Question

Fallout from nuclear weapons tests in the atmosphere is mainly 90Sr and 137Cs, which have 28.6- and 32.2-y half-lives, respectively. Atmospheric tests were terminated in most countries in 1963, although China only did so in 1980. It has been found that environmental activities of these two isotopes are decreasing faster than their half-lives. Why might this be?

a) Increased decay rate due to cosmic radiation
b) Environmental cleanup efforts
c) Migration of isotopes to deep layers of the Earth
d) Chemical reactions altering the isotopes

Answer 1

Environmental cleanup efforts have contributed to the faster decrease in the environmental activities of 90Sr and 137Cs compared to their half-lives.

Step-by-step explanation:

The reason that the environmental activities of 90Sr and 137Cs are decreasing faster than their half-lives is primarily due to b) Environmental cleanup efforts.

After the termination of atmospheric nuclear tests, countries have implemented measures to clean up and reduce the presence of these isotopes in the environment.

For example, contaminated soil and vegetation can be removed, and water sources can be treated to remove radioactive materials.

These efforts have led to a faster decrease in environmental activities of 90Sr and 137Cs compared to their half-lives.