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Within the cycle, there are organisms which reduce the most oxidized form of the element and different organisms complete the cycle by oxidizing the reduced element to the initial state. In the selenium cycle it has been found that bacteria, fungi, and plants, especially species of Astragalus , metabolize the most oxidized forms of selenium ...
Selenium also occurs in organic compounds, such as dimethyl selenide, selenomethionine, selenocysteine and methylselenocysteine, all of which have high bioavailability and are toxic in large doses. Selenium poisoning of water systems may result whenever new agricultural runoff courses through normally dry, undeveloped lands. This process ...
Selenium pollution of waterways also occurs when selenium is leached from coal flue ash, mining and metal smelting, crude oil processing, and landfill. [103] High selenium levels in waterways were found to cause congenital disorders in oviparous species, including wetland birds [ 104 ] and fish. [ 105 ]
Selenium concentrations in water entering Lake Koocanusa have been increasing for decades, and studies have shown it’s coming from coal mines in the Elk River valley of British Columbia.
A biogeochemical cycle, or more generally a cycle of matter, [1] is the movement and transformation of chemical elements and compounds between living organisms, the atmosphere, and the Earth's crust. Major biogeochemical cycles include the carbon cycle, the nitrogen cycle and the water cycle. In each cycle, the chemical element or molecule is ...
Since liquid water flows, ocean waters cycle and flow in currents around the world. Since water easily changes phase, it can be carried into the atmosphere as water vapour or frozen as an iceberg. It can then precipitate or melt to become liquid water again. All marine life is immersed in water, the matrix and womb of life itself. [7]
The water cycle is essential to life on Earth and plays a large role in the global climate system and ocean circulation. The warming of our planet is expected to be accompanied by changes in the water cycle for various reasons. [3] For example, a warmer atmosphere can contain more water vapor which has effects on evaporation and rainfall.
Houston — Donna Thomas is a pollution warrior in Houston, Texas. She wears a mask because she believes a lifetime of breathing polluted air in her community contributed to a stroke four years ago.