Determination of hydrogen ion concentration in softwater lakes using carbon dioxide equilibria

摘要: Abstract A strategy for determining the hydrogen ion content of fresh waters is proposed that involves total dissolved inorganic carbon (DIC or σCO2) and CO2 partial pressure (PCO2) measurements rather than pH electrode measurements. This recommendation derives from discrepancies between dioxide equilibria made on several softwater lakes at Experimental Lakes Area, northwestern Ontario. The calculated DIC, PCO2, first dissociation constant carbonic acid (K1) data was consistently higher directly measured with a electrode. Similarly, calculation PCO2 surface pH, K1 gave values up to twice atmospheric saturation despite repeated equilibrations PCO2. Laboratory experiments demonstrated high organic these appears alter response yielding lower true values. Furthermore, uptake protons by weak anions appear be cause difference (Gran) carbonate — CO2) alkalinity. Therefore bicarbonate concentration must uncharged content. These procedures should provide more accurate consistent results in trend hence yield solid baseline against which effects precipitation can assessed.