Compost teas are defined as water extracts leached from composted materials. The residues are further leached with sulfuric acid, yielding a solution of copper sulfate. The calcine is subsequently leached with sulfuric acid from the spent copper recovery electrolyte. This can be an advantage in excessively leached tropical rain forest soils. Excess nitrogen must be leached from the soil by addition of large quantities of water. Cobalt can also be leached from the slag of copper smelting. This causes a sharp increase in phosphorus concentration in solution and phosphorus can be leached. The soil is generally leached and infertile. Nutrients may then be leached and lost from the ecosystem entirely. Dissolved ions, such as calcium (Ca), are leached out and transported in solution some distance. Harvested acorns must be properly leached of the tannins prior to consumption. Elements were leached from the already solidified portions of the pluton. Then the meat is minced and rinsed, and the water is leached out. Excess salt in the preserved vegetable is leached out by soaking in fresh water. Concern arose that the milk contained unsafe levels of lead leached from this solder plug.