PNNL

Abstract

Samples of a naturally bioreduced, U contaminated aquifer sediment from Rifle, CO were characterized with various microscopic and spectroscopic techniques and wet chemical extraction methods. The objective was to investigate U association and interaction with the soil minerals of the sediment. The naturally bioreduced sediment was elevated in solid-phase U, total organic carbon and acid-volatile sulfide, and depleted in bioavailable Fe(III) indicating that sulfate and Fe(III) reduction have occurred naturally in the sediment. XRD and SEM/EDS analyses demonstrated that framboidal pyrites (FeS2) of different sizes (~10 – 20 µm in diameter), and of various microcrystal morphology, degree of surface weathering and internal porosity were abundant in the