Open AccessGeochemical Controls on Contaminant Uranium in Vadose Hanford Formation Sediments at the 200 Area and 300 Area, Hanford Site, Washington
Author(s) -
McKinley James P.,
Zachara John M.,
Wan Jiamin,
McCready David E.,
Heald Steven M.
Publication year - 2007
Publication title -
vadose zone journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.036
H-Index - 81
ISSN - 1539-1663
DOI - 10.2136/vzj2006.0184
Subject(s) - hanford site , uranium , vadose zone , uranyl , geology , groundwater , environmental remediation , radioactive waste , geochemistry , environmental chemistry , mineralogy , radiochemistry , contamination , chemistry , nuclear chemistry , ecology , materials science , geotechnical engineering , biology , metallurgy
Long‐term historic spills of uranium at the 300 Area fuel fabrication site (58,000 kg of disposed uranium over 32 yr) and at the 200 East Area BX tank farm (7000 kg of spilled uranium in one event), both within the Hanford formation in the Hanford Site, Washington State, were investigated by subsurface sampling and subsequent microscale investigations of excavated samples. The 200 Area sediments contained uranyl silicate mineralization (sodium boltwoodite) in restrictive microfractures in granitic clasts, in the vadose zone over a narrow range in depth. Well logging and column experiments indicated that tank wastes migrated deeper than observed in core samples. The 300 Area sediments included metatorbernite and uranium at low concentrations associated with detrital aluminosilicates, along with other mineral phases that could accommodate uranyl, such as uranophane and calcium carbonate. The association of contaminant uranyl with Hanford formation sediments provided a persistent source of uranium to groundwater. The results of both studies suggest that the formation of secondary solid uranyl‐bearing phases influences the subsequent release of uranium to the environment and that our understanding of these processes and individual waste sites is incomplete.