Spectrophotometric determination of the bicarbonate dissociation constant in seawater
نویسندگان
چکیده
The aqueous carbon dioxide (CO2) system stoichiometric dissociation constants K1 and K2 express the relative concentrations of CO2, HCO3? (bicarbonate), CO32? (carbonate) in terms pH. These are critical study seawater oceans because any mathematical expression that relates four major CO2 parameters (pH, here expressed on total hydrogen ion concentration scale, pHT; dissolved inorganic carbon, CT; alkalinity, AT; fugacity, fCO2) requires use K2. Uncertainties associated with current characterizations pK1 pK2 (where pK = ?log K), order 0.01 0.02, limit accuracy marine calculations. This work reports results a spectrophotometric method to experimentally determine product K1K2 over environmentally relevant ranges temperature (288.15 ? T 308.15 K) salinity (19.6 Sp 41) where denotes practical scale. Using previously published parameterizations K1, values could then be calculated from new values. resulting set was fitted as function obtain parameterization (denoted SWpK2) Waters Millero (2013) revised by et al. (2014): SWpK2 116.8067 ? 3655.02 ?1 16.45817 ln + 0.04523 0.615 Sp0.5 0.0002799 Sp2 4.969 (Sp/T) average root mean square deviation between equation observed data is 0.003. Residuals this fitting (i.e., measured minus parameterized pK2) substantially smaller than residuals obtained previous works. Similarly, standard uncertainty reduced 0.015 (previous characterizations) 0.010 (this work). Internal consistency assessments (comparisons versus AT, CT, pHT, were used evaluate computational utility parameterization. Assessments both laboratory shipboard indicate internal calculations improved using work. provides most precise, potentially accurate, bicarbonate constant characterization presently available for open ocean conditions.
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ژورنال
عنوان ژورنال: Geochimica et Cosmochimica Acta
سال: 2021
ISSN: ['1872-9533', '0016-7037']
DOI: https://doi.org/10.1016/j.gca.2021.02.008