The process by which soluble substances are dissolved out of a material. When rain falls on farmlands, for example, it dissolves weatherable minerals, pesticides, and fertilizers as it soaks into the ground. If enough water is added to the soil to fill all the pores, then water carrying these dissolved materials moves to the groundwater—the soil becomes leached. In soil chemistry, leaching refers to the process by which nutrients in the upper layers of soil are dissolved out and carried into lower layers, where they can be a valuable nutrient for plant roots. Leaching also has a number of environmental applications. For example, toxic chemicals and radioactive materials stored in sealed containers underground may leach out if the containers break open over time.

See Also

Landfill; Leaking Underground Storage Tank