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Proton‐Transfer Reaction Dynamics and Energetics in Calcification and Decalcification
Author(s) -
Suwa Ryota,
Hatta Masayuki,
Ichikawa Kazuhiko
Publication year - 2014
Publication title -
chemistry – a european journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.687
H-Index - 242
eISSN - 1521-3765
pISSN - 0947-6539
DOI - 10.1002/chem.201402210
Subject(s) - chemistry , bone decalcification , titration , dissociation (chemistry) , titration curve , dissolution , solubility , proton , inorganic chemistry , organic chemistry , medicine , physics , pathology , quantum mechanics
CaCO 3 ‐saturated saline waters at pH values below 8.5 are characterized by two stationary equilibrium states: reversible chemical calcification/decalcification associated with acid dissociation, Ca 2+ +HCO 3 − ⇌CaCO 3 +H + ; and reversible static physical precipitation/dissolution, Ca 2+ +CO 3 2− ⇌CaCO 3 . The former reversible reaction was determined using a strong base and acid titration. The saturation state described by the pH/ P CO2 ‐independent solubility product, [Ca 2+ ][CO 3 2− ], may not be observed at pH below 8.5 because [Ca 2+ ][CO 3 2− ]/([Ca 2+ ][HCO 3 − ]) ≪1. Since proton transfer dynamics controls all reversible acid dissociation reactions in saline waters, the concentrations of calcium ion and dissolved inorganic carbon (DIC) were expressed as a function of dual variables, pH and P CO2 . The negative impact of ocean acidification on marine calcifying organisms was confirmed by applying the experimental culture data of each P CO2 /pH‐dependent coral polyp skeleton weight (Wskel) to the proton transfer idea. The skeleton formation of each coral polyp was performed in microspaces beneath its aboral ectoderm. This resulted in a decalcification of 14 weight %, a normalized CaCO 3 saturation state Λ of 1.3 at P CO2 ≈400 ppm and pH ≈8.0, and serious decalcification of 45 % and Λ 2.5 at P CO2 ≈1000 ppm and pH ≈7.8.