Cadmium cycle
From Wikipedia, the free encyclopedia
The cadmium cycle is a biogeochemical cycle of dispersion and deposition of cadmium through the atmosphere, biosphere, pedosphere, and hydrosphere. Cadmium typically exists in the environment with an oxidation state of +2 but can be found with an oxidation state of +1 (though quite uncommon).[1]
| Part of a series on |
| Biogeochemical cycles |
|---|
 |
Atmospheric sources are dominated by anthropogenic emissions (non-ferrous metal production, fossil fuel combustion, iron and steel production, waste disposal, and cement production), with minor introduction of cadmium through natural emissions (volcanoes, dust, biomass burning, and sea spray).[1] Cadmium introduced as powders and aerosols through anthropogenic sources and natural sources can be detected in almost all corners of the globe. Cadmium is highly soluble and cadmium concentrations are rapidly depleted after wind transport as particles, aerosols, and water droplets.[1] Typically, cadmium deposition decreases latitudinally from the source.
Terrestrial cycling
The majority of cadmium deposition to soils and freshwater is due to anthropogenic atmospheric emissions, contaminants in biosolids, and contaminants in fertilizers. Dry deposition accounts for 30-70% of terrestrial inputs.[1] Cadmium is highly mobile in soils and becomes mineral-associated over time. Higher pH and temperature favor cadmium incorporation into minerals, while lower pH and temperature makes cadmium more soluble. Dissolved cadmium circulates through freshwater systems before introduction to larger bodies of water. In rivers, dissolved cadmium ranges from nanomolar to micromolar concentrations.[1]