Investigations of Microplastics - Guanajibo

Investigation of Microplastics In The Unique Coastal Environment of Guanajibo Beach, Puerto Rico: New Constraints in a Polluted Environment

Researchers, Department of Geology and Environmental Earth Science

Introduction

Research Questions

Researchers, Department of Geology and Environmental Earth Science

Ethan Belak, Ethan Krekeler, Mark P.S. Krekeler

Introduction

Microplastics are defined as plastics smaller than 5mm in diameter. Microplastics are a relatively new pollutant of investigation, with the term microplastic first appearing in 2004 by Thomson et al, with over ninety percent of all papers on the topic being published after 2009 (Schmid et al. 2021; Sorensen and Jovanovic, 2021). They have been shown to be ubiquitous, even in remote ecosystems (Feng et al. 2020).

The main concern surrounding microplastics comes from their ability to be bioaccumulated and biomagnified, especially in marine environments (Zhou et al, 2022). It has been shown that in sufficient quantities they can disrupt lysosomal membrane function in mussels, which presents a potential hazard if this effect is widespread or universal (Moos et al. 2012). This study aims to quantify microplastics in the marine environment of Guanajibo Beach, Puerto Rico. While there are no universal methods for microplastic analysis, common methods include floatation, centrifugation, peroxide digestion, and microscopy. All of these methods were utilized in this initial investigation to find comparative levels of pollution. Previous work has been done on this beach to characterize the sand and microplastic. Aiming to the understand the correlation between macroplastic and microplastic pollution could potentially reveal best mitigation practices for this invisible environmental concern.

Research Questions

How prevalent are microplastics in this setting?

How do we separate microplastics from sediment?

How do we identify microplastics?

What's the geologic background of the pollution?

Background

The dark sands of Guanajibo beach are defined by a higher mafic concentration, rich in pyroxenes and serpentinite. The beach itself it also very high in plastic pollution, largely old car tires.

Methods

Sediment from the beach surface was collected and dried. A sample (~30g) was heated to 75 C for thirty minutes in 30 mL hydrogen peroxide (30%) to dissolve organics. This sediment was then added to ~400 mL of a calcium chloride solution with a density of 1.3 g/mL. It was stirred and allowed to sit for ten minutes. The supernatant was then vacuum filtered, this was repeated twice more. The filter paper was then thoroughly rinsed and the microplastics were then concentrated via centrifugation. The liquid was then examined under light microscopy to obtain point counts. Identification methods are shown below. Image of centrifuge set to 3000 RPM for 10 min to the right.

Identification

Non-microplastics

Figure 1. These are three structures that look like microplastics but have some attributes that indicate they are of organic or geologic origin. Image A has an abundance of branching and additional structures that would not be found on microplastics, this is most likely cellulose. Image B looks very circular like that of microbeads, however, the patterned shape and colony like structures indicate this is most likely algae that was separated. Hydrogen peroxide digestion can reduce this occurrence. Image C lacks a uniform color and does not appear “waxy” like a microplastic fragment would. This is most likely a porous sand grain that floated with the microplastics.

Microplastics

Figure 2. These are all good examples of what microplastics might look like, a good example of a fiber can be seen in Figure 4. Image A likely originated from a car tire, it is discernable from dark sand grains due to a solid color around the perimeter and inability to shatter when pressure is applied. Image B likely came from a plastic bag as it has a deep blue color and very flat and flexible appearance. Image C is hard to see, but has very rigid borders (uncharacteristic of air bubbles) and has a very uniform coloration and structure.

Results

Background levels of pollution are gathered from QinghaiTibet Plateau and quantified by Feng et al. 2020. Heavy Urbanization and high industrial activity were described areas from the Amazon near the City of Manuas, Brazil (Gerolin et al. 2020). Manuas has a population of roughly 2.2 million individuals and the area is characterized by heavy industry. Guanajibo Beach is roughly 5 km from Mayaguez PR with a population of around 80,000 people.

Discussion

The microplastic pollution is similar to that of Solimoes, Brazil. Guanajibo beach and surrounding area is less populated but presents a similar microplastic concentration. This is likely due to the large amount of microplastic debris located in the area. The moderate level of pollution is largely clear colored fibers, which matches many other regional descriptions. Interestingly, while Guanajibo beach has a very large car tire pollution concern, from this initial investigation, synthetic rubber is not a major microplastic contributor. This could be due to the additives present in car tires to make them more durable, such as rutile, described by reflective spectroscopy. Future work aims to look at more samples to build a more comprehensive understanding, and to observe contamination controls. Light microscopy counts are planned to be supported by nile red staining and fluorescent microscopy. Obtaining information on the extent of this pollution is crucial as it is likely to increase inflammation, cause digestive and cardiovascular issues, and damage cells (Jadoun et al. 2023).

References

[1] Feng, S., Lu, H., Tian, P., Xue, Y., Lu, J., Tang, M., Feng, W. (2020). Analysis of microplastics in a remote region of the Tibetan Plateau: Implications for natural environmental response to human activities. Science of The Total Environment. 739, 140087. [2] Gerolin, C., Pupim, F., Sawakuchi, A., Grohmann, C., Labuto, G., Semensatto, D. (2020). Microplastics in sediment from Amazon Rivers, Brazil. Science of The Total Environment. 749, 141604. [3] Moos, N., Burkhardt-Holm, P., Köhler, A. (2012). Uptake and Effects of Microplastics on Cells and Tissue of the Blue Mussel Mytilus edulis L. after an Experimental Exposure. Environmental Science and Technology. 46(20), 11327-11335. [4] Schmid, C., Cozzarini, L., Zambello, E. (2021). Microplastic’s story. Marine Pollution Bulletin. 162, 11820. [5] Sorensen, R., Jovanovic, B. (2021). From nanoplastic to microplastic: A bibliometric analysis on the presence of plastic particles in the environment. Marine Pollution Bulletin. 163, 111926. [6] Thompson, R., Olsen, Y., Mitchell, R., Davis, A., Rowland, S., John, A., McGonigle, D., Russel, A. (2004). Lost at Sea: Where is All the Plastic? Science. 304(5672), 838. [7] Zhou, A., Zhang, Y., Xie S., Chen, Y., Li, X., Wang, J., Zou, J. (2020). Microplastics and their potential effects on the aquaculture systems review. Reviews in Aquaculture. 13(1), 719-733. [8] Liu, S., Shi, J., Wang, J., Dai, Y., Li, H., Li, J., Liu, X., Chen, X., Wang, Z., Zhang, P. (2021). Interactions Between Microplastics and Heavy Metals in Aquatic Environments: A Review. Frontiers in Microbiology. (12). Jadoun, S., Fuentes, J., Yepsen, O., Yanez, J. (2023). Removal of Environmental Microplastics by Advanced Oxidation Processes. ResearchGate. 109(125).

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