Chemically enhanced CO2 gas exchange in a eutrophic lake: A general model1

The exchange of carbon dioxide between the atmosphere and water is governed by the kinetics of diffusion and reaction in the interfacial boundary layer. Previous derivations of the equations describing this process are not always applicable to lakes. A general model, developed to explain the CO 2 exchange rate in eutrophic Lake 227 of the Experimental Lakes Area, indicates that carbon dioxide invasion into this lake is five to ten times that predicted if there were no reaction. The model results conform with data from laboratory CO 2 invasion experiments. The large chemical enchancement in Lake 227 is caused by a strong CO 2 gradient resulting from an epilimnion depleted of carbon dioxide by eutrophication. These results indicate that calculations of the CO 2 gas exchange rate, especially in eutrophic lakes, must consider the possibility of a relatively large enhancement factor.