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Ocean Surface Chemistry


Project A6, Cluster of Excellence "The Future Ocean" at Kiel University
G. Friedrichs (Junior Research Group), F. Temps und D. W. R. Wallace (Coordinators)

The ocean surface resembles a vast chemical reactor where many heterogeneous and photochemically (i.e. started by solar radiation) chemical and biological processes take place. The characterization of the biogeochemical coupling of the ocean and atmosphere has to rely on a comprehensive understanding of these processes. This also includes knowledge about reactions occuring on ice surfaces and inside or at the surface of aerosols and bubbles. Moreover, processes like dust input from the atmosphere (e.g., Sahara dust) have to be taken into account as well. Therefore, answering the question about the potentially important role and possible feedback mechanisms induced by these processes in a future world with expected changes in environmental forcing (e.g., change of atmospheric CO2 concentration, of aerosol production, of dust deposition, and of radiative forcing) is difficult.

Our goal is to gain a better understanding of the role of the ocean surface with respect to ocean-atmosphere coupling, which is certainly more than just providing a boundary layer for non-reactive gas exchange. Systematic and detailed studies on potential keysteps including investigations on the scale of molecular interactions and structure, will serve as a database to derive a broader macroscopic picture of the ongoing chemistry. In many cases, however, the most important keysteps are still unknown and, consequently, as a start we have to identify potentially important sub-processes in the first place.

Within the framework of the excellence cluster we aim to link expertise from physical chemistry and marine chemistry at the University of Kiel to approach some of these research issues. Recently, a new junior research group was set up focusing on the development and application of modern laser-based spectroscopic methods in order to strike a new path in ocean surface chemistry research.


Examples


Organic monolayers are prevalent at the ocean surface. What is the role of these monolayers for direct and indirect (via capillary wave formation) gas transfer across the water-air interface?

What is the chemical composition of the monolayer? Are there potential heterogeneous reactions that influence the stability and lifetime of the monolayer?

internet_sfg


Sum frequency generation (SFG) spectroscopy makes possible the investigation of composition, structure, and reactivity of organic monolayers on water samples. The photograph displays the SFG spectrometer (right) operated by a picosecond laser system (left). Short pulses of light in the visible (green arrow) and infrared (red arrow) spectral range are used for non-linear generation of sum frequency photons (blue arrow) at the water air interface - provided that the frequency of the infrared laser pulse is resonant to a vibrational transition of the molecule present at the air-water interface.



To what extent do heterogeneous reactions have an impact on the growth dynamics and chemical reactivity of marine aerosols?

Is there an effect of direct surface reactions on the ozone chemistry of the troposphere, e.g., via bromine activation?

What are the chemical, photochemical, and biological processes that determine the availability of nutrients such as nitrogen and iron in ocean surface waters?

What are the crucial processes that determine the formation and speciation of halogenated hydrocarbons in the ocean and what is the amount of these compounds released to the atmosphere?

The atmospheric oxidation products of DMS (dimethylsulfide), which is emitted from the ocean, play a keyrole as condensation nuclei for cloud formation. What determines the amount of DMS formed in the oceans, where is it formed, and how does it contribute to the global budgets of “gaseous sulfur”?

Is it possible to develop new field-deployable trace gas sensors based on modern detection techniques of optical spectroscopy (e.g., cavity ringdown spectroscopy) and mass spectrometry? (CO2 isotope ratio measurements, DMS, halogenated hydrocarbons)

What are the molecular mechanisms of interface reactions? Is it possible to gain insight into water-air interface reactions and to elucidate the dominating molecular interactions by applying molecular modeling techniques?


Contributing researchers: G. Friedrichs, F. Temps, D.W.R. Wallace, A. Körtzinger, B. Hartke, P. Croot


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Last Updated on Monday, 07 June 2010 08:35
 
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