An oil storage area, abandoned 19 yr ago, had spilled oil on the ground and saturated the soil at a concentration of perhaps 400 mg/kg of soil. A fast food chain wants to build a restaurant there and samples the soil for contaminants only to discover that the soil still contains oil residues at a concentration of 20 mg/kg. The local engineer concludes that, since the oil must have been destroyed by the soil microorganisms at a rate of 20 mg/kg each year, in one more year the site will be free of all contamination. a. Is this a good assumption? Why or why not? (Hint: Consider kinetics.) b. How long would you figure the soil will take to reach the acceptable contamination of 1 mg/kg?

Question

Jazmine

Geography

12 October, 11:17

An oil storage area, abandoned 19 yr ago, had spilled oil on the ground and saturated the soil at a concentration of perhaps 400 mg/kg of soil. A fast food chain wants to build a restaurant there and samples the soil for contaminants only to discover that the soil still contains oil residues at a concentration of 20 mg/kg. The local engineer concludes that, since the oil must have been destroyed by the soil microorganisms at a rate of 20 mg/kg each year, in one more year the site will be free of all contamination. a. Is this a good assumption? Why or why not? (Hint: Consider kinetics.) b. How long would you figure the soil will take to reach the acceptable contamination of 1 mg/kg?

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Answers (1)

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Rebecca Davies · Answer 1

The answer is 19 years.

Explanation:

A) One year is wrong, This will decrease as an asymptote, never reaching exactly zero. In 19 more years, the contamination will likely by mg/kg.

B) L = LoE^-kt

20 = 400 (e^-K (19))

K = 0.158

L = Loe^-kt

1 = 20 (e^-0.158t)

t = 19 years.