Originally created 08/31/97

Scientists mimic Mother Nature to clean water pollution

SAVANNAH, Ga. - "Phyto-remediate this, you toxic blob!" the marsh grass said to the mercury spill.

Far-fetched, but not too far away if scientists on Skidaway Island can figure out how to use coastal plants and soils to naturally filter polluted water.

The process is called phyto-remediation and it could be a safe, long-term solution to large, low-level toxic sites around the world, said Herb Windom, director of the state-owned Skidaway Institute of Oceanography.

"There are a lot of areas with fairly low levels of contaminants, but they're still a problem," Windom said. "They may affect 100 acres of salt marsh and it's just not feasible, or advantageous, to dig it up. We're finding ways to maximize nature's processes."

Plants already are used to clean industrial wastewater, sewage and oil spills. The scientists at Skidaway are working on the next step: finding the combination of plants and bacteria that can best clean "mixed" wastes - toxic metals and organic pollutants.

"Finding a silver bullet would be an important move forward, but you have to make sure it doesn't result in a secondary problem," said Doug Rader, senior scientist in Raleigh, N.C., for the Environmental Defense Fund.

"You'll have to harvest these plants to prevent an accumulation in them or to prevent threats to herbivores eating in a natural-looking setting," Rader said. "If you harvest the plants, that still constitutes just a transfer, to who knows where, from a site that's known. This is one of the toughest problems."

Phyto-remediation, Rader said, would be best done to intercept pollutants on the move, such as in West Virginia, where metals from old mines are floating into water sources.

The lottery-funded Georgia Research Alliance, an economic-development partnership of government, academia and industry, gave $750,000 to build and equip the Bioremediation and Environmental Research Mesocosms facility (BERM). It includes a greenhouse, laboratory and mesocosms, which are basically large outdoor test tubes.

The facility falls between the too-controlled conditions in a lab and uncontrollable conditions in the wild.

"You hear about a lot of things that are wonderful discoveries in the lab, but not field-tested - and then you never hear about them again," said Dick Lee, a Skidaway faculty member. "The reason why is that out in the field, it's a mess. It's dirty, it rains, there are all kinds of mixtures of pollutants. This is as close to the field as we can come without being in the field. It's a large-scale model of the environment."

The BERM opened last October. Now that federal and private grants are in place for ongoing studies, scientists from the institute, Clark Atlanta University, Georgia Tech and the University of Georgia are gathering there to learn how to naturally filter toxic mercury, polychlorinated biphenyls (PCBs), creosote and radioactive cesium and uranium.

Working on metallic and organic pollutants at the same time is a realistic approach to research, Lee said, because most toxic sites - except for petroleum spills - contain both. Metals generally come from industries, and organics from pesticides.

The tanks are such realistic recreations of natural settings that tiny fiddler crabs stuck to the marsh grasses that were placed in them are thriving, Lee noted.

It's here that scientists hope to show that marsh grass can take methyl mercury - the most toxic form of mercury - into its roots, gradually transform it into safer, elemental mercury, then release it into the air.

Security is a priority at the outdoor tanks, so that scientists don't end up with a toxic site of their own making. Each tank is draped in plastic to prevent leaks. The water is kept only in dedicated reservoirs and holding tanks. A tall fence edged in barbed wire keeps out animals and uninvited visitors.

So far, there have been no accidents at such mesocosms, Rader said.

"I get more nervous, though, as the consequences for failure get more severe," Rader said. "But then, unless you do experiments, you can't hope to solve problems."

Testing in real marshes is about three years away, Lee said. Experiments with creosote show the most promise.

If work with the other pollutants continues to show promise, the research could aid the cleanup of the Amazon River Basin, where miners use toxic mercury to find gold, and Texas' Lavaca Bay, turned by manufacturers into a toxic stew of leftover chemicals.

It also might allow people again to eat large-mouth bass caught in south Florida. They're banned now because they contain dangerous levels of mercury.


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