Columbia River water is supersaturated with respect to atmospheric carbon dioxide by 200 to 870 parts per million. An equilibrium exists between the carbon dioxide partial pressure and pH, and Henry's law is obeyed in this natural water. The carbon dioxide pressure can be calculated by a determination of the pH, total carbon dioxide, and temperature.
During 1966, 1.8 × 1014 liters of water; 8.3 × 107, 2.1 × 109, and 2.7 × 1010 moles of phosphate, nitrate, and reactive silicate; 1.9 × 1011 equivalents of alkalinity; and 1.9 × 1011 moles of total carbon dioxide passed through Clatskanie, 87 km above the mouth of the Columbia River into the Astoria estuary and the Pacific Ocean. Along the main stream, phosphate, nitrate, and silicate concentrations show a definite seasonal change; their maxima occur in winter and minima in summer. On‐stream primary production greatly affects the formation of the summer minima. At Clatskanie, the nitrate: phosphate ratio is 3:1 during summer months and over 19:1 at other seasons.
Bicarbonate ion is the major dissolved carbon dioxide species in the entire Columbia River system, where water pH measured at 20C ranges from 6.63 to 8.68. The major portion of the river system is undersaturated with respect to calcite solubility. Along the main stream, the river is supersaturated with respect to the atmospheric carbon dioxide pressure of 320 ppm.
Columbia River alkalinity essentially consists of carbonate alkalinity (94% ) with some silicate alkalinity where dissolved silicate concentration is high. Phosphate and borate contribute insignificantly to the overall alkalinity. The river delivered 2.3 x 10" equivalents of alkalinity to the Pacific Ocean during the water year 1963, or 11 megatons of calcium carbonate.Regardless of high seasonal flow-rate variance, the river alkalinity near the river mouth shows little variation with an average value of 1 mcq/liter.
Two major processes that affect the vertical distribution of hydrogen-ion concentration in the sub-Arctic region of the northeastern Pacific Ocean are the apparent oxygen utilization by marine organisms and, to a lesser extent, carbonate dissolution.
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