摘要 : The oscillating stability of coral reef seawater pH has been maintained at around physiological pH values over the past 300 years (Pelejero et al., 2005). The stability mechanism of its pH has been interpreted in terms of the buff... 展开 The oscillating stability of coral reef seawater pH has been maintained at around physiological pH values over the past 300 years (Pelejero et al., 2005). The stability mechanism of its pH has been interpreted in terms of the buffering dissolution/formation reaction of CaCO3 as well as the proton consumption/generation reaction in CaCO3-saturated water. Here the pH-dependent solubility product [HCO3-][Ca2+] has been derived on the basis of the actual pH-dependent reactions for the atmospheric CO2/CO2(aq.)/ HCO3-/CO32-/Ca2+/CaCO3 system. Overbasic pH peaks appeared between pH approximate to 8 and approximate to 9.5 during sodium hydroxide titration, as a result of simultaneous CaCO3 formation and proton generation. The spontaneous and prompt water pH recovery from the acidic to the physiological range has been confirmed by the observation of acid/base time evolution, because of simultaneous CaCO3 dissolution and proton consumption. The dissolution/formation of CaCO3 in water at pH 7.5 - 9 does not take place without a proton consumption/generation reaction, or a buffering chemical reaction of HCO3-+Ca2+=CaCO3+H+. SEM images of the CaCO3 fragments showed that the acid water ate away at the CaCO3 formed at physiological pH values. Natural coral reefs can thus recover the physiological pH levels of seawater from the acidic range through partial dissolution of their own skeletons. 收起