Environmental Selenium Challenges
Why Test for Discrete Selenium Species?
In order to predict the behaviour and impact of selenium in the environment, including how bioaccumulation to toxic levels can occur, the concentrations of discrete selenium species should be measured and understood. In the aqueous environment, selenium exists predominantly as the dissolved oxyanions selenite [Se(IV)] and selenate [Se(VI)], but can also occur as Se(-II) in organic compounds. Organoselenium compounds can occur in many forms, with common examples including volatile organoselenides such as dimethyl selenide (DMSe) and dimethyl diselenide (DMDSe), selenols (similar to alcohols), selenocyanate (the selenium analog of thiocyanate), and the selenium analogs of amino acids such as selenomethionine and selenocysteine. Dimethyl selenoxide and methylseleninic acid can occur as oxidative byproducts of dimethyl selenide and dimethyl diselenide.
To prevent environmental harm, industries that produce waste streams with high selenium content must invest in treatment systems to capture selenium. State-of-the-art treatment systems often use bioremediation reactors to microbially reduce toxic selenite and selenate to insoluble elemental selenium [Se(0)], which can then be physically removed. Measurement and control of discrete selenium species concentrations is important for the optimization and reliable operation of these complex biosystems.