A simple model, in which deposition is limited by diffusion through a thin laminar film of water, has successfully described the deposition of several gases to the sea. However, the deposition velocity of ozone to seawater is 10–30 times greater than this model predicts. This enhancement is attributed to significant reactions of ozone with halides and other components of seawater within the laminar surface layer, and a modified version of the model for ozone, and possibly other reactive gases, is proposed. To test the model, comparisons were made of predicted and observed deposition velocities for ozone to solutions of sodium sulphite and nitrite. Measurements of the rate constants for the reaction of ozone with these solutions and with some components of seawater were made with a stopped flow apparatus. The reaction with iodide was too rapid for direct observation, but the rate constant was inferred from measurements of the deposition of ozone to iodide solutions. According to the model, iodide makes a substantial contribution to the deposition of ozone to seawater, but an additional, unidentified reaction is necessary to explain fully the deposition rate. A surfactant species may well be involved. The model indicates that the ozone is destroyed and the oxidation products produced in the top few microns of the sea. The production of molecular iodine at the surface may have significant geochemical consequences.

No abstract

rn Quantitative structure-property relationship (QSPR) models have been developed which accurately calculate the congener-specific aqueous solubilities (S) and Henry's Law constants (HLCs) of polychlorinated biphenyls (PCBs). QSPRs were generated based on molecular models which were sensitive to slight changes in chemical structure. PCB aqueous solubilities were found to be a function of total surface area, melting point, and third shadow area. Observed HLCs were a function of the second moment of inertia, path-four connectivity index, path-three K index, and the second and third principal polarizabilities. These newly developed models agree well with other model predictions and expand, as well as complement, previous approaches because the new models are capable of accurately calculating S and HLC for structurally similar PCB congeners. Results from this work provide a better understanding of the chemical and structural characteristics governing the solubility of hydrophobic compounds.

No abstract

No abstract