Research Modul
Sequential extraction of mofette soil to determine element (im)mobilisation under CO2 influence
Kai Jansen (02/2018-02/2018)
Support: Britta Planer-Friedrich, Judith Forberg
Background. Mofettes are natural exhalations of CO2. In the case of the mofettes we are currently studying in Czech Republic this exhalation is related to mantle degassing. In a previous master thesis focusing on two mofettes and CO2-free references soils in their vicinity we have been able to show that many elements show quite different mobilization or immobilization in the mofette compared to “normal” soil. The reason is a complex interplay between more organic matter in the mofette due to slower degradation and more iron mineral dissolution due to stronger reducing conditions. One major motivation for being interested in element mobilization in mofettes is that they are perfect analoga for what might happen with water chemistry at CO2 storage sites in case of leakages or storage capture failure.
During studies in autumn 2017, we have now screened one mofette in greater detail, taking depth-resolved transects from non-influenced via partially influenced to fully CO2-influenced sites. We have sampled both solid phase as well as liquid phase with dialysis chambers. First results on total element concentrations look interesting but for further information on mobilization/immobilization mechanisms we would like to do sequential extractions of the samples collected. Work will include using different extraction procedures as well as analysis by ICP-MS and interpretation of results.