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A p H‐DEPENDENT MODEL FOR THE CHEMICAL SPECIATION OF COPPER, ZINC, CADMIUM, AND LEAD IN SEAWATER
Author(s) -
Zirino Alberta,
Yamamoto Sachio
Publication year - 1972
Publication title -
limnology and oceanography
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.7
H-Index - 197
eISSN - 1939-5590
pISSN - 0024-3590
DOI - 10.4319/lo.1972.17.5.0661
Subject(s) - seawater , cadmium , chemistry , zinc , genetic algorithm , copper , inorganic chemistry , divalent , stability constants of complexes , metal , ligand (biochemistry) , ion , chemical stability , coordination number , organic chemistry , biochemistry , oceanography , receptor , evolutionary biology , biology , geology
A p H‐dependent model for the speciation of divalent Cu, Zn, Cd, and Pb ions in seawater was constructed with available and estimated thermodynamic stability constants and individual ion activity coefficients. This model was used to calculate the degree of interaction between each of the metal ions and the anions Cl − , SO 4 2− , HCO 3 − , CO 3 2− , and OH − as a function of p H. Interactions between a cation and an anion were assumed to result only in the formation of complexes with coordination numbers of 1 to 4; polynuclear and mixed‐ligand complexes were not included in the model. The calculations showed the following: All four metals are complexed to a considerable extent in seawater; with the exception of Cd, the distributions of chemical species of the metals vary greatly with changes in pH; Cu interacts primarily with OH − and CO 3 2− , Zn with OH − , Pb with CO 3 2− and Cl − , and Cd with Cl − ; complexes with high coordination numbers (i.e. 3 and 4) are not formed to any appreciable extent in seawater.