Selenium in the Environment
Selenium (Se) was identified as an element in 1817 and it is classified as a metalloid. All four oxidation states of Se (denoted -II,O,IV and VI) can be found in nature.In geology,marine sedimentary rocks can become seleniferous through erosion of seleniferous volcanic materials.It is thought that bioaccumula tion of Se in ancient seas,followed by deposition and diagenesis of the selenium-rich organic matter,constitutes a primary mechanism of Se enrichment in ancient sedimentary deposits.Much of the Se in the Earths crust co-occurs in pyrite and other sulphide minerals. Although elemental Se is not commonly found in nature,it can exist in several allotropic forms,and usually is quite stable and insoluble.Selenites (IV) can be readily reduced by ascorbic acid or sulphur dioxide,and in alkaline media tend to oxidise slowly to the VI state.Selenites are firmly bound to Al and Fe oxides,rendering them insoluble in soils and sparingly bioavailable.In the VI or selenate state,Se is stable under alkaline and oxidising conditions.If present in alkaline soils,Se (VI) is readily available for plant uptake,but is easily leached out of the soil profile.
S.P.McGrath
Rothamsted Research,Harpenden,Hertfordshire,AL5 2JQ,United Kingdom
国际会议
The First International Conference on Selenium in the Environment and Human Health(第一届硒与环境和人体健康国际会议)
苏州
英文
3-4
2009-10-01（万方平台首次上网日期，不代表论文的发表时间）