A Return to the Laser Lab

This week I got to journey back to the laser lab to start analyzing more of my microplastic samples. As a reminder, not all of the particles I remove from the sediment are microplastics, since it is incredibly challenge to distinguish microplastics from cotton microfibers or cellulose microparticles. The laser analysis helps me assess the chemical makeup of all the particles in my samples, since each chemical scatters light in a unique way. I currently have ~450 particles to assess with the laser, which will give me plenty to do in the next few months, but it feels nice to change my research schedule by adding another step. Although the machine itself is quite large (pictured here), the basic process of the laser analysis is comparable to using a compound microscope in a general biology class. I focus the sample underneath the lowest power objective lens and then increase to the next highest power objective lens. Once I focus the sample under the second lens, I ensure that the laser will contact the center of the particle by checking the alignment. Finally, I put on the protective cover and let the machine do its work. Laser scatter can be dangerous, but the protective cover and the clear instructions on the display ensure user safety.

Once the raman spectrum (the peaks and valleys of the chemical material) is displayed I can compare the data to known substances and determine the type of material I am working with. There are some in-between steps to make sure that dust and materials that are not part of the samples are not included in the final results, but those are far less interesting to show and talk about. My hope is to assess the polymers found in different parts of my research sites to see if there is a difference between the types of plastics I find at wastewater treatment plants and at other parts of the bay. I'm also interested in what types of polymers there are in the sediments, as most microplastics research reports the composition of plastics in the water column, which may be substantially different from what we find in the underlying sediments.

Next week I hope to show some of the next steps of microplastics analysis; I need to wait on a few items to arrive before I can get good pictures of the next steps, but I think you will find the final pieces of this research interesting, and I can't wait to share them with you.

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