HOME HELP FEEDBACK SUBSCRIPTIONS ARCHIVE SEARCH TABLE OF CONTENTS		QUICK SEARCH:   [advanced] Author: Keyword(s): Year:  Vol:  Page:

This Article Abstract Full Text Free Full Text (PDF) Free Alert me when this article is cited Alert me if a correction is posted Services Similar articles in this journal Alert me to new issues of the journal Download to citation manager Citing Articles Citing Articles via Google Scholar Google Scholar Articles by Glassley, W. E. Articles by Grant, C. W. Search for Related Content PubMed Articles by Glassley, W. E. Articles by Grant, C. W. GeoRef GeoRef Citation Agricola Articles by Glassley, W. E. Articles by Grant, C. W. Related Collections Isotopes Software Vadose Zone Processes and Chemical Transport

The Impact of Climate Change on the Chemical Composition of Deep Vadose Zone Waters

Lawrence Livermore National Laboratory, Livermore CA 94550

View larger version (19K): [in a new window]   Fig. 1. Temperature as a function of time at depths of about 200 and 400 m. Dashed red lines labeled Temp indicate temperature change due to an increase in surface temperature from 12.7 to 17.7°C, at a constant infiltration flux of 8.75 mm yr-1. Solid blue lines labeled Flux indicate temperature change due to a decrease in infiltration flux from 87.5 to 8.75 mm yr-1, at constant surface temperature of 17.7°C. The rate of temperature change for the portion of the curve indicated by the arrow is 0.002°C yr-1. The curves have been plotted such that the time at which the perturbations were initiated exactly correspond. Approximately 4000 yr of the initial steady-state conditions are shown.

View larger version (23K): [in a new window]   Fig. 2. Negative log of the aqueous SiO2 concentration in fractures and matrix as a function of time at about 200 and 400 m, for the conditions represented in Fig. 1. The negative log of the aqueous SiO2 concentrations associated with surface temperature change are plotted as red lines, and those associated with surface flux change are plotted as blue lines. Fracture waters are represented as dashed lines, and matrix waters by solid lines. The curves have been plotted such that the time at which the perturbations were initiated exactly correspond, and 4000 yr of the initial steady-state conditions are shown.

View larger version (23K): [in a new window]   Fig. 3. Negative log of the aqueous HCO-3 concentration in fractures and matrix as a function of time at about 200 and 400 m, for the conditions represented in Fig. 1. The color scheme, line patterns and layout are the same as for Fig. 2.

View larger version (14K): [in a new window]   Fig. 4. Changes in mineral saturation indices (Q/K) at 200- and 400-m depths for selected minerals, for the change in surface infiltration flux scenario. Saturation indices for fracture waters are indicated by square symbols, and matrix water by round symbols. Open black symbols indicate the initial saturation indices, and the red filled symbols indicate the new steady-state saturation indices. The minerals represented in the figure are labeled along the horizontal axis. Values of Q/K <1.0 indicate solutions that are undersaturated with respect to the indicated minerals, and which would dissolve the mineral if present, while values >1.0 indicate supersaturated waters from which the indicated minerals would precipitate. Illite, mordenite, and smectite are strongly supersaturated (Q/K >2.0) in matrix and fractures at 200 m, but exhibit more complex relationships at 400 m. Note that Q/K for illite and smectite initially exceeds 2.0 in the matrix at 400 m. Q/K for kaolinite is consistently >>1.0 under all conditions.

View larger version (15K): [in a new window]   Fig. 5. The rate of temperature change (°C) as a function of time (years) vs. depth, for the case in which surface temperature and infiltration flux change simultaneously over 10000 yr, after 20000 yr of steady-state conditions (line labeled 19900 yr). The line labeled 30160 yr indicates the rate of temperature change 160 yr after climate change has ceased, and approximately defines the maximum values achieved for dT/dt. Note that even after about 10000 yr after perturbation at the surface, the rate of temperature change is still >0 (line labeled 39940 yr).

View larger version (23K): [in a new window]   Fig. 6. Negative log of the aqueous SiO2 concentration in fractures (dashed lines) and matrix (solid lines) as a function of time at about 200 (red) and 400 (blue) m, for the conditions and time span represented in Fig. 5. Approximately 10000 yr of the initial steady-state conditions are shown. The period of time over which the infiltration flux and surface temperature changes occur is indicated by the shaded region labeled Perturbation Period.

View larger version (24K): [in a new window]   Fig. 7. Negative log of the aqueous HCO-3 concentration in fractures (dashed lines) and matrix (solid lines) as a function of time at about 200 (red) and 400 (blue) m, for the conditions and time span represented in Fig. 5. Approximately 10000 yr of the initial steady-state conditions are shown. The period of time over which the infiltration flux and surface temperature changes occur is indicated by the shaded region labeled Perturbation Period.