reduktionskapacitet

Reduktionskapacitet, or reduction capacity, is a concept used in environmental geochemistry and soil science to describe the ability of a system to donate electrons to reduce oxidized species. It reflects the total pool of electron donors available to sustain reductive reactions under prevailing conditions.

In soils and sediments, reductive capacity arises from both organic matter and reduced minerals, such as Fe(II)-bearing oxides and sulfides, as well as dissolved and gaseous reductants like hydrogen. Microbial activity plays a central role, coupling the oxidation of electron donors to the reduction of contaminants or other oxidants.

Assessment is not a single measurement; researchers estimate reductive capacity by quantifying reducible material, measuring redox potential (Eh) and pH, performing batch or column experiments with known electron acceptors, or using reactive-transport models. Results can be expressed as mass of reducible material per unit weight, or as equivalents of electrons per kilogram, sometimes summarized as reducing equivalents.

Relevance: Reductive capacity controls the fate of contaminants such as chlorinated solvents, nitrate, and metal(VI) species, influencing the efficacy of natural attenuation and bioremediation strategies. Enhancements of capacity can be achieved by adding electron donors or stimulating microbial communities; conversely, oxidation or depletion of reductants reduces capacity over time.

Related concepts include redox potential, electron donors and acceptors, and environmental chemistry. The term is widely used in Scandinavia and in international environmental science to describe the long-term ability of soils and aquifers to sustain reductive transformations.