Disintegration half-life of biodegradable plastic films on different marine beach sediments.
Andreas EichMiriam WeberChristian LottPublished in: PeerJ (2021)
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.
Keyphrases
- heavy metals
- polycyclic aromatic hydrocarbons
- microbial community
- organic matter
- drug delivery
- risk assessment
- high density
- antibiotic resistance genes
- heart failure
- climate change
- acute heart failure
- computed tomography
- molecular dynamics
- health insurance
- atrial fibrillation
- wastewater treatment
- magnetic resonance
- image quality
- liquid chromatography
- lactic acid
- anaerobic digestion