dissimilatory iodate reduction by Hanford microbial isolates - 15226
- Pacific Northwest National Laboratory (United States)
Microbial radioactive iodine ({sup 129}I) redox cycling in saturated soils is not well understood and provides a novel avenue for bioremediation studies. {sup 129}I is a major by-product of nuclear fission, and is of environmental concern due to its long half-life (∼16 million years), toxicity, and mobility in the environment. The 200 West area of the Hanford Site contains two separate plumes covering 1,500 acres where {sup 129}I concentrations are ∼3.5 pCi/L in Hanford soils. Speciation analysis shows that iodate comprises 70.6% of the iodine present, and organo-iodide and iodide comprise 25.8% and 3.6% respectively. Microbial redox activity within these iodine plumes affects iodine speciation, consequently impacting iodine mobility within the subsurface and the potential options available for bioremediation. An iodate reducing organism, designated as Agrobacterium tumefaciens strain AD35, was isolated from trap material incubated for 50 days in a high {sup 129}I concentration plume. Iodate (200μm) was reduced 47.8% in anaerobic cultures and by 36.3% in transitional cultures in the presence of 10 mM nitrate, which was reduced 80.9% and 81.4% respectively. Iodate was also shown to be reduced by 69.2% and 84.0% in anaerobic and transitional growth conditions respectively with steady spiking of nitrate throughout. No iodate reduction was demonstrated without nitrate present. These data indicate there is a coupled reduction of nitrate and iodate by strain AD35. These data provide novel information on microbial iodate reduction in the groundwater at the 200 West Area. These organisms, along with other nitrate/iodate reducing organisms, which have been presently identified and are being characterized, can be employed in an engineered bioremediation approach for the removal of nitrate and iodate in the groundwater. Additionally, applications for stabilizing radioactive iodine in the subsurface are lacking. Results presented allow us to develop an understanding of iodine speciation throughout the Hanford Site, along with providing novel microbial systems for the bioremediation of iodine and also nitrate, which is not well understood to date. (authors)
- Research Organization:
- WM Symposia, Inc., PO Box 27646, 85285-7646 Tempe, AZ (United States)
- OSTI ID:
- 22822756
- Report Number(s):
- INIS-US--19-WM-15226
- Country of Publication:
- United States
- Language:
- English
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