The shallow ground water chemistry of Eastern Owens Lake, CA And its subsequent evaporite deposition and particulate air pollution Levi Moxness NDSU Geochemistry GEOL /02/10

Overview 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 Levy et al., (1999)

Evaporite Minerals in Surface Salts Halite Thenardite Trona Pirssonite Nesquehonite NaCl Na 2 SO 4 Na 3 H(CO 3 ) 2 ·2H 2 O Na 2 Ca(CO 3 ) 2 ·2H 2 O MgCO 3 ·3H 2 O 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 SO 4 Owens Valley residents have attributed eye irritation, respiratory complications, and psychological problems to the dust 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)

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 Keeler AW-2 Sulfate Station 1 SP-1 MP-1 MP-2 Station 2 SP-2 MP-3 MP-4 Depths (m) 37.5 Unknown >

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 As and F Speciation Modelling Low depth ground water precipitate mineral predictions PHREEQC

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 Cahill, T. A., Gill, T. E., Reid, J. S., Gearhart, E. A. and Gillette, D. A., 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),