The shallow ground water chemistry
of Eastern Owens Lake, CA
And its subsequent evaporite deposition and
particulate air pollution
Levi Moxness
NDSU Geochemistry GEOL 428
12/02/10
Overview
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Lake history and Chemistry
Health Risks
Local Ground Water
Levy et al., PHRQPITZ Modelling
Additional WATEQ4F Contrast
Conclusions
Formation of a Playa
Prior to 1913 Owens Lake was a 280
sq km body of water
7-15 m deep
Diversion of the Lake’s primary
water source, the Owens river, into
the Los Angeles Aqueduct caused it
to all but evaporate by 1921
Left behind 130 sq km of exposed
lakebed with large amounts of
carbonate and sulfate-rich salts
http://oceanworld.tamu.edu/resources/environment-book/dyingseas.html
Levy et al., (1999)
Evaporite Minerals in Surface Salts
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Halite
Thenardite
Trona
Pirssonite
Nesquehonite
NaCl
Na2SO4
Na3H(CO3)2·2H2O
Na2Ca(CO3)2·2H2O
MgCO3·3H2O
Toxins like Arsenic can partition into surface
salts from evaporating groundwater
Resulting Health Hazards
The lake bed is the source of the highest levels of
particulate air pollution in North America
Efflorescent salt clouds contain high levels of As and SO4
Owens Valley residents
have attributed eye
irritation, respiratory
complications, and
psychological problems
to the dust
http://exiledonline.com/wp-content/uploads/2010/03/OwensLake-dustStorm-469x317.jpg
Cahill et al., (1996)
Hydrologic Basin
The igneous Cosco Mountains
on the south end of the valley
restrict groundwater outflow
Up to 2400 m of
unconsolidated sedimentary
materials form the reservoir
Dissolved solids increase as
you approach the
evaporation at the surface
Levy et al., (1999)
http://earthobservatory.nasa.gov/IOTD/view.php?id=3273
Levy et al., (1999)
The shallow ground water chemistry of arsenic, fluorine,
and major elements: Eastern Owens Lake, California
Studied he geochemical evolution of near-surface ground water
Focused on trace element concentrations, particularly the toxic
As and F
Compared “fresh” water from three deep Artesian wells with
water near the surface (< 3 m) in two locations on the eastern
playa, which have elevated element concentrations due to
evaporation
Sample Well Locations
Well
Depths (m)
Keeler
AW-2
Sulfate
37.5
Unknown
>145
Station 1
SP-1
MP-1
MP-2
0.6
1.5
3.0
Station 2
SP-2
MP-3
MP-4
0.6
1.5
3.0
Results
The Artesian wells show an increase in pH, alkalinity, and TDS as you
move closer to the center of the lake
The shallow samples show much greater amounts of all major
elements, and higher pH, alkalinity, and TDS than the Artesian
samples, decreasing with depth from the surface
PHRQPITZ Modelling
Low depth ground water precipitate mineral predictions
PHREEQC
As and F Speciation Modelling
WATEQ4F Modelling
Compared with WATEQ4F, which contained an output of all the
mineral saturations except Pirssonite, and had As, F, and Li inputs
Conclusions
• Ground water depleted in Ca alkalinity evolve
into high pH brines as they concentrate at the
surface due to evaporation
• As and F partition to surface salts in very
saline ground water, and can be released to
blow under expose to rainwater
• PHRQPITZ and WATEQ4F models show
increasingly saline conditions toward the
exposed surface of the (dry) lake
References
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Cahill, T. A., Gill, T. E., Reid, J. S., Gearhart, E. A. and Gillette, D. A., 1996. Saltating particles,
playa crusts and dust aerosols at Owens (dry) Lake, California. Earth Surf. Proc. Land. 21, pp.
621–639
Levy et al., 1999 D.B. Levy, J.A. Schramke, K.J. Esposito, T.A. Erickson and J.C. Moore, The
shallow ground water chemistry of arsenic, fluorine, and major elements: Eastern Owens
Lake, California, Appl. Geochem. 14 (1999),