Riverbeds are densely populated with microorganisms which catalyze ecologically relevant processes. To study this complex zone, we tested pore-water extraction with microfilter tubes. The method was found to be suitable for the measurement of dissolved solutes but less so for gases. The pumping rate during sample extraction strongly influenced gas analyses in the samples. The combination with an optical oxygen sensor and a temperature monitoring system was found to be highly valuable.

Data on geothermal properties are notoriously scarce, both on a good temporal and spatial resolution. We compared two data sets of a geothermal well in Bavaria (one had yearly analyses of a great number of ions, the other one tested the water every five minutes but only on a small number of variables) and found that yearly data systematically neglect seasonal variations taking place in the aquifer. Virtual sensors might help to combine the two data sets when the aquifer is well known.

The greenhouse gas methane (CH₄) drives climate change. Microorganisms in river sediments produce CH₄ when degrading organic matter, but the contribution of rivers to atmospheric CH₄ concentrations is uncertain. To better understand riverine CH₄ cycling, we measured concentration profiles of CH₄ and relevant reactants that might influence the CH₄ cycle. We found substantial CH₄ production, especially in fine, organic-rich sediments during summer and signs of microbial CH₄ consumption.