Title: EFFECT OF CO-CONTAMINANTS URANIUM AND NITRATE ON IODINE REMEDIATION 
Resource Type: document --> technical publication --> report 
Country: USA 
Language(s): English
 
Year: 2017 
Author 1/Producer: Szecsody, J.E.,  
Other Authors/Producers: B.D. Lee, A.R. Lawter, et al 
Author / Producer Type: Agency, regulator or other governmental or inter-governmental body 
Report/Document number/description: PNNL-26955, 
Publisher Country: USA 
Publisher web link (root): http://www.pnnl.gov
Report / download web link (=direct link): http://www.pnnl.gov/main/publications/external/technical_rep ...  
EUGRIS Keyword(s): Contaminated land-->Contaminants-->Others
Contaminated land-->Remediation options-->In situ treatment technologies
 
Short description: Iodine exists in different states in the subsurface, as different isotopes, as different species, and in different phases. Predominant isotopic compositions are I-127 and I-129, although only the latter is radioactive. Subsurface fate and transport of iodine is also largely dependent on its chemical speciation, as iodine can be present in both aqueous and solid phases. Unlike most aqueous species, iodine in its reduced form as iodide is more mobile than when it is in its oxidized form as iodate. The impacts of co-contaminants on the migration and transformation of iodine species in the Hanford subsurface environment are being studied because remedies that target individual contaminants like iodine may affect not only the fate and transport of other contaminants in the subsurface but also inhibit the effectiveness of a targeted remedy. For example, iodine as iodate co-precipitates with calcite and has been identified as a potential remedy because it immobilizes iodine; however, uranium also co-precipitates with calcite in field sediments and so uranium presence might inhibit iodine co-precipitation. In the case of iodine and nitrate, the presence of nitrate promotes biogeochemical reduction of iodate to iodide, thereby increasing iodine species subsurface mobility (as iodide exhibits less sorption). This study reports on experiments that investigated (a) the change in iodate uptake mass and rate of uptake into precipitating calcite due to the presence of differing amounts of uranium, (b) the amount of change of the iodate bioreduction rate due to the presence of differing nitrate concentrations, and (c) whether nitrite can reduce iodate in the presence of microbes and/or minerals acting as catalysts.  
Submitted By: Professor Paul Bardos WhoDoesWhat?      Last update: 09/10/2018