Title: Mechanical formation of micro- and nano-plastic materials for environmental studies in agricultural ecosystems

Abstract

Release of microplastics (MPs) and nanoplastics (NPs) into agricultural fields is of great concern due to their reported ecotoxicity to organisms that provide beneficial service to the soil such as earthworms, and the potential ability of MPs and NPs to enter the food chain. Most fundamental studies of the fate and transport of plastic particulates in terrestrial environments employ idealized MP materials as models, such as monodisperse polystyrene spheres. In contrast, plastics that reside in agricultural soils consist of polydisperse fragments resulting from degraded films employed in agriculture. There is a need for more representative materials in fundamental studies of the fate, transport, and ecotoxicity of MPs and NPs in soil ecosystems. The aim of this study was therefore to develop a procedure to produce MPs and NPs from agricultural plastics (a mulch film prepared biodegradable polymer polybutyrate adipate-co-terephthalate (PBAT) and low-density PE [LDPE]), and to characterize the resultant materials. Soaking of PBAT films under cryogenic conditions promoted embrittlement, similar to what occurs through environmental weathering. LDPE and cryogenically-treated PBAT underwent mechanical milling followed by sieve fractionation into MP fractions of 840 μm, 250 μm, 106 μm, and 45 μm. The 106 μm fraction was subjected to wet grinding tomore » produce NPs of average particle size 366.0 nm and 389.4 nm for PBAT and LDPE, respectively. A two-parameter Weibull model described the MPs' particle size distributions, while NPs possessed bimodal distributions. Size reduction did not produce any changes in the chemical properties of the plastics, except for slight depolymerization and an increase of crystallinity resulting from cryogenic treatment. This study implies that MPs form from cutting and high-impact mechanical degradation as would occur during the tillage into soil, and that NPs form from the MP fragments in regions of relative weakness that possess lower molecular weight polymers and crystallinity.« less

Authors:

Astner, A. F. ^[1]; Hayes, D. G.  ^[1];

• Search DOE PAGES for author "Hayes, D. G."
• Search DOE PAGES for ORCID "0000-0003-0303-1411"

O'Neill, H.  ^[2];

• Search DOE PAGES for author "O'Neill, H."
• Search DOE PAGES for ORCID "0000-0003-2966-5527"

Evans, B. R.  ^[2];

• Search DOE PAGES for author "Evans, B. R."
• Search DOE PAGES for ORCID "0000-0002-2574-2567"

Pingali, S. V.  ^[2];

• Search DOE PAGES for author "Pingali, S. V."
• Search DOE PAGES for ORCID "0000-0001-7961-4176"

Urban, V. S.  ^[2];

• Search DOE PAGES for author "Urban, V. S."
• Search DOE PAGES for ORCID "0000-0002-7962-3408"

Young, T. M. ^[1]

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+ Show Author Affiliations

1. Univ. of Tennessee, Knoxville, TN (United States)
2. Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Publication Date:

Mon Jun 17 00:00:00 EDT 2019

Research Org.:

Oak Ridge National Lab. (ORNL), Oak Ridge, TN (United States)

Sponsoring Org.:

USDOE

OSTI Identifier:

1530063

Grant/Contract Number:  

AC05-00OR22725

Resource Type:

Accepted Manuscript

Journal Name:

Science of the Total Environment

Additional Journal Information:

Journal Volume: 685; Journal Issue: C; Journal ID: ISSN 0048-9697

Publisher:

Elsevier

Country of Publication:

United States

Language:

English

Subject:

54 ENVIRONMENTAL SCIENCES; agricultural soils; low-density polyethylene (LDPE); microplastics; 33 nanoplastics; polybutylene adipate-co-terephthalate (PBAT); terrestrial ecosystems