In this report the term pollution refers to elevated levels (above natural background levels for naturally occurring substances and levels above zero for man-made synthetic substances) of oil components/hydrocarbons, radioactive substances and environmentally hazardous substances. In addition, noise (see chapter Pollution), marine litter and ocean acidification are included.
Environmentally hazardous substances are those substances that may be dangerous to the environment. Their properties vary: they may be acutely toxic, corrosive, irritating to skin, sensitizing and explosive. Environmentally hazardous substance are not readily biodegradable and are bioaccumulative (accumulate in food chains and in the human body) and may cause damage to the environment even in low concentrations. They are categorised as ecological toxins. The most hazardous substances that are found in the Barents Sea environment are persistent organic compounds (POPs) such as polychlorinated biphenyls (PCBs), alkyl phenols and heavy metals like mercury (Hg) and cadmium (Cd).
Radioactive substances emit ionising radiation. Radiological toxicity (harmfulness to living organisms) varies widely from one substance to another depending on how readily they are absorbed by living organisms, the type of radiation they emit and its intensity. Radioactive substances are unstable and decay over time. Half-life is used as a measure of how long-lived a radioactive substance is, and can vary from only a few seconds to several hundred thousand years. The most environmentally hazardous radioactive substances that can be found in the Barents Sea area are anthropogenic 99Tc (technetium), 137Cs (caesium), 90Sr (strontium), 241Am (americium) and plutonium isotopes (239+240Pu) as well as the naturally occurring radionuclides 226Ra (radium), 228Ra 210Pb (lead) and 210Po (polonium).
Pollution caused by discharges of oil or other hydrocarbons is measured as total level of hydrocarbons (THC) and levels of polyaromatic hydrocarbons (PAH). These are both used as indicators for oil pollution. PAH can however originate both from natural (e.g erosion of coal-bearing bedrock, possible leakage of oil and gas from the seabed) and human made (e.g offshore industry and wood-burning) sources.
Naturally occurring substances do also contribute to the contamination of the Barents Sea. In addition to hydrocarbons, such substances include radioactive substances and heavy metals such as arsenic and nickel, which seep out of the sea-floor sediments. It is important to know the background level of these substances to enable realistic estimates of the level of human impacts and the effect of these.
Ocean acidification is a decrease in the pH in the oceans caused by uptake of anthropogenic carbon dioxide (CO2) from the atmosphere. When carbon dioxide is absorbed by the oceans it reacts with seawater to form carbonic acid. The absorption of CO2 is generally faster in colder waters such as the Barents Sea. Acidification can profoundly affect phytoplankton (coccolithophores), corals, molluscs, echinoderms and crustaceans, but recent research also indicates that eggs and larvae of fish may be endangered. For more information, see chapter Biotic interactions and Ocean acidification.