科研之友
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摘要
The effect of pressure (P) on the activity coefficients (gamma(P)(i)/gamma(0)(i)) of ions (i) in seawater can be estimated from the partial molal volumes and compressibilities of the ions in water ((V) over bar (0) and (kappa) over bar (0)) and seawater ((V) over bar* and (kappa) over bar*) In(gamma(P)/gamma(0)) = ((V) over bar*-(V) over bar*)P/RT-0.5((kappa) over bar*-(kappa) over bar (0))P(2)/RT where R and T have their normal meaning. One can also use the partial molal volumes and compressibilities of ions to estimate the effect of pressure (K(P)/K(0)) on ionic equilibria constants M(2+) + X(2-) = MX, K = [MX]/[M(2+)][X(2-)] from the changes in the volume for the chemical reaction in seawater Delta V* = (V) over bar*(MX)-(V) over bar*(M(2+))-(V) over bar*(X(2-)), Delta kappa* = (kappa) over bar*(MX)-(kappa) over bar*(M(2+))-(kappa) over bar*(X(2-)) using In(K*(P)/K*(0)) = (Delta VRT)(P)-0.5(Delta kappaRT)P(2) The densities and sound speeds of a number of transition metal chlorides have been determined in 0.725 m NaCl solutions (the ionic strength of average seawater, S similar to 35) at 25 degrees C. These results have been used to determine the partial molal volumes and compressibilities of transition metal ions (Mn(2+), Co(2+), Ni(2+), Cu(2+), Zn(2+) and Cd(2+)). These results and our earlier measurements (Me(2+), Ca(2+), Sr(2+) and Ba(2+)) were used to develop correlations between the values in water and NaCl. These correlations were used to predict the values of other divalent ions in water and NaCl (Be(2+), Pb(2+), He(2+) and Fe(2+)) that were difficult to directly measure. These studies allow one to make estimates of the effect of pressure on the activity coefficients of these ions in seawater and ionic equilibria in the deep oceans. The lower stability constants will result in increased concentrations of free transition metals in the deep ocean.
- 出版日期2011-3
