Nickel is the heavy metal, with chemical symbol Ni and atomic number 28. Nickel is silvery-white with a slight golden tinge that takes a high polish. It is one of the four elements that are magnetic at room temperature and is hard and ductile. It is an chemical element, and as such very stable. Very small amounts of nickel have been shown to be essential for normal growth and reproduction in some species of animals .
Nickel is a significant contaminant in the sediments of industrialised areas and serious attempts have been made to reduce nickel inputs to the sea. It has been used in steel, batteries and is also used as a catalyst. Fossil fuels are usually rich in nickel and combustion of oil and coal results in a significant contribution to atmospheric deposition, but the mayor input of nickel to the sea is through rivers. Most of the nickel is particulate and is therefore present in the soils of estuaries.
No organisms have been found to contain very high concentrations of nickel. Molluscs commonly bioaccumulate metals, however there is no evidence that they, or any other species bioaccumulate or biomagnify nickel.
Nickel is regarded as only moderately toxic, although it can cause lethal effects to some algae species at concentrations above 600 µg/l. Some crustacean species might die by exposure to concentrations of 150 µg/l although most survive short exposure to concentrations up to 42 mg/l. Estuarine fishes experience acute toxicity at concentrations above 38 mg/l.
Concentrations in the ocean are usually around 0.2 µg/l, those in the open North Sea around 0,3 µg/l, but near the Dutch coast concentrations of 1 µg/l can be measured. A few studies have suggested that soil concentrations of nickel of around 30 mg/kg might have resulted in a loss of species diversity and caused lethal effects to the larvae of oysters. However, it couldn't be ruled out that these effects might also have been caused by other pollutants.
Environmental standards and legislation