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We are now back in the lab analyzing the results. Please stay tuned!


  About the Volcanoes

Rincon de la Vieja
Laguna Poco Sol
Journal Entry

Photo courtesy Michael Smith

The Precious Acid Gas Bubbles

It is the end of our third and final day at the foot of Volcan Arenal, and we are beginning to feel that we will miss the spectacular view of the summit as we leave tomorrow morning for our next destination.

We spent this morning climbing down through the most dense and steep rain forest canyon we have yet encountered in order to reach a remote spring site. Here, our scientific party sampled gases emanating from springs within the stream bed. Clamoring back up the slippery, muddy canyon wall was a real test of the groupıs climbing skills. In the afternoon, we split into two groups, with one returning to the vicinity of yesterdayıs spa resort, while the other trekked up the west flank of Arenal. This proved to be a long and arduous hike through trackless rain forest frequently interspersed with rock slides, the aftermath of recent pyroclastic flows. We were fascinated by the sound of the mountain as it grumbled with bursts of gas, much like snorts of an angry bull.

Our quest was to find a tiny fracture in a dry stream bed, where years ago an anomalous vent of cool gas was discovered. Miraculously, having only visited the site once, our skilled guide, Chico, found the fissure, and Alison was able to sample it. More on the special techniques of gas sampling follows in todayıs scientific report:

Toby uses a so-called Giggenbach sample flask after the geochemist (Werner Giggenbach) who invented it. The gases are bubbled through a solution of caustic soda which reacts with the CO2 and hence removes it. The residual gases (nitrogen, oxygen, methane, and the noble gases including helium) pass into the head-space of the evacuated flask. Because CO2 is the major gas phase ­ and it is removed by the solution, the amounts of the other (residual) gases can really build up in the head space. The more gas there is, the easier it is to make the concentration measurement on Tobyıs gas chromatograph in the laboratory. Dave uses evacuated gas bulbs which are constructed of a special type of glass containing lead known to have an extremely low diffusivity for helium. Hence, it acts as a good storage vessel until the sample is extracted in the laboratory.

He also uses copper tubes for some samples, with the crimper tool forming a cold-weld seal trapping the sample in the copper tube. Because some of the gas samples, particularly those with high sulphur contents, are corrosive to copper, we would prefer to use the glass samplers in these cases. However, there isnıt a hard-and-fast rule ­ itıs determined more by the total number of samples that will be collected on the trip versus the number of available glass samplers.

Back in the laboratory, the gases we have collected will be extracted from their various containers and the analyses can begin. Stay tuned!

  Daily Log  
January 2001
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