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cate the ag or the shell. 42. Rember et al. (1993) measured the concentrations o

ID: 934532 • Letter: C

Question

cate the ag or the shell. 42. Rember et al. (1993) measured the concentrations of 137Cs in the bottom sediments of Medicine Lake, northern Idaho. Heavy-metal-laden tailings from the Coeur d'Alene mining district were deposited in this lake. Tailings were deposited during floods as Atmospheric test- ar bombs, the source of 13Cs, began in 1951 and reached a maximum in well-stratified, heavy-metal, contaminated silts on the lake bottom ing of nuclear bombs, the source of 137Cs, began in 1951 and reached a maximum in 1964. 13"Cs is first detected in the varved sediments at a depth of 30-32 em and the 137Cs maximum occurs at a depth of 16-18 cm.

Explanation / Answer

Your question is not quite clear. You should have attched full question. Anyway i will try my best to solve it.

It will be 1st order reaction.

Initial deplth = 30 -32 cm. Average = 31 cm

After 13 years (In 1964), average depth = 17 cm

Use:

[R]=[R]o* e^ (-k*t)

17 = 31 * e^ (-k*13)

k=0.04369 years-1

Part b :

Final depth = 11 cm (Average). to find time t use:

[R]=[R]o* e^ (-k*t)

11 = 31 * e^ (-0.04369*t)

t= 24 years

Answer: 24 years