Year-Long Microbial Succession on Microplastics in Wastewater: Chaotic Dynamics Outweigh Preferential Growth.

Microplastics are a globally-ubiquitous aquatic pollutant and have been heavily studied over the last decade. Of particular interest are the interactions between microplastics and microorganisms, especially the pursuit to discover a plastic-specific biome, the so-called plastisphere. To follow this up, a year-long microcosm experimental setup was deployed to expose five different microplastic types (and silica beads control) to activated aerobic wastewater in controlled conditions, with microbial communities being measured four times over the course of the year using 16S rDNA (bacterial) and ITS (fungal) amplicon sequencing. The biofilm community shows no evidence of a specific plastisphere, even after a year of incubation. Indeed, the microbial communities (particularly bacterial) show a clear trend of increasing dissimilarity between plastic types as time increases. Despite little evidence for a plastic-specific community, there was a slight grouping observed for polyolefins (PE and PP) in 6-12-month biofilms. Additionally, an OTU assigned to the genus Devosia was identified on many plastics, increasing over time while showing no growth on silicate (natural particle) controls, suggesting this could be either a slow-growing plastic-specific taxon or a symbiont to such. Both substrate-associated findings were only possible to observe in samples incubated for 6-12 months, which highlights the importance of studying long-term microbial community dynamics on plastic surfaces.

Agricultural application of microplastic-rich sewage sludge leads to further uncontrolled contamination.

Municipal sewage sludge has been shown to be high in microplastics (MP) and is applied to agricultural land as fertiliser in many countries. The authors recently proposed in a viewpoint article that MP applied to land in this way may well contaminate other areas in an uncontrolled way. This study examined experimental plots with known history of application of sewage sludge. Results showed that 44% of the MP load found on sludge-applied land was found on nearby land never directly applied with sludge. Examination of polymer type compositions demonstrated marked similarity between the two fields indicating the sludge-applied field was a source of contamination for surrounding areas. Furthermore, MP was detected at a depth of 60-90 cm in the sludge-applied soil indicating that MP may also penetrate deep enough to reach agricultural drainage systems, although this effect is slight (1.6% of surface load). These results show that application of municipal sewage sludge on agricultural land can lead to further uncontrolled contamination, paving the way for future research to improve understanding of the extents of such effects on real farms to better inform future agricultural policy.

High-Throughput Analyses of Microplastic Samples Using Fourier Transform Infrared and Raman Spectrometry.

Determining microplastics in environmental samples quickly and reliably is a challenging task. With a largely automated combination of optical particle analysis, Fourier transform infrared (FT-IR), and Raman microscopy along with spectral database search, particle sizes, particle size distributions, and the type of polymer including particle color can be determined. We present a self-developed, open-source software package for realizing a particle analysis approach with both Raman and FT-IR microspectroscopy. Our software GEPARD (Gepard Enabled PARticle Detection) allows for acquiring an optical image, then detects particles and uses this information to steer the spectroscopic measurement. This ultimately results in a multitude of possibilities for efficiently reviewing, correcting, and reporting all obtained results.

When every particle matters: A QuEChERS approach to extract microplastics from environmental samples.

The identification of microplastics (MP), especially small (<500 µm) MP, using automated surface-chemistry approaches requires the best possible reduction of natural particles whilst preserving the integrity of the targeted synthetic polymers particles. In general, both natural and synthetic particles can be highly diverse physically and chemically and MP extraction, particularly from complex matrices such as sediments, sludge and soils, requires efficient method pipelines. Our paper presents a universal framework of modular protocols (presented in a decision tree) that fulfil predefined user requirements (QuEChERS: Quick, Easy, Cheap, Effective, Rugged, Safe) as well as providing best practises for reasonable MP working conditions within a standard laboratory. New procedures and technical innovations for density separation of particle-rich matrices are presented, such as a spiral conveyor developed and validated for MP recovery. In sharing such best-practice protocols, we aim to help in the push towards MP quantification method standardisation. •Publication of protocols of an entire MP extraction (10 µm - 5 mm) pipeline for particle-based analysis of various environmental matrices•Modularity: Optimised quantitative sample preparation adapted to particle sizes and sample matrices•New protocols and technical innovations (e.g. spiral conveyor) optimise MP extraction.

Paint particles are a distinct and variable substrate for marine bacteria.

While paint particles are an important part of the microplastic sphere, they have, as yet, received much less research coverage, particularly regarding microplastic-microbiological interactions. This study investigated the biofilm communities of a variety of paint particles from brackish sediment using 16S rRNA gene sequencing. Paint particle biofilm communities appear to be distinct from natural (water and sediment), non-synthetic particle (cellulose) and common microplastic biofilm communities. Notably, there appears to be 1 group of sulphate-reducing bacteria from the Desulfobacteraceae family, Desulfatitalea tepidiphilia, that dominate certain paint biofilms. Of the 8 investigated paint-associated communities, four paints displayed this high Desulfobacteraceae presence. However, it is currently unclear from the chemical analysis performed of the paint surface chemistry (ATR FT-IR spectroscopy, Raman spectroscopy, SEM-EDX) what the drivers behind this might be. As such, this study provides important insights as the first to analyse microplastic-paint biofilm communities and paves the way for future research.

Is this your glitter? An overlooked but potentially environmentally-valuable microplastic.

As microplastic pollution evolved to a well-established research field, microplastic scientists started to explore new avenues in the field. Yet, while a multitude of different types of microplastics (microbeads, fibres, fragments) have been well-documented in microplastic literature, our analysis of this literature shows that glitter particles have been overlooked by the field. However, due to the presence of glitter-based research in forensic science, we explore the idea that glitter may have the potential to act as "flag items" - or markers - of a likely source, due to the often complex and individual composition of glitter particles compared to traditional microplastics, such as microbeads. As such, this article demonstrates glitter has insofar been overlooked as a microplastic particle, and demonstrates that glitter may have an important role in explaining microplastic pollution dynamics from source to sink.

Residual Monomer Content Affects the Interpretation of Plastic Degradation.

Plastic degradation rates in the marine environment are essential to understand. This study demonstrates that in plastic-microbial interaction experiments, residual monomeric and oligomeric content of PA6 significantly influences the development of dissolved organic carbon. While it is well recognized that additives in plastics should be considered during the inception of plastic-exposure experiments, residual monomers have yet to be prominently considered in the same light. As such, in degradation studies where residual contents of monomers and/or oligomers are not considered, degradation of synthetic polymers could be significantly overestimated. The substantial conversion of these monomeric and oligomeric leachates also has implications for plastic-biofilm development studies and microplastic-biota-based ingestion experiments.

Identification and Quantification of Microplastics in Wastewater Using Focal Plane Array-Based Reflectance Micro-FT-IR Imaging.

Microplastics (<5 mm) have been documented in environmental samples on a global scale. While these pollutants may enter aquatic environments via wastewater treatment facilities, the abundance of microplastics in these matrices has not been investigated. Although efficient methods for the analysis of microplastics in sediment samples and marine organisms have been published, no methods have been developed for detecting these pollutants within organic-rich wastewater samples. In addition, there is no standardized method for analyzing microplastics isolated from environmental samples. In many cases, part of the identification protocol relies on visual selection before analysis, which is open to bias. In order to address this, a new method for the analysis of microplastics in wastewater was developed. A pretreatment step using 30% hydrogen peroxide (H2O2) was employed to remove biogenic material, and focal plane array (FPA)-based reflectance micro-Fourier-transform (FT-IR) imaging was shown to successfully image and identify different microplastic types (polyethylene, polypropylene, nylon-6, polyvinyl chloride, polystyrene). Microplastic-spiked wastewater samples were used to validate the methodology, resulting in a robust protocol which was nonselective and reproducible (the overall success identification rate was 98.33%). The use of FPA-based micro-FT-IR spectroscopy also provides a considerable reduction in analysis time compared with previous methods, since samples that could take several days to be mapped using a single-element detector can now be imaged in less than 9 h (circular filter with a diameter of 47 mm). This method for identifying and quantifying microplastics in wastewater is likely to provide an essential tool for further research into the pathways by which microplastics enter the environment.