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SUMMARY:Methane ebullition (bubbling) in the Rhone River delta of Lake Gen
 eva
DTSTART:20120417T161500
DTSTAMP:20260604T020741Z
UID:3c6b6519bdcfb3630ceed7ad44df3613fddb81aaa4149e0e07ea29f5
CATEGORIES:Conferences - Seminars
DESCRIPTION:Dr Tonya Del Sontro\, Aquatic Chemistry\, EAWAG\nThe Rhone Riv
 er delta of Lake Geneva is a complex system consisting of a deep (up to 40
  m) and long (~16 km) canyon extending from the current river mouth\, as w
 ell as several former canyons lying to the east. We hypothesized that the 
 proximal part of the active canyon is a strong source of methane (CH4) to 
 Lake Geneva and possibly the atmosphere via ebullition\, mostly due to the
  organic loading of the present day location of the Rhone River. We also h
 ypothesized that the older canyons would contribute much less to the CH4 b
 udget of the delta area. Using a bubble-size calibrated echosounder we dis
 covered that ebullition is prevalent throughout the proximal active delta\
 , and also along the tops of the canyon walls in the middle and distal par
 ts of the active canyon. Ebullition is present but to a much lesser degree
  in two of the older canyons. Preliminary data will also be shown for the 
 work performed within the elemo project using the MIR submersibles. In ord
 er to understand what sedimentalogical features influence CH4 bubbling\, c
 ores were taken from the MIR submersibles along 3 transects in the active 
 canyon and one transect in the two older canyons. Porosity\, grain size\, 
 CH4\, and organic matter content were compared at bubbling and non-bubblin
 g areas\, as well as between canyons. An in situ mass spectrometer (Tethys
 ) was used aboard one of the MIRs on a transect along the active canyon fl
 oor to map dissolved CH4. High levels of CH4 were observed and water sampl
 ing in the deep canyon complimented these findings.
LOCATION:GR A3 31 http://plan.epfl.ch/?room=GR%20A3%2031
STATUS:CONFIRMED
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