1. Occurrence and Significance
Lithium (Li) is the second element in Group IA of the periodic table. It has an atomic number of 3, an atomic weight of 6.94, and a valence of 1. The average abundance of Li in the earth’s crust is 18 ppm; in soils it is 14 to 32 ppm; in streams it is 3 μg/L, and in groundwaters it is <0.1 mg/L. The more important minerals containing lithium are lepidolite, spodumene, petalite, and amblygonite. Lithium compounds are used in pharmaceuticals, soaps, batteries, welding flux, ceramics, reducing agents (e.g., lithium aluminum hydride), and cosmetics.
Many lithium salts are only slightly soluble, and the metal’s concentration in water is controlled by incorporation in clay minerals of soils. Lithium is considered nonessential for plants and animals, but it is essential for some microorganisms. Some lithium salts are toxic by ingestion. The United Nations Food and Agriculture Organization recommended maximum level for lithium in irrigation waters is 2.5 mg/L.