The solubility of very low concentratiions of carbon monoxide in aqueous solution

The solubility of carbon monoxide in natural waters has been determined when the partial pressure of carbon monoxide in the gas phase approaches atmospheric concentrations. For both pure water and seawater the solubilities were found to be more than eight times the values which have previously been observed with an atmosphere of pure carbon monoxide present. Carbon monoxide therefore does not obey Henry’s law over the pressure range from approximately 10^-5 atmospheres to greater than one atmosphere. The exchange constant for the exchange of carbon monoxide across the boundary layer of aqueous solutions has also been determined. Values for seawater range from 1.5 ×10^-7 m s^-1 under calm conditions to 1 ×10^-6 m s^-1 under the most turbulent conditions studied. The data obtained has been used to re-evaluate the existence and size of the proposed oceanic source of carbon monoxide. A value of 10¹¹ g of carbon monoxide has been calculated for the amount of carbon monoxide produced annually by the world’s oceans, and this represents only 0.05% of the estimated carbon monoxide produced by man, and less than 0.002% of the largest natural source of carbon monoxide, which is the atmospheric oxidation of methane.