Plastic pollution has emerged as one of the foremost environmental contaminants in aquatic systems worldwide. Plastics are multifaceted, encompassing a variety of sizes (macro/meso: >5 mm, micro: 1 um – 5 mm, and nano: <1 um), shapes (fragments, fibers, beads) and chemistries (different polymers and chemical additive compositions). Plastic reaches the aquatic environment through various sources and, once there, is subject to natural weathering processes including physical abrasion, biodegradation, and photooxidation. As such, this aquatic contaminant presents significant and unique analytical challenges. These challenges have hindered the scientific community's ability to fully measure their extent and composition, or assess ultimate environmental impact. In ‘taking the pulse’ of aquatic environments, an understanding of current plastic pollution levels as well as best-methods for analyzing their future concentration, composition and toxicity is paramount. This session invites presenters to share research on a variety of plastic-related topics, including but not limited to: current plastic pollutions levels in different aquatic ecosystems; methods for improved plastic polymer/additive detection in aquatic matrices; methods to improve analysis of small micro- and nanoplastics and related chemical constituents; analysis of plastic fate and weathering in aquatic environments; novel techniques or perspectives for measuring plastic impacts and toxicity; studies elucidating the interactions between plastics and natural aquatic biogeochemical and ecological systems. All presenters are invited to highlight key research needs related to their work. In all, this session will provide attendees with an opportunity to discuss research gaps and identify opportunities for future research collaboration on plastic pollution in aquatic environments.
Lead Organizer: Meredith Seeley, Virginia Institute of Marine Science (VIMS), William & Mary (meseeley@vims.edu)
Co-organizers:
Zhanfei Liu, University of Texas Marine Science Institute (zhanfei.liu@utexas.edu)
Mara Walters, Virginia Institute of Marine Science (VIMS), William & Mary (mfwalters@vims.edu)
Presentations
02:30 PM
Synthesis of Approaches to Estimating Global Marine Reservoirs of Plastic Pollution (9070)
Primary Presenter: Xia Zhu, Memorial University of Newfoundland (xzhu13@mun.ca)
Elucidating how much plastic debris by mass is contained in major reservoirs in the marine environment, and solving the mass balance, have long been knowledge gaps in the field. Our objective was to synthesize estimates of global marine reservoirs of plastic pollution to date, as well as the approaches used to generate these estimates. We identified a total of 22 global marine reservoir estimates across 14 studies, including 4 estimates of the coastlines reservoir spanning 0.049 to 2.06 million metric tonnes (MMT), 12 estimates of the ocean surface reservoir spanning 0.0027 to 4.9 MMT, one estimate of the ocean column reservoir (40-90 MMT), one estimate of the ocean floor reservoir (3-11 MMT), and four estimates of the ocean sediment reservoir spanning 3.05 to 905 MMT. We classified reservoir estimation approaches as data-driven or process-driven. Studies that used a data-driven approach based their reservoir estimates off of empirical data. The amount of environmental plastic data incorporated into data-driven estimates ranged from < 100 sample points to 10,000+ sample points. Studies that took a process-driven approach used mechanistic numerical models to estimate the mass of plastics in reservoirs. Interestingly, no two studies considered the same hydrodynamic processes, particle properties, and compartment-level processes in their model. Given the current state of knowledge, we discuss next steps that are necessary to further constrain estimates of global marine reservoirs of plastic pollution to achieve the ultimate goal of a mass balance.
02:45 PM
Assessing the impact of microplastics on the aquatic realm at scale: Applying newly developed microscopy, elemental analysis, and semi-automated identification techniques to Viet Nam (9106)
Primary Presenter: Max Webb, Heriot-Watt University (max.webb@hw.ac.uk)
Microplastics are omnipresent in the aquatic environment, these particles can be ingested by marine life and act as surfaces to which pathogens and heavy metals can become attached. However, their breakdown and distribution into increasingly smaller particles can make them difficult and time-consuming to analyse. Scanning electron microscopy with backscattered electron and x-ray imaging (SEM-BEX) represents a novel way to conduct regional-scale assessment of microplastics in environmental samples and characterise their physio-chemical properties. SEM-BEX provides discrete element maps alongside backscattered electron imaging in a single detector, allowing microplastics to be characterised at higher speeds than previously possible. When combined with semi-automated and machine learning image analysis, this new SEM-BEX approach has high potential to be applied as a more rapid screening tool for initial broad-scale environmental assessment, before targeting areas of greatest environmental impact. The applications of SEM-BEX to microplastics research are shown here using case studies from the Red River and Cát Ba islands in Viet Nam, and include microplastic budget calculations for a given environment, toxicity assessments by tracing the absorption and delivery of heavy metals through environments by microplastics, and in tracking the potential ingestion of microplastics by micro-organisms. Ultimately, this shows how the transfer of microplastics from the terrestrial to marine realms can be better tracked and helps to determine the environmental impact of these microplastics.
03:00 PM
Microplastic type, abundance, and distribution in the surface sediments of reservoirs within a large central Texas, USA, metropolitan area (9259)
Primary Presenter: Brent Bellinger, City of Austin (brent.bellinger@austintexas.gov)
Microplastics (MPs; <5 mm) are pollutants that increasingly pose risk to environmental and human health. MPs are closely coupled to human activities and are concentrated in urban areas. Types of MPs are primary, i.e., manufactured (e.g., beads found in personal care products, nurdles), or secondary, i.e., resulting from the breakdown of primary macroplastics (e.g., tires, synthetic textiles, fishing materials, consumer packaging). A significant amount of MPs pollution is concentrated proximally to where MPs are created, making urban aquatic systems especially vulnerable to MP pollution. In the rapidly growing Central Texas region, two reservoirs that flow through the Austin metropolitan area, Lake Austin and Lady Bird Lake, with the former system serving as the primary drinking water reservoir for the city. We therefore sought to understand the composition, abundance, and spatial distribution of microplastics within each reservoir. Surface (~top 5 cm) sediments were collected from the centerlines and near creek outlets in both reservoirs and 100 g was processed for microplastics. In both reservoirs, there was a general longitudinal trend of increasing microplastic particles counted moving downstream. Tire tread was the dominant microplastic type (range 128–2012 particles), followed by fibers (6–70) and miscellaneous “fragments” (1–42) across both reservoirs. These preliminary findings suggest that dense road networks and human activities proximal to tributaries to the reservoirs are contributing a significant amount of microplastic pollution to the reservoirs.
03:15 PM
Monitoring Microplastics In Situ with Scout, a Field-Going Microplastics Instrument (9138)
Primary Presenter: Beckett Colson, Woods Hole Oceanographic Institution (bcolson@whoi.edu)
Scout is a newly developed sensor that can detect microplastics directly in water, circumventing many of the challenges of manual analysis. The presence of microplastics has been difficult to determine due to their size and potential for contamination in manual analytical approaches. Quantifying this widespread contaminant to date has required labor-intensive manual analysis steps and costly equipment. As such, the impacts of microplastics on health and ecosystems are not fully understood. The Scout sensor uses impedance spectroscopy, an electrical technique, to monitor particles as they flow through the sensor. Microplastics can be distinguished from naturally occurring materials such as leaf litter or zooplankton using the unique electrical characteristics of plastic. This is critical for in situ measurements, as microplastics can be rare compared to naturally occurring suspended particulates. Scout can quantify microplastic size and concentration and can evaluate the relative abundance of microplastics to other particulates. We will present an overview of the measurement technique, latest improvements on Scout, and results from fieldwork in local waterways. To validate the instrument, the field measurements will be compared with results from discrete samples, analyzed in the laboratory using microscopy and ATR-FTIR.
03:30 PM
Understanding the Impacts of UV-Weathering and Plastic Additives on Microplastic Toxicity to Ammonia-Oxidizing Bacteria (9814)
Primary Presenter: Mara Walters, Virginia Institute of Marine Science/William & Mary (mfwalters@vims.edu)
Nitrification is a key nitrogen cycle pathway, essential for nutrient bioavailability and denitrification in various environments. Recent studies have shown that some microplastics can affect the nitrification activities of sedimentary and wastewater-associated microbial communities. However, it remains unclear which nitrifying taxa are negatively impacted by exposure to microplastics and to what degree variable chemical factors of microplastics in the environment, including plastic additive composition and degree of UV photooxidation, drive these effects. To investigate these questions, we conducted a four-day exposure experiment using cultures of the ammonia-oxidizing bacterium Nitrosospira sp. AV. Untreated or UV-weathered microplastics composed of polyethylene (PE), polylactic acid (PLA), polyurethane foam (PUF), or polyvinyl chloride (PVC) were added to cultures at a concentration of 1 mg/mL. Changes in nitrite and nitrate concentrations were measured to determine impacts on nitrification rates. Among polymer types, only unweathered PVC inhibited the nitrification activity of Nitrosospira sp. AV after four days. Interestingly, no inhibition was observed with UV-weathered PVC. To identify possible chemical differences driving these effects, pyrolysis-gas chromatography/mass spectrometry (Py-GC/MS) as well as solvent extraction of microplastics followed by gas chromatography coupled to quadrupole time-of-flight mass spectrometry (GC-QTOF-MS) were utilized to characterize the additive composition of the microplastics before and after UV-weathering. Both mass spectrometry analyses revealed changes in the composition of several plastic additive chemicals. Furthermore, we conducted an exposure experiment to investigate the toxicity of one additive of interest, which was detected in the toxic unweathered PVC microplastics but absent from the non-toxic UV-weathered microplastics. Our results indicated that this additive may have driven the observed effects. Overall, this work provides additional insight into the influence that microplastics and their additives may have on microbes involved in the nitrogen cycle. Furthermore, this study provides an example of how strategic analyses can pinpoint drivers of effect—a success story towards identifying practical mitigation strategies for impacts of plastics on the environment.
SS12B - Identifying, measuring and responding to plastics in the aquatic environment
Description
Time: 2:30 PM
Date: 29/3/2025
Room: W208