(Photo credit: Emma Lee/WHYY)

By Rupika Ketu, Master of Environmental Studies Student and Jaydee Edwards, PhD Student
Department of Earth and Environmental Sciences
University of Pennsylvania 

It is becoming increasingly apparent that microplastics are among the most persistent pollutants found in marine and freshwater systems [1]. Initially noted in North America in the 1970s, there has been an increase in scientific research attempting to understand the abundance and impacts of microplastics throughout the environment [2]. When plastics begin to break down into smaller particles, they become known as microplastics (MPs): an emerging contaminant of concern in the world’s waterways. MPs are plastic debris of various colors and shapes, ranging from 1 mm to 5 mm. They can be separated into two categories based on their origin: primary and secondary MPs. 

Primary MPs originate from commercial items, such as health products, beauty products, and textiles while secondary MPs result from plastic litter degradation, such as water bottles and plastic bags [3,4]. Primary MPs are mainly dispersed into waterways from industrial or domestic drainage systems, as well as wastewater treatment facilities; and secondary MPs can be fragmented due to Ultraviolet (UV) light exposure or physical abrasion and directly run off into bodies of water nearby [4]. Microplastics present themselves in various forms including beads, fibers, films, fragments, and pellets [5]. They can be made up of polymers such as polyethylene (PE), polypropylene (PP), polyvinyl chloride (PVC), polyethylene terephthalate (PET), and polystyrene (PS) [6].

Impacts of Microplastics

Microplastics are contaminants of rising concern due to the increasing abundance, possible ingestion by aquatic organisms, and potential chemical transfer of toxins [7]. MP factors such as size, shape, or surface structure contribute to the potential of these particles causing physical harm to organisms [7]. In a study on blue mussels, microplastics were found to affect tissue and cellular functions causing inflammatory tissue response and decreasing digestive cell membrane stability [7]. 

Research has also indicated that microplastics act as transport carriers for contaminants such as persistent organic pollutants (POP) which include polychlorinated biphenyls (PCBs) as well as types of heavy metals (e.g., Al, Zn, Cu, etc.) [8]. The type of plastic and surface structure of MPs influences the adsorption rates for these POPs resulting in microplastics as possibly transporting these contaminants to organismal systems [7,8]. As this research continues to surface, it is essential for studies to document types and concentrations of found microplastics to better understand their influence in the ecosystem and potential health threats.

Research Gaps

Currently, microplastics research is exponentially rising, however, standardization of sampling and analysis methodology is still being determined. Unfortunately, data is difficult to compare and confirm. Microplastics are a diverse set of particles due to factors such as size, color, surface characteristics, density, plastic type, etc. which makes it difficult to identify and quantify MPs in the environment [9,10]. Sampling methods include the use of net collections systems such as manta and neuston nets or grab sampling (collecting water in increments) [9,10]. However, inconsistencies remain when utilizing these different methods and researchers have yet to agree and standardize the range of sampling techniques [9,10]. 

Furthermore, characterization and identification require a multi-analytical approach involving instrumentation ranging from visualizing methods like scanning electron microscopy (SEM) or optical microscopy to structural techniques such as Fourier-transform infrared spectroscopy (FTIR), Raman spectroscopy, or mass spectrometry coupled with gas chromatography [8]. The issue with current analytical methods is the high expense to operate each of these instruments paired with the complexity of the technique and the significant time required to gain valuable data [8]. 

Since MP studies are still relatively new, research is two-fold. First, MP scientists are working toward inexpensive and time-sensitive solutions to current analytical methods. Second, it is essential for samples to be collected and studied in order for data to be analyzed for future studies. So far, the majority of microplastic research has been conducted in marine environments indicating a significant need for freshwater studies [7]. Microplastics have a large presence in freshwater systems meaning research in any freshwater source is essential to better understanding the impact on ecosystems [11]. 

Philadelphia Context

Particularly for Philadelphia, to date no research has been conducted for any freshwater sources in the area to the best of the authors’ knowledge. In order to better understand the current distribution of microplastics in Philadelphia’s waterways and develop a standardized analytical technique, Penn students Rupika Ketu and Jaydee Edwards from the Department of Earth and Environmental Sciences have been collaborating on their microplastic research efforts. 

Figure 1: An unknown microplastic fiber with unknown particles clinging to the surface observed under a scanning electron microscope at 1366X magnification

Rupika has been collecting surface water samples from the Poquessing Creek, a small tributary of the Delaware River located on the border of Philadelphia and Bucks County and analyzing them using FTIR with guidance from the Philadelphia Water Department. Current morphologic findings show MPs such as fibers, films, and fragments are present in the creek. FTIR analyses suggest these MPs are polymers such as polyester, polyhexamethylene isophthalate, and poly(dimer-poly-acid-co-alkyl polyamine). Coming samples will additionally be analyzed by Jaydee using an SEM which provides detailed images of MP particles. SEM can provide size estimation and surface characterization of these particles, as well as structural details (Figure 1). These particles can be studied at magnifications beyond a typical optical microscope and thereby visualized in greater detail helping us explore the fragmentation of plastic in the environment. 

Jaydee and Rupika hope to use this research to better understand the sources of these MPs and answer additional questions such as: Where do these particles originate based on their composition? How do they make their way into creeks like the Poquessing? Are MPs coming from stormwater or wastewater outlets? Jaydee and Rupika will continue to document their observations throughout the duration of their programs to find answers to these questions. The two students see their collaboration as a chance to develop a multi-analytical approach for analyzing MPs in freshwater systems in Philadelphia for the first time. 


[1] National Oceanic and Atmospheric Administration (NOAA). 2020. What are microplastics? https://oceanservice.noaa.gov/facts/microplastics.html 

[2] Masura, J., et al. 2015. Laboratory methods for the analysis of microplastics in the marine environment: recommendations for quantifying synthetic particles in waters and sediments. NOAA Technical Memorandum NOS-OR&R-48.  

[3] Cera, Alessandra & Cesarini, Giulia & Scalici, Massimiliano. 2020. Microplastics in Freshwater: What Is the News from the World?. Diversity. 12. 276. 10.3390/d12070276. 

[4] Bellasi A, Binda G, Pozzi A, Galafassi S, Volta P, Bettinetti R. 2020. Microplastic Contamination in Freshwater Environments: A Review, Focusing on Interactions with Sediments and Benthic Organisms. Environments. 2020; 7(4):30.

[5] Sartain, M., Wessel, C., Sparks, E. 2018. Microplastics Sampling and Processing Guidebook. http://extension.msstate.edu/sites/default/files/publications/p3243.pdf 

[6] Sharma V, 2020. Polymers and Microplastics: Implications on Our Environment and Sustainability. Emerging Technologies, Environment and Research for Sustainable Aquaculture. 10.5772/intechopen.89571

[7] Eerkes-Medrano, D., Thompson, R. C., Aldridge, D. C. 2015. Microplastics in freshwater systems: A review of the emerging threats, identification of knowledge gaps and prioritisation of research needs.  Water Research. 75, 63-82.

[8] Zhang, S., Wang, J., Xu, L., Qu, F., Wang, X., Wang, X., Li, Y., Sun, Y. 2019. Microplastics in the environment: A review of analytical methods, distribution, and biological effects. Trends in Analytical Chemistry. 111, 62-72. 

[9] Rocha-Santos, T., Duarte, A. C. 2015. A critical overview of the analytical approaches to the occurrence, the fate and the behavior of microplastics in the environment. Trends in Analytical Chemistry. 65, 47-53. 

[10] Gong, J., Xie, P. 2020. Research progress in sources, analytical methods, eco-environmental effects, and control measures of microplastics. Chemosphere. 254, 126790. 

[11] J.K.H. Wong et. al. 2020. Science of the Total Environment. 719, 137512.

Rupika is currently working towards a Master of Environmental Studies degree with a concentration in environmental biology. Her professional interests include water quality management including contaminants of emerging concern, such as microplastics. Rupika currently works as a research intern at both The Water Center at Penn and the Philadelphia Water Department. Prior to this, she was working in non-profit settings, analyzing and advocating for stronger watershed protection policies throughout the Delaware River Basin. She holds a B.S. in Environmental Policy, Institutions, and Behavior from Rutgers University.

Jaydee Edwards is a first-year Ph.D. student from the Department of Earth and Environmental Sciences at the University of Pennsylvania in Dr. Reto Giere’s lab group. She received her B.S. in Chemistry (May 2020) and is excited to enter into the geochemistry field studying microplastic particles. This research is exciting to her as this field is still relatively new. She looks forward to exploring the issue of MP pollution particularly in freshwater sources beginning with the Philadelphia community. Through a combination of fieldwork and lab analysis, her hope is to both contribute to the standardization of sampling techniques and methodologies for analysis while providing a thorough dataset of MPs found in Philadelphia’s freshwater.