Polyethylene microplastics and substrate availability can affect emergence responses of the freshwater insect Chironomus sancticaroli.

Pollution caused by polyethylene microplastics (MP) has been reported for aquatic environments worldwide. However, despite recurrent research for several aquatic organisms, the effects of MP on the emergence stage of freshwater insects from tropical environments are little known. This study is the first to assess the emergence of the Brazilian native species Chironomus sancticaroli Strixino & Strixino, 1981 when exposed to primary polyethylene microplastics (size 40-48 µm). We performed two exposure scenarios, with a substrate (standard assays) and without substrate (as a stressful experience), and recorded emergence responses. The MP did not affect the species' emergence rate, but these rates were statistically different for the standard and stressful exposure scenarios. In bioassays without substrate, the high concentrations of MP caused anticipation of the insect's emergence (5-6 days). On the other hand, female emergence time was longer than males in standard bioassays. The substrate absence caused a slight increase in the left female wing's length and the potential female fecundity. These findings suggest that the polyethylene microplastics and substrate availability can affect the emergence dynamics of the tropical insect C. sancticaroli.

Environmental occurrences, fate, and impacts of microplastics.

Microplastics (MPs) are small plastic pieces with size less than 5 mm that have entered and polluted the environment. While many investigations including several critical reviews on MPs in the environment have been conducted, most of them are focused on their occurrences in marine environment. Current understanding on the occurrences, behaviors, and impacts of MPs in the terrestrial environment is far from complete. A systematic review of the literature was thus conducted to promote the research on MPs in the environment. This work is designed to provide a comprehensive overview that summarizes current knowledge and research findings on environmental occurrences, fate and transport, and impacts of MPs. In addition to discussing the occurrences, characteristics, and sources of MPs in the ocean, freshwater, sediments, soils, and atmosphere, the review also summarizes both the experimental and modeling data of the environmental fate and transport of MPs. Research findings on the toxic effects, bioaccumulation, and bioavailability of MPs in the environment are also covered in this critical review. Future perspectives are discussed as well.

Primary Microplastics in the Ecosystem: Ecological Effects, Risks, and Comprehensive Perspectives on Toxicology and Detection Methods.

Recent discoveries of microplastics in cities, suburbs, and even remote locations, far from microplastic source regions, have raised the possibility of long-distance transmission of microplastics in many ecosystems. A little is known scientifically about the threat that it posed to the environment by microplastics. The problem's apparent size necessitates the rapid development of reliable scientific advice regarding the ecological risks of microplastics. These concerns are brought on by the lack of consistent sample and identification techniques, as well as the limited physical analysis and understanding of microplastic pollution. This review provides insight regarding some unaddressed issues about the occurrence, fate, movement, and impact of microplastics, in general, with special emphasis on primary microplastics. The approaches taken in the earlier investigations have been analyzed and different recommendations for future research have been suggested.

Scientific Uncertainty of Marine Microplastic Pollution and the Dilemma of Future International Unified Legislation.

Several countries or regions have issued bans on microplastic pollution. This paper conducted a textual analysis on the provisions of the referenced countries or regions, and it was noticed that most of the existing bans only regulate and control microbeads instead of legal rules regarding all types of marine microplastic pollution. Existing international conventions can solve some of the problems of marine microplastic pollution, but they cannot solve all of them. Scientific uncertainty of marine microplastic pollution leads to the dilemma of future legislation. Specifically, based on the theory of legal norms, there are several issues faced by future international uniform legislation. The basic elements of legal rules are the hypothesis, disposition, and sanctions. At present, the scientific uncertainty of marine microplastic pollution cannot establish the three elements (hypothesis, disposition, and sanctions) of legal rules, so the existing bans in various countries can only target microbeads, and it is difficult to regulate other types of marine microplastic pollution. Consequently, we conclude that the time for comprehensive legislation on marine microplastics pollution is not yet ripe.

The Raman spectroscopy and SEM/EDS investigation of the primary sources of microplastics from cosmetics available in Poland.

The increasing amount of marine microplastics and nanoplastics is due to primary (P-MPs) and secondary sources (S-MPs). Among small P-MPs and fibres from textiles, nurdles or industrial dust, the microbeads from cosmetics (peelings, scrubs) are dominant. The polyethylene and polypropylene debris, already <5 mm, enlarge Plastisphere and have a complex influence on environmental processes. Fortunately, the situation has changed with the limitation of synthetic materials in scrubs in recent years. This paper summarizes the six years of studies (2015-2021) on microplastics in cosmetics available on the Polish market. It focuses on those still available and presents the potential of Raman spectroscopy for the efficient qualitative and quantitative characterization of those materials. Finally, surface morphology's vital role in microplastics' general behaviour is underlined. The SEM/EDX and numerical modelling enables a more detailed description of particles.

Adsorption mechanisms of chlorobenzenes and trifluralin on primary polyethylene microplastics in the aquatic environment.

Microplastics are ubiquitous in aqueous media, and the importance of considering their impact on the behaviour of other compounds in water has often been highlighted. This work thus investigates the adsorption mechanism of six priority substances (as defined by European Union legislation: trichlorobenzenes (1,2,3-TeCB, 1,3,5-TeCB, 1,2,4-TeCB), pentachlorobenzene (PeCB), hexachlorobenzene (HeCB), and trifluralin (TFL)) on primary polyethylene (PE) microplastics (polyethylene standard and polyethylene microparticles isolated from two personal care products) in Danube river water and a synthetic matrix. The maximum adsorbed amounts of the compounds investigated on PEs ranged from 227 µg/g for 1,2,3-TeCB to 333 µg/g for TFL. Equilibrium data was analysed using five isotherm models, with the best fit being described by the Langmuir model and the Dubinin-Radushkevich model indicating chemisorption as the likely sorption mechanism. In general, the Langmuir model showed that the investigated compounds will be better adsorbed on PEs in real river water, with the exception of 1,3,5-TeCB on all studied PEs, where the model predicts better sorption in the synthetic matrix. Compound characteristics and the polymer properties were the most important factors affecting the sorption process, while a significant matrix effect was also observed on PE behaviour. The fact that polyethylene particles derived from personal care products showed greater adsorption capacities than virgin PE demonstrates the necessity of investigating real-world PE samples when assessing the potential impact of MPs in the environment.

Microplastic pollution in surface water and sediments in the urban section of the Vistula River (Poland).

The main hypothesis of this study was that the microplastic (MP) concentration would be higher in the city centre. The MP (<5 mm) abundance and distribution in the urbanized section of the Vistula River were examined. Samples were collected from three different sites: 1) the less urbanized part of the city, 2) the area close to the tributary outlet and wastewater treatment plant (WWTP), and 3) the city centre. The abundance of MPs in water ranged from 1.6 to 2.55 items L-1, whereas in the sediments, it varied from 190 to 580 items kg-1. The highest MP concentration was observed in the water collected in the city centre. However, in the case of sediments, the most polluted sample was collected from a sampling point located near the WWTP and tributary outlet. The diversity of the MPs abundance along the river was associated with the hydrological and sedimentological conditions, which was confirmed by the grain size analysis of sediments. The dominant type of MPs in both the water and sediment samples was fibre. The MPs were characterized by Raman spectroscopy as polystyrene (PS), polypropylene (PP), and a variety of other materials with different levels of deterioration. The images obtained by scanning electron microscopy (SEM) showed different disintegration features. Moreover, the SEM analyses revealed the occurrence of adhered particles and diatoms on the surface of MPs. The adsorption of various elements onto the MPs surface and the adhered particles was confirmed by energy-dispersive X-ray spectroscopy. The conducted studies emphasized the significance of the impact of large urban agglomerations, such as the Warsaw metropolitan area, on the concentration of MPs in rivers. Further studies are needed to better assess, for instance, the precise mode through which MPs in urban regions are transported by rivers to the seas.

Emission of primary microplastics in mainland China: Invisible but not negligible.

Primary microplastics are mostly produced as part of the daily plastic product use. The emission process is often invisible but poses potential ecological hazards. Thus, primary microplastics deserve public attention. Due to China's huge population base and its rapid economic development, primary microplastics emissions are of both regional and global significance. This study is the first to establish the emission inventory of primary microplastics in mainland China. It was estimated that the primary microplastic waste from mainland China amounts to 737.29 Gg, and one-sixth of this amount entered the aquatic environment in 2015. The highest proportion of this waste was attributable to tire dust and synthetic fiber, accounting for 53.91% and 28.77% of the total respectively, in mainland China. The primary microplastics emissions mainly depend on the population, followed by the level of economic development. It was roughly estimated that 538 g of microplastics is produced by each person in China. At the grid scale, the spatial difference in the total primary microplastics emissions in mainland China primarily depends on the population density distribution and transportation network. We studied the entire life cycle of several sources of microplastics, from production to discharge into the aquatic environment. We suggested different control measures under different nodes. Increasing microplastics treatment in sewage treatment plants should be a short-term viable way to achieve some measure of reduction in their entry to the environment in mainland China. Our research can not only raise public awareness about primary microplastics, but can also guide the development of environmental policies to reduce plastic pollution.

Repeated detection of polystyrene microbeads in the Lower Rhine River.

Microplastics are emerging pollutants in water bodies worldwide. The environmental entry areas must be studied to localise their sources and develop preventative and remedial solutions. Rivers are major contributors to the marine microplastics load. Here, we focus on a specific type of plastic microbead (diameter 286-954 µm, predominantly opaque, white-beige) that was repeatedly identified in substantial numbers between kilometres 677 and 944 of the Rhine River, one of Europe's main waterways. Specifically, we aimed (i) to confirm the reported abrupt increase in microbead concentrations between the cities of Leverkusen and Duisburg and (ii) to assess the concentration gradient of these particles along this stretch at higher resolution. Furthermore, we set out (iii) to narrow down the putative entry stretch from 81.3 km, as reported in an earlier study, to less than 20 km according to our research design, and (iv) to identify the chemical composition of the particles and possibly reveal their original purpose. Surface water filtration (mesh: 300 µm, n = 9) at regular intervals along the focal river stretch indicated the concentration of these spherules increased from 0.05 to 8.3 particles m-3 over 20 km. This spot sampling approach was supported by nine suspended solid samples taken between 2014 and 2017, encompassing the river stretch between Leverkusen and Duisburg. Ninety-five percent of microbeads analysed (202/212) were chemically identified as crosslinked polystyrene-divinylbenzene (PS-DVB, 146/212) or polystyrene (PS, 56/212) via Raman or Fourier-transform infrared spectroscopy. Based on interpretation of polymer composition, surface structure, shape, size and colour, the PS(-DVB) microbeads are likely to be used ion-exchange resins, which are commonly applied in water softening and various industrial purification processes. The reported beads contribute considerably to the surface microplastic load of the Rhine River and their potential riverine entry area was geographically narrowed down.