Now you Se it, now you don't

摘要

Selenium is a naturally-occurring element in the Earth's crust that is redistributed in the environment through multiple natural and geological processes. The major geologic sources of selenium include crustal rock, such as black shale, phosphate rocks and coal, while other formations such as igneous rock and limestone are minor sources. Natural processes that redistribute selenium include volcanic activity, terrestrial weathering of rocks and soils, wildfires and volatilisation from plants and water bodies.