Abstract
Dissolved gases produce a gas pressure. This gas pressure is the appropriate physical quantity for judging the possibility of bubble formation and hence it is central for understanding exchange of climate-relevant gases between (limnic) water and the atmosphere. The contribution of ebullition has widely been neglected in numerical simulations. We present measurements from six lacustrine waterbodies in Central Germany: including a natural lake, a drinking water reservoir, a mine pit lake, a sand excavation lake, a flooded quarry, and a small flooded lignite opencast, which has been heavily polluted. Seasonal changes of oxygen and temperature are complemented by numerical simulations of nitrogen and calculations of vapor pressure to quantify the contributions and their dynamics in lacustrine waters. In addition, accumulation of gases in monimolimnetic waters is demonstrated. We sum the partial pressures of the gases to yield a quantitative value for total gas pressure to reason which processes can force ebullition at which locations. In conclusion, only a small number of gases contribute decisively to gas pressure and hence can be crucial for bubble formation.
Highlights
We demonstrate under which conditions total gas pressure can be raised to absolute pressure to result in bubble formation and ebullition
We present six lacustrine water bodies, including (1) a natural lake, (2) a drinking water reservoir, (3) one gravel pit lake, (4) one salt-affected mine pit lake and (5) one flooded quarry, and (6) one mine pit lake temporarily used as a dumping side (Figure 1)
Gas pressure is clearly dominated by nitrogen N2 and oxygen O2
Summary
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations. The concentrations of both gases keep rising in the atmosphere This fact emphasizes the need for elucidating the involvement of lakes and rivers in global carbon fluxes [4]. This fact may put the reputation of hydropower as green energy at stake at least in some cases [2,5] Beyond their recognition as being climate-relevant, gases are central players in the ecology of limnic waters, especially oxygen (O2 ) for all breathing organisms and carbon dioxide (CO2 ) for photosynthetic organisms. We demonstrate the contributions of the most relevant gases to gas pressure and complement the gas measurements with profiles from numerical model simulations to depict them together with their contributions to gas pressure This gas pressure can be affected by chemical reactions (produced or removed) or temperature change. We demonstrate under which conditions total gas pressure can be raised to absolute pressure to result in bubble formation and ebullition
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