Innovative approaches in experimental biogeochemistry - analytics on the sub-micron scale for a better process understanding

The fate of contaminants such as heavy metals and sorbents in heterogeneous environmental systems such as soils or biofilms is often controlled by (redox-) reactions, mineral precipitation / dissolution / transformation processes, or by the sorption to surface functional groups.

Analysis on the bulk scale hide (sub-)-micron heterogeneities and often fail at the identification of intermediate products that appear at low concentrations only. These drawbacks often limit a fundamental process understanding. Novel analysis approaches that combine chemical sensitivity with high spatial resolution and innovative concepts for data analysis can help to identify these processes and the underlying mechanisms.

In this talk I will present several examples wherein novel and innovative, spatially resolved analysis approaches were required to understand environmental redox processes and the fate of contaminants such as Cd and As. These methods include synchrotron-based scanning transmission X-ray microscopy (STXM) that provides analytical capabilities such as speciation- and quantitative chemical mapping of environmental samples at ~20-30 nm spatial resolution. Furthermore, the talk will include examples of analytical electron microscopy and confocal laser scanning microscopy in biogeochemical research, as well as innovative concepts and software tools for data analysis. The following examples will be presented:

1. Influence of submicron-scale heterogeneities in biogenic Fe-minerals on the sorption of arsenate – the importance of microbial extracellular polymers.
2. Sorption of heavy metals/metalloids to cell-mineral aggregates formed by Fe-oxidizing bacteria.
3. Soil remediation with Cd hyper-accumulating plants – new insights into the influence of microbial Fe-reduction on the fate of Cd in contaminated soils.

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Invited by Stefan Peiffer, Department of Hydrology

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