Plastics Pollution in Aquatic Environments

Dear Colleagues,

The aquatic environment is known to be heavily polluted with plastics, including microplastics that are released into the environment directly from everyday-use plastic items, wastewater treatment plants, polymer degradation and industries. One of the current concerns is that when these contaminants enter the water, aquatic life may feed on them, and the microplastics may enter the food chain and cause serious health risks. However, little is known about their distribution and fate in the environment, and more research is needed to answer questions such as the following: What happens to the plastics when in the aquatic environment in relation to degradation, biodegradation and fragmentation? How does the environment affect the plastics?

Another important aspect is the plastic products from biodegradable sources that are presented as a sustainable alternative to conventional plastics and a solution to marine plastic pollution. However, concern regarding bioplastics is that the use of additives could leach more effectively to the environment through microplastics.

This Special Issue welcomes manuscripts on all aspects related to studies on plastic pollution in the aquatic environment, including the fate and distribution of plastics, plastic degradation, fragmentation, biodegradation, and the production of materials that involve greater sustainability and less harm to the environment. Both research and review papers are welcome.

Dr. Juliana Aristéia De Lima
Dr. Karin Mattsson
Guest Editors

Manuscript Submission Information

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Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Environments is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 1800 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

• degradation
• fragmentation
• biodegradation
• polymer characteristics
• micro- and nanoplastics
• aquatic environment
• characterisation methods
• microscopy
• spectroscopy
• green materials
• bioplastics
• microplastics

Plan paper 1:

Title: Kinetics of enzymatic decomposition of amylose-based bioplastics at low water activity.

Authors: Marwa Faisal ^{1, †}, Camilla Frederikke Skovbjerg ^{1, †}, Yu Tian ^{1, †} Kim Henrik Hebelstrup ² Bent Larsen Petersen¹ and Andreas Blennow ^1,*

Affiliation: 1. Department of Plant and Environmental Sciences, Faculty of Science, University of Copenhagen, Frederiksberg C, DK-1871, Denmark; 2. Department of Agroecology, Aarhus University, 4200 Slagelse, Denmark

Abstract: Starch-based bioplastics offer a promising alternative to conventional plastics, especially as a fully compostable. However, its microbial degradation is not well-known, especially plastics made of robust starch materials such as amylose and at varying water activity. In this study, amylose granules and subsequently amylose-based bioplastics were subjected to amyloglucosidase-assisted degradation at different water activities spanning 60 – 100% water using polyethylene glycol (PEG) to reduce water activity during degradation. The interfacial kinetics of degradation was tested at the optimal water activity using interfacial Michaelis-Menten combined with a Langmuir adsorption approach allowing enzymatic attack sites onto the amylose and amylose-based bioplastics to be calculated. Our data show that, due to molecular organization, the bioplastics were surprisingly resistant towards hydrolysis and that enzyme hydrolytic activity was dependent on the water activity following the Sabatier principle, i.e., optimal adsorption of the enzyme onto the bioplastics surface was directed by the water activity.

Submission date: June 2024

Plan paper 2:

Title: Temporal and Spatial Variations in Microplastic Concentrations in Small, Headwater Basins in the Southern Blue Ridge Mountains of North Carolina, USA.

Authors: Miller, Jerry¹; Barrett, Nathaniel¹; Love, Jason², Youker, Robert³; Hall, Chloe², McGraw, Emma¹; Meiri², Noa; Randall, Georgeanna³; Gray, Austin⁴

Affiliation: 1. Western Carolina University; 2. Virginia Tech.

Abstract: Microplastics (MPs), small pieces of plastic < 5 mm in size, are considered a pollutant of emerging concern on a global scale, and have increasingly become a research topic of widespread interest. Unlike marine environments, data pertaining to freshwater streams remain limited, particularly within relatively undeveloped headwater basins. In this paper, we examine the spatial and temporal variations in MP concentrations and character (color, shape, composition) within two headwater basins of the southern Blue Ridge Mountains by collecting and analyzing samples at multiple sites over a range of flow conditions. A subset of collected particles were characterized to the polymer or additive level, indicative of anthropogenic particles. Particle concentrations ranged from 0 to ~60 particles/L, about 90 % of which were red, purple, or black/blue fibers. As expected, particle concentrations tended to increase with increasing development in both basins but were surprisingly high in small, undeveloped, high-elevation subbasins. We hypothesize that elevated concentrations in these latter subbasins are related to the atmospheric deposition of MPs (and other anthropogenic particles), and limited flow volumes (discharge) in stream channels, particularly during rainfall events. Temporally, concentrations varied between sites and between storms at a site. While particle concentrations increased during runoff events at some sites, at others, they either decreased or remained the same as stream flows increased. We speculate that these temporal variations are related to the complex interplay between precipitation and runoff intensities, as well as MP source locations and contributions, including road crossings, storm drains, channel bed sediments, and tributaries.