Disintegration half-life of biodegradable plastic films on different marine beach sediments

Abstract

The seafloor is considered the major sink for plastic debris in the world’s oceans. Biodegradable polymers are available on the market as a substitute for conventional plastic and could potentially end up in the same environment. To gain more insight into the effects of different sediments on the degradation rate of biodegradable plastic we performed two iterative seawater tank experiments. First, to test the effect of sediment grain size, film of Mater-Bi HF03V, a blend of thermoplastic starch and biodegradable polyesters, was placed on the surface of mud as well as on four different grain size fractions of beach sand. Disintegration half-life was shortest on mud (139 days) and increased with the grain size of the beach sediment fractions (63–250 µm: 296 days; 250–500 µm: 310 days; 500–1,000 µm: 438 days; >1,000 µm: 428 days). We assume that the higher surface-to-volume ratio in fine sediment compared to coarse sediment led to a higher bacterial abundance and thus to faster disintegration rates. In a follow-up experiment, the <500 µm fraction of sediment from four different beaches around Isola d’Elba, Italy, was used to test plastic disintegration as above. Additionally, polyhydroxybutyrate (PHB, MIREL P5001) was used as a positive control and high-density polyethylene (HD-PE) as a negative control. No disintegration was observed for HD-PE. Mater-Bi HF03V and PHB disintegrated significantly differently on sediment from different sites, with half-lives of Mater-Bi HF03V ranging from 72 to 368 days and of PHB from 112 to 215 days. Here, the half-life was shortest on slightly coarser sediment and at potentially anthropogenically impacted sites. We assume that the effect of the grain size on the disintegration rate was masked by other parameters influencing the microbial community and activity. Understanding the parameters driving biodegradation is key to reliably report the range of disintegration rates occurring under the various conditions in different ecosystems.

µCT‐Based Topography Analysis of Inaccessible Surfaces Exemplified by a Biofouling‐Covered Plastic

“…Polyhydroxybutyrate (PHB) is known to be a biodegradable polymer and often serves as positive control in degradation experiments [16][17][18]. PHB samples were fabricated of the material P209 (Biomer, Schwalbach, Germany) by injection molding.…”

Biodegradable plastics in the marine environment: a potential source of risk?

“…(ii) Chain length: The chain length is related to the number of bonds to be hydrolyzed, the abundance of hydrolysates, and the hindrance of intermolecular contact during the reaction. Lower initial molecular weight (low average chain length) makes the mineralization process progress faster [58] . (iii) Structure of BPs: Crystallinity and surface hydrophilicity [10] affect the diffusion of water molecules in BPs, hence the hydrolysis.…”

Effects of three tebuconazole nanopesticides on the survival of Daphnia magna

“…Both PCL and PHB are examples of biodegradable polymers that decompose effectively in natural settings like aquatic environments, soil, and compost. [17][18][19][20] PCL has variable degradation rates in different environments, including compost and various aquatic habitats. 20 For instance, it was shown that PCL was completely assimilated over a period of six weeks in seawater and after forty-two weeks in natural fresh water.…”