Selenium can build up in a toxic form in the evaporation ponds commonly used to dispose of wastewater from farms. The effectiveness of wetlands in removing selenium was discovered inadvertently during an experimental clean-up project for the Chevron Oil refinery near San Francisco Bay.
Further work is needed to find a safe way to use this technique, to avoid transferring toxins back into the eco-system via birds, insects or fish feeding on contaminated plants, says the report.
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