Phytoremediation of selenium-contaminated soils and waters: fundamentals and future prospects

Interest in selenium pollution and remediation technology has escalated during the past two decades. Although not known to be essential for plants, selenium is an essential micronutrient for humans and animals, having important benefits for their nutrition. At high concentrations, however, selenium becomes toxic to animals and humans. A major selenium controversy in the 1980s emerged in California at the Kesterson National Wildlife Refuge; hence, scientists, environmental regulators, politicians, and the general public in the United States became aware of selenium's potential as an environmental contaminant. Consequently, extensive research has been conducted in the western United States, and a vast amount of financial resources have been allocated to develop management strategies and remediation technologies for reducing the impact of naturally occurring selenium on the biological environment. A plant-based technology, defined as 'phytoremediation', has received increasing recognition as a low-cost, environmentally friendly approach for managing the toxic effects of selenium. Plants have the ability to absorb and sequester selenium and to convert inorganic selenium to volatile forms of organic compounds that are released harmlessly into the atmosphere. The present review summarizes recent research findings and information about strategies on using phytoremediation systems to detoxify selenium-contaminated soils and waters in natural and agricultural ecosystems.