184
Therefore, it seems very important to estimate Kz with the
highest precision as possible. In particular, taking into
account the variability in time of Kz seems important to
obtain more reliable modelling results.
10.3 Conclusion
Temperature and conductivity microstructure data completed
by continuous measurements collected in Lake Pavin from
May 2006 to June 2007 constitute a unique data set. This
database is very useful to understand the reasons leading to
and contibuting to keep meroximis. Among these reasons,
the role of a sublacustrine spring and of winter meteorologi-
cal conditions seem to be crucial to understand the maintain-
ing of meromixis over time.
During the 2 years observed, the mixolimnion of Lake Pavin
was more stable in 2006 and progressively destabilized in
- Gradients are steeper at the interface mixolimnion-
monimolimnion in 2007. Moreover, in 2007, the hypolimnion
is more unstable and clear convective processes due to a subla-
custrine inlet at the bottom of the mixolimnion are observable.
Finally, temperature and conductivity microstructure data
enable the estimate of dispersion coefficient in the water
body. The use of the calculated dispersion coefficient and tak-
ing into account its variability in the modelling of the biogeo-
chemical behaviour of the lake is of primary importance in
the assessment of the fate of both major and trace elements.
The biogeochemical behaviour of Lake Pavin as well as its
rather small dimensions makes it a life-size laboratory reactor.
Acknowledgments The authors would like to thank the French
National Agency for Research which founded the Metanox program
(2006–2007). The different physical observations detailed in this chap-
ter are related to this program and were performed in this framework.
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