1. Theoceans a. The annual input of SO4 2- into theoceans by rivers is estimated
ID: 688324 • Letter: 1
Question
1. Theoceans
a.The annual input of SO42-into theoceans by rivers is estimated to be 3 x 1012 mole/yr. If SO42- were at a steady-stateconcentration in sea water and the only significant sulfate inputto the oceans were the river flux, what would the residence time ofSO42-in theoceans be? The mass of the oceans is 1.4 x1024 g and the SO42- concentration in the oceans is0.028mol/kg.
b. If there were no SO42- flux out of the oceans tobalance the above input flux, so that its concentration wasconstantly building up due to the river flux, how long would ittake to increase the SO42-concentration by15%?
Explanation / Answer
flow rate SO42- = 3e12 mol/yr *(1 kg/0.028 mol) =1.07142857e14 kg/yr Residence time = mass ocean / flow rate = (1.4e21 kg) /(1.07142857e14 kg/yr) Residence time = 13066666.7 = 1.31 x 107 yr b) d(c*M)/dt = flow rate c = flowrate*t/M +c0 M = mass ocean. c = 1.15*c0 0.15*c0 = flowrate*time/M time = 0.15c0*M/flowrate = (0.15*0.028 mol/kg *1.4e21 kg)/(3e12mol/yr) time = 1960000 yr = 1.96 x106 yr
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