Degradation of microplastic seed film-coating fragments in soil. (July 2019)

• Record Type: Journal Article
• Authors: Accinelli, Cesare; Abbas, Hamed K.; Shier, W. Thomas; Vicari, Alberto; Little, Nathan S.; Aloise, Maria Rosaria; Giacomini, Sara
• Is Part Of: Chemosphere. Volume 226(2019)
• Page Start: 645
• Page End: 650
• Publication Date: 2019-07
• Subjects: Seed film-coating -- Biodegradable plastic -- Microplastic -- Neonicotinoids -- Seed dust-off -- Bioplastic; Pollution -- Periodicals; Pollution -- Physiological effect -- Periodicals; Environmental sciences -- Periodicals; Atmospheric chemistry -- Periodicals; 551.511
• DOI: 10.1016/j.chemosphere.2019.03.161
• Languages: English
• ISSNs: 0045-6535

Abstract

Abstract: Encapsulating fungicides and/or insecticides in film-coatings applied to agronomic seeds has become a widely accepted method for enhancing seed germination and overall seedling health by protecting against many diseases and early-season insect pests. Despite advancements in seed film-coating technologies, abrasion of the seed coating can occur during handling and mechanical planting operations, resulting in variable amounts of detached fragments entering the soil. The present study investigated the degradation in soil of these plastic-like, small-sized fragments, referred to here as microplastic coating fragments. Degradation of microplastic coating fragments in soil was found to be highly variable. The lowest degradation rate (≤48 days) was observed in fragments detached from seeds coated with a commercial polymer mixture, while fragments from a biodegradable plastic formulation degraded completely within 32 days. When spores of the plant growth-promoting bacterium, Bacillus subtilis, were incorporated into the bioplastic, degradation was even more rapid (≤24 days). The fragment degradation rate was unaffected by incorporating two commonly used neonicotinoid insecticides, imidacloprid or thiacloprid, into either coating formulations, but insecticide dissipation rates in soil were more rapid when added associated with seed coating fragments than when spiked in directly. Half-lives of these two insecticides were reduced by up to 27% in fragments from bioplastic-coated seeds. These results are consistent with variable and not easily predicted soil degradation rates for seed coating fragments, with enhanced dissipation of coating-entrapped pesticides and with a higher degradation rate for biodegradable seed coating incorporating selected microbial strains. Highlights: Corn seeds are commonly film-coated before planting. Film-coat includes pesticides, polymers, fillers and dye. Film-coat fragments can be detached by abrasion. Seed dust-off is defined as the release of fragments from treated seeds. Seeds coated with bioplastic showed reduced dust-off values.