ABSTRACT
In a global context, selenium (Se) is a complex but interesting element. Its properties make the boundaries between animal toxicity and deficiency relatively narrow, and, indeed, both phenomena are common around the globe. There is also a contrasting distribution and rate of transfer between different environmental compartments. Most recently, human interference in the global cycling of Se has added to this heterogeneity. This chapter introduces the global significance and distribution of Se and considers the factors that control its fate and transport within and between major environmental media.
