Fern Soaks Up Arsenic Like a Sponge

Jan 31 2001 @ 08:50

A common fern has been found to soak up extraordinary amounts of arsenic without any ill effects, potentially offering a natural way of cleaning up polluted soil and water.

The plant, known as the brake fern, grows naturally in the Southeast and California.

``It looks lush green,'' said Lena Ma, a soil chemist who led the research at the University of Florida at Gainesville. ``When I take people to my greenhouse to look at a fern with 8,000 parts per million of arsenic, they can't imagine it's toxic waste.''

The brake fern, whose scientific name is Pteris vittata, is the first plant known to accumulate arsenic in extremely high concentrations and still flourish, scientists said. The discovery was reported in Thursday's issue of the journal Nature.

A crystalline chemical, arsenic is one of the best known poisons. It has often been the poison of choice in the arts, as in the classic film ``Arsenic and Old Lace.''

Arsenic taints many sources of drinking water in the United States and abroad. People who drink arsenic-contaminated water over long periods are believed to run a higher risk of bladder, lung and skin cancer, as well as other heart and lung ailments.

Some arsenic is naturally present in soil. It also comes from some farm chemicals, wood preservatives and other industrial products.

Ma said that, unlike many ferns, this one likes the sun. It could potentially be cultivated in water and act as a natural arsenic filter. And the fern's arsenic-loving genes could potentially be spliced into other plants.

``The fact that it can take something that is toxic at extremely low concentration and accumulate it at high concentrations is very useful,'' said Stephen Ebbs, a plant researcher at Southern Illinois University.

Some plants are already used to remove other pollutants from the environment, a process known as phytoremediation. But the plants do not concentrate the toxins as strongly as the brake fern.

Other powerful accumulators are being tested, but these plants are generally small and thus collect chemicals in very small amounts.

By contrast, the brake fern collects the arsenic in fronds that grow up to 5 feet long. Unlike roots - where some plants accumulate pollutants - the fronds are easy to harvest when it is time to clear away the arsenic. Scientists said more work is needed on how to dispose of the plants.

The report of the fern's special properties comes at a time of intensified worry about arsenic in drinking water. Last year, a World Health Organization study said that up to 77 million of Bangladesh's people are at risk of poisoning from naturally occurring arsenic in drinking water.

Two weeks ago, the Environmental Protection Agency announced a much tighter standard for arsenic in American drinking water, forcing about 3,000 communities to take stronger action.

The Florida researchers were looking for a plant that could take in soil arsenic in high concentrations and then be hauled away. They tested 14 species from an abandoned lumber yard contaminated by arsenic in Archer, Fla.

Their tests showed that the brake ferns growing there concentrated up to 200 times the arsenic level in the soil. In other tests, the researchers spiked soil with varying levels of arsenic and found that brake ferns absorbed the poison at 10 to 64 times the original concentrations.

``She got incredibly lucky. She happened to pick the 14 and found one good one,'' said David Salt, a Northern Arizona University biochemist who specializes in such pollution-absorbing plants.

It is unclear if the fern is taking in arsenic as a nutrient or for some other reason.

Edenspace, a company in Dulles, Va., has bought rights and already begun to market the fern commercially.
 

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