Real-Time Quantification of Microplastics in Aquatic Systems via Fluorescence Microscopy

Reservoirs around the world are contaminated with up to 182,000 microplastics (MP) per m3 of water. MP contamination in reservoirs poses a threat to human and environmental health. Three stages of research are necessary for the study and eventual remediation of MP contamination in aqueous systems. First, MP contamination in reservoirs must be characterized with precise and accurate quantification. Then, MP contamination must be quantified and characterized under naturally weathered conditions. Finally, a MP removal process must be designed and implemented. An accurate and precise method of quantifying naturally degraded MPs in aqueous samples must be developed for MP research and remediation because current MP quantification technology does not suit researcher needs. Here, a fluorescence-based method that consistently and accurately quantifies MPs in approximately 45 minutes was presented. The device is user-friendly and safe for both the researcher and the environment. The pilot test method used 1 L samples initially concentrated through filtration. A 20-minute, high concentration acid-base treatment was used to remove biofilms, organic pollutants, and algal contaminants from the surface of MPs. The cleaned MPs were dyed with Nile red fluorescent dye. The dyed MPs were photographed with a microscope camera mounted on a CNC mill. The microscope-mill setup took 420 40X photos-covering the entire filter-in 14 minutes. ImageJ image analysis program quantified MPs by fluorescence wavelength, size, and circularity. A modified quantification process used bright field instead of fluorescence microscopy. The process provides a reliable quantification method with less than an hour of processing time and 30 mins processing time if samples are run sequentially. The process does not face significant legal, regulatory, economic, or safety obstacles.