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Title: Mechanisms controlling the distribution and transport of {sup 14}C in a clay-rich till aquitard

Abstract

The distribution and transport of radiocarbon in dissolved inorganic carbon (DIC) in a thick clay-rich till aquitard was investigated. Radiocarbon activities decreased with depth from 109 percent modern carbon (pmC) in the surficial oxidized and fractured zone through the thick underlying unoxidized and nonfractured aquitard, reaching minimum values of between 3 and 5 pmC at between 29 and 37 m depth. Numerical simulations of diffusive transport of radiocarbon from the oxidized zone into the unoxidized zone during the Holocene closely approximated the measured values and showed that diffusive transport and radioactive decay fully described the transport of radiocarbon in the aquitard. The lack of geochemical reactions involving DIE permitted the age of DIC in the pore water deposited with the till to be estimated at 25 to 31 ka BP. Results of this study showed that the use of radiocarbon in the study of solute transport in aquitards provides age information that cannot be obtained from natural conservative tracers such as {delta}{sup 2}H and {delta}{sup 18}O. Their results also showed that the application of conventional radiocarbon age-dating models based on piston-flow transport assumptions, is inappropriate in diffusion-dominated environments and considerably overestimates the age of the ground water.

Authors:
;
Publication Date:
Research Org.:
National Water Research Inst., Saskatoon, Saskatchewan (CA)
OSTI Identifier:
20080435
Alternate Identifier(s):
OSTI ID: 20080435
Resource Type:
Journal Article
Journal Name:
Ground Water
Additional Journal Information:
Journal Volume: 38; Journal Issue: 3; Other Information: PBD: May-Jun 2000; Journal ID: ISSN 0017-467X
Country of Publication:
United States
Language:
English
Subject:
54 ENVIRONMENTAL SCIENCES; AQUIFERS; ENVIRONMENTAL TRANSPORT; CARBON 14 COMPOUNDS; ISOTOPE DATING; SOLUTES; GROUND WATER; INTERSTITIAL WATER; GEOCHEMISTRY

Citation Formats

Wassenaar, L.I., and Hendry, M.J. Mechanisms controlling the distribution and transport of {sup 14}C in a clay-rich till aquitard. United States: N. p., 2000. Web. doi:10.1111/j.1745-6584.2000.tb00219.x.
Wassenaar, L.I., & Hendry, M.J. Mechanisms controlling the distribution and transport of {sup 14}C in a clay-rich till aquitard. United States. doi:10.1111/j.1745-6584.2000.tb00219.x.
Wassenaar, L.I., and Hendry, M.J. Thu . "Mechanisms controlling the distribution and transport of {sup 14}C in a clay-rich till aquitard". United States. doi:10.1111/j.1745-6584.2000.tb00219.x.
@article{osti_20080435,
title = {Mechanisms controlling the distribution and transport of {sup 14}C in a clay-rich till aquitard},
author = {Wassenaar, L.I. and Hendry, M.J.},
abstractNote = {The distribution and transport of radiocarbon in dissolved inorganic carbon (DIC) in a thick clay-rich till aquitard was investigated. Radiocarbon activities decreased with depth from 109 percent modern carbon (pmC) in the surficial oxidized and fractured zone through the thick underlying unoxidized and nonfractured aquitard, reaching minimum values of between 3 and 5 pmC at between 29 and 37 m depth. Numerical simulations of diffusive transport of radiocarbon from the oxidized zone into the unoxidized zone during the Holocene closely approximated the measured values and showed that diffusive transport and radioactive decay fully described the transport of radiocarbon in the aquitard. The lack of geochemical reactions involving DIE permitted the age of DIC in the pore water deposited with the till to be estimated at 25 to 31 ka BP. Results of this study showed that the use of radiocarbon in the study of solute transport in aquitards provides age information that cannot be obtained from natural conservative tracers such as {delta}{sup 2}H and {delta}{sup 18}O. Their results also showed that the application of conventional radiocarbon age-dating models based on piston-flow transport assumptions, is inappropriate in diffusion-dominated environments and considerably overestimates the age of the ground water.},
doi = {10.1111/j.1745-6584.2000.tb00219.x},
journal = {Ground Water},
issn = {0017-467X},
number = 3,
volume = 38,
place = {United States},
year = {2000},
month = {6}
}