CLiP Vanuatu Microplastics in sediment 2018

notPlanned

The Commonwealth Litter Project (CLiP) supported Solomon Islands to take action on plastics entering the oceans. The assessment of microplastics in seawater was part of the action plan to define scientific baselines for future monitoring purposes and comparison. Samples were acquired deploying a small Van Veen grab (Duncan and Associates, UK, sampled area 0.025 square metre) off small vessels by hand. Grab were done only if the bottom was well visible and clear of live coral. Sediment grabs were subsampled with a steel spoon into sample jars for microplastics and PSA. Sample were then frozen (-18 degrees Celsius). A control jar was left exposed to the atmosphere during the subsampling to investigate background contamination. In the lab, visible plastic particles greater than 5mm were removed and analysed using ATR-FT-IR to identify particle composition comparing their spectrum to a polymers library. The rest of the sample was dried and homogenised, chemically digested with 30 percent KOH:NaClO solution for 3 days at 50 degrees Celsius. Samples were then filtered, stained with Red Nile dye and a digital image was acquired through a microscope. Number of particles was counted and corrected for blank samples. ATR-FT-IR 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. Particulate size analysis was performed measuring the weight of the sample and of its gravel, sand and mud components. The percentage of the three components over the total weight was also measured.