Heavy metals

Infobox heavy metals

Although there is no universally accepted definition, metals with a density of 5 g/cm3 are generally referred to as heavy metals.

Heavy metals occur naturally in the environment. However, urban soils in particular often contain higher levels of heavy metals than the surrounding area. Sources of heavy metals in soils include industry, transport, fertilisers (e.g. sewage sludge) and mining.

Some of them, such as iron, zinc, copper and manganese, are important nutrients for plants, animals and humans (‚essential trace elements‘). However, they are harmful in excessive amounts. Other heavy metals, such as lead, cadmium and mercury, are toxic to living organisms even at relatively low levels.

The extent to which heavy metals end up in plants and thus in our food depends not only on the total amount in the soil, but also on the properties of the soil and the type of plant grown.