GG325 -- PRINCIPLES OF GEOCHEMISTRY
1. The oceans
a. The annual input of SO42- into the oceans by rivers is estimated to be 3 x 1012
mole/yr. If SO42- were at a steady-state concentration in sea water and the only
significant sulfate input to the oceans were the river flux, what would the residence time
of SO42- in the oceans be? The mass of the oceans is 1.4 x 1024 g and the SO42-
concentration in the oceans is 0.028 mol/kg
b. If there were no SO42- flux out of the oceans to balance the above input flux, so that
its concentration was constantly building up due to the river flux, how long would it take
to increase the SO42- concentration by 15%
2. Hydrosphere composition
a. What is the Alkalinity of seawater of the following composition:
Na+ 0.481 M Cl- 0.560 M
Mg2+ 0.0544 M SO42- 0.0283 M
Ca2+ 0.011 M HCO3- 0.00238 M
K+ 0.011 M
b. write the charge balance equation for this solution and substitute in the numbers
above. Is this solution balanced? If not, what other ion(s) that are not listed might be
present in seawater to help balance the charge?
3 Weathering
A sediment has a CEC of 70 meq/100 g. The following exchangeable cations make up
the CEC: Ca2+, Mg2+, Na+, K+ and H+. The first 4 were measured at concentrations of
19, 5.9, 4.1 and 1.2 meq/100g, respectively. What is the ECS of H+ on this sediment?
4. Soils
a. Name 2 chemicals (or minerals) that precipitate from soil water as the pH changes
b. what is the name of the soil zone where the precipitation occurs?
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