A COMPARISON BETWEEN LIGHT AND FLUORESCENCE MICROSCOPY
FOR THE QUANTIFICATION OF MICROPLASTICS IN WASTEWATER AND SLUDGE SAMPLEs
2018-2020
Graduate Student Researcher
MS Environmental Studies, Science and Technology
Advisors: Dr. Phillip Gedalanga, Public Health Department and Dr. Violet Renick, Orange County Sanitation District
California State University, Fullerton
Graduate Student Researcher
MS Environmental Studies, Science and Technology
Advisors: Dr. Phillip Gedalanga, Public Health Department and Dr. Violet Renick, Orange County Sanitation District
California State University, Fullerton
Plastic has become an integral part of our daily existence due to its wide range of daily uses. Recently, microplastics have become an important and emerging contaminant of concern (Plastics Europe, 2018; Rochman et al., 2019). Microplastics (< 5 mm in size) enter aquatic environments by several pathways including stormwater, industrial and residential runoff, the biodegradation of macro-plastic, as well as the discharge of treated wastewater from Wastewater Treatment Plants (WWTPs) (Kay et al., 2018). The purpose of this study was to conduct a comparison of the two most commonly used visual examination techniques for microplastic analyses—light and fluorescence microscopy—in real wastewater samples. We hypothesized that light microscopy would result in greater total fiber counts, and that fluorescence microscopy would result in greater overall particle counts. Samples were collected at a secondary WWTP in June and July 2019 and analyzed using light and fluorescence microscopy at California State University, Fullerton. Overall, 24,649 suspected microplastic particles (SMPs) were visually identified using fluorescence microscopy compared to 10,539 SMPs in the same samples analyzed with light microscopy. Of these suspected particles, fragment counts were greater using fluorescence microscopy at all sampling locations and fiber counts were greater using light microscopy across all samples. These results suggest that the use of one visual identification technique—light or fluorescence—may bias results for either fibers or fragments. Furthermore, it suggests that visual identification alone is not sufficiently accurate and that advanced confirmation techniques are needed to provide an accurate assessment of SMP concentrations in wastewater treatment.