eluvial

Eluvial refers to the processes and materials involved in the removal of soluble or fine components from a soil profile by downward-percolating water, a process known as eluviation. The term is used in pedology and geomorphology to describe both the process and the material affected by it.

In soils, eluviation produces an eluviated or E horizon, typically a lighter-colored layer depleted in clay, organic matter, and oxides relative to underlying horizons. The eluviated material, consisting mainly of coarser particles such as quartz sand, may stand in contrast to the horizon below. The material removed from the upper horizons is called eluvium, and it is translocated downward; when leached material accumulates in a lower horizon, the process is called illuviation.

Elution occurs most readily in climates with substantial rainfall and long weathering durations; it is less intense in arid regions. The presence and characteristics of an E horizon help differentiate soil types and indicate nutrient movement and soil fertility dynamics.

Eluvium is distinct from alluvium and colluvium, which are transported and deposited by surface water or gravity, respectively. The concept of eluviation and eluvium is central to understanding soil profile development and the distribution of minerals within soils.