Eliminating Uranium from the Food Chain: Are Fungi the Key?
Portland, Ore., USA: For decades, mining companies unearthed uranium in the
American Southwest. Today, the remnants of those mines pepper the
landscape, especially in the Navajo Nation, in northeast Arizona. Mine
tailings and dust still circulate through the ecological system, spreading
radioactive particles on soils, waterways, and homes.
This radioactive dust is taken up by plants and spreads through the leaves
and shoots. Grazing animals like sheep, a common livestock consumed by
Navajo people, eat the contaminated plants and incorporate the radioactive
materials into their tissues. Thus, uranium exposure is concentrated
further through the food chain.
presented at the Geological Society of America’s Connects 2021 annual
meeting on Tuesday examines how chronic uranium exposure in the food chain might be
reduced. Professor Laura Wasylenki, of Northern Arizona University, is
presenting the work of her former graduate student Katherine Dunlap, where they examined how
root fungi might alter the uptake of uranium in plants.
Plants absorb elements, including uranium, from the soil and spread the
material from “root to shoot,” says Wasylenki. Animals that graze on the
plants will then ingest uranium, where it accumulates in tissue. The Navajo
community raises sheep, which are an important source of food and part of
their cultural heritage. The uranium stored in the sheep move up the food
web into humans.
Wasylenki says hardly anything is known about the role of fungi in the
uptake of elements by plants. “We saw one experimental paper saying the
fungi made the plants take up more uranium total, but only in the roots—it
didn't transport up into the shoots or leaves of the plants.”
She explains that in grazers, some pull up the whole plant to munch on,
while others (like sheep) pluck the tops of the plants. Wasylenki
and Dunlap wanted to test whether there was a way to stimulate growth of
the right fungi and sequester uranium underground. “Then at least you would
be helping to reduce the uranium consumption of guys that just crop the
tops [of the plants],” notes Wasylenki.
The team grew sunflowers with and without symbiotic root fungi (called
arbuscular mycorrhizal fungi). In particular, they were curious how the
mineralogy of the soil and the presence of fungi would influence the uptake
of uranium in sunflowers. Artificial soil (Turface) with no uranium present
was used in the pots, and a layer of clay-rich material was added. Uranium
was added in a known concentration when the plants were watered.
When they looked at the uranium concentrations in plant tissues, they found
that the presence of fungi decreased the spread of uranium from roots to
shoots. They also found that the presence of a clay layer in the soil
increased the uptake of uranium in the plants. Wasylenki hypothesizes that
“uranium would sorb to the clay surfaces, holding it there, so that it had
a longer residence time around the roots.” She adds that while more uranium
was taken up in clay-rich soils, less was translocated throughout the
plant—more was stored in the root system of the sunflowers.
Wasylenki notes that their sample size for the initial experiment was small
but has plans to expand the testing with a larger sample size and various
soil types. The team notes that this work is an important first step in
understanding whether fungi can help mitigate uranium exposure for grazing
animals, which ultimately make their way into the human food chain,
especially for those in the Navajo community.
Northern Arizona University, email@example.com
Paper No. 134-8:
Can Root Fungi Interrupt Trophic Transfer of Uranium from Soil to
Plants to Sheep to Navajo People?
Tuesday, 12 Oct., 9:50 a.m. PDT
Session 132: T26. Environmental Geochemistry and Health:
# # #
The Geological Society of America, founded in 1888, is a scientific society
with members from academia, government, and industry in more than 100
countries. Through its meetings, publications, and programs, GSA enhances
the professional growth of its members and promotes the geosciences in the
service of humankind. Headquartered in Boulder, Colorado, USA, GSA
encourages cooperative research among earth, life, planetary, and social
scientists, fosters public dialogue on geoscience issues, and supports all
levels of earth science education.