Radioactive
elements are part of our ecosystem, part of the air we breathe, the water we
drink and the food we eat.
· Radionuclides
can occur naturally, or can be man-made.
· Over
half of the average annual radiation exposure of people comes from natural
sources.
About
Radionuclides in Environment
An
ecosystem is a place with a one-of-a-kind combination of air, water and land.
An ecosystem has habitats that support plant and animal life. Ecosystem science
focuses on all parts of the system, including the interaction among the water,
air, land, plants, humans and other animals. Ecosystem science can tell us how
minerals and other chemicals in nature (including radionuclides) move through
Earth’s different natural systems.
Radionuclides
enter an ecosystem in three ways:
·
As
minerals present in Earth’s original crust.
·
As
radionuclides created by cosmic rays hitting atoms in Earth’s atmosphere.
·
From
human activity.
Radionuclides
in Earth‘s Crust
Some
radionuclides have been present in rocks since the formation of Earth. Others
are their decay products. Examples of these natural radionuclides include
potassium-40, rubidium-87, uranium and thorium and decay products, such as
radium and radon.
These
radionuclides end up naturally in soil, water and air. Rocks containing them
are broken down into soil by the weather, bacteria and fungi. When radionuclides
are in soil particles, they can be blown around by wind. Some will dissolve in
water and end up in surface or ground water. Some radionuclides dissolve more
easily than others. Also, the makeup of the water affects how much of the
radionuclide will dissolve.
More
half of the average annual radiation exposure of people comes from natural
sources. The natural radionuclide, radon, is the single biggest natural source
of exposure. It comes from the breakdown of radium. Breathing indoor air
containing radon is the most common exposure route.
Radon
is one radionuclide that dissolves easily in water. Radon concentration in
water is usually low enough that they are not a serious health threat.
Radiation
from Space
Cosmic
rays come from stars, our sun, other stars and exploding stars. The rays
continuously strike atoms in Earth’s atmosphere. The atmosphere stops most of
the cosmic rays, however, the collisions leave some atoms unstable
(radioactive). These radioactive atoms are called cosmogenic radionuclides.
They are rare, but some of them do reach Earth’s surface and settle on the soil
and water.
Radionuclides
from Human Uses of Radioactive Material
Nature
is the major source or of radionuclides in an ecosystem. Much smaller amounts
of radionuclides come from sources developed by humans. Examples include
uranium mines, nuclear power plants and research facilities that use
radionuclides. However, for most people the annual exposure from these sources
is very low. Only in certain areas where there are open uranium and other
mineral mines and mining wastes present is there a serious health hazard.
· Nuclear
Weapons Testing:
Nuclear weapons tests released large amounts of radionuclides that spread and
remained in ecosystems until the radionuclides decayed away. Today, nuclear
events include nuclear accidents and potentially terrorist acts.
· Nuclear
Facility Releases: The
small amounts of airborne radionuclides released from facilities that handle
and process radioactive materials can get into the soil, water or air. The
facilities operating permits allow only very small releases because they result
in very small exposures.
· Radioactive
Waste: Improper disposal of
radioactive waste is another way radionuclides can enter an ecosystem. For
example, water seeping thorough mining wastes can dissolve some radionuclides
and carry them into the water system. Public water systems are monitored
carefully to make sure the drinking water is safe. This kind of waste accounts
for less than a tenth of one percent of the average annual radiation exposure.
