An official website of the United States government
Abstract Microplastics (MPs) are an emerging class of pollutants in air, soil and especially in all aquatic environments. Secondary MPs are generated in the environment during fragmentation of especially photo-oxidised plastic litter. Photo-oxidation is mediated primarily by solar UV radiation. The implementation of the Montreal Protocol and its Amendments, which have resulted in controlling the tropospheric UV-B (280–315 nm) radiation load, is therefore pertinent to the fate of environmental plastic debris. Due to the Montreal Protocol high amounts of solar UV-B radiation at the Earth’s surface have been avoided, retarding the oxidative fragmentation of plastic debris, leading to a slower generation and accumulation of MPs in the environment. Quantifying the impact of the Montreal Protocol in reducing the abundance of MPs in the environment, however, is complicated as the role of potential mechanical fragmentation of plastics under environmental mechanical stresses is poorly understood.
more »
« less
Insights into the mechanism of plastics’ fragmentation under abrasive mechanical forces: An implication for agricultural soil health
Abstract The application of agricultural plastic products such as mulch, greenhouse covers, and silage films is increasing due to their economic benefits in providing an early and better‐quality harvest. However, mechanical abrasion of these plastic materials by soil particles could result in generation of microplastic (MP) pollutants that could harm soil organisms and impact food safety. This study aims to better understand the physicochemical mechanisms resulting in the fragmentation of low‐density polyethylene (LDPE). Herein, we used pellets and films to study the impacts of abrasive wear forces on their surface morphology variations and fragmentation behavior. An innovative laboratory approach was developed to abrade the plastic surface under controlled normal loadings and abrasion durations. The investigation of the plastics’ surface morphology variations due to the abrasion process revealed microcutting as the dominant process at low normal force (4 N). However, a combination of microploughing and microcutting occurred for new LDPE films by increasing the normal force to 8 N. Despite the significant surface morphology variations of the new LDPE film due to the abrasion process; the water contact angle did not alter. Furthermore, the fragmentation behavior of photodegraded LDPE pellets and films was compared to the new plastics. The extent of MPs (3 µm < dp < 162 µm) generation due to fragmentation was studied using fluorescence microscopy imaging. The localized stress and strains at the contact sites of plastic and sand particles resulted in abrasion of the plastic surface. According to the results, the normal loadings and duration of abrasion played a significant role in the degree of fragmentation of plastics. Increasing the normal loading applied during the abrasion process from 2 to 8 N linearly increased the number of generated plastic fragments by more than five times for pellets and more than three times for film. Photodegradation significantly enhanced the extent of MPs fragmentation. Moreover, the limitations of this study and the implications for agricultural soil health were discussed.
more »
« less
- Award ID(s):
- 2305189
- PAR ID:
- 10497023
- Publisher / Repository:
- Wiley
- Date Published:
- Journal Name:
- CLEAN – Soil, Air, Water
- Volume:
- 51
- Issue:
- 8
- ISSN:
- 1863-0650
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
More Like this
-
-
Abstract Plastics have become an integral component in agricultural production as mulch films, nets, storage bins and in many other applications, but their widespread use has led to the accumulation of large quantities in soils. Rational use and reduction, collection, reuse, and innovative recycling are key measures to curb plastic pollution from agriculture. Plastics that cannot be collected after use must be biodegradable in an environmentally benign manner. Harmful plastic additives must be replaced with safer alternatives to reduce toxicity burdens and included in the ongoing negotiations surrounding the United Nations Plastics Treaty. Although full substitution of plastics is currently not possible without increasing the overall environmental footprint and jeopardizing food security, alternatives with smaller environmental impacts should be used and endorsed within a clear socio-economic framework. Better monitoring and reporting, technical innovation, education and training, and social and economic incentives are imperative to promote more sustainable use of plastics in agriculture.more » « less
-
While microplastics (MPs) are globally prevalent in marine environments, extending to the Arctic and sub-Arctic regions, the extent and distribution of MPs in terrestrial waters, drinking water sources, and recreational water in these areas remain unknown. This field study establishes a baseline for MPs in surface water sources, including lakes, rivers, and creeks, as well as in snow across three geo-locations (i.e., Far North, Interior, and Southcentral) in Alaska. Results (mean ± SE) show that the highest MP counts exist in snow (681 ± 45 L−1), followed by lakes (361 ± 76 L−1), creeks (377 ± 88 L−1), and rivers (359 ± 106 L−1). The smallest MPs (i.e., 90.6 ± 4 μm) also happened to have occurred in snow, followed by their larger sizes in lakes (203.9 ± 65 μm), creeks (382.8 ± 136.5 μm), and rivers (455.4 ± 212 μm). The physical morphology of MPs varies widely. MP fragments are predominant (i.e., nearly 62–74%) in these sites, while MP fibers (nearly 13–21%), pellets (nearly 13–18%), and films (<6%) also exist in appreciable quantities. Geolocation-wise, the Far North, where MPs were collected from off-road locations, shows the highest MP counts (695 ± 58 L−1), compared to Interior (473 ± 64 L−1) and Southcentral (447 ± 62 L−1) Alaska. Results also indicate that the occurrence of MPs in the source waters and snow decreases with increasing distance from the nearest coastlines and towns or communities. These baseline observations of MPs in terrestrial waters and precipitation across Alaska indicate MP pollution even in less-explored environments. This can be seen as a cause for concern with regard to MP exposure and risks in the region and beyond.more » « less
-
As the levels of plastic use in global society have increased, it has become crucial to develop statute, regulation, and policy to regulate plastics of all sizes including both microplastics and nanoplastics (MPs/NPs). In this paper, the published literature on the current laws passed by Congress and regulations developed by various federal agencies such as the EPA and the FDA in the USA that could be used to regulate MP and NPs have been reviewed and analyzed. Specifically, statutes such as CWA, SDWA, TSCA, RCRA and the CAA can all be used to address plastic pollution. However, these statutes have not been invoked for MP and NP waste in water or air. The FFDCA provides guidance on how the FDA should evaluate plastics use in food, food packaging, cosmetics, drug packaging, and medical devices. Currently, the FDA has recommended that acceptable levels of ingestible contaminate from recycled plastic is less than 1.5 µg /person/day which is 476,000 times less than the possible ingested daily dose. Plastic regulation is also present at the state level. Local states have banned plastic bags, and several cities have banned plastic straws. California is the only state to begin to focus on monitoring MPs in drinking water. The future of MP regulation in the USA should use TSCA to test for the safety of plastics. The other statutes simply need to include MPs in their definitions. In terms of the FDA, MPs should be redefined as contaminants—allowing tolerances for MPs to begin to be set for MPs in food and beverages. Through minor changes of how MPs are classified, it is possible to begin to use the current statutes to understand and begin to minimize the possible effects of MPs on human health and the environment.more » « less
-
Although the relationship between plastics and their embedded small molecules has been previously hypothesized, direct and systematic evidence remains limited. Herein, we introduced an innovative approach to validate this relationship by screening specific small molecules as markers to decode plastic information. Given the mature techniques available for polymer identification, enabling subsequent validation, this study focused on screening polymer-specific small molecule markers. Specifically, plastic samples of various polymer types─including raw plastic pellets and postprocessed plastic products─were collected, extracted, and analyzed with a nontargeted method. Distinct polymer-based features were observed in raw plastic pellets: 21 in polyethylene (PE), 69 in polypropylene (PP), 119 in poly(ethylene terephthalate) (PET), and 14 in polystyrene (PS). Of these, 2, 28, 101, and 10 features were also detected in postprocessed plastic products of the same polymer, indicating these co-occurring features could serve as polymer-specific markers. Representative markers were identified, including Irganox 1010 transformation products in PP-based plastics, PET oligomers in PET-based plastics, and dibenzoylmethane in PS-based plastics. These markers were then used to identify the polymer type of two additional plastic bottles as PET, consistent with results obtained from pyrolysis-gas chromatography/mass spectrometry. This work provides a proof-of-concept for employing small molecule markers to decode plastic-related information.more » « less
- Free Publicly Accessible Full Text
-
Accepted Manuscript
- Journal Article:
- https://doi.org/10.1002/clen.202200395
