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[en] Nitrilotriacetic acid (NTA) forms strong water soluable complexes with a wide range of radionuclide and metal ions. Knowledge of sorption-biodegradation interactions is essential to predict the environmental transport of radionuclide-NTA complexes. Biodegradation of NTA and cobalt-NTA by Chelatobacter heintzii was investigated

[en] The co-disposal of EDTA with radionuclides (e.g., ⁶⁰Co, U), has been implicated in the radionuclide migration observed in ground waters at DOE sites. The adsorption of EDTA and equimolar Co-EDTA by δ-Al₂O₃ as investigated over a range of pH (5 to 9.5), adsorbate concentration (0.2 to 10 μM), adsorbent concentration (0.1 to 10 g.L) and ionic strength (0.001 to 0.1 M NaClO₄), in the presence of dissolved Al in equilibrium with δ-Al₂O₃. Independent measurement of both Co and EDTA adsorption, using dual-label scintillation counting and γ-counting of ⁶⁰CO and ₁₄C-labeled EDTA, allowed mass balance equations in FITEQL simulations of adsorption data to be simultaneously constrained by both of these adsorbing components. Significant ionic strength shifts in Co and EDTA adsorption edges suggest an important electrostatic contribution to adsorption reactions. Simulations of the data using the triple layer model and numerous possible surface reactions are consistent with the hypothesis that (1) outer-sphere surface complexes of both AlEDTA and CoEDTA chelates form; (2) the surface complexes formed with protonated surface groups are AlEDTA-(5.6), AlOHEDTA (4.0), CoEDTA²-(4.5) and CoHEDTA-(9.3), with intrinsic Log K values given in parenthesis and; (3) above pH 7 surface sites begin to compete effectively with the EDTA for the Co at the highest adsorbent concentration examined

[en] For the past several years, data on radionuclide migration in groundwater at a low-level disposal site were collected. Most of the radionuclides were removed in the disposal basin and trench by either precipitation or adsorption mechanisms. However, three radionuclides ⁶⁰Co, ¹⁰⁶Ru, and ¹²⁵Sb showed somewhat greater than expected mobility. The elements of these three isotopes were found to be in either anionic or nonionic charge-forms. Complexes with both natural and man-made organics were implicated in the increased mobility, particularly in the case of ⁶⁰Co. Characterization studies of the organic fraction were performed. Ruthenium-103, ⁶⁰Co, and ¹²⁵Sb were found to be associated with the higher molecular weight organics, particularly humic and fulvic acids with molecular weights greater than 1000. Studies were also performed that proved the hypothesis that the adsorption behavior of ²³⁵Np on soils of the site is dominated by adsorption on iron hydroxide. Finally, geochemical modeling of the chemical and charge form data showed the groundwater to be in equilibrium with several solids that could be important in controlling the concentrations of trace elments and radionuclides. 47 references, 14 figures, 3 tables

[en] Staff at Pacific Northwest Laboratory for the past several years have been collecting the available data concerning radionuclide migration in the groundwater at a low-level disposal site and studying the physicochemical processes that control the mobility of radionuclides in the groundwater. This report summaries the results obtained and progress made during FY83. 21 figures, 24 tables

[en] The codisposal of synthetic chelating agents [e.g., ethylenediaminetetraacetic acid (EDTA), diethylenetriaminepentaacetic acid (DTPA), and nitrilotriacetic acid (NTA)] and radionuclides has been implicated in increased radionuclide transport in the subsurface environment. Microbial transformations of chelates in the subsurface are currently unknown, but could influence chelate persistence and thus alter the transport of radionuclides. Surface soil and subsurface sediments from five formations (36- to 376-m depth) were collected near Allendale, SC. Aerobic mineralization of ¹⁴C-labeled EDTA, DTPA, and NTA occurred in select sediments indicating that subsurface microorganisms can degrade chelates, whereas chelates may be relatively stable in strata where limited mineralization occurred. The chelates were not mineralized more rapidly or to a greater extent in the surface soil than in the subsurface sediments. The relative order of chelate persistence was EDTA > DTPA > NTA, with the maximum amount mineralized during 115 d at 15, 26, and 43%, respectively. Maximum mineralization of all three chelates did not occur in the same sediment, indicating that different microbial populations were responsible for the degradation of each chelate. Mineralization of chelates was minimal under denitrifying conditions and was reduced when additional soluble C was added. There was no relationship between chelate mineralization and the adsorption of chelates to sediments or the aqueous speciation of the chelates. 47 refs., 4 figs., 3 tabs

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No abstract available