Thx Don...good report.

ref: The d13C values (-3.5 to -3.7‰) of elevated CO2 concentrations confirm that it does indeed come from old groundwater rather than the more surficial groundwater which accounts for 20-40% of spring output.

+ Any idea wht the d13C values (acronym) are ?

ref: During the 1993 observation period, concentrations of radon were stable at 20Bq/l.

+ What is the unit being used ? Bq/l ?

ref:
The researchers have examined other possible reasons for the observed increase in Radon levels, but no satisfactory alternate explanation could be found.

+ Recap...Deep CO2 carries deep radon to the surface ? Is this the current thinking?

+ I wonder if any body is monitoring CO2 (as a way to get radon levels ...maybe...)

Thx again. Good report.

Anyway, I figured with all the money spent on Parkfield by USGS...you'd think they would tap all available "clues" including radon sampling. Maybe such data is out there...and being sampled regularly...time will tell.