HR: 1400h
AN: GS23B-09    [Abstracts]
TI: Stable Carbon Isotope Characterization of CO₂ Loss in Acid Mine Drainage Impacted Stream Water: Observations from a Laboratory Experiment
AU: Ali, H N
EM: hendrat@okstae.edu
AU: * Atekwana, E A
EM: eliot.atekwana@okstate.edu
AF: Oklahoma State University, 105 Noble Research Center, Stillwater, OK 74078, United States
AB: Water from an acid mine drainage spring, ground water from a mine tailings pile, stream water and tap water were acidified to simulate acid mine drainage (AMD) contamination. The objective was to determine how acidification of stream water by AMD affected DIC loss and carbon isotope fraction. Two 20 L HDP containers (reactors) containing samples from each source were left un-acidified and allowed to evolve under ambient conditions for several weeks in the laboratory and two others were acidified. Acidification was carried out progressively with sulfuric acid to pH <3. For acidified samples, one reactor was acidified open to the atmosphere and the other closed from contact with atmosphere and CO_2(g) was collected under vacuum. The un-acidified samples did not show significant alkalinity and DIC loss, and the ¹³C of DIC was enriched with time. The acidified samples showed decrease in alkalinity and DIC and increase in the ¹³C of DIC and CO_2(g) with progressive acidification. The enrichment of ¹³C of DIC for un-acidified samples was due to exchange with atmospheric CO₂. On the other hand, the ¹³C enrichment in the acidified samples was due to fractionation during dehydration of HCO₃^- and diffusive loss of CO_2(g) from the aqueous phase. The actual values measured depended on the amount of CO₂ lost from the aqueous phase during acidification. Samples with greater CO₂ loss (closed acidification) had greater ¹³C enrichment. Beyond the HCO₃^- titration end point, the δ¹³C of DIC and CO_2(g) was similar and nearly constant. The result of this study suggests that AMD effects on DIC can be modeled as a first order kinetic reaction and the isotope enrichment modeled using Rayleigh distillation.
DE: 1009 Geochemical modeling (3610, 8410)
DE: 1803 Anthropogenic effects (4802, 4902)
DE: 1816 Estimation and forecasting
DE: 1831 Groundwater quality
DE: 1871 Surface water quality
SC: Geochemical Society [GS]
MN: 2007 Joint Assembly