3. Assuming sulfate (SO42-) in the ocean is in steady state, what is its residen

Question

3. Assuming sulfate (SO42-) in the ocean is in steady state, what is its residence time in millions of years?
Concentration of SO42- in ocean: 2.65 g/kg
Amount of seawater: 1.4×1021 kg

Rate SO42- is added to the ocean: 3.3×1014 g/yr

4. How many kilograms of phytoplankton does it take to support a 200 kg shark that is a fourth-level consumer (i.e., it eats seals that eat fish which fed on zooplankton which ate phytoplankton). Assuming that the energy transfer efficiency is 10% between the trophic levels.

5. If 1000 GtC are stored in living organisms (the “biosphere”) and the flux of carbon into the biosphere is 100 GtC per year. Assuming that the biosphere is in steady state, what is the residence time of carbon in the biosphere?

6. The average pH of the ocean is 8.1, and pure water has a pH of 7.0. What is the concentration of H+ ions in seawater? How does this compare with pure water? In other words, what is the ratio of H+ ion concentration between seawater and pure water?

7. If the pH of the surface ocean changes from 8.2 in 1750 to 8.0 by the year 2050, what would be the H+ ion concentration in 2050 as a percent of the concentration in 1750?

8. On a sunny day (no clouds), a wheat field with an albedo of 30% receives 300 W/m2 of sunlight. How much radiation will be reflected off of the field and back to space?
How much energy will be absorbed and converted into heat?

9. If sea level rises by 1 meter between the years 2016 and 2100, what will be the average rate of sea level rise in cm/yr? How does this compare with the current rate of sea level rise, which is 3 mm/yr?

Explanation / Answer

(3) 2.65*1.4*10^21=3.3*10^14*x

x=1.1242*10^7=11million years

()5) the residence time is 1000/100=10years

(6) the equation used to find pH given the concentration of Hydrogen ion is:
pH = - log [H+] in which you take the negative log of the concentration of hydrogen ion.

however since you are given the pH: 8.1= -log [H+]

therefore you must take the anti-log of the pH:
[H+]= 10^ -8.1 = 7.94 x 10^ -9

for pure water = 10^-7

the ratio of H+ ion concentration between seawater and pure water=7.94 x 10^ -9 /10^-7=7.94*10^-2

(7) percentage change=(10^-8 - 10^-8.2)/2050-1750=1.23e^-13

(8)700W/m2 of sunlight

(9) average rate of sea level rise in cm/yr=

100cm/84=1.19cm/y

it is greater than the current rate

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