Plastic particles act like magnets to bind pollutants and toxins
A research team has revealed that microplastics has the ability to bind much more pollutants and toxins than previously thought. In fact, they are generally three to four times more contaminated than the already contaminated sediment. The team had examined the sediments in the estuaries of the Elbe, Weser, Trave and Bodden, as well as the North and Baltic Seas. The greatest amount of pollution had been found near the sewer treatment plant in Lübeck.
Since 2015, Professor Dr Gesine Witt of the Hamburg University of Applied Sciences (HAW Hamburg) and her team have been studying microplastic litter in the sediments in the marine environment, working within the framework of the Federal Ministry of Education and Research (BMBF). Over three months, two expeditions focusing on microplastic contamination in the sediment were conducted on board the ALDEBARAN research vessel (aldebaran.org). Samples were retrieved using special plastic pollutant collectors developed by HAW Hamburg, and examined in the laboratory.
To date, it has been ascertained that plastic granules act upon the pollutants in the same way as magnets; the longer they are in the water, the more toxins would bind to them and form into a sort of poisonous cocktail. In this way, they would be consumed by small marine organisms like worms, mussels and fish, and eventually find its way into the human food chain.
Microplastics three to four times more heavily polluted than surrounding sediment
So far, the research team suspects that the concentration of contaminated microplastics was at least as high as that of the surrounding sediment. Elaborating on their findings, Prof Witt said in German, “Using fifty sample collectors, we have shown how prominently microplastics are found in the sediments. The plastic particles are actually three to four times more contaminated than the sediment, which is already contaminated. In addition, we now better understand where particles of different sizes end up in the water or sediment.”
Polyethylene binds more pollutants
The team also discovered that silt containing sediment was able to absorb significantly more pollutants than suspended silt, assuming that there was an increased load of microplastics in the marine environment. Hence, the results of the examined silicone samples from the sample collections and the comparative laboratory tests on the pollutant-binding properties of polyethylene has found that polyethylene binds about twice as many pollutants as silicone. Prof Witt regards this as a cause for concern, as polyethylene is currently widely used in the industry.
The results of the survey show that the microplastics from the Weser and the sediment from the Elbe, in particular, have been polluted with polychlorinated biphenyls (PCB). In these areas, depending on the lipid solubility, the pollutant concentrations are in the range of 1.5 to 280 microgrammes for every kilogramme of polyethylene.
Another group of substances – polycyclic aromatic hydrocarbons (PAH) – was discovered in the sediments of the Stralsund harbour and the port of Marienehe in Rostock. This is mainly due to the oil and oil products such as diesel fuels (some of which are carcinogenic) that had entered the water. The highest pollutant level, up to 1,400 microgrammes of fluoranthene per kilogramme, of silicone was measured near the Lübeck treatment plant. However, the team had also measured high pollutant levels at the Weser estuary and the Warnow at Rostock.
More information: www.haw-hamburg.de