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Assignment 3 (2^nd PDF from the portal)

Part A:

1.                  Food selection from USDA

Selected food: Chocolate chip, Branded (393124).

2.                  Mention amount of potassium in mg per 100g from USDA site

There is nearly about 309mg of K in 100g of the food taken (FoodData Central). 309mg = 309 x 10^-3 grams K.

3.                  Calculation of k-isotopes in 52 grams of the food

52 grams of Chocolate Chips x 309 x 10-3 grams K/ 100 grams of Chocolate Chip = 160.68 x 10-3 grams K = 160.68 mg K.

4.                  Calculation of ⁴⁰K from fact 1(given in the PDF)

160.68 x 10-3 grams K x 1.2 x 10^-4 g ⁴⁰K/ 1 gram K = 193 x 10^-7 grams ⁴⁰K = 19.3 x 10^-6 g

Therefore, there is about 19.3 mg of ⁴⁰K in 52 grams of Chocolate chip.

5.                  Calculation of radioactivity from fact 2

19.3 x 10^-6 g ⁴⁰K x 7.1. x 10^-6 Ci / 1 gram ⁴⁰K = 137.03 x 10^-12 Ci

Hence, 52 grams of chocolate chip has only 137.03 x 10^-12 curies or 137 pCi of radioactive decay.

6.                  Translation of picocuries in beta disintegration/minute

137 pCi x (2.2 disintegrations /min)/pCi = 301.4 disintegrations / minute (at least 4 chocolate chips are needed for this)

Part B:

1.                  Choose an animal, write down its weight in pounds and kilograms

Selected animal: one Big American Bison. Weight: 1544 pounds or 700kgs (Kock and Joel 627).

2.                  Calculation of total potassium in the animal in grams

Consider, there are 2 grams of potassium for every kilogram of body mass.

700-kilogram x 2 grams K/kilogram = 1400 grams K (all different isotopes) for an adult male American Bison.

3.                  Disintegration per second

1400 grams of potassium x 31 Bq / gram of K = ~ 43 x 10³ Bq occur in an American Bison.

4.                  Total energy in keV

(43 x 10³ d/ sec) x 560 keV/d = ~ 24 x 10⁶ keV/sec

5.                  Conversion of keV in picojules

(24 x 10⁶ keV/sec) x (1.6 x 10^-4 pJ/keV) = 38.4 x 10² pJ/sec = 3916.8 pJ/sec

6.         Calculation of picowatts into beta disintegration per minute

3916.8 pJ/sec = ~ 3917 picowatts, in an American Bison

References

Kock, Michael D., and Joel Berger. "CHEMICAL IMMOBILIZATION OF FREE-RANGINGNORTH AMERICAN BISON (BISON BISON) IN BADLANDS NATIONAL PARK, SOUTH DAKOTA." Journal of Wildlife Diseases 23.4 (1987): 625-633. < https://www.jwildlifedis.org/doi/pdf/10.7589/0090-3558-23.4.625 >

usda.gov, 2019. GoodData Central/Nutrients, Retrieved on 23^rd November 2019 from: https://fdc.nal.usda.gov/fdc-app.html#/food-details/393124/nutrients