Sediment subduction and magma genesis in the central Aleutian arc

Introduction Uranium mobility, and therefore its potential hazard, is highly dependent on its chemical speciation and redox state. Recently there has been great interest in the possibility of remediation of uranium contaminated sites through uranium immobilization via in situ reduction of U(VI) to U(IV) by dissimilatory metal reducing bacteria. A variety of organisms, including Shewannella Putrafaciens (CN32), have been shown to reduce both Fe(III) to Fe(II) and U(VI) to U(IV). Additionally, batch studies have shown that CN32 will simultaneously reduce both Fe(III), as ferrihydrite, and aqueous U(VI) at significant rates. Previous investigations of microbial induced ferrihydrite reduction under dynamic flow conditions have shown significant soluble Fe(II) production that in turn drives extensive down gradient ferrihydrite to magnetite conversion. The current study examines uranium dynamics in the presence of both CN32 and ferrihydrite under flow conditions. Uranium (U(VI)) in a synthetic groundwater medium was introduced in to a column packed with ferrihydrite coated sand that was inoculated with Shewanella Putrafaciens (CN32).