### Abstract

The effect of pressure (P) on the activity coefficients (γ_{i}^{P}/γ_{i}^{0}) of ions (i) in seawater can be estimated from the partial molal volumes and compressibilities of the ions in water (V^{-0} and κ^{-0}) and seawater (V^{-*} and κ^{-*}) ln(γ^{P}/γ^{0})=(V^{-*}-V^{-0})P/RT-0.5(κ^{-*}-κ^{-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. δV^{*}=V^{-*}(MX)-V^{-*}(M^{2+})-V^{-*}(X^{2-}), ΔV^{*} = V^{-*}(MX)-V^{-*}(M^{2+})- V^{-*}(X^{2-}) using ln (K^{*P}/K^{*0})=(ΔV^{*}/RT)P-0.5 (Δκ^{*}/RT)P^{2} The densities and sound speeds of a number of transition metal chlorides have been determined in 0.725m NaCl solutions (the ionic strength of average seawater, S~35) at 25°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 (Mg^{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+}, Hg^{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.

Original language | English (US) |
---|---|

Pages (from-to) | 298-305 |

Number of pages | 8 |

Journal | Deep-Sea Research Part I: Oceanographic Research Papers |

Volume | 58 |

Issue number | 3 |

DOIs | |

State | Published - Mar 2011 |

### Fingerprint

### Keywords

- Complex formations
- Compressibility
- Pressure
- Seawater
- Transition metals
- Volume

### ASJC Scopus subject areas

- Aquatic Science
- Oceanography

### Cite this

*Deep-Sea Research Part I: Oceanographic Research Papers*,

*58*(3), 298-305. https://doi.org/10.1016/j.dsr.2011.01.003

**The effect of pressure on transition metals in seawater.** / Millero, Frank J; Huang, Fen.

Research output: Contribution to journal › Article

*Deep-Sea Research Part I: Oceanographic Research Papers*, vol. 58, no. 3, pp. 298-305. https://doi.org/10.1016/j.dsr.2011.01.003

}

TY - JOUR

T1 - The effect of pressure on transition metals in seawater

AU - Millero, Frank J

AU - Huang, Fen

PY - 2011/3

Y1 - 2011/3

N2 - The effect of pressure (P) on the activity coefficients (γiP/γi0) of ions (i) in seawater can be estimated from the partial molal volumes and compressibilities of the ions in water (V-0 and κ-0) and seawater (V-* and κ-*) ln(γP/γ0)=(V-*-V-0)P/RT-0.5(κ-*-κ-0)P2/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 (KP/K0) on ionic equilibria constants M2++X2-=MX, K = [MX]/[M2+][X2-]from the changes in the volume for the chemical reaction in seawater. δV*=V-*(MX)-V-*(M2+)-V-*(X2-), ΔV* = V-*(MX)-V-*(M2+)- V-*(X2-) using ln (K*P/K*0)=(ΔV*/RT)P-0.5 (Δκ*/RT)P2 The densities and sound speeds of a number of transition metal chlorides have been determined in 0.725m NaCl solutions (the ionic strength of average seawater, S~35) at 25°C. These results have been used to determine the partial molal volumes and compressibilities of transition metal ions (Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+). These results and our earlier measurements (Mg2+, Ca2+, Sr2+ and Ba2+) 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 (Be2+, Pb2+, Hg2+ and Fe2+) 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.

AB - The effect of pressure (P) on the activity coefficients (γiP/γi0) of ions (i) in seawater can be estimated from the partial molal volumes and compressibilities of the ions in water (V-0 and κ-0) and seawater (V-* and κ-*) ln(γP/γ0)=(V-*-V-0)P/RT-0.5(κ-*-κ-0)P2/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 (KP/K0) on ionic equilibria constants M2++X2-=MX, K = [MX]/[M2+][X2-]from the changes in the volume for the chemical reaction in seawater. δV*=V-*(MX)-V-*(M2+)-V-*(X2-), ΔV* = V-*(MX)-V-*(M2+)- V-*(X2-) using ln (K*P/K*0)=(ΔV*/RT)P-0.5 (Δκ*/RT)P2 The densities and sound speeds of a number of transition metal chlorides have been determined in 0.725m NaCl solutions (the ionic strength of average seawater, S~35) at 25°C. These results have been used to determine the partial molal volumes and compressibilities of transition metal ions (Mn2+, Co2+, Ni2+, Cu2+, Zn2+ and Cd2+). These results and our earlier measurements (Mg2+, Ca2+, Sr2+ and Ba2+) 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 (Be2+, Pb2+, Hg2+ and Fe2+) 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.

KW - Complex formations

KW - Compressibility

KW - Pressure

KW - Seawater

KW - Transition metals

KW - Volume

UR - http://www.scopus.com/inward/record.url?scp=79951809051&partnerID=8YFLogxK

UR - http://www.scopus.com/inward/citedby.url?scp=79951809051&partnerID=8YFLogxK

U2 - 10.1016/j.dsr.2011.01.003

DO - 10.1016/j.dsr.2011.01.003

M3 - Article

AN - SCOPUS:79951809051

VL - 58

SP - 298

EP - 305

JO - Deep-Sea Research Part I: Oceanographic Research Papers

JF - Deep-Sea Research Part I: Oceanographic Research Papers

SN - 0967-0637

IS - 3

ER -