CLiP South Africa Microplastics in the Port of Durban 2019

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The Commonwealth Litter Project (CLiP) supported South Africa to take action on plastics entering the oceans. The abundance of microplastics was investigated within The Port of Durban in the Durban Harbour (east coast of South Africa). A handheld CTD multi-channel logger (RBRconcerto3 C.T.D++, RBR Ltd., Canada), with attached optical backscatter turbidity (STM, Seapoint Sensors Inc, USA), was used to measure temperature, salinity and turbidity. Microplastics in water were sampled using a microplastic pump (KC Denmark Plankton Pump for Microplastics, Model 23.580) deployed through a crane from the quayside. The pump filtered 2000lt of water several sieves: 5mm, 500µm, 300µm, 200µm and 100µm . Sediment samples were collected at each microplastic pump site for sediment particle size analysis (PSA) and sediment microplastic analysis. Also, 15 additional sediment samples were taken from a boat on channels and areas of deposition. Five additional samples were taken in the harbour and surrounds where substrate was suitable. Each sediment and water sample was transferred to glass collecting pots. The sediment samples were dried at 50 degrees Celsius and, once dried, 5g triplicates were taken from a homogenised sample and underwent density separation before being chemically digested with a 30 percent KOH:NaClO solution. Each sample was then incubated for 72 hours before filtration Identification of the extracted microplastics was carried out using the fluorescence tagging of polymers using Nile Red coupled with digital imaging (Maes et al., 2017). For each sediment sample, a PSA was carried-out to relate abundance of microplastics to sediment type. Samples were freezed and then underwent PSA, based on a modified NMBAQC protocol from Mason (2011) for fast PSA screening based on wet splitting into silt/clay (< 63 µm), sand (63 µm – 4 mm) and gravel (> 4 mm) fractions. Once dry, samples were weighed, and the proportion of each fraction was calculated. Surface water samples were inspected for any suspected anthropogenic particles. Mesoplastics were manually removed, dried and characterised with ATR-FTIR. Samples with low to no organic content were filtered and stained with Nile Red before imaging and particle counting (Maes et al., 2017). For samples with high organic content, sieve rinse water was digested with a 30% KOH:NaClO solution with 24 hours incubation. Visible particles were analysed using ATR-FT-IR to identify polymer composition, comparing their spectrum to a polymers library. ATR-FTIR is the attenuated total reflection Fourier Transform infrared spectroscopy. A Thermo Fisher Scientific Nicolet iS5 ATR-FTIR with an OMNIC software (version 9.9.473) was used and polymers were identified based on the percentage match of IR spectra to a polymer library. Only spectra matched greater than 70 percent were accepted. Spectra were collected in the range 4000 – 650 1/cm at a resolution of 4 1/cm.