Assessment of cryogenic pretreatment for simulating environmental weathering in the formation of surrogate micro- and nanoplastics from agricultural mulch film.

Autor: Astner AF; The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America., Hayes DG; The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America. Electronic address: dhayes1@utk.edu., O'Neill H; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Evans BR; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Pingali SV; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Urban VS; Oak Ridge National Laboratory, 1 Bethel Valley Road, Oak Ridge, TN 37831, United States of America., Schaeffer SM; The University of Tennessee, Biosystems Engineering and Soil Science, 2506 E J. Chapman Dr, Knoxville, TN 37996, United States of America., Young TM; The University of Tennessee, School of Natural Resources, 2505 E.J. Chapman Dr, Knoxville, TN 37996, United States of America.
Jazyk: angličtina
Zdroj: The Science of the total environment [Sci Total Environ] 2023 Apr 20; Vol. 870, pp. 161867. Date of Electronic Publication: 2023 Jan 28.
DOI: 10.1016/j.scitotenv.2023.161867
Abstrakt: Microplastics (MPs) and nanoplastics (NPs) from mulch films and other plastic materials employed in vegetable and small fruit production pose a major threat to agricultural ecosystems. For conducting controlled studies on MPs' and NPs' (MNPs') ecotoxicity to soil organisms and plants and fate and transport in soil, surrogate MNPs are required that mimic MNPs that form in agricultural fields. We have developed a procedure to prepare MPs from plastic films or pellets using mechanical milling and sieving, and conversion of the resultant MPs into NPs through wet grinding, both steps of which mimic the degradation and fragmentation of plastics in nature. The major goal of this study was to determine if cryogenic exposure of two biodegradable mulch films effectively mimics the embrittlement caused by environmental weathering in terms of the dimensional, thermal, chemical, and biodegradability properties of the formed MNPs. We found differences in size, surface charge, thermal and chemical properties, and biodegradability in soil between MNPs prepared from cryogenically treated vs. environmentally weathered films, related to the photochemical reactions occurring in the environment that were not mimicked by cryogenic treatment, such as depolymerization and cross-link formation. We also investigated the size reduction process for NPs and found that the size distribution was bimodal, with populations centered at 50 nm and 150-300 nm, and as the size reduction process progressed, the former subpopulation's proportion increased. The biodegradability of MPs in soil was greater than for NPs, a counter-intuitive trend since greater surface area exposure for NPs would increase biodegradability. The result isassociated with differences in surface and chemical properties and to minor components that are readily leached out during the formation of NPs. In summary, the use of weathered plastics as feedstock would likely produce MNPs that are more realistic than cryogenically-treated unweathered films for use in experimental studies.
Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.
(Copyright © 2023 Elsevier B.V. All rights reserved.)
Databáze: MEDLINE
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