TRANSPORT OF ANTHROPOGENIC URANIUM FROM SEDIMENTS TO SURFACE WATERS DURING EPISODIC STORM EVENTS

Remobilization of sediment-associated uranium (U) from contaminated fl oodplain sediments to a stream adjacent to a nuclear weapons processin g facility during episodic rain events was investigated. In addition, U solid phase associations in suspended sediments were assessed by a s equential chemical extraction procedure to gauge U chemical lability. Mass flux estimates determined from base flow measurements potentially underestimate the amount of U transported from contaminated terrestri al sources to surface water systems. Erosional processes can effective ly mobilize sediment-associated contaminants during storms or flooding . During the various storm events measured, approximately 1500 to 2800 % more U was exported to Upper Three Runs Creek (UTRC) relative to bas e Row measurements. Sequential extraction results suggest the suspende d sediment load transports the bulk of U in labile forms predominantly as acid soluble (specifically adsorbed), MnO2 occluded and organicall y bound phases. This implies that U may be available to the ecosystem under a range of environmental conditions likely to be encountered wit hin depositional environments (e.g., Eh and pH) or as a result of indu strial processes. This study demonstrates the need to evaluate contami nant transport during storm events from exposed contaminated sediments , or from industrial waste stockpiles subject to erosion.