Persistence in soil of microplastic films from ultra-thin compostable plastic bags and implications on Aspergillus flavus population

Authors: ACCINELLI, CESARE - UNIVERSITY OF BOLOGNA; Abbas, Hamed; BRUNO, VERONICA - UNIVERSITY OF BOLOGNA; NISSEN, LORENZO - UNIVERSITY OF BOLOGNA; VICARI, ALBERTO - UNIVERSITY OF BOLOGNA; Bellaloui, Nacer; Little, Nathan; SHIER, WAYNE - UNIVERSITY OF MINNESOTA

Submitted to: Waste Management
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 6/12/2020
Publication Date: 6/16/2020
Citation: Accinelli, C., Abbas, H.K., Bruno, V., Nissen, L., Vicari, A., Bellaloui, N., Little, N., Shier, W.T. 2020. Persistence in soil of microplastic films from ultra-thin compostable plastic bags and implications on Aspergillus flavus population. Waste Management. 113: 312-318. https://doi.org/10.1016/j.wasman.2020.06.011.
DOI: https://doi.org/10.1016/j.wasman.2020.06.011

Interpretive Summary: There is expanding use of compostable plastic materials in agriculture, such as mulching films, which will subsequently be plowed into the soil. This study investigated the effect of various indigenous Aspergillus flavus levels in soil on the formation and persistence of compostable film microplastic particles (CFMPs) from starch-based bioplastic used to manufacture things like grocery bags and mulching films. Soils with small, medium or large populations of indigenous A. flavus, caused 5.9, 9.8, and 17.1% reduction in total surface area of buried compostable film samples over a 12-month period. Despite the low levels of degradation, the number of CFMPs released increased steadily over the incubation period, particularly fragments with size <0.05 mm. Up to 88.4% of the released fragments had A. flavus associated with them and more than 68% of the A. flavus isolates from CFMPs were aflatoxigenic. A. flavus levels associated with CFMPs increased rapidly at the beginning of the 12-month incubation period, whereas the percent aflatoxigenicity continued to increase after A. flavus incidence leveled off. If confirmed in field studies, these results suggest that burying compostable mulching films in soil may reduce soil quality and increase risk of adverse impacts from elevated aflatoxigenic A. flavus populations in soil.

Technical Abstract: An increasing number of states and municipalities are choosing to reduce plastic litter by replacing plastic items, particularly single-use ones, with same-use products manufactured from compostable plastics. This study investigated the formation and persistence of compostable film microplastic particles (CFMPs) [CFMP works better in English and emphasizes the film nature more.] from ultra-thin compostable carrier bags in soil under laboratory conditions, and the potential impact of CFMPs on Aspergillus flavus populations in the soil. During a 12-month incubation period, compostable film samples in soils with small, medium or large populations of indigenous A. flavus, underwent 5.9, 9.8, and 17.1% reduction in total surface area, respectively. Despite the low levels of deterioration, the number of CFMPs released increased steadily over the incubation period, particularly fragments with size <0.05 mm. Up to 39.2% of the released fragments had associated A. flavus and more than 27.1% of isolates from CFMPs produced aflatoxins. A. flavus levels associated with CFMPs increased over the 12-month incubation period, whereas the percent aflatoxigenicity increased initially then leveled off. During 12 months incubation, A. flavus DNA amounts recovered from CFMPs increased in soils with all levels of indigenous A. flavus, with the largest increases (119.1%) occurring in soil containing the lowest indigenous A. flavus. If confirmed in field studies, these results suggest that burying compostable film in soil, or application of compost containing CFMPs, may reduce soil quality and increase risk of adverse impacts from elevated aflatoxigenic A. flavus populations in soil.