An Environmental case study of the Inner Drammensfjord: Environmental conditions and microplastic accumulation - Drammensfjorden, Eastern Norway

Microplastic has become a well known term the last decade, but how well known is the issue of microplastic pollution into the marine environment? An attempt on determining the microplastic accumulation in Drammensfjorden and its evolution through industrialisation, were done by collecting sediment cores in Drammensfjorden, August 25th, 2020. The impact of the industrialisation can be mirrored by the sediment accumulated in the same period of time. Polymers stay hidden in the sediment to tell the story of over-polluted rivers and poorly handled waste. The accumulated plastic polymers can give an overall picture of pollution into the fjord throughout history. How the environmental condition of Drammensfjorden change in times of industrialisation, and if it has changed since introducing framework regarding contamination of the fjord. \\ Sediment cores were collected at 80 meters water depth with a Gemini-twin-corer, field parameters of the water column were taken with a CTD-device. The core DRA2A was sub-sampled in intervals of 1 or 2 cm slices. Samples were frozen before freeze dried, for less disturbance of the sediment. The samples were treated with hydrogen peroxide for organic material removal. A density separation process was done with the help of NaI solution, to separate possible microplastic form the sediment. The lab process produced four separate glassfiber filter papers per sample, which were manually picked and described for observed microplastic through microscope. A portion of the picked microplastic was tested with Raman and FTIR spectroscopy, to determine the type of plastic. The results of the identification of microplastic were inconclusive, due to oxidation of iodide contaminating the material, both Raman and FTIR spectra struggled to identifying the polymers. The sediment core was dated according to research done by Norconsult in 2018/19. The visual data indicated higher accumulation of smaller particles down core. The characteristics in shape of the observed microplastics had a shift when the industrialisation of Drammen happened, and the introduction of synthetic polymers in the industry. The establishment of treatment plants appears to have a direct correlation with the accumulated microplastic in the sediment, as a decrease in microplastic in the core can be seen shortly after the establishments. Comparing microplastic observed in DRA2A with microplastic in samples taken closer to the harbour in Drammen at 60 meters water depth, show accumulation of larger quantities, and higher density microplastic. Larger particles and fragments dominate the samples taken closer to shore, compared to smaller fibers further out in the fjord. The CTD-data measured very low concentrations of oxygen in deep water, and close to the seafloor. Drammensfjorden is closed off from the larger Oslofjord by glacial moraines at Svelvik, which causes very low circulation in deeper waters. The low concentrations of oxygen classifies the environmental condition of the fjord as "Very Bad", which does not give the true condition of the fjord, due to the lack of circulation in deeper water