This award is to support research to improve understanding of air-water mass transfer. The liquid film coefficient relates to low solubility and relatively unreactive compounds where air-water transfer is controlled by the water phase or by both phases, such as O2, N2, CO2, DDT, most PCB's, and several mercury compounds. The coefficient describes the resistance to transfer in the liquid phase. A unique flume has been designed and built to study water-phase controlled mass transfer on the scale of a laboratory flume, while maintaining the measurement accuracy of a contained tank or laboratory beaker. The most fundamental objective of this research is to determine the basic mechanism by which a flowing open channel interacts with the free water surface to reduce the liquid film coefficient. The results are expected to provide a basis for the evaluation of existing natural stream data and to specify the important parameters to be measured when determining the liquid film coefficient in natural streams. The principal investigator is highly qualified to carryout the proposed research. A two year continuing grant is recommended. This award is for $75,827 for the first year.
