Greenhouse gases and initial findings on the carbon circulation in two reservoirs and their watersheds

the overlying water. Bubbles containing mainly CO2, and CH4 also rise from this fresh sediment layer. We draw the lower boundary at the surface below which all carbon is permanent (i.e. not susceptible to mobilization and on its way to fossilization). We estimate that this boundary is somewhere between 5‐20 cm below the water-sediment interface. At this depth humic substances are already resistant to further carbon decomposition, as can be seen from the constant C/Si ratio starting at about this depth. In fact, the lower boundary could be described as lying in the two-dimensional region where this ratio is constant from this point down. Reservoir carbon inputs into the black box come through rivers, underground water, rainfall, and occasional diffusive absorption. Carbon outputs are effluent outflow, permanent sedimentation, and diffusive and bubbling emissions such as CH4 and CO2.