Leaching

Leaching is the dissolution of substances by a solvent from a solid. Often it is the leaching of water-soluble substances such as salt relatively well, gypsum or lime from a solid by water.

Leaching can in many cases to building materials such as watching concrete, it also plays a role, among others, in geology in the chemical weathering of rocks and Subrosion or in soil science in the transport of nutrients from the upper soil layer in deeper. In the field of environmental geology is the " leaching " ( herein referred to as leaching or mobilization) of pollutants from contaminated sites and waste an important issue. In the extraction of ingredients in medicine and in the food industry, for example in the production of liqueurs, the process plays a role ( maceration ).

Leaching as a geological process, often referred to as Ablaugung or Subrosion, usually affects rocks such as rock salt, gypsum or limestone. Has ground water, for example, access to underground salt, gypsum or limestone layers and performs these substances in dissolved form away, can create voids in which to sink the overlying rock layers or may decline as a result of this Ablaugung. Arise Subrosions Auslaugungssenken or on the surface. In the case of limestone, one also speaks generally of karstification and this expression both the superficial and underground draining solution of limestone is understood. With the collapse of the outer layers into the cavities created a special form of breccia Auslaugungsbrekzie or Einsturzbrekzie.

By chemical weathering in the effect relatively aggressive climate of the tropics also silicate and metal compounds are removed from rocks and elsewhere reprecipitated by aqueous solutions. The leached rock is referred to as saprolite.

In the late Middle Ages and early modern period were many water-permeable soils - soil and forest floor - strongly leached. In the 19th century it was recognized in many places the causes, improved crop rotations and fertilization and grabbed ecological measures (eg afforestation of hill tops ). As a result of increased coal mining and urbanization less firewood was brought out of the woods (see coppice ).