the subway and inevitably inhale the fine particles (PM2.5) on subway platforms. This study revealed whether and how subway PM2.5 causes lung inflammation. Herein, the pulmonary inflammatory response to subway PM2.5 was observed in mice, manifesting as the inflammatory cells infiltration and collagen deposition in tissue, inflammatory cytokine enhancement in bronchoalveolar lavage fluid and Toll-like receptors signal pathway activation in the lungs. Furthermore, single-cell RNA sequencing unearthed subway PM2.5-induced cell-specific responses in the lungs. Twenty immune subsets were identified by the molecular and functional properties. Specific cell populations of CD4+ T and γδ T cells were regarded as the predominant sources of pneumonitis induced by subway PM2.5. Moreover, we demonstrated that the lung inflammatory injury was significantly more attenuated in Rag1-/- mice lacking functional T cells and B cells than that in wild type mice. We proved the slight inflammation of lung tissue in Rag1-/- mice may be dependent on monocytes and neutrophils by activation of the intracellular molecular network. This is the first experimental study on subway PM2.5 causing pulmonary inflammatory damage. It will set an alarm for people who usually travel by subway and efficient measures to reduce PM2.5 should be developed in subway stations.

The threat of micro/nanoplastic to aquatic plants: current knowledge, gaps, and future perspectives.

Plastics have been recognized as an emerging pollutant and have raised global concerns due to their widespread distribution in the environment and potential harm to living systems. However, research on the threat of micro/nanoplastics (MPs/NPs) to the unique group of aquatic plants is far behind, necessitating a comprehensive review to summarize current research progress and identify future research needs. This review explores the sources and distribution patterns of MPs/NPs in aquatic environments, highlighting their uptake by aquatic plants through roots and leaves, and subsequent translocation via the vascular system facilitated by the transpiration stream. Exposure to MPs/NPs elicits diverse effects on the growth, physiology, and ecological interactions of aquatic plants, with variations influenced by plastic properties, plant species, and experimental conditions. Furthermore, the presence of MPs/NPs can impact the toxicity and bioavailability of other associated toxicants to aquatic plants. This review shows critical knowledge gaps and emphasizes the need for future research to bridge the current understanding of the limitations and challenges posed by MPs/NPs in aquatic ecosystems.

Intratracheally administered iron oxide nanoparticles induced murine lung inflammation depending on T cells and B cells.

Iron oxide nanoparticles (Fe2O3 NPs), produced in track traffic system and a wide range of industrial production, poses a great threat to human health. However, there is little research about the mechanism of Fe2O3 NPs toxicity on respiratory system. Rag1-/- mice which lack functional T and B cells were intratracheally challenged with Fe2O3 NPs, and interleukin (IL)-33 as an activator of group 2 innate lymphoid cells (ILC2s) to observe ILC2s changes. The lung inflammatory response to Fe2O3 NPs was alleviated in Rag1-/- mice compared with wild type (WT) mice. Infiltration of inflammatory cells and collagen deposition in tissue, leukocyte numbers (neutrophils, macrophages and lymphocytes), cytokine levels, such as IL-6, IL-13 and thymic stromal lymphopoietin (TSLP), and expression of Toll-like receptor (TLR)2, TLR4, and downstream myeloid differentiation factor (MyD)88, nuclear factor (NF)-κB and tumor necrosis factor (TNF)-α were decreased in lungs. Fe2O3 NPs markedly elevated ILC2s compared with the control, but ILC2s numbers were much lower compared with IL-33 in both WT and Rag1-/- mice. Furthermore, ILC2s amounts were strongly greater in Rag1-/- mice than WT mice. Our results suggested that Fe2O3 NPs induced sub-chronic pulmonary inflammation, which is majorly dependent on T cells and B cells rather than ILC2s.

Inhalation of subway fine particles induces murine extrapulmonary organs damage.

Because of its speed and convenience, the subway has become the first choice for travel by many residents. However, the concentration of fine particles (PM2.5) in the air of a subway platform is higher than that of the ground level or carriage. Moreover, the composition and source of subway PM2.5 differ from those of atmospheric PM2.5. Currently, there is insufficient research on the impact of subway PM2.5 on health. In this study, intratracheally subway PM2.5-inoculated wild type (WT) and Rag1-/- mice, lacking functional T cells and B cells, were used to investigate the potential of subway PM2.5 exposure to cause extrapulmonary organ injuries. Subway PM2.5 increased inflammatory cells infiltration, tumor necrosis factor (TNF)-α, interleukin (IL)-6, as well as monocyte chemotactic protein (MCP)-1 gene and protein expression, cyclooxygenase-2 (COX-2) induction, and Toll-like receptor (TLR)-2, TLR4, myeloid differentiation factor 88 (MyD88), and nuclear factor (NF)-κB levels in liver, kidney, spleen, and thymus in a dose-dependent fashion in WT mice. Subway PM2.5 exposure resulted in slight macrophage (F4/80+) and neutrophil (Ly6G+) infiltration and caused no increase in the protein levels of TNF-α, IL-6, MCP-1, or COX-2 in the liver, kidneys, spleen, and thymus of Rag1-/- mice. These results demonstrate a dose-response manner between subway PM2.5 exposure and inflammatory injuries of extrapulmonary organs, which could be related to the TLR/MyD88/NF-κB signaling pathway. Subway PM2.5-induced extrapulmonary organ damage was dependent on T cells and B cells; this finding may provide insight for research on the mechanisms responsible for the health hazards posed by air pollution.

Tracing and trapping micro- and nanoplastics: Untapped mitigation potential of aquatic plants?

Micro- and nanoplastics are emerging concerns due to their environmental ubiquity and currently largely unknown ecological impacts. Leveraging on a recently developed method using europium-doped polystyrene particles (PS-Eu), our present work aimed to accurately trace the uptake and transport of micro- and nanoplastics in aquatic plants and shed insights into the potential of different aquatic plants for trapping and removal of plastics from water environment. Seedlings of Vallisneria denseserrulata Makino (submerged plant), Iris tectorum Maxim (emergent plant), and Eichhornia crassipes Solms (floating plant) were exposed to 100 nm and 2 µm PS-Eu in freshwater (5 µg/mL) or sediments (5 µg/g) for 8 weeks. Fluorescence imaging clearly evidenced that PS-Eu mainly accumulated in the intercellular space and were transported from roots to leaves via the apoplastic path and vascular bundle. Mass spectrum analysis demonstrated that up to 6250 µg/g nanoplastics were trapped in aquatic plants (mainly in roots) with a bioconcentration factor of 306.5, depending on exposure routes and plant species. Owing to their excellent capture capability and high tolerance to plastic exposures, floating plants like E. crassipes are promising for immobilizing and removing fine plastics from the water environment.

Environmental fate of microplastics in the world's third-largest river: Basin-wide investigation and microplastic community analysis.

Rivers have been recognized as major transport pathways for microplastics into the sea but large-scale quantitative data on the environmental fate of riverine microplastics remains limited, hindering proper risk assessment and development of regulatory measures. Microplastics in the whole Yangtze River Basin of China were systematically investigated by sampling the water, sediment, and soil. Microplastics were detected in all samples, with an average abundance of 1.27 items/L, 286.20 items/kg, and 338.09 items/kg for water, sediments, and soils, respectively, with polypropylene and polyethylene being the most abundant polymers. A generally increasing trend of microplastic abundance from upstream to downstream was identified, which were co-attributed by geographical and anthropogenic factors including elevation, longitude, distance from the nearest city, population density, urbanization rate, and land use. Microplastics in the sediments showed more prominent vertical migration than those in the soils, and the density and size of microplastics may be the key factors governing the migration of microplastics across different compartments. Community analysis showed that microplastics in different compartments were significantly different and highly correlated with geographical distance. Major cities at the middle and lower reaches were considered pivotal nodes of microplastic pollution in the Yangtze River Basin. Policy recommendations were also proposed towards better remediation of microplastic pollution involving riverine systems.

Stronger environmental adaptation of rare rather than abundant bacterioplankton in response to dredging in eutrophic Lake Nanhu (Wuhan, China).

Deciphering responses of rare versus abundant bacterioplankton to environmental change, crucial for understanding and mitigating of cyanobacterial blooms, is an important but poorly investigated subject. Using MiSeq sequencing, we investigated the taxonomic and phylogenetic diversity of rare and abundant bacterioplankton in eutrophic Lake Nanhu before and after dredging. We estimated environmental breadths and phylogenetic signals of ecological preferences of rare and abundant bacterioplankton, and investigated community function and bacterioplankton assembly processes. Both taxonomic and phylogenic distances of rare and abundant bacterioplankton communities were significantly positively correlated with the dissimilarity of environmental factors. Threshold indicator taxa analysis and Blomberg's K statistic indicated that rare taxa held broader environmental thresholds and stronger phylogenetic signals for ecological traits than abundant taxa. Environmental adaptations of both rare and abundant taxa exhibited distinct changes after dredging. Higher functional redundancy occurred in the abundant compared to the rare bacterioplankton, with functions of rare bacterioplankton decreasing and for the abundant ones increasing after dredging. The null model revealed that dispersal limitation belonging to stochastic processes determined the abundant bacterioplankton community assembly, whereas variable selection belonging to deterministic processes drove the rare one. Rare bacterioplankton was more environmentally constrained than the abundant one. Dissolved oxygen was the decisive factor in determining the balance between stochasticity and determinism in both rare and abundant bacterioplankton. Our study extends our knowledge of environmental adaptation of rare versus abundant bacterioplankton to massive disturbing measures, i.e. dredging, and allows to estimate dredging performance for mitigating cyanobacterial blooms from a molecular ecology viewpoint.

Dredging alleviates cyanobacterial blooms by weakening diversity maintenance of bacterioplankton community.

Disentangling ecological mechanisms behind dredging is meaningful to implement environmental policy for improving water quality. However, environmental adaptation and community assembly processes of bacterioplankton in response to dredging disturbance are poorly understood. Based on Illumine MiSeq sequencing and multiple statistical analyses, we estimated interactions, functions, environmental breadths, phylogenetic signals, phylogenetic clustering, and ecological assembly processes of bacterioplankton community before and after dredging. We found distinct change in community composition, comparable decreases in diversity, functional redundancy and conflicting interaction, relatively low phylogenetic clustering, and relatively weak environmental adaptation after dredging. The bacterioplankton community assembly was affected by both stochastic and deterministic processes before dredging, but dominated by stochasticity after dredging. Sediment total phosphorus was a decisive factor in balancing determinism and stochasticity for bacterioplankton community assembly before and after dredging. Consequently, taxonomic and phylogenetic α-diversities of bacterioplankton exhibited higher contributions to the water trophic level represented by chlorophyl α before dredging than afterwards. Our results emphasized bacterioplankton in response to environmental changes caused by dredging, with nutrient loss and ecological drift playing important roles. These findings extend knowledge of contribution of bacterioplankton diversity to water trophic level and decipher mechanisms of bacterioplankton diversity maintenance in response to dredging, which is useful for guiding mitigation of cyanobacterial blooms.

Toxicological effects of microplastics and heavy metals on the Daphnia magna.

Microplastics (MPs) are gradually spreading around the world and becoming a ubiquitous environmental contamination in aquatic environments. Due to its unique physicochemical properties, MPs are considered to be strong adsorbents for environmental pollutants and may affect their fate and toxicity in the environment. In this study, the adsorption behaviors of four typical heavy metal ions (Pb2+, Cu2+, Cd2+, and Ni2+) on two sizes of polystyrene MPs (10 µm and 50 µm) were investigated based on batch experiments, and the combined effects of heavy metals and MPs were assessed using Daphnia magna as model. The results showed that smaller MPs (SMPs) exhibited higher adsorption capacities for metal ions (0.261-0.579 mg/g) than that of the larger MPs (LMPs) (0.243-0.525 mg/g), and the affinity sequence of heavy metals on MPs is Pb2+ > Cu2+ > Cd2+ > Ni2+. There are better admirable agreements for pseudo-second-order model and Langmuir model to fit the adsorption kinetics and adsorption isotherms, respectively. Additionally, the combined toxicity of MPs and heavy metals was negatively correlated with the adsorption capacity between them. The combined effects of mixtures toward D. magna changed from antagonism to additive effect with increasing MPs concentrations, and SMPs exhibited higher toxicological risk than LMPs. Our findings compared the accumulative effects of various heavy metals on MPs and can contribute to understanding the combined effects of plastics and heavy metals on biota.

Microplastics in surface waters of Dongting Lake and Hong Lake, China.

Microplastics pollution is an environmental issue of increasing concern. Much work has been done on the microplastics pollution in the marine environments. Although freshwaters are potential sources and transport pathways of plastic debris to the oceans, there is a lack of knowledge regarding the presence of microplastics in freshwater systems, especially in China, the world's largest producer of plastics. This study investigated the occurrence and properties of microplastics in surface waters of two important lakes in the middle reaches of the Yangtze River. The concentration ranges of microplastics in Dongting Lake and Hong Lake were 900-2800 and 1250-4650n/m3, respectively. Fiber was the dominant shape. Colored items occupied the majority. Particles with a size of <330µm comprised >20% of total microplastics collected in both lakes. Most of the selected particles were identified as plastics, with polyethylene (PE) and polypropylene (PP) being the major components. This study can provide valuable reference for better understanding the microplastics pollution in inland freshwater ecosystems.