Washout

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When leaching is known in the soil science a soil-forming process in which substances in the soil in solution go and this solution by percolating water is discharged.

Salts are dissolved by hydration , most other minerals - especially carbonates and much less soluble silicates - by hydrolysis . Most minerals are hardly soluble in pure water. However, small amounts of carbonic acid and humic acid are usually dissolved in the water, which makes it easier for many minerals to dissolve. Soil acidification increases leaching accordingly. Due to the different solubility, there is a temporal differentiation in soil formation, so that different soil types can develop one after the other at one point .

The leaching leads to a horizontal differentiation in the soil profile and thus contributes to the formation of soil horizons . One of the fastest soil-forming processes is decalcification , i.e. H. the leaching of finely divided lime in the soil. Substances that are washed out in the topsoil can be precipitated again in the subsoil . This is particularly the case with podsolization , in which humic substances as well as iron and manganese oxides are displaced in this way .

If the dissolved substances are not precipitated again but are carried away with the groundwater, the leaching contributes to chemical weathering . This must not be confused with the mechanical effect of flowing water . Therefore, the limestone weathering that leads to the formation of karst , which consists of the steps of carbonic acid weathering and solution removal, is sometimes referred to as leaching for short.

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