Ancient ground water being tapped by Jordan, one of the 10 most water-deprived nations in the world, has been found to contain 20 times the radiation considered safe for drinking water in a new study by an international team of researchers.
"The combined activities
of 228 radium and 226 radium – the two long-lived isotopes of radium – in the ground
water we tested are up to 2,000 percent higher than international drinking
standards," says Avner Vengosh, associate professor of earth and ocean
sciences in the Nicholas School of the Environment at Duke University.
Making the water safe for
long-term human consumption is possible, he says, but it will require extra
steps to reduce its radioactivity.
Vengosh and his research
team, made up of scientists from Jordan, Palestine, Israel and the United
States, published their findings in a recent issue of Environmental Science
Jordan's annual water use
exceeds the natural replenishment of its major river, the Yarmouk, and its
local aquifers that are becoming salinized as a result of over-pumping.
In 2007, the Jordanian
government announced plans for a $600-million project to pump low-saline fossil
ground water from the Disi aquifer, located along the nation's remote southern
border with Saudi Arabia, and pipe it 155 miles north to the capital, Amman, a
city of 3.1 million people, and other population centers.
Fossil ground water is a
nonrenewable supply of water trapped underground in aquifers. In recent years,
policymakers in countries facing chronic water shortages have increasingly
viewed low-saline supplies of fossil ground water as an important potential
source of water for human and agricultural use. Libya and Saudi Arabia, for
example, have relied extensively on fossil ground water from Nubian sandstone
aquifers similar to the Disi to meet their water needs in recent decades.
Most fossil ground water
resources in North Africa and the Middle East are characterized by high-quality
water with low salinity. "The assumption has been that unsafe radioactive
levels occur primarily in high-saline ground water, so low-saline sources, such
as water from a Nubian sandstone aquifer, are relatively safe resources just
waiting to be tapped," Vengosh says.
To test that hypothesis,
Vengosh and his colleagues investigated water from 37 pumping wells in the Disi
aquifer's Rum Group, where low-saline ground water is extracted from
Cambro-Ordovician sandstone, and from wells in the Khreim Group, where saltier
water is extracted from an aquifer containing larger amounts of clay minerals
and oxides. All samples were analyzed for major and trace elements and for four
radium isotopes. For comparative purposes, sandstone rocks from the Disi
aquifer, along with Nubian sandstone rocks from the nearby Negev Desert in
Israel, also were measured for radium.
"We found a lack of
correlation between salinity and radioactivity," Vengosh reveals.
"Instead, our findings suggest that an aquifer's geological properties may
be a much more significant factor."
Vengosh and his group
hypothesize that an aquifer with a higher content of clay minerals and oxides
provides more adsorption sites for radium, and this results in lower
radionuclide levels in the water itself. Sandstone aquifers, on the other hand,
offer fewer adsorption sites, and, as a result, generate radium-rich ground
"Given that most of the
aquifers in the region that contain fossil water are composed of Nubian
sandstone and are characterized by low-saline ground water, similar to that in
the Disi aquifer, we suggest that high-radioactive ground water may also exist
in these basins. This could pose health risks for a large population,"
Vengosh says. Ground water from the Disi aquifer already is used for drinking
water in parts of Jordan and, more extensively, in Saudi Arabia, where it is
known as the Saq aquifer.
"Making ground water from
the Disi aquifer and similar sandstone basins in the region safe for long-term
human use will require a significant reduction of radionuclide levels,"
Health officials could reduce
radioactivity to safe levels by diluting radium-rich water with low-radium
water from other sources, he explains, or by treating it with ion exchange,
reverse-osmosis desalination or lime softening. Each of these three treatment
technologies does a good job of removing radium, Vengosh notes, but each
produces solid and liquid residues that would have to be handled and disposed
of as low-level radioactive waste.
The U.S. Environmental
Protection Agency (EPA) classifies radium as a Group-A carcinogenic material,
which means exposure to it could cause cancer.