Heavy metals occur naturally in the environment as constituents of the earth's crust. They fulfil the criteria of persistence: the law of conservation of matter ensures that the elemental material can neither be destroyed nor produced. The total amount of metals in the environment is therefore constant. However, due to anthropogenic activities (mining, agricultural activities, waste disposals, fuel combustions) metal distribution patterns can be rearranged, resulting in site specific elevated concentrations.
When heavy metals enter aquatic systems, they partition among various compartments: they can stay in solution as free ions, soluble salt, associated with dissolved inorganic or organic ligands, or can be bound to particulate matter.
It is like stating the obvious: trace metals can be accumulated by organisms living in metal contaminated areas. Although some metals like copper and zinc are essential for life, metals, essential or not, above a certain threshold level can exert adverse biological effects. Metals, once accumulated, can cause different metabolic alterations and potentially can interfere with the organism’s biochemical machinery thereby causing toxic effects on several organismal levels. Moreover, heavy metal accumulation not only can exert numerous toxic effects on the individual organism itself but may also give rise to populations or community-wide problems.
Although is has long been recognized that metal pollution is a serious environmental problem and much work has been performed, it is still not straightforward to find accurate relationships between exposure level, accumulation and the possible effects. To understand the impact of metal pollution on either individual organisms or whole ecosystems, it is therefore important to understand the mechanisms underlying the chemical and physiological processes that control metal availability, accumulation and toxicity. In order to get more insight into these processes, knowledge about chemical speciation, different routes of uptake and the organismal mechanisms to deal with metal accumulation is very important.
This was the aim of this present research project: to study the complex route from exposure via accumulation to toxicity. This was done by using pharmacokinetic modeling techniques. Since environmental systems are often far from equilibrium we developed dynamic models which can deal with changing environmental conditions like water hardness, concentration, time, exposure routes, speciation, etcetera.
Experiments wee performed using the aquatic oligochaete Tubifex tubifex as a test organism. Field studies were performed along parts of the Scheldt River.
Responsible scientist