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Microplastics & Nanoplastics: Fate & Behavior:
10:30am - 12:30pm USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Souhail Al-Abed, Organizer, Presider, US EPA; Xingmao Ma, Organizer, Presider, Texas A&M University; Phillip Potter, Organizer, Presider, EPA
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Division/Committee: [ENVR] Division of Environmental Chemistry

About 380 million tons of plastics are currently manufactured each year and this number could triple by 2050. They are used in wide variety of industries and rapidly accumulate in the environment after disposal. They undergo natural weathering and release microplastics (MPs) and nanoparticles (NPs), which has become a global concern due to their potential toxicity and accumulation to aquatic lives and human beings. These MPs and NPs display some typical colloidal behaviors, but also exhibit unique phenomenon in the environment, such as the establishment of unique plastisphere. In addition to investigating the environmental fate and transport of MPs and NPs, however, exciting research results are emerging that reveals that MPs and NPs can undergo photolytic or biological degradation in natural environment. Pure bacterial strains and functioning enzymes have been identified, opening doors for the potential development of effective artificial enzymes to address the plastic concerns. This symposium aims to provide a central venue for the scientific community to focus on this emerging concern and share their recent findings in the fate and behavior of MPs and NPs.

Tuesday
Investigation on the altered plant uptake of poly- and per- fluorinated substances (PFAS) by co-present microplastics
10:30am - 10:50am USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Xingmao Ma, Presenter, Texas A&M University; Xiaoxuan Wang; Weilan Zhang; Virender Sharma, Texas AM University
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Plastic products are broadly used in industries and our daily lives. Accompanied with this widespread popularity is the alarming accumulation of plastic wastes in the environment. Some of the plastic products gradually degrade into smaller plastic particles through weathering and mechanical abrasiveness, collectively called microplastics (MOs) and nanoplastics (NPs) when the particle diameter is less than 5 mm and 100 nm, respectively. The direct environmental risks posed by these MPs/NPs have attracted significant attention recently. However, due to their very large specific surface area, MPs exhibit strong adsorption capacity for a large number of environmental contaminants. Under light irradiation, MPs/NPs induce reactive oxygen species (ROS). In addition, MPs/NPs typically carry a layer of biofilm on their surface which can potentially break down environmental pollutants biologically. Therefore, MPs/NPs could alter the fate and plant uptake of co-existing environmental pollutants. Poly- and per- fluorinated substances (PFAS) are a group highly recalcitrant and hazardous chemicals. Many of these compounds are ionized under environmental conditions and display different behaviors than neutralspecies. The goal of this study was to evaluate how the co-occurring MPs/NPs could alter the plant uptake and accumulation of two common PFAS compounds: polyfluorooctanoic acid (PFOA) and its replacement hexafluoropropylene oxide dimmer acid (HFPO-DA) or GenX in a hydroponic system. Detailed results will be presented and the impact of the properties of MPs/NPs and PFAS will be discussed.
Tuesday
Removal of microplastics from water using plant based polysaccharides
10:50am - 11:10am USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Dr. Rajani Srinivasan, Tarleton State University; Jeri Laneice Gill, Presenter
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Microplastics are a new emerging contaminant that is becoming detrimental to aquatic environments globally. Scientists are developing new technologies to remove microplastics (Rachdi, 2017). In previous research in our laboratory, polysaccharides from plants such as Fenugreek, Cactus mucilage, Aloe Vera mucilage, Okra mucilage and Psyllium mucilage have been proven successful in the removal of microplastics as compared to synthetic polymers. Polysaccharides are non-toxic, biocompatible, biodegradable, polyfunctional, and highly chemically reactive (Pitkänen, 2018). They also have chelation and absorption capacities that allow them to better flocculate than synthetic polymers. The polysaccharide particle absorbs the microplastics and becomes heavy in weight and settles at the bottom, which is later filtered off (Dao, 2015).
Simulated microplastic contaminated water will be prepared by spiking deionized water with commercially available microplastics in the laboratory. Live water samples will be collected from various surface water, in and around major cities in Texas. A polymer solution, combining two or more of the above organic polymers listed with varying concentrations, will be prepared. Qualitative and quantitative microplastic analysis will be performed using a hemocytometer by observing them under a dissecting microscope at 40X magnification. Fourier transform Infrared spectroscopy will be used to study the interaction and mechanism of the polymer with microplastics. Samples will be analyzed using Raman Spectroscopy to identify the types of microplastic found in the sample.
The goal of the present research is to extract mucilage from the organic polymers Cactus, Okra, Fenugreek, Aloe Vera, and Psyllium, using them in the flocculation method. This will provide a better alternative to Polyacrylamide in the process of water treatment. The major focus of the present research is to study the efficiency of combining the polymers, listed above, in different ratios to remove microplastics more efficiently than the single polymer method.

Tuesday
Dynamics of microplastic particle deposition in porous media
11:10am - 11:30am USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
The majority of microplastic particles in the environment are located in sediments at the bottom of oceans, seas, and lakes; in groundwater aquifers; or in contaminated soils. All of these examples involve the transport of microplastic particles in a disordered, three-dimensional (3D) porous medium. In this case, not only do confinement and tortuosity imposed by the medium alter microplastic particle transport, but the particles in turn can alter the medium by depositing onto its solid matrix as they are transported, yielding coupled dynamics that pose a challenge to current understanding. Here, we elucidate these coupled dynamics by directly visualizing microplastic particle transport and deposition in transparent, 3D porous media over a broad range of length and time scales. We find that while the pore-scale distribution of deposited particles is sensitive to particle charge, their distribution throughout the entire medium is tuned by imposed pressure in unexpectedly similar ways, independent of particle charge. Specifically, at high injection pressures, hydrodynamic stresses cause particles to both deposit on and become eroded from the solid matrix continually—strikingly, forcing them to be distributed throughout the entire medium. By contrast, at low injection pressures, the relative influence of erosion is suppressed, causing particles to be localized near the inlet of the medium. Guided by these findings, we describe the evolution of the overall permeability of the medium over time, providing a quantitative description of how deposition in turn impacts fluid flow. Our results thus deepen our understanding of the multi-scale interactions between flowing fluid, microplastic particles, and a porous medium during colloidal transport, yielding guidelines for prediction and control of microplastic transport in environmental settings.
Tuesday
Leaching of bisphenol S from polyethersulfone (PES) and polyphenylsulfone (PPSU) microplastics during environmental weathering processes
11:30am - 11:50am USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Yang Li; Ms. Xinjie Wang, Presenter, Beijing Normal University; Wen Zhang, New Jersey Institute of Technology
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
This study evaluated the leaching or release behavior of Bisphenol S (BPS), a common plastic additives, from Polyethersulfone (PES) and Polyphenylsulfone (PPSU) microplastics (MPs) that may derive from commercial products such as baby bottles and battery covers. Ultraviolet (UV) irradiation, temperature and humic acid (HA) were shown to affect the BPS release kinetics, which followed the first-order kinetics. The released BPS underwent immediate photolysis under UV254 irradiation. Under UV365 nm, the highest released concentration of BPS reached 473.6 μg●L-1 at 50°C, 7.9 times that at 35°C and 36.1 times that at 25°C, suggesting that the release kinetics sped up under high solution temperatures. As the HA concentration in water incrementally increased to 50 mg●L-1, the BPS release rate first increased and then declined, probably because HA primarily acted as a photosensitizer at low concentrations to increase light absorption on MPs with HA coating. However, at high HA concentrations, HA may shield the light and scavenge the reactive radicals responsible for the degradation of MPs. Our results also revealed that photo oxidation of MPs led to the breakage of diphenyl ether sulfone group due to the attack of reactive oxygen species (ROS), which contributed to the leaching mechanisms of BPS. Finally, the COMSOL Multi-physics simulation described the BPS release process of different MPs at 25°C and predicted a BPS release of up to 6862.1 μg per gram of MPs within 8000 h, which provides further understandings of the fate of aquatic MPs and secondary micropollutant release.
Tuesday
Aquatic biodegradation of wood-based bathroom tissue, cotton microfibers, and flushable wipes in a wastewater treatment plant condition and a seawater environment
11:50am - 12:10pm USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
The International Union for Conservation of Nature (IUCN) estimates that between 0.8 and 2.5 Mt per year of primary microplastics are directly released into the ocean. Micro-size fibers generated from the abrasion of textiles during laundering represents 35% of these polluting microplastics. It is believed that these microfibers enter wastewater treatment plants (WWTPs) with the effluents of the washing machines and eventually make their way to the ocean waters. Along with microfibers created from laundering, microfibers are also generated and released into aquatic environments through the flushing of paper and nonwoven materials. Most wipes and paper products recommended for flushing are primarily cellulosic and, although cellulose has been found to biodegrade, this research aims to further analyze their fate in wastewater treatment plants and ocean waters. Microcrystalline cellulose, cotton microfibers, toilet paper, flushable cellulosic wipes, and polypropylene-based wipes were biodegraded in two aerobic conditions: activated sludge from a wastewater treatment plant and microbes found in seawater. Previous research has shown a potential for microfibers to biodegrade in both wastewater and seawater environments; however, this research focused on the biodegradation of paper and nonwoven materials to simulate more realistic, home-use conditions. Percent biodegradation is calculated for each material in each condition as the amount of CO2 released relative to the total amount of elemental carbon in the raw material. Materials were characterized with FTIR, SEM, XRD, and TGA to determine their polymeric composition, construction, and crystallinity. We hypothesize biodegradation should be higher for materials with greater amounts of cellulose with the polypropylene-based wipes having the lowest amount of biodegradation in both conditions. Results aim to provide a more robust and complete picture of the fate of microfibers, bathroom tissue, and wipes in aquatic environments as well as their existence as an ocean pollutant.
Tuesday
Post-consumer recyclates (PCR) in asphalt pavement: Is the production of microplastics a concern?
12:10pm - 12:30pm USA / Canada - Eastern - August 24, 2021 | Room: Thomas Murphy Ballroom Sections 1 & 2
Division: [ENVR] Division of Environmental Chemistry
Session Type: Oral - Hybrid
Waste plastics have attracted much attention because of their potential environmental impact. A possible circular economy approach is to utilize Post-Consumer Recyclates (PCR) to create high-performance asphalt pavement, while simultaneously sequestering PCR. The potential production of microplastics (MP) from PCR in the asphalt pavement, however, is currently unknown. In this presentation, we report on methods developed to evaluate potential MP production using the Hamburg wheel-track test and a water permeability test. Variants of these tests commonly used to assess asphalt pavement materials were developed, where lab-accelerated deformation, abrasion, and cracking were imposed, followed by water sampling and analysis. The identification and quantification of MPs in water samples were accomplished by Nile red staining, followed by fluorescence microscope imaging and Image J analysis. Additionally, environmental scanning electron microscopy was conducted to characterize the nanoscale morphology of the embedded PCRs. The results showed that while MP could be released from the PCR-amended pavement, its level is about 3 orders of magnitude less than what could be emitted from tire wear, so the relative impact of MP from PCRs in the asphalt pavement might be minimal.
Oxygen and Carbon elements of pavement leachate

Oxygen and Carbon elements of pavement leachate