It was during a walk along the coast that Ravi Naidu found the answer to his problem: "Seaweed! The idea just popped up." The ubiquitous and cheap plant material held the solution to his biore-mediation experiments DDT-contaminated soils. He and colleague Mallavarapu Megharaj of the University of South Australia found that sodium enhances bacteria's ability to degrade DDT in anaerobic environments. Throwing in some organic matter as fertilizer further accelerated the process. "Seaweed contains sodium and is a source of dissolved organic carbon," explains Megharaj.
Their recipe worked, as they reported in a recent paper.1 When DDT-contaminated soils were treated with powdered green and red algae (
Peter Adriaens of the Center for Microbial Ecology at Michigan State University, East Lansing, admits that he's never heard of the seaweed solution. "But it makes sense," he comments. "Sodium breaks apart soil particles, making the contaminants readily available to the bacteria performing the biodegradation reactions. And as an added benefit, the natural organic matter in seaweed provides food for the microbes."
Overfeeding is detrimental though, the researchers found; just the right amount of the powdered material, 0.5% by weight, works best. Megharaj mentions another benefit of technique: "It works especially well in problem soils that are waterlogged or have been contaminated for more than 15 years."
- Silvia Sanides