reductieflenzen

Reductieflenzen, literally "reduction fronts" in Dutch, are boundaries within soils, sediments, or groundwater systems where redox conditions shift from more oxidizing to more reducing. The term is commonly used in geochemistry, hydrogeology, and environmental engineering to describe zones where the dominant chemical reactions change as oxygen or other oxidants are depleted and alternative electron acceptors become prevalent. In practice, reductieflenzen delineate distinct redox environments that influence mineral stability and fluid chemistry.

These fronts form where there is a gradient in oxygen supply, organic matter availability, or groundwater flow. Microbial activity often drives the redox transitions, with sequences of possible electron-accepting reactions such as nitrate reduction, manganese and iron reduction, sulfate reduction, and methanogenesis. As redox conditions shift, minerals can dissolve or precipitate (for example, iron oxides may dissolve under reducing conditions and sulfides may form), which in turn alters the mobility of elements like iron, manganese, arsenic, uranium, and other contaminants.

Detecting reductieflenzen involves measuring redox potential (Eh), pH, dissolved oxygen, and concentrations of redox-sensitive species in pore waters and solid phases. Geochemical modeling and spectroscopic techniques are also used to map the extent and activity of these fronts. Understanding reductieflenzen is important for groundwater remediation, nutrient cycling, and the interpretation of mineral deposits, as the position and activity of the front influence contaminant fate and the effectiveness of treatment strategies. In Dutch-language literature the term is widely used in relation to redox fronts, and is often discussed alongside English equivalents such as redox front or reduction front.