New Methods In Biogeochemistry:The Development of Electrochemical Tools for the Measurement of Dissolved and Solid State Compounds in Natural Systems

This PhD thesis deals with biogeochemical processes of transition metals (i.e., iron, manganese). Depending on chemical, physical, and biological processes these elements change their speciation. Thus, the knowledge about the distribution of solid, dissolved, or complexed compounds of these metals is an important factor in evaluating biogeochemical cycles. The possibilities for determination are limited due to their reactivity and their appearance in several solid state forms. In natural ecosystems iron and manganese minerals occur as amorphous to crystalline nanosize solid compounds. Solid state extraction methods allow only the description of different solid state iron and manganese pools, but a detailed analysis of the single mineral composition was only possible with high technological expenditure. On the other hand, in-situ detection of aqueous iron, manganese, and trace metals at the scale of the processes is so far limited due to the size of the available instruments. The primary aim of this thesis was to develop new tools and methods allowing a detailed characterization of solid and dissolved compound distribution in natural ecosystems.