Abstract
Once in the environment, preproduction plastic polymers between 2–5 mm in size, also known as pellets, can cause physical harm to animals that mistake them for food as they have been reported to accumulate toxic substances, including on their surface. However, the rate of metal enrichment on pellets is not well investigated. In October 2018, Durban experienced a storm that resulted in ±2000 tons of polyethylene pellets being spilt into Durban Harbour, which caused environmental pollution concerns. This event provided a unique opportunity to study metal accumulation on pellets. Pellets were collected at one-month intervals for 6 months following the spill from October 2017 to March 2018, and metal concentrations were compared to concentrations found on pellets collected before the spill. The pellets were digested using a mixture of concentrated nitric acid (55%) and sulphuric acid (60%) at a ratio of 3:1 and analysed for numerous trace metals (Al, As, Pb, Cd, Cr, Fe, Cu, Mn, Ni, and Zn) using the Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES). Pellets collected in Durban Harbour prior to the spill in a related study (unpublished data) showed higher metal accumulation; however, there was no evident linear increase in metal concentration in pellets over time. ANOVA showed no significant difference for all metals (p > 0.05) in metal concentration between months; however, there was a significant difference between aged and newly introduced pellets.
Highlights
Apart from Cr and Fe, metals reported in this study showed high concentration in pellets shortly after the spill, and a decrease was noticed, which was subsequently followed by a more gradual increase in metal concentration
It is unclear whether metal concentration on the pellet was originally high or whether there may have been accumulation shortly after the spill
This study reported a high affinity of metal to newly introduced pellets, which was attributed to the polarity on the surface of virgin pellets
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. Pellets are important feedstock for the production of plastic items [1]. They are typically less than 5 mm in size with a regular round or ovoid shape [2] and can be mistaken for food by marine organisms including birds, fish and crustaceans [3,4,5]. During transportation and in loading and offloading areas [6], make them available to organisms in the marine environment
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