HR: 14:40h
AN: H33H-05    [Abstracts]
TI: Arsenic speciation in the shallow aquifer, Churchill County, Nevada
AU: * Meinert, M
EM: mmeinert@unr.edu
AF: University of Nevada, Reno, Mail Stop 370 132 Fleischmann Agriculture, Reno, NV 89557-0013 United States
AU: Walker, M J
EM: mwalker@cabnr.unr.edu
AF: University of Nevada, Reno, Mail Stop 370 132 Fleischmann Agriculture, Reno, NV 89557-0013 United States
AU: Gustin, M S
EM: mgustin@cabnr.unr.edu
AF: University of Nevada, Reno, Mail Stop 370 132 Fleischmann Agriculture, Reno, NV 89557-0013 United States
AB: Wells that tap the shallow aquifer in Churchill County, Nevada over a period of seven months have shown significant fluctuations in the As(III):As(V) proportion. Eleven wells were chosen that showed substantial fractions of each species, and were sampled once-monthly near the farming town of Fallon beginning in February, 2004 to the present. The region has an arid climate receiving approximately eight inches of rain annually. The Carson River flows through the region, however, most of its waters has been diverted to the Newlands Project, which provides irrigation water to surrounding farms. Groundwater recharge, therefore, is dominated by infiltration of this irrigation water, which is supplied primarily in the spring and summer months. Water tables in the area are fairly shallow (between 2.5 and 7 meters) and fluctuate seasonally due to irrigation. Total arsenic concentrations of between 10 and 440 ppb exist in the wells, although As concentrations have remained fairly stable during the sampling period. Two wells have shown complete reversal of the As(III):As(V) ratio, some have shown remarkable stability, and others have shown significant variation from the ratio expected from pH-pE diagrams for arsenate and arsenite. Additional groundwater constituents are being sampled to determine their contribution to the speciation process, and deuterium and oxygen-18 analysis is on-going to determine the provenance of groundwaters at the sampling locations. Adsorption/desorption pertaining to iron oxides and hydroxides as well as oxidation-reduction are being investigated to determine their contribution to variations in speciation.
DE: 0399 General or miscellaneous
SC: Hydrology [H]
MN: 2004 AGU Fall Meeting