Microplastics in different water samples (seawater, freshwater, and wastewater): Methodology approach for characterization using micro-FTIR spectroscopy

EnderScope: a low-cost 3D printer-based scanning microscope for microplastic detection

Low-cost and scalable technologies that allow people to measure microplastics in their local environment could facilitate a greater understanding of the global problem of marine microplastic pollution. A typical way to measure marine microplastic pollution involves imaging filtered seawater samples stained with a fluorescent dye to aid in the detection of microplastics. Although traditional fluorescence microscopy allows these particles to be manually counted and detected, this is a resource- and labour-intensive task. Here, we describe a novel, low-cost microscope for automated scanning and detection of microplastics in filtered seawater samples-the EnderScope. This microscope is based on the mechanics of a low-cost 3D printer (Creality Ender 3). The hotend of the printer is replaced with an optics module, allowing for the reliable and calibrated motion system of the 3D printer to be used for automated scanning over a large area (>20 × 20 cm). The EnderScope is capable of both reflected light and fluorescence imaging. In both configurations, we aimed to make the design as simple and cost-effective as possible, for example, by using low-cost LEDs for illumination and lighting gels as emission filters. We believe this tool is a cost-effective solution for microplastic measurement. This article is part of the Theo Murphy meeting issue 'Open, reproducible hardware for microscopy'.

Validation of an FT-IR microscopy method for the monitorization of microplastics in water for human consumption in Portugal: Lisbon case study

The growing anthropogenic contamination of natural water by microplastics (MPs) confirms the urgent need to preserve this precious resource. MPs are part of the group of contaminants of emerging concern, and the occurrence studies in surface water and water for human consumption (WHC) are mandatory for environmental and human health risk assessment. This study aims to optimize and validate a Fourier transform infrared spectroscopy method coupled with optical microscopy (micro-FTIR) in transmission mode to monitor MPs in WHC. Water sample (250 mL; without sample pre-treatment) was filtered through 5 µm silicon filters. The infrared spectra identification was performed by OMNIC mathematical correlation, using various spectra libraries for polymers (including the in-house IR spectra library), a background reading on a clean silicon filter, and an aperture of 100 µm × 100 µm. The validated method showed good accuracy, with an average recovery for representative polymers of 91%, a relative standard deviation of 13%, and a reporting limit (RL) of 44 MPs/L. Sixty WHC samples from the Lisbon water supply system showed MPs ranging from 0 (< RL) to 934 MPs/L, with an average value of 309 MPs/L. The most representative polymers were polyethylene (PE, 76.8%), polyethylene terephthalate (PET, 6.9%), polypropylene (PP, 6%), polystyrene (PS, 4%), and polyamide (PA,4%). In terms of size, the microplastic particles had an average length and width of 76 µm and 39 µm, respectively.

Microplastics in different water samples (seawater, freshwater, and wastewater): Removal efficiency of membrane treatment processes

The distribution and fate of microplastics in different water sources and their treatment plants (seawater, three municipal wastewaters, a pharmaceutical factory wastewater, and three drinking waters) in France were studied. Currently, research in this field is still under exploration since almost no relevant standards or policies have been introduced for the detection, the removal, or the discharge of microplastics. This study used an improved quantitative and qualitative analytical methodology for microplastic detection by μ-FTIR carried out with siMPle analytical software. By investigation, wastewater was determined to contain the most abundant microplastics in quantity (4,203-42,000 MP·L^-1), then followed by surface water/groundwater (153-19,836 MP·L^-1) and seawater (around 420 MP·L^-1). Polyethylene was the dominant material in almost all water types followed by polypropylene, polystyrene, and polyethylene terephthalate. Almost all treatment technologies could remove microplastics whatever the feed water types and concentration of microplastics, though some treatment processes or transport pipes could cause additional contamination from microplastics. The four WWTPs, three DWTPs, and SWTP in France provided, respectively, 87.8-99.8%, 82.3-99.9%, 69.0-96.0% removal/retention of MPs in quantity, and provided 97.3-100%, 91.9-99.9%, 92.2-98.1% removal/retention of MPs in surface area. Moreover, ultrafiltration was confirmed to be an effective technology for microplastic retention and control of dimensions of microplastics in smaller ranges both in field-scale and lab-scale experiments. The 200 kDa ultrafiltration membrane could retain 70-100% and 80-100% of microplastics in quantity and in surface area, respectively.