What determines accuracy of chemical identification when using microspectroscopy for the analysis of microplastics?

Microplastic and other anthropogenic microparticles in Arctic char (Salvelinus alpinus) and their coastal habitat: A first-look at a central Canadian Arctic commercial fishery

In the recent monitoring guidelines released by the Arctic Monitoring and Assessment Program's Litter and Microplastic Expert Group, Arctic salmonids were recommended as an important species for monitoring plastics in Arctic ecosystems, with an emphasis on aligning microplastic sampling and analysis methods in Arctic fishes. This recommendation was based on the minimal documentation of microplastics in Northern fishes, especially Arctic salmonids. In response, we worked collaboratively with local partners to quantify and characterize microplastics in Arctic char, Salvelinus alpinus, and their habitats in a commercial fishery near Iqaluktuuttiaq (Cambridge Bay), Nunavut. We sampled Arctic char, surface water, and benthic sediments within their summer foraging habitat at Palik (Byron Bay). We found microplastics in 95 % of char with an average of 26 (SD ± 19) particles per individual. On average, surface water samples had 23 (SD ± 12) particles/L and benthic sediment <1 particles/gww. This is the first documentation of plastic pollution in Arctic char and their coastal habitats. Future work should evaluate seasonal, temporal and spatial trends for long-term monitoring of microplastics in Arctic fishes and their habitats.

Development and validation of an acid/alkaline digestion method for efficient microplastic extraction from wastewater treatment plant effluents: Sulfuric acid concentration and contact time do matter

Accurate analysis of microplastic particles (MPs) in environmental samples requires removal of interferences during sample preparation. Wastewater samples are interference-rich and thus particularly challenging, with concentrated sulfuric acid currently deemed impractical as a reagent. Therefore, this study aimed to establish a straightforward, effective, and safe method employing concentrated sulfuric acid and potassium hydroxide to eliminate interferents from effluent samples obtained from wastewater treatment plants (WWTPs). We found that 80 % sulfuric acid at room temperature with a brief contact time of 5 min was viable through a qualitative spot test involving 37 plastics categorized into three types (I, II, and III) based on their polymer structure's oxygen position. A quantitative assessment revealed that treatments involving H2SO4 and KOH (20 %, 24 h, 48 °C), either separately or in combination, had no discernible physical impact on the overall plastics, except for a subtle one for Type III plastics (e.g., nylon and PMMA) known to be labile under harsh pH conditions. This acid/alkaline digestion (AAD) method, incorporating such conditions for H2SO4 and KOH treatments, yielded a high mass removal efficacy (97.8 ± 2.4 %, n = 13) for eliminating natural particle interferents for primary, secondary, and tertiary effluent samples. Furthermore, the AAD method allowed for the determination of MPs in effluents with high surrogate particle recoveries (e.g., 95.1 % for larger than 500 μm size fraction). This method is readily adaptable to create appropriate protocols for different types of environmental matrices.

Microplastics absent from reef fish in the Marshall Islands: Multistage screening methods reduced false positives

Island communities, like the Republic of the Marshall Islands (RMI), depend on marine resources for food and economics, so plastic ingestion by those resources is a concern. The gastrointestinal tracts of nine species of reef fish across five trophic groups (97 fish) were examined for plastics >1 mm. Over 2100 putative plastic particles from 72 fish were identified under light microscopy. Only 115 of these from 47 fish passed a plastic screening method using Fourier-transform infrared microspectroscopy (μFTIR) in reflectance mode. All of these were identified as natural materials in a final confirmatory analysis, attenuated total reflectance FTIR. The high false-positive rate of visual and μFTIR methods highlight the importance of using multiple polymer identification methods. Limited studies on ingested plastic in reef fish present challenging comparisons because of different methods used. No plastic >1 mm were found in the RMI reef fish, reassuring human consumers.

Critical gaps in nanoplastics research and their connection to risk assessment

Reports of plastics, at higher levels than previously thought, in the water that we drink and the air that we breathe, are generating considerable interest and concern. Plastics have been recorded in almost every environment in the world with estimates on the order of trillions of microplastic pieces. Yet, this may very well be an underestimate of plastic pollution as a whole. Once microplastics (<5 mm) break down in the environment, they nominally enter the nanoscale (<1,000 nm), where they cannot be seen by the naked eye or even with the use of a typical laboratory microscope. Thus far, research has focused on plastics in the macro- (>25 mm) and micro-size ranges, which are easier to detect and identify, leaving large knowledge gaps in our understanding of nanoplastic debris. Our ability to ask and answer questions relating to the transport, fate, and potential toxicity of these particles is disadvantaged by the detection and identification limits of current technology. Furthermore, laboratory exposures have been substantially constrained to the study of commercially available nanoplastics; i.e., polystyrene spheres, which do not adequately reflect the composition of environmental plastic debris. While a great deal of plastic-focused research has been published in recent years, the pattern of the work does not answer a number of key factors vital to calculating risk that takes into account the smallest plastic particles; namely, sources, fate and transport, exposure measures, toxicity and effects. These data are critical to inform regulatory decision making and to implement adaptive management strategies that mitigate risk to human health and the environment. This paper reviews the current state-of-the-science on nanoplastic research, highlighting areas where data are needed to establish robust risk assessments that take into account plastics pollution. Where nanoplastic-specific data are not available, suggested substitutions are indicated.