Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis Page: 3 of 8
This article is part of the collection entitled: Office of Scientific & Technical Information Technical Reports and was provided to Digital Library by the UNT Libraries Government Documents Department.
The following text was automatically extracted from the image on this page using optical character recognition software:
10 20 3 KILOMETERS ,'4
BLACK PN rf MS
\MESA -------r ---
v M1 RAINIER
RCOBATUS \ to
. k, FLAT TIMBER-
c MTN I FLAT
GBE ATTYC IP
CRA TER % I
AGO O i FR Irs
-9 1 s ~
, 9 \-- FLATS gKU
ti Z s y(' \ " - MERCURY
v o "Q ) AMAR OSA 2
Figure 1. Soil gas sampling sites in the vicinity of Yucca Mountain. USE = U.S. Ecology; YC = Yucca Crest; FR = Fran Ridge;
40M = Fortymile Wash; PWT = Pagany Wash; PIA = roadcut on side of Rainier Mesa; and RM1 = top of Rainier Mesa.
extracted CO2. Soil samples for analysis of soil moisture, of
the H and O isotopic composition of soil water, and 5'3C of
associated organic and inorganic soil carbon, were also col-
lected by auger, and frozen for later analysis.
Extraction of CO2 for isotopic analysis was accom-
plished by cryogenic trapping in the laboratory. Replicate
extractions from single balloons made within a few days typi-
cally agreed within mass spectrometric precision for both
813C and 81O (about .05 %oa ), and replicate balloons
typically agreed within 0.2 %o. Some isotopic drift has
a S13C and d1 80 values are reported as the %o (parts per thousand)
deviations of the unknowns from the isotopic compositions of the
International Standards PDB (for C) and SMOW (for O).
however been noted over periods of several months, pre-
sumably reflecting CO2 leakage through the mylar balloons
or their septa. Other limitations on the data stem from the
creation of flow fields within the soils during sampling, and
from spatial heterogeneities related to nearby vegetation,
animal burrows, etc. For samples collected between March
and September 1993, soil gas 813C ranges from about -22
to -8 %o PDB, with the following trends (Fig. 2):
1) Soil gas 813C decreases with depth within the top
meter, while CO2 concentrations increase. These observa-
tions are consistent with larger contributions of isotopically
light CO from soil respiration, deeper within the soils.
About half of the depth-dependent variation often occurs
within the top 10 cm, while the S13C minimum or asymp-
Here’s what’s next.
This article can be searched. Note: Results may vary based on the legibility of text within the document.
Tools / Downloads
Get a copy of this page or view the extracted text.
Citing and Sharing
Basic information for referencing this web page. We also provide extended guidance on usage rights, references, copying or embedding.
Reference the current page of this Article.
McConnaughey, T.A.; Whelan, J.F.; Wickland, K.P. & Moscati, R.J. Isotopic studies of Yucca Mountain soil fluids and carbonate pedogenesis, article, December 31, 1994; Denver, Colorado. (https://digital.library.unt.edu/ark:/67531/metadc619823/m1/3/: accessed April 20, 2019), University of North Texas Libraries, Digital Library, https://digital.library.unt.edu; crediting UNT Libraries Government Documents Department.