Concentrations and Risk Assessment of Metals, Antifouling Paint Particles and Microplastics in Coastal Sediment of a Marina in Simon’s Town, South Africa


 Maintenance of maritime vessels includes the removal of paint from hulls that ultimately ends up the aquatic environment. Coastal maritime vessel maintenance is a source of metals, antifouling paint particles (APPs) and microplastics (MPs) that ends up in the coastal environment. Simon’s Town is a small urban town in False Bay, Cape Town, South Africa, where maritime activities take place (there is a naval harbour, marina and boat maintenance facility). The aim of this study was to measure metals, APPs and MPs in Simon’s Town, to assess the impact of maritime activities and a storm water pipe in a protected marina. Sediment samples were collected from 6 sites during winter 2018. Sediment and extracted APPs were analysed for metal content and MPs characterised based on type (visual and polymer), colour and size. Metal and MP fragment concentrations were highest at the slipway of a boatyard / maintenance facility, decreasing with increased distance from the slipway. MP filaments were highest close to the storm water outfall pipe. Our results suggest that boating maintenance facilities are potential sources metals and MP APP fragments, with storm water pipes potential sources of MP filaments. Various indices applied to assessed the potential impacts of metals and MPs, suggests that these contaminants have the potential to severely adversely impact the intertidal ecosystem investigated.

. 146 The geoaccumulation index (Igeo) is defined by the following equation  Table 1 for index category   151 values.

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The contamination factor (CF) is an index that assesses the status of contamination of a metal.      to the presence of a storm water pipe (Fig. 1). Respective metal concentrations (for sediment 256 only) that were significantly higher than site 6 are indicated by being underlined values in Table   257 2.

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Increased anthropogenic activities have resulted in essential metals reaching levels that  Table 2 and threshold effect levels in Table 4).
The potential effect of metals in sediment were assessed using a variety on indices.

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Enrichment factors were low for most elements at all sites (Table 3)

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The PLI risk category values decreased from sites 1 to 6 as follows: site 1 (9.2), site 3 (6.1), site  Table 1 for risk categories). The Er for the seven metals analysed was > 80 (high however no significant differences in MP concentrations between sites (KW = 11.1, p = 0.05).

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The low p value could suggest a type II error as evident from the high MP concentrations at site 317 1 and we consider MP concentrations at site 1 to be significantly higher than other sites sampled 318 (Fig. 2). Only filaments and fragments were recorded at all sites sampled, and fragments were 319 predominantly APPs (fragment prevalence for all sites = 89%), with the highest prevalence 320 recorded at site 1 (Fig. 3a). Sites 1 to 4 were situated in the protected area of the marina, in 321 close proximity to the boatyard, which could account for the higher prevalence of fragments 322 (APPs) at these sites. Site 5 was directly in front of a storm water pipe (see Fig. 1) and site 6 at an open beach that is an area used for bathers that could have accounted for the higher 324 prevalence of filamentous MPs at these sites.

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Blue was the dominant colour recorded for filaments at sites 3 and 5 (Fig. 3b) and for 326 fragments, red was most prevalent at site 2, black at site 3 and blue at sites 5 and 6 (Fig. 3c).

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Filament MP sizes varied across sites (Fig. 3d) with smaller MP filaments (< 1 mm) recorded 328 at sites 1 to 3 and sites 4 to 6 were mainly larger than 2 mm. Fragments were generally smaller 329 than 0.5 mm for all sites, with higher concentrations of MPs 2 to 5 mm in size at site 2 ( Fig.   330 4e), further confirming the presence of APPs at the sites sampled.

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We processed 10% of MPs counted for FTIR analyses and confirmed that 95% of MPs  Table 1 and 3 for risk analyses). The 351 high filamentous MP concentrations and high PLI at site 5 (Fig. 6a) is cause for concern as 352 filamentous MP polymers are considered a greater risk for marine organisms than other types