HEAVY METALS

Heavy metals, metallic elements that are relatively dense, are commonly occurring in environmental studies. Many of these elements are essential for life. One of the characteristics of heavy metals is that they are persistent and tend to accumulate in organic matter, making them toxic in higher doses.

There are different ways of classifying the toxicity of heavy metals in sediments. One commonly used method in Norway and Sweden is the sediment quality criteria by Bakke et al. (2010) which is based on the concentration of heavy metals in sediments and the toxicity of the specific metal. The information on this website focuses on Copper (Cu) Lead (Pb) and Zink (Zn) in marine sediments and Fjällbacka harbour (see further details under Case study - Fjällbacka harbour).

Copper is vital for plants, animals and humans but can also act as a toxin if life forms are exposed to higher doses. The concentration of copper in the sediment in Fjällbacka harbour are in some cores in excess of level 5 in the quality classification, indicating severe acute toxic effects for life forms living in the sediment. Copper occurs as an anthropogenic source, in for example pesticides and antifouling-paint (Jönsson; Fahl, 2014).

Zink is, in a similar way as copper, an element necessary for life and a toxin in higher doses. The zink concentration in Fjällbacka exceeds level 3 in the classification, with toxic effects for life forms after long-time exposure. Zink is often used in alloys and as coating against oxidation (Jönsson; Fahl, 2014).

Lead is often considered an element related to negative environmental impact. If lead is involved in biological processes is not known, or possibly debated. The concentrations of lead in the sediment in Fjällbacka is considered good but above background levels, level 2 according to the quality criteria. The main use of lead is in batteries, paint, industrial uses, and earlier it was used in petrol (Jönsson; Fahl, 2014, and articles therein).