Environmental chemistry and pollution
cores from the Oslofjord. This example shows a reduction in
mercury content in seabed sediments from 1965 to 2005.
Illustration: Aivo Lepland.
Many pollutants occur naturally in the seabed sediments, often in high concentrations. It is therefore necessary to map background levels before concluding that the pollutants have been anthropogenically introduced.
Heavy metals include all metals with high density. Heavy metals are naturally occurring ingredients of the earth’s crust, in varying concentrations. Many heavy metals are poisonous even in low concentrations. They tend to be bioaccumulative, meaning that their concentration in living organisms may be higher than in the surroundings. Thus, high concentrations of heavy metals in the marine environment may have a toxic effect on marine organisms that eat them. There are many anthropogenic sources of heavy metals, e.g. mines, smelters, sewage and more diffuse sources like motor vehicles.
Organic pollutants originate from hydrocarbons like coal and oil. They are toxic and degrade slowly, and accumulate in living organisms. Some of the most poisonous are PCB, dioxins, PAHs, phthalates and flame inhibitors. Some of the pollutants are manmade, while others occur naturally in low, but locally higher concentrations. The Norwegian Environmental Agency has established a system to classify the degree of contamination of fjord and coastal sediments.
NGU maps environmental conditions and pollution in several projects, e.g. MAREANO (www.mareano.no). The investigations have shown that ocean areas are generally unpolluted, while the pollution in some fjords and coastal areas may locally be high.
