Revisiting Polymer Characterization of Plastic Types in Lake Tahoe

Back in 2023, researchers from the Desert Research Institute in Nevada used attenuated total reflection Fourier transform infrared spectroscopy (ATR-FT-IR) to investigate the polymer composition of plastic litter from the lakebed of Lake Tahoe (1).

In the lead up to Earth Day 2025, we revisit this interview with Monica Arienzo, the lead author of this study, which discusses how ATR-FT-IR spectroscopy was used to classify polymers in plastic litter types found in Lake Tahoe (1,2). In part one of my interview with Arienzo, I asked her about what the study was designed to accomplish and what question her team wanted the study to answer.

Will Wetzel: I wanted to ask you about what your study was seeking to answer. Recently, there was a previous study that was conducted by clean up the lake. So what question was your study seeking to answer?

Monica Arienzo: In 2022, Clean Up The Lake, which is a nonprofit based in Nevada, led a scuba and a cleanup along the lakebed of Lake Tahoe at six transects, and we ended up studying five of them. Basically, what Clean Up The Lake had done during that initial work was that they took the litter that they collected and brought it back to shore. They categorized the litter based on different litter type categories, and they looked at everything from aluminum cans to ceramics to the type of plastic we were interested in, which was the plastic type.

They weighed each category, and that was kind of what their first study was based on. It gave a broad overview of all these different litter classes and looking at the weights of them. And one of the things they found, which I think is important to think about, is that metal was the most prevalent category by weight, followed by plastic. So, in the study that my group led, we were interested in the plastics of that, but it also is important to remember that wasn't the largest category by weight.

What we wanted to do was clean up the lake while they were doing all this litter sorting. We helped them with the sorting, the weighing, the data recording, and then we went in at the very end. And the last thing we did was for each of the plastic categories, we subsampled the plastics, and then we counted the number of plastics for each category. So in addition to their weights by category, we have for the plastic categories, we have counts, and then we also have these subsamples that we took. What we really wanted to do is to compare this trash litter sorting technique, where you have litter sorted by item type. So, for example, bottles, food containers, straws, those sort of things. We wanted to look to see if the polymer composition of those litter types had any certain trends to it. We also wanted to just broadly look at what are the most prevalent litter types, polymer types in the litter categories across all of them. And then we also want to look at spatial variation from the litter counts, and then also from the polymers that we were finding.

You can see my full-length video interview with Arienzo in reference (2).

References

1. Davidson, J.; Arienzo, M. M.; Harrold, Z.; West, C.; Bandala, E. R.; Easler, S.; Senft, K. Polymer Characterization of Submerged Plastic Litter from Lake Tahoe, United States. Appl. Spectrosc. 2023, ASAP. DOI: 10.1177/00037028231201174
2. Wetzel, W. Polymer Characterization of Plastic Litter Using ATR-FT-IR Spectroscopy: An Interview with Monica Arienzo. Spectroscopy. Available at: https://www.spectroscopyonline.com/view/polymer-characterization-of-plastic-litter-using-atr-ft-ir-spectroscopy-an-interview-with-monica-arienzo (accessed 2025-04-15).