Please Write Legible and show all work thank you Estimating Bioaccumulation: DDT

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Please Write Legible and show all work thank you

Estimating Bioaccumulation: DDT in a Lake Note: this is a hypothetical example.) A medium sized lake can serve as a major food source for a subsistence community. Suppose that a community of about 100 people gets much of its protein from fishing on such a lake. Every day, each person eats one or two fish, which weigh on average about 150 grams. The fish feed primarily on shrimp, as well as insects and other small animals. You have learned that algac, one of the primary food sources for shrimp in the lake, is contaminated with DDT, a persistent organic pesticide that farmers upstream have begun using to control ants in food crops. You want to know how much of this DDT might eventually end up in members of the community The following shows how to calculate the concentration of DDT in the shrimp, given the concentration in algae and the eating habits of the shrimp Knowns: Algae contain about 0.0002 mg of DDT per gram of algae. That is about 0.2 parts per million (ppm). Over its (short) life, a shrimp will grow to weigh about 1 gram The average shrimp eats about 10 grams of contaminated algae during its life. - The amount of DDT consumed by the shrimp can then be calculated DDT consumed by shrimp-amount algae consumed concentration of DDT in algae So DDT consumed by shrimp = 10 galgae x 0.0002 mgDOT per glpe-0002 mgDor Since a shrimp weighs 1 gram, the concentration of DDT in the shrimp is 0.002 mgpDT/Bshrimp or about 2 mg /kg (ppm) This assumes that ALL of the DDT consumed by the shrimp stays in its body (a "worst case" assumption that is probably not true) Now, use this same method to estimate the eventual concentration of DDT in fish and in humans, given the following information | The average fish eats about 1.7 kg of shrimp as it grows to weigh 150 g. The average person eats 1 -2 fish per day over a 60 year life. The average adult weighs about 70 kg. Note that you will have to compute the total amount of fish eaten by multiplying the amount eaten per day by the number of days in the individual's life.

Explanation / Answer

Let us first look at what is given to us

Food Chain : Human -> Fish -> Shrimp -> Algae

For Algae, Every gram of algae contains 0.0002 mg of DDT

For Shrimp, Shrimp's weight over lifetime = 1 gram

Algae Eaten during lifetime = 10 gram

For Fish, Fish's weight over lifetime = 150 gram

Shrimp eaten during lifetime = 1.7 kg

For Human, Weight over lifetime = 70 kg

Average life expectancy = 60 years

Fish eaten = 1 or 2 per day.

FISH -

As we know from the first part, Concentration of DDT in shrimp or Amount of DDT per gram of shrimp is equal to 0.002 mg DDT or 2 mg DDT per kilogram of shrimp.

DDT consumed by Fish in its lifetime = Amount of shrimp consumed * Concentration of DDT in shrimp

= 1.7 kg * 2 mg/kg (Always remember to write units, so that you dont get confused with the answer. Here, since shrimp consumed is in kg, I took the amount of DDT also as per kg of shrimp)

Therefore, DDT consumed by Fish in its lifetime = 3.4 mg DDT

Since, weight of fish is 150 grams for lifetime so this is 3.4 mg of DDT per 150 gram of fish.

Therefore, concentration of DDT in fish = 3.4 mg DDT/150 g

= 0.0227 mg DDT / gram of fish

= 22.7 mg DDT / kg of fish

Concentration of DDT in fish = 22.7 ppm

HUMAN -

First, we need to find out the amount of fish consumed by human. Since, we are finding how much DDT might end up in the community letes assume the maximum case where every human eats 2 fishes per day.

Weight of fish consumed per day =

1 fish = 150 g

2 fish = 300 g

Number of days in human life = 365 * 60 (60 years is the life expectancy and 365 days per year)

= 21900 days

Therefore, in full lifetime a human consumes, 21900 * 300g (Max case) = 6570000 g of fish or 6570 kg of fish

Now,

DDT consumed by Human in its lifetime = Amount of fish consumed * Concentration of DDT in fish

= 6570 kg * 22.7 mg/kg

Therefore, DDT consumed by Human in its lifetime = 149,139 mg DDT

Since, weight of human is 70 kg for lifetime so this is 22.7 mg of DDT per 70 kg of human.

Therefore, concentration of DDT in human = 149139 mg DDT/70 kg

= 2130.56 mg DDT / kilogram of human

Therefore concentration of DDT in a human is around 2131 ppm

For a community of 100 humans, the concentration is about 213100 ppm (Numbers increased drastically as we moved up the food chain)

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