1. In the 1950s and 1960s, a series of atomic bomb tests added large amounts of
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Question
1.
In the 1950s and 1960s, a series of atomic bomb tests added large amounts of Carbon-14 to the atmosphere. The figure above shows the change in the 14C concentration in the atmosphere over the last ~60 years. The spike you see around 1965 corresponds to the accumulation from atomic bomb tests. Remember: 14C is basically (14C/12C).
Due to radioactive decay alone, how much would the atmospheric 14C have decreased since 1965 (i.e. in the last 53 years)? Given: half-life of Carbon-14 is 5730 years.
< 1%
< 10%
< 50%
< 90%
n the previous question, you looked at the amount of radioactive decay expected for the C-14 added through bomb tests in the 1960s. Knowing that the half-life of C-14 is 5730 years, what you do think the reduction in atmospheric 14C since 1965 is due to?
Remember: 14C is basically (14C/12C).
A. Radioactive decay
B. Ocean uptake
C. Dilution by fossil fuel emissions because fossil fuels contain lots of Carbon-12
D. B & C
E. A & C
A< 1%
B< 10%
C< 50%
D< 90%
Long term trend of CO, in the Northern Hemisphere 1000 - tree rings .- Vermunt 800 Jungfraujoch 8 600 CO 400 period of the strongest 200 bomb tests Carbon Cycle Group Institut für Umweltphysik, Univ. Heidelberg 1950 1960 1970 1980 1990 2000 2010 natural reference level YearExplanation / Answer
1 B
2 E
Radioactive decay is one of the main cause for reduction of 14C. There are many other causes like reducing energy consumption, reducing waste.
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