A pH-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 bctwccn each of the metal ions and the anions Cl-, Sod'-, HCOX-, CO,'-, and OH-as a function of pH. Interactions between a cation and an anion were assumed to result only in the formation of complexes with coordination numbers of 1 to 4; polynuclcar and mixedligand complexes wcrc 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 COs2-, Zn with OH-, Pb with COa2-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.
This study reports the potential contribution of organic bases to the alkalinity of seawater samples. The concentration of organic bases in these samples was inferred from the difference between the measured alkalinity and that calculated from a knowledge of pH and concentrations of the various inorganic acid‐bases species such as total carbon, total boron, and so on. Significant concentrations of such organic bases were measured in cultures of the marine microalgae Rhodomonas sp. (800 µmol kg−1) and Isochrysis aff. Galbana (400 µmol kg−1), as well as in three marine environments (northern gulf of California, México; San Quintín Bay, B.C., Mexico; and San Diego Bay). These three sites are characterized by significant biological activity and restricted mixing, and the organic bases were found at concentrations greater than 50 µmol kg−1 in each of these three locations.
The overall effect of the number of boats on the copper (Cu) levels in the water column and sediment along with their spatial variability within Shelter Island Yacht Basin (SIYB), San Diego Bay, California was examined. We identified a horizontal gradient of increasing dissolved Cu and Cu in sediment from outside to the head of SIYB. which was coincident with the increasing number of boats. Spatial models of Cu distribution in water and sediment indicated the presence of "hot spots" of Cu concentration. From outside to the head of SIYB, dissolved Cu ranged from 1.3 µg L-1 to 14.6 µg L-1 , in surface water, and 2.0 to 10.2 µg L-1 in bottom water. Cu in sediment exceeded the Effect Range Low of 34 mg kg-1 (i.e. where adverse effects to fauna may occur), with a peak concentration of 442 mg kg-1 at the head of the basin. "Free" Cu ++ in surface water was several orders of magnitude higher than in sediment porewater. High-resolution data of Cu species together with probability maps presented in this paper will allow managers to easily visualize and localize areas of impaired quality and to prioritize which areas should be targeted to improve Cu-related conditions.
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