Activity 3: Observing & Counting Microplastics

There are many options for capturing images using microscopy with a digital camera and/or smartphone adapter. These methods culminate in highly engaging activities for students to examine samples for microplastics and hone their microscopy skills.

Procedures

1. Allow the filter paper/slides sandwich to dry overnight wrapped loosely in foil. Excess filter paper extending outside of glass slide “sandwiches” can be trimmed with a razor blade or scissors.
2. Leave the filter paper sample between the glass slides for purposes of counting and general microscopy. This will also assist in limiting contamination from microfibers in the air.
3. Count each gridded filter paper sample at least three times for consistency using a random sampling method to select the grids on the filter paper to be counted. The number of grids counted will also be determined by the amount of time that can be dedicated to the project and the density of the sample. If not too dense, ideally the entire filter should be counted.
4. Take an in-depth look at the whole surface of the filter paper with a good quality stereoscope or compound microscope at low power. Another alternative is to use a stereoscope with a 2.0× Barlow lens threaded onto the bottom of the body tube. This will allow for a macro view of the sample, and reflective lighting makes easy viewing.
5. If necessary, take a picture of an area of the sample for viewing and count at a later time. It is helpful to use a copy of the blank gridded filter paper as a way to mark the location of microplastic that is found on the sample without disturbing the sample.
6. Microfibers, fragments, and other types of microplastics should all be included in the counts.

Summative assessment prompt.

(It is suggested that this prompt be performed after students have completed activities 1–3 and have familiarized themselves with background related to microplastics.) Students will work in small groups (3–4) to propose ideas about the frequency and potential impacts of microplastic contamination in and on the school campus. Students should think creatively about sources of microplastics and how they might be managed so that there is a reduction in air, water and soil microplastics. It is suggested that students perform this activity in a research poster session format.