Modeling in-situ uranium(VI) bioreduction by sulfate-reducing bacteria.
نویسندگان
چکیده
We present a travel-time based reactive transport model to simulate an in-situ bioremediation experiment for demonstrating enhanced bioreduction of uranium(VI). The model considers aquatic equilibrium chemistry of uranium and other groundwater constituents, uranium sorption and precipitation, and the microbial reduction of nitrate, sulfate and U(VI). Kinetic sorption/desorption of U(VI) is characterized by mass transfer between stagnant micro-pores and mobile flow zones. The model describes the succession of terminal electron accepting processes and the growth and decay of sulfate-reducing bacteria, concurrent with the enzymatic reduction of aqueous U(VI) species. The effective U(VI) reduction rate and sorption site distributions are determined by fitting the model simulation to an in-situ experiment at Oak Ridge, TN. Results show that (1) the presence of nitrate inhibits U(VI) reduction at the site; (2) the fitted effective rate of in-situ U(VI) reduction is much smaller than the values reported for laboratory experiments; (3) U(VI) sorption/desorption, which affects U(VI) bioavailability at the site, is strongly controlled by kinetics; (4) both pH and bicarbonate concentration significantly influence the sorption/desorption of U(VI), which therefore cannot be characterized by empirical isotherms; and (5) calcium-uranyl-carbonate complexes significantly influence the model performance of U(VI) reduction.
منابع مشابه
In situ bioreduction of uranium (VI) to submicromolar levels and reoxidation by dissolved oxygen.
Groundwater within Area 3 of the U.S. Department of Energy (DOE) Environmental Remediation Sciences Program (ERSP) Field Research Center at Oak Ridge, TN (ORFRC) contains up to 135 microM uranium as U(VI). Through a series of experiments at a pilot scale test facility, we explored the lower limits of groundwater U(VI) that can be achieved by in-situ biostimulation and the effects of dissolved o...
متن کاملModeling the Kinetics of Removal for Uranium(vi) and Sulfate from Aqueous Solutions in the Presence of Sulfate-reducing Bacteria
The objective of these studies is to describe and characterize the reactions involved in the reduction and precipitation of heavy metal ions by both a mixed culture of sulfate-reducing bacteria (SRB), as well as a pure culture of Desulfovibrio desulfuricans (ATCC 7757). The enzymatic reduction of soluble hexavalent U(VI) to insoluble tetravalent U(IV) by Desulfovibrio desulfuricans has been rep...
متن کاملEffects of supplemental organic carbon on long-term reduction and reoxidation of uranium
Bioreduction of mobile uranyl(VI) (UO2 ) to sparingly soluble uraninite (U(IV)O2(s)) is a strategy that has been proposed for in situ remediation of uranium contaminated aquifers. That strategy faces the challenge of reoxidation of uraninite, with consequent release of soluble uranyl when the stimulation of U(VI) bioreduction is terminated. We tested the effects of supplemental organic carbon (...
متن کاملPhysicochemical heterogeneity controls on uranium bioreduction rates at the field scale.
It has been demonstrated in laboratory systems that U(VI) can be reduced to immobile U(IV) by bacteria in natural environments. The ultimate efficacy of bioreduction at the field scale, however, is often challenging to quantify and depends on site characteristics. In this work, uranium bioreduction rates at the field scale are quantified, for the first time, using an integrated approach. The ap...
متن کاملMicrobial populations stimulated for hexavalent uranium reduction in uranium mine sediment.
Uranium-contaminated sediment and water collected from an inactive uranium mine were incubated anaerobically with organic substrates. Stimulated microbial populations removed U almost entirely from solution within 1 month. X-ray absorption near-edge structure analysis showed that U(VI) was reduced to U(IV) during the incubation. Observations by transmission electron microscopy, selected area di...
متن کاملذخیره در منابع من
با ذخیره ی این منبع در منابع من، دسترسی به آن را برای استفاده های بعدی آسان تر کنید
برای دانلود متن کامل این مقاله و بیش از 32 میلیون مقاله دیگر ابتدا ثبت نام کنید
ثبت ناماگر عضو سایت هستید لطفا وارد حساب کاربری خود شوید
ورودعنوان ژورنال:
- Journal of contaminant hydrology
دوره 92 1-2 شماره
صفحات -
تاریخ انتشار 2007