Selenium contamination of freshwater ecosystems is an ongoing environmental health problem around the world. A naturally occurring trace element, selenium levels are high in some geologic formations like sedimentary shales that form much of the bedrock in the Western United States. Soils derived from this bedrock, and weathering of shale outcrops, can contribute high levels of selenium to surrounding watersheds.
For selenium in rivers, timing matters
- 23. 2 2021 (19:16)