Comparison of Mean River Water and Seawater

Shown in Table 8.9 are chemical analyses of mean river water and seawater, along with residence times of the species and a comparison of relative concentrations in mean river water and the ocean. As in the discussion of the hydrologic cycle, the residence time of species in seawater, t, equals the amount of that species in the reservoir (the ocean), divided by its rate of input or output (which must be equal at steady state). The input is in streams and groundwaters discharging into the ocean. The output is through adsorption and/or precipitation in and on solids that end up in marine sediments. 

Chloride and sodium, those species most inert (least reactive) in seawater, have the longest residence times and are most concentrated in seawater relative to their amounts in rivers. Iron and alu- 

General Controls on Natural Water Chemistry Chap. 8 

Mechanisms controlling world water chemistry. Science, 170 1088-90. NaCt Used by permission. 

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