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News: Subtropical Grass May Help Remove Lead from Urban Soils

From: Ashwani V.
Sent on: Monday, March 12, 2012 11:51 PM
Exotic grass could help clean lead from soil

Monday March 12, 2012, 12:02 AM
The Record

A subtropical grass might one day be grown in yards across North Jersey as an affordable way to deal with a lingering childhood health concern - lead contamination.

Illustration Omitted:
     Montclair State University Professor Dibyendu Sarkar, left, and post doctoral research associate Ramesh Attinti with plantings of vetiver, a subtropical grass they hope can be used to remove lead from soil.

Dibs Sarkar, a local scientist, is studying how the long roots of the grass can absorb lead from the soil and store it. Tests in a greenhouse have so far been successful; the lead contamination was consumed by the plant so fast that the soil met federal standards in about two years.

"We're confident this will work fantastically," said Sarkar, a researcher at Montclair State University.

There's a caveat, though. Some experts on the subtropical grass - called vetiver - are skeptical that it could survive cold winters in the northern United States, especially when the ground freezes. Even if it doesn't survive up north, the grass has already been grown successfully in Southern states and California, and has proven it can be a powerful weapon in removing various contaminants from soil, wastewater and road runoff.

Lead contamination remains a serious problem in New Jersey. Though lead has been banned from paint since 1978 and leaded gasoline was phased out in the 1990s, lead paint chips remain buried in urban and suburban soil and lead particulate that belched long ago from cars burning leaded gas remains bonded to the dirt. Lead poisoning among children has been declining, but there were still more than 1,300 cases reported statewide in 2010.

At a Superfund site, contaminated soil can easily be dug up. "They take it to a treatment facility and basically flush the lead out," Sarkar said. But that's hard to do around homes - and the process kills off the soil's useful microbes, making it ecologically unsustainable.

Vetiver, then, could provide a low-cost and relatively simple solution to removing lead from around urban and suburban homes, reducing lead exposure for children, Sarkar said. Depending on the results of Sarkar's research, the grass could potentially be planted around New Jersey for this purpose within the next four years.

"It could be an inexpensive option for use in back yards," said Rupali Datta, a biological sciences professor at Michigan Technological University, who is collaborating with Sarkar. "I fell in love with this plant."

Growing up in India, Sarkar couldn't avoid vetiver, which is native to his continent. The grass grows fast in dense bunches. People weave the shoots into baskets. Its oil is used in men's fragrances. And the long roots are crafted into window shades. "People sprinkled water on it, and it would be like natural air conditioning," Sarkar said.

For years, experts have used the plant to reduce erosion, and researchers in India, Thailand and China have studied vetiver's ability to absorb heavy metals. Companies now plant the non-invasive species on landfills to reduce contamination, and in California it is being used to filter out a slew of contaminants from parking lot rainwater runoff.

Dick Grimshaw, a former World Bank agricultural expert who helped introduce the use of vetiver for such purposes, said non-profit organizations have begun pushing the plant in Haiti for its value to prevent erosion, a chronic problem there. And work is under way to pelletize the plant's leaves so they could potentially be used as a cheap fuel for stoves in Haiti. Now, Sarkar is trying to prove the plant can survive New Jersey's colder climate and help clean up the region's legacy of contamination.

"Children playing outside are easily exposed to the lead, and young children with hand-to-mouth behavior can ingest it," Sarkar said. "The poorest in society are most impacted by this," since they often live in buildings that have not been renovated.

A higher proportion of lead poisoning cases in New Jersey occurs in cities and urban areas, but lead poisoning has also been found across suburban communities. Among the limited number of children under age 6 who were even tested in 2010, there were 177 cases of lead poisoning reported in Bergen and Passaic counties, including 73 cases in Paterson alone.

"In New Jersey, elevated lead levels are still a concern," said Joe Eldridge, the New Jersey Health Department's director of consumer, environmental and occupational health services.

A sizable chunk of North Jersey homes were built before 1950 - 37 percent in Bergen and 42 percent in Passaic - and are therefore more likely to have lead paint.

"Lead can affect the nervous system and the brain and cause kidney damage," Eldridge said. "It can reduce IQ and affect a child's ability to learn."

Plants are being used more often to clean soil and water of many kinds of contamination, a process known as phytoremediation. Some environmental cleanups involve planting Chinese brake fern to absorb arsenic from the ground. Mustard plants have been used to remove heavy metals.

Other scientists are using products found in the kitchen cupboard to clean up contamination of cancer-causing solvents. In a process called bioremediation, soybean oil and molasses have been pumped into the ground in North Jersey as food for microbes that occur naturally in the soil. The microbes feed on the molasses, multiply, and then "breathe" in the solvents, breaking them down into non-toxic byproducts - just the way humans breathe in oxygen and exhale carbon dioxide.

Researchers are interested in finding more plants that are "hyperaccumulators" - those that can absorb large amounts of toxic material and still thrive, said Michael Gochfeld, a Robert Wood Johnson Medical School environmental toxicologist who is particularly familiar with the use of plants to absorb cadmium from the soil. "If the contamination is at a superficial depth, it is an accepted form of environmental management," he said.

But there is one issue: "At the end of the story you still have to dispose of the now-contaminated plant material as a hazardous waste, so it's not a free lunch," he said.

Sarkar said the plant biomass can be burned to ash and buried at a hazardous waste landfill - taking up far less space than contaminated soil scraped off a site.

"It provides volume reduction - you can contain the lead in a much smaller amount of biomass to discard," he said.

Sarkar and Datta began their research on vetiver in 2004 when they were both on the faculty at the University of Texas at San Antonio.

Vetiver shoots reach 3 to 6 feet tall. The roots, however, can extend much deeper. Because of that, the grass has been used as a ground cover to reduce erosion at mining areas in South Africa and Australia. Since those soils were contaminated with heavy metals, Sarkar and Datta thought vetiver might do well in soil with lead. But would the plant pull the lead up out of the soil?

"The hard part of remediating lead is that it's not generally soluble, and the lead remains attached to the soil," Datta said.

To help the process, Sarkar and Datta prepare the soil with a chemical that separates the lead from the soil particles, making it easier for the plant to absorb. The chemical biodegrades in 15 days.

Vetiver has a defense mechanism - it produces phytochelatin, a protein that forms a sheath around the lead, giving the plant protection, Datta said. It's similar to what an oyster does by secreting a mucus-like substance around an irritant particle to form a pearl.

The researchers first gathered lead-laced soil from sites in San Antonio and tried to grow the grass in it. They had good results - the lead was absorbed and stored in the roots and shoots. But could the grass survive colder climates? Sarkar, by now at Montclair State, collaborated with a researcher at Richard Stockton College of New Jersey to find out. They set up plywood planter boxes and started growing the grass last August.

The soil had lead concentrations of at least 1,200 parts per million.

The researchers wanted to see how long it would take to reduce that to the Environmental Protection Agency's cleanup standard of 400 parts per million.

Their results showed that, at least in the greenhouse, soil with 1,200 parts per million of lead would be cleaned to the EPA standard over eight growth cycles - about two years in a greenhouse. In the Northeast, there would only be one growth cycle per year.

The shoots can be harvested and disposed of each season, and when the lead has been reduced to cleanup standards, the roots can be removed as well, leaving cleaner soil that still has the microbes necessary for a healthy ecosystem.

Datta, meanwhile, has been growing samples in an even harsher climate: Michigan's Upper Peninsula. The shoots die off in the winter, but the roots remain and send new shoots out the next season, she said.

Grimshaw, however, remains skeptical of the plant's ability to thrive in the cold.

"I don't think it will survive the sustained freezing of the ground," said Grimshaw, founder of the Vetiver Network, an international information-sharing group of vetiver researchers. He said he tried growing the plant at his home in Bellingham, Wash., but his specimens didn't survive the winter. Vetiver grown in Maryland in 1990 as part of a United States Department of Agriculture experiment  also was wiped out by subfreezing temperatures, he said.

Datta acknowledged the skepticism, but does not agree. "Mulching is a way to keep the ground from freezing, but we do not think that will be even necessary," she said.

Sarkar is also optimistic, saying: "I think we have a very good chance of seeing the plants survive winter here."

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