Sampling for Micro-Plastics
Selecting the Ideal Site
Once you've built a collection device and have sieves, it's time to identify a site (or multiple sites) where you would like collect samples. Microplastics often enter rivers through sewage or post-processing effluent from wastewater treatment plants, so we focused our study on one wastewater treatment plant and at multiple combined sewer overflows, which release sewage into the Hudson during significant rain events. Sound gross? It is! You can learn more about them here.
Here are some links to get you started in finding good spots across New York City:
For more information on wastewater treatment plants throughout the City, visit the NYC DEP's website.
For more information on CSOs, visit the Open Sewer Atlas or view locations in this interactive map.
Other places that might be interesting for sampling could be near industrial sites, in slow-moving vs. fast-moving water, or just near a spot you care about. In order to get more consistent data, it is better to pick a spot that is most convenient for you to access.
Get Out There and Sample
Once you've selected a site, go visit! We sampled during slack tide, and tried to always have two people present for safety-purposes, to help with note-taking, and to make collection easier.
To sample, get as close to your desired spot as possible. Carefully lower your DIY sample collector down into the water, allowing for the mason jar to completely fill. Then, use both hands to pull up the mason jar, dump out any excess over 600 mL, and pour it through your stacked set of sieves. Be sure to pour slowly, to ensure that all water filters through the mesh without overflowing. Repeat this procedure as much as your protocol demands--we repeated this process 15 times, so that we would have samples representing 9-Liters of water [15 x .6L].
Next, have some small glass vials ready; one for each sieve you use, plus a couple extra in case of any breakage. Use distilled water to loosen material on your sieves, and then use this water to direct all material into your vials. A stainless steel funnel can make this process easier. Please see the videos below for a brief walk-through on using the DIY sampler, as well as rinsing the sieves post-collection.