From February 6, 2001
Fern Found to Soak
Up Arsenic
The brake fern, a common
fern native to the Southeast and California, has been found to soak up
extraordinary amounts of arsenic. According to The Association for the
Environmental Health of Soils, this fern has an extraordinary capability
to uptake a large quantity of arsenic from soils and translocate them
to aboveground biomass. In laboratory studies conducted by Lena Q. Ma,
Cong Tu, and Elizabeth Kennelley of the University of Florida, fern samples
were both collected from an arsenic contaminated soil and grown in a greenhouse
in artificially contaminated soils for up to 8 weeks, and then analyzed
for arsenic concentrations. The ferns harvested from the arsenic contaminated
soil were shown to have an arsenic concentration in the aboveground biomass
of up to 7,500 parts per million (ppm), a concentration up to 200 times
greater than those of the contaminated soils. In greenhouse soils spiked
with 500 ppm arsenic, the concentration in the aboveground biomass reached
over 2% after 4 weeks.
The process by which vegetation is used for treatment of contaminated soils, sediments, or waters to degrade, assimilate, metabolize, or detoxify inorganic and organic chemicals is called phytoremediation. It is considered an attractive technology because of its relatively low cost and aesthetic nature of using plants to clean up sites. The brake fern is the first arsenic hyperaccumulating plant to be discovered.
Arsenic is a naturally
occurring element in rocks, soils, and the waters in contact with them.
Before 1968, inorganic forms of arsenic were used extensively in agriculture
as insecticides and herbicides. Frequent applications of these chemicals
at high rates have resulted in significant arsenic accumulation in soils.
Arsenic is also a major contaminant of the surface, ground, and drinking
water in the United States abroad. Arsenic contamination poses a significant
health risk to humans and animals. It is a known carcinogen, contributing
to skin, lung, bladder, and other cancers, a known mutagen, and has adverse
effects on the heart, lungs, and immune system.