Chemical stability of 99mTc-DTPA under aerobic and microbially mediated Fe(III)-reducing conditions in porous media

99mTc-DTPA has been used as a conservative tracer to quantify water transport through porous media. However, more information on the reactivity of this 99mTc compound under varying geochemical conditions is desirable to better understand its potential uses. We measured the speciation of Tc following amendment of 99mTc-DTPA to batch systems spanning a range of controlled biogeochemical conditions. Our results suggest that 99mTc-DTPA is stable under the reducing conditions tested. However, freshly precipitated Al-ferrihydrite may displace Tc(IV) from DTPA in the absence of Fe(III)-reducing conditions.