Clay Minerals Affect Technetium (99Tc) Mobility in the Environment


99Tc is a major risk driver at DOE sites due to its long half life, high solubility and potential for possible uptake into the food chain as a phosphate analog.  Researchers at Miami University-Ohio, Pacific Northwest National Laboratory and Argonne National Laboratory have found that ferrous iron, produced by metal reducing bacteria, within clay minerals, can readily reduce 99Tc to an insoluble form thereby removing it from solution.  Once reduced much of the immobilized 99Tc remains physically protected from potential oxidants, that would otherwise remobilize the contaminant, inside clay particle aggregates.  99Tc is a product of nuclear reactions and is found in the subsurface at some DOE sites due to inadvertent disposal of wastes stemming from Cold War era production of nuclear weapons.  Clay minerals are common components of soils and sediments. The results indicate that bioreduced clay minerals could naturally play an important role in reducing 99Tc mobility at key biologically active interfaces in soils and sediments in the environment or within bioremediation strategies aimed at limiting 99Tc transport in groundwater at contaminated sites.


Chemical Geology, 2009, 264:127-138.