Rock pit water samples were collected in June and October. Well water samples were collected on a weekly to monthly basis during the years 1983-1985. Water processing and analysis are described in detail by Claassen et al. (1986).
Regolith samples and unweathered tuf were analyzed for BET surface area, bulk chemistry, particle size distribution and XRD mineralogy.
Smaller regolith size fractions (less than 0.5mm) were examined using electron microscopy, and larger regolith rock fragments (~2 cm diameter) were examined in petrographic thin section.
In order to determine the relative release rates of solutes during dissolution, tuff from Seven Parks was reacted in pure water for 10 weeks.
The experiment was conducted using crushed, ultrasonically-cleaned, tuff from Seven Parks (150-495um fraction) in a flow-through reactor at 25oC ± 4oC, with a flow rate of 4 ml/hr, and a reactor volume of 100 ml. Details of sample preparation and solution analyses are the same as those of Hoch et al., 1996.
pH, which was unbuffered, was slightly alkaline through the duration of the experiment, and resulting ionic strength of reactor solutions range from 10-3.3 to 10-3.9 M), which bracket solutions produced by water-rock interactions in the regolith (10-3.3 to 10-3.9 M), indicating that the experiment is, chemically, a reasonable analog to processes occurring in the field. However, we acknowledge that the temperature is significantly different.
