Indium [In, 49]

Indium is very rarely found as grains of native metals, and its primary sources are Zinc ores. A large amount of Indium is obtained from scraps recycling. Its current primary applications are to form transparent electrodes indium tin oxide and in touchscreens. Because Indium is associated with organic matter, it is likely to be concentrated in surface-soil horizons. Indium contents in soils of different countries are reported as follows: Brazil, 0.15; China, 0.03-4.1; Japan, 0.08-1.92; Sweden, 0.007-0.6; the United States, <0.2-0.5. Its contents in the Atlantic Ocean is given as 6.25-10.71 pmol/kg. The main anthropogenic source of Indium in air is from waste and coal combustions. Physiological effects of increased Indium levels in plants are associated with Indium-induced toxicity in roots, which occur in plants grown in culture solution, with its contents within 1-2 mg/kg. Worldwide mean In contents in mineral soils are reported to range from 0.01 to 0.5 mg/kg, with the mean value of 0.06 mg/kg.