| dc.description.abstract | Methane emissions from freshwater systems contribute significantly to the total methane flux to the atmosphere.
Not much is known, however, about the individual contribution of freshwater environments. Estimating
quantities and understanding processes delivering methane from aquifers to rivers and streams is crucial to
understand carbon cycling in freshwater systems. In order to assess methane dynamics in freshwater systems and
possibilities for modelling on a larger scale, first a literature review was conducted in which production,
consumption, transport and modelling of methane are discussed. After the literature review, groundwater methane
was identified as an important part of the methane dynamics in freshwater systems. Data on groundwater methane
concentrations were assembled and a data-analysis was conducted using statistical software programs SPSS and
Microsoft Excel. From the data-analysis, DOC and sulfate were identified as important predictors of dissolved
methane in groundwater. Both variables could explain 63.6% of variation of methane concentrations in
groundwater. Applying these results to a global biogeochemical freshwater model (IMAGE-DGNM) was
unsuccessful because the topsoil DOC concentrations used as model input did not relate to measured groundwater
DOC concentrations. In order to improve these results, it is recommended that following research makes a
division between confined and unconfined aquifers. Increasing the number and spatial spread of assembled data
entries would further increase the reliability of the data-analysis. Using this method to integrate methane into
biogeochemical models will, however, not simulate the heterogeneous character of methane concentrations in
aquifers. In order to simulate methane delivery from aquifers to surface waters, there is a need for a process-based, numerical model that calculates methanogenesis, methanotrophy and aquifer-surface water exchange. | |
