Tin [Sn, 50]

Tin (Sn), a silvery metal of group 14 in the periodic table of elements, occurs in the Earth’s crust at an average amount of 2.5 mg/kg. It is easily fixed by organic matter, and thus, its concentration in coal may be up to 30 mg/kg. The average Sn abundance in soils is 2.5 mg/kg. Tin forms several complexes with soluble organic matter, and thus is generally enriched in surface soil horizons and in organic soils. Marine plants are important in the cycling of Sn; its contents in algae and macrophytes vary within 0.5–101 mg/kg. Algae may immobilize Sn from seawaters and stimulate the degradation of toxic methyl-Sn. The most significant sources of Sn are industrial emission and coal burning plants. There are no evidences that Sn is essential to plants, and it is considered as toxic to both higher plants and fungi. Human exposure to Sn may occur by inhalation, ingestion, or dermal absorption.