An oil storage area, abandoned 19 yr ago, had spilled oil on the ground and satu
ID: 1827985 • Letter: A
Question
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?
please i want the steps of part b
Explanation / Answer
Not linear. One year is wrong. The contamination will decrease as an asymptote, never reaching exactly zero. In 19 more years, the contamination will likely be one mg/kg, which is likely acceptable for building a restaurant. At low oil concentrations the micro-organisms become less efficient at converting the oil. The micro-organisms are starving at 20 mg/kg. Besides micro-organisms, some other mechanisms are likely at work reducing the pollution, but they are also non-linear.