CLiP Solomon Islands Microplastics in sediment 2017

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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. Number of microplastic items per 5g dried sediment in samples from riverine, transitional and coastal environments in Guadalcanal Island (Solomon Islands). Sediment samples were taken from 6 riverine locations and five coastal ones. Samples were dried for 3 days (less than 50 degrees centigrade) and weighted. Density separation using NaCl solution and a centrifuge, filtering the supernatant. This was followed by a chemical digestion with a KOH:NaClO solution for 3 days at 50 degrees centigrade whilst shaking. Plastic particles were then stained with Nile Red dye and a digital image was acquired through a microscope. Microplastic particles were then counted and a subsample of particles (between 1 and 10 percent) was processed through a ATR—FTIR to identify particle composition comparing their spectrum to a polymers library. The presence and number of particles of plastic more than 5mm was also noted for each sample.