Biogeochemistry of marine gases and air/sea exchange
Many geochemical processes are associated with the production and/or consumption of gases dissolved in seawater. Hence, the determination of the temporal changes in the concentrations of these gases constitute a tool to quantify the rates of the corresponding processes. This approach is applied to determine the biomass production in the surface water and the organic matter mineralization in the deep water on the basis of CO2 and O2 measurements. To estimate rates for nitrogen fixation and denitrification, total gas tension measurements will be performed which in combination with O2 measurements may be used to determine changes in the N2 concentrations. Other studies are related to the marine mercury cycle with special emphasis on the mechanisms of the reduction of oxidized Hg and the subsequent release of Hg0 into the atmosphere.
A second focus of our research is related to the dynamics of the air/sea gas exchange. Continuous measurements of the CO2 and O2 partial pressures on a cargo ship are used to determine the gas exchange transfer velocity on the basis of coupled CO2/O2 mass balances. Additional laboratory investigations are dealing with the effect of organic surface films on the transfer velocity. The experimental studies are complemented by the development of a microphysical model that aims at a theoretically well-founded parameterization of the transfer velocity.
