Since the emergence of mass-produced plastics in the 1940s, the global appetite for these materials has rapidly increased. Estimates of cumulative plastic waste generated are as much as 6.3 billion metric tons. Less than 10% of this material is recycled, while nearly 80% is sent to landfills or released into the natural environment. Because of this, microplastics are now ubiquitous in the environment. Their presence has been detected in surface waters, groundwater sources such as Karst waters, sediments, wildlife, and even consumer products.
The major drawback with current microplastic sample preparation and counting is that researchers use different methods. The National Oceanic and Atmospheric Administration (NOAA) was the first to publish a standard method to measure these materials. However, it only addressed large plastic debris in surface water and beach samples. Furthermore, it can only isolate and account for materials with a density less than 1.2 g/cm3. Many microplastics, including polyvinyl chloride, polyesters, and fluoropolymers, have a density greater than 1.3 g/cm3 and are unaccounted for in preparation by NOAA’s method.
When the researchers analysed samples from the Lake Muskegon and Missouri surface waters, they discovered that they would have missed the most abundant microplastics, those less than 300 µm, if they had processed them using the standard NOAA method. Their new method achieves a lower size detection limit and greater microplastic density limit.
The researchers also designed an innovative reporting method that uses detailed size measurements of the microplastic in the sample. This new approach for data reporting allows researchers to estimate the mass of microplastics present. This measurement is important because although particle sizes can change in a sample, the overall mass remains the same.
Following development, the researchers demonstrated the method with surface waters collected from three locations and fish larvae samples archived by the Illinois Natural History Survey.
The work is detailed in ISTC’s new research report, Development and Demonstration of a Superior Method for Microplastics Analysis: Improved Size Detection Limits, Greater Density Limits, and More Informative Reporting.