Hello everybody,

For a brief discussion on various designs for field precipitation
collectors that can be left unattended for 6 months, see

Scholl, M.A., Ingebritsen, S.E., Janik, C.J. and Kauahikaua, J.P., 1996,
Use of precipitation and groundwater isotopes to interpret regional
hydrology on a tropical volcanic island:  Kilauea volcano area, Hawaii,
Water Resources Research, v. 32, no. 12, p. 3525-3537.

We found the best design was a collector with a layer of mineral oil to
prevent evaporation, however, you need to use at least a 1-cm thick layer
of oil, or evaporation can occur through the oil layer, especially in
hot, dry climates.

Martha Scholl

U.S. Geological Survey
431 National Center
Reston, VA  20192


On Tue, 29 Sep 1998 18:58:54 -0400
"Daniel H. Doctor" said:
> Hello Isabella,
> I believe that Carol Kendall at the USGS (in Reston, Virginia?) knows of a
> design for building a rain collection system that rests underground, such
> that the cooling effect of the soil provides natural refrigeration and
> helps reduce risks of fractionation due to evaporation.  Also, I've heard
> that a simple layer of mineral oil in the bottom of your collection vessel
> can act as a nice evaporation seal without risking fractionation via
> chemical reaction.  I don't know how rigorously this has been tested,
> though (quick publication potential?).  Either way, two other things will
> greatly help reduce the risk of fractionation: don't let your samples sit
> in the field for very long, and be sure to collect as large an amount of
> sample water as possible!
> Anybody else out there have a suggestion?
> Isabella, please keep me updated as to what you discover, as this is
> concern for me in my research as well.  Thanks!
> -Dan
> On Tue, 29 Sep 1998 08:41:23 -0400 wrote...
> >        Hello everyone!
> >
> >        I'm a graduate student at the University of Virginia beginning a
> >project on Oxygen-18 and deuterium in rain water.  I'm building a rain
> >collector that allows for collection at 5 minute increments for 12
> >hours and I am worried about the possibility of sample fractionation. I
> >read a paper suggesting the creation of a dodecane bi-layer when analyzing
> >for oxygen, but I am unsure how this would effect deuterium results.
> >Does anyone know of a reference or have an opinion of using such a
> >technique when analyzing for deuterium?  Due to field constraints,
> >refrigeration really isn't an option and I was curious if anyone
> >had ever run into this problem before or had a good solution to
> >fractionation in the field.
> >
> >        Thanks!,
> >                Isabella Angelini
> >                University of Virginia
> >                [log in to unmask]
> >
> *****************************************************
> Dan Doctor
> Dept. of Geology & Geophysics
> Univ. of Minnesota
> 310 Pillsbury Dr. SE
> Minneapolis, MN 55455
> (612) 624-1333
> Email: [log in to unmask]