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.

Bioavailability and toxicity of microplastics to fish species: A review.

The prevalence of microplastics in aquatic environments has raised concerns about their availability and risks to aquatic biota. Since fish is an important source of animal protein for human beings, the occurrence and potential impacts of microplastics in fishes deserve special attention. Although there have been an increasing number of studies concerning microplastics ingestion and effects in fish, review papers specifically focusing on this issue are few. This review summarized the current knowledge about the bioavailability and toxicity of microplastics to fish species. By collating literatures, it can be concluded that microplastics contamination could occur in almost all types of aquatic habitats around the globe. Both field and laboratory studies suggest that fishes are very susceptible to microplastics ingestion. Compared with marine species, freshwater fishes have been less studied. Microplastics alone or in combination with other contaminants could cause various health problems to fish after exposure. There still exist some debates over the environmental relevance of the laboratory-based effect studies and the relative contribution of microplastics in increasing the exposure of fish to hazardous chemicals. Hopefully, this review could extend the current knowledge on the ecotoxicological impacts of microplastics contamination to fish and provide guidance for future research.

The ecotoxicological effects of microplastics on aquatic food web, from primary producer to human: A review.

The prevalence of microplastics in global waters raises the concern about their potential effects on aquatic biota. In aquatic environment, microplastics are almost ubiquitously present in all compartments from surface water to benthic sediment, making them accessible to a wide range of aquatic biota occupying different habitats. Exposure to microplastics may induce detrimental implications to the health of aquatic organisms. This review describes the wide occurrence of microplastics ingestion by aquatic fauna and evaluates the ecotoxicological effects of microplastics as well as the associated chemicals on aquatic biota including phytoplankton and fauna from both freshwater and marine environments. Trophic transfer of microplastics and associated contaminants along the aquatic food chain and potential impacts on human health are also discussed. Finally, this review emphasizes the current knowledge gaps and gives recommendations for the future work.

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.

Different partition of polycyclic aromatic hydrocarbon on environmental particulates in freshwater: Microplastics in comparison to natural sediment.

Microplastics pollution in the aquatic ecosystems has aroused increasing concerns in recent years. Though microplastics are known to sorb organic contaminants from water, the interaction mechanisms between microplastics and organic chemicals are not yet well understood. Here we investigated the partition characteristics of phenanthrene (Phe) in three mass-produced plastic particles, including polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)， and one natural sediment, as a comparison. The sorption kinetics of Phe onto microplastics and natural sediment were successfully described by the pseudo-second-order model (R2 > 0.992), while the equilibrium data were best-fitted to the Langmuir isotherm (R2 > 0.995). Compared with natural sediment, microplastics exhibited higher capacities for Phe which followed an order of PE > PS > PVC. As the aqueous concentration of pyrene (Pyr) increased, both uptakes and distribution coefficients (Kd) of Phe within the solids decreased, with natural sediment giving the largest decline. Although proportions of Phe desorbed from the contaminated microplastics were low, due to the high Phe uptake, microplastics released larger amounts of the sorbed Phe to water than the natural sediment during the desorption process. Given their minimal abundance relative to natural sediment, microplastics may play a less important role in the transport of organic pollutants in a natural aquatic environment.

Characterization of heavy metal contamination in the habitat of red-crowned crane (Grus japonensis) in Zhalong Wetland, northeastern China.

Heavy metal enrichment in the prey of red-crowned cranes in Zhalong Wetland, northeastern China was researched. Lead and Cd were the most abundant elements in the sediments; their concentrations ranged from 9.85 to 127 ppm and from 1.23 to 10.6 ppm, respectively. Six aquatic animal taxa contained detectable levels of heavy metals, in the decreasing order of Cyprinidae > Cobitidae > Dytiscidae > Odontobutidae > Viviparidae > Aeshnidae. Metal concentrations in these taxa followed the order: Zn > Cu > Cr > Pb > Hg > Cd. Metals in tissues of the red-crowned crane varied in the following order: Zn > Cr > Cu > Pb > Cd > Hg in feathers, and Zn > Cu > Hg > Cr > Pb > Cd in eggshells. Cadmium concentrations in the feathers of the red-crowned crane exceeded a level considered to be potentially toxic in birds (i.e., 0.22 ppm), ranging from 1.42 to 3.06 ppm.

The impacts of microplastics on the cycling of carbon and nitrogen in terrestrial soil ecosystems: Progress and prospects.

As contaminants of emerging concern, microplastics (MPs) are ubiquitously present in almost all environmental compartments of the earth, with terrestrial soil ecosystems as the major sink for these contaminants. The accumulation of MPs in the soil can trigger a wide range of effects on soil physical, chemical, and microbial properties, which may in turn cause alterations in the biogeochemical processes of some key elements, such as carbon and nitrogen. Until recently, the effects of MPs on the cycling of carbon and nitrogen in terrestrial soil ecosystems have yet to be fully understood, which necessitates a review to summarize the current research progress and propose suggestions for future studies. The presence of MPs can affect the contents and forms of soil carbon and nitrogen nutrients (e.g., total and dissolved organic carbon, dissolved organic nitrogen, NH4+-N, and NO3--N) and the emissions of CH4, CO2, and N2O by altering soil microbial communities, functional gene expressions, and enzyme activities. Exposure to MPs can also affect plant growth and physiological processes, consequently influencing carbon fixation and nitrogen uptake. Specific effects of MPs on carbon and nitrogen cycling and the associated microbial parameters can vary considerably with MP properties (e.g., dose, polymer type, size, shape, and aging status) and soil types, while the mechanisms of interaction between MPs and soil microbes remain unclear. More comprehensive studies are needed to narrow the current knowledge gaps.

Experimental determination of the charge neutrality level of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV).

The charge neutrality level (CNL) of poly[2-methoxy-5-(2'-ethylhexyloxy)-p-phenylene vinylene] (MEH-PPV) was determined. This was achieved by measuring the hole injection barrier at the MEH-PPV/Al interface with X-ray and ultraviolet photoemission spectroscopies in combination with in situ multistep electrospray-based thin film deposition. This deposition technique allows the deposition of polymers into a vacuum environment from solution, preventing significant contamination of the interface. Hence, the hole injection barrier energy at the interface between MEH-PPV and Al could be determined without the presence of significant amounts of ambient contamination. The result of this measurement was combined with published barrier energies for Au and Ag measured with the same technique. This enabled the correlation between barrier heights and substrate work functions as prescribed by the "induced density of states" (IDIS) model. This yielded a CNL of MEH-PPV of 3.76 eV relative to the vacuum level. The corresponding "screening factor" was calculated to be 0.21. The results are discussed in light of the IDIS, which was initially developed for small molecular materials, as well as the integer charge transfer model (ICT). The ICT model was determined for contaminated polymer interfaces featuring only weak interaction.

Low-density polyethylene microplastics and biochar interactively affect greenhouse gas emissions and microbial community structure and function in paddy soil.

Paddy soils are susceptible to microplastics (MPs) contamination. As a common soil amendment, biochar (BC) has been extensively applied in paddy fields. The co-occurrence of MPs and BC may cause interactive effects on soil biogeochemical processes, which has yet been well studied. In this study, a 41-days of microcosm experiment was conducted using paddy soil added with 0.5-1.5 wt% of low-density polyethylene (LDPE) and 5 wt% of BC individually or jointly. Application of BC, LDPE, or their mixture into soil significantly increased the emission of methane (CH4), but suppressed the emission of carbon dioxide (CO2). LDPE addition lowered soil nitrous oxide (N2O) emissions, while BC exerted an opposite effect. Proteobacteria was the most dominant phylum with a relative abundance range of 35.1-51.0%, followed by Actinobacteria (19.3-30.9%) and Acidobacteria (7.5-23.5%). The abundances of the mcrA gene and pH values were increased in soils added with BC or/and LDPE, which were the possible reasons for the higher CH4 emissions in these treatments. The emission of N2O was positively related to the abundances of norB and narG genes, suggesting denitrification was a major pathway to produce N2O. Results of structural equation modeling demonstrated that addition of BC or/and LDPE MPs could affect greenhouse gas emissions from paddy soil by altering soil chemical properties, microbial community structure, and functional gene abundances.

Ecotoxicological effects of micro- and nanoplastics on terrestrial food web from plants to human beings.

Micro- and nanoplastics (MNPs) are present in almost all environmental compartments. Terrestrial soils are major environmental reservoirs for MNPs, but the ecotoxicological effects of MNPs on terrestrial biota remain relatively understudied. In this review, we collated findings of previous research on the uptake and impact of MNPs in terrestrial organisms, including flora, fauna, and human beings. Terrestrial plants can take up MNPs via the roots or leaves and translocate them to other parts. MNPs have been detected in the gastrointestinal tracts or feces of many terrestrial animals, including some high trophic-level predators, indicating the incidence of direct ingestion or trophic transfer of MNPs. The presence of MNPs in food items and human feces combines to verify human intake of MNPs via the dietary pathway. Exposure to MNPs can cause diverse effects on terrestrial organisms, including alterations in growth performance, oxidative stress, metabolic disturbance, cytotoxicity, genotoxicity, and mortality. The biological internalization and impact of MNPs are influenced by the physicochemical properties of MNPs (e.g., particle size, polymer type, surface chemistry, and exposure concentrations) and the physiology of the species. MNPs can also affect the bioavailability of co-occurring intrinsic or extrinsic contaminants to terrestrial biota, but their specific role is under dispute. Finally, we underlined the current research gaps and proposed several priorities for future studies.

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.

Environmental fate and impacts of microplastics in soil ecosystems: Progress and perspective.

The wide and intensive application of plastics and their derived products has resulted in global environmental contamination of plastic waste. Large-sized plastic litter can be fragmented into microplastics (<5 mm), which have attracted increasing concerns from the general public and scientific communities worldwide. Until recently, the majority of microplastics research reported in literatures has been focusing on the aquatic settings, especially the marine environment, while information about microplastics contamination in terrestrial soil systems is highly insufficient. In this paper, we reviewed the latest data regarding the occurrence of microplastics in terrestrial soils and discussed their potential pathways into the soil environment. We also summarized the currently used methodologies for extraction and characterization of microplastics in soil matrices and evaluated their advantages and limitations. Additionally, we assessed the ecotoxicological consequences of microplastics contamination on soil ecosystems, including the effects on soil physiochemical properties, terrestrial plants, soil fauna, and soil microbes. Finally, based on the most current progress summarized in this review, we suggested several directions for future research on microplastics in soil ecosystems.

Manuscript prepared for submission to environmental toxicology and pharmacology pollution in drinking water source areas: Microplastics in the Danjiangkou Reservoir, China.

As the source of water for the South-to-North Water Diversion Project of China, the water quality of the Danjiangkou Reservoir (DJKR) is related to the safety of drinking water for billions of residents. Consequently, microplastics in surface water and sediment samples of the DJKR were investigated in this study. Microplastics were observed in all water and sediment samples with abundances varying from 467 to 15,017 n/m3 and 15 to 40 n/kg wet weight, respectively. Microplastics were rich in colour and dominated by fibrous items. Small-sized particles (< 2 mm) were more frequently observed than other sizes. Analysis by micro-Raman spectroscopy showed that polypropylene was the major polymer type. These systematic results demonstrated that the DJKR is suffering from the pollution of microplastics, which should be paid more attention based on its potential threat to the aquatic organisms and residents impacted by the drinking water source pollution.

Comparative evaluation of sorption kinetics and isotherms of pyrene onto microplastics.

Concerns regarding microplastics pollution and their potential to concentrate and transport organic contaminants in aquatic environments are growing in recent years. Sorption of organic chemicals by microplastics may affect the distribution and bioavailability of the chemicals. Here sorption process of pyrene (Pyr), a frequently encountered polycyclic aromatic hydrocarbon in aquatic environments, on three types of mass-produced plastic particles (high-density polyethylene (PE), polystyrene (PS) and polyvinylchloride (PVC)), was investigated by comparative analysis of different sorption kinetic and isotherm models. Optimum kinetic and isotherm models were predicted by the linear least-squares regression method. The pseudo-second-order kinetic model was more appropriate in describing the entire sorption process (R2 > 0.99). Sorption rates of Pyr onto microplastics were mainly controlled by intraparticle diffusion. PE exhibited the highest affinity for Pyr, followed by PS and PVC. The sorption equilibrium data were best fitted to the Langmuir isotherm (R2 > 0.99), indicating monolayer coverage of Pyr onto the microplastics.

Fast repair of deoxythymidine radical anions by two polyphenols: rutin and quercetin.

The effects of rutin and quercetin on the repair of the deoxythemindine radical anion (dT*) were studied using the technique of pulse radiolysis. The radical anion of dT was formed by the reaction of hydrated electron with dT. After pulse irradiation of nitrogen-saturated aqueous solutions containing dT, 0.2M t-BuOH and either rutin or quercetin, the initially formed dT*(-), detected spectrophotometrically, rapidly decayed with the concurrent formation of the radical anion of rutin or quercetin. The results indicated that dT*(-) can be rapidly repaired by rutin or quercetin. The rate constants of the repair reactions were determined to be 3.1 and 4.1 x 10(9)M(-1)s(-1) for rutin and quercetin, respectively. With substitution by glycosyl groups at C(3)-OH bond being neighbor to C(4) keto group, which is the active site for electron transfer, rutin has a lower repair reaction rate constant toward dT*(-) than quercetin. Together with findings from our previous studies, the present results demonstrated that nonenzymatic fast repair may be a universal form of repair involving phenolic antioxidants.

Immobilization of heparin on the surface of polypropylene non-woven fabric for improvement of the hydrophilicity and blood compatibility.

A polypropylene non-woven fabric (PPNWF) was exposed to oxygen plasma to produce peroxides on its surface. These peroxides were used to initiate graft polymerization of acrylic acid (AA) on the surface of PPNWF. Direct heparinization was accomplished via a reaction between heparin and PP-PAA (AA grafted PPNWF) which was activated by EDC (N-ethyl-N'-[3-(dimethylamino)propyl] carbodiimide). Indirect heparinized PPNWF was prepared by grafting poly(ethylene oxide) (PEO) on a PP-PAA surface to form PP-PAA-PEO, followed by reaction with heparin which was activated by EDC before use. The surface modified PPNWFs were characterized by attenuated total reflection Fourier transform infrared (ATR-FT-IR) spectroscopy, electron spectroscopy for chemical analysis (ESCA) and contact angle goniometry. It was found that hydrophilicity was greatly improved, as indicated by the decrease of the water contact angle from 142 to 33°. In vitro blood compatibility evaluation of modified PPNWFs, including hemolysis rate, platelet adhesion, plasma protein adsorption and activated partial thromboplastin time (APTT) was investigated. The results suggested that both heparinized PPNWFs showed lower hemolysis rates and better platelet anti-adhesion than non-heparinized controls. Furthermore, PPNWF obtained via indirect immobilization of heparin showed better hydrophilicity and blood compatibility than direct heparinization of PPNWF.

A fabrication strategy for nanosized zero valent iron (nZVI)-polymeric anion exchanger composites with tunable structure for nitrate reduction.

To reveal how the distribution of nanoscale zero-valent iron (nZVI) affect their reduction efficiency of its polymer-based composites and to further develop a simple strategy to tune the structure of the composites, we prepared four nZVI-polymerstyrene anion exchanger composites with similar nZVI loadings (13.5-14.4 Fe % in mass) but different distributions just through varying the concentration of NaBH(4) (0.9, 1.8, 3.6, and 7.2% in mass) solution during reduction of nZVI precursor (FeCl(4)(-) anions). As observed by SEM-EDX images, increasing the NaBH(4) concentration resulted in a more uniform nZVI distribution within the polymer, and thereto higher NH(4)(+)N production, faster reaction rate and more gaseous products during its reduction of nitrate and nitrite. nZVI distribution of the composites was suggested to greatly depend upon two processes, the hydrolyzation of anionic FeCl(4)(-) into cationic Fe(3+) and the reduction of both Fe(III) species by NaBH(4). Higher NaBH(4) concentration favored its faster diffusion into the inside polymer and in situ reduction of Fe(III) species into nZVI, causing a more uniform nZVI distribution. The results reported herein suggest that adjusting the NaBH(4) concentration was a simple and effective method to control the nZVI distribution in the supporting polymers, and indirectly tune the reactivity of the resultant nZVI hybrids.