Exotic grass could help clean lead from
soil
Monday March 12, 2012, 12:02 AM
BY JAMES M. O'NEILL
STAFF WRITER
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.
DON SMITH/STAFF PHOTOGRAPHER
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."
Email: [address removed]
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