Biological Controls on the Precipitation of Chromium in Harbor Sediments

摘要

The overall goal of this project was to evaluate the processes involved in the attenuation of hexavalen chromium (Cr(VI)) contamination in harbor sediments. Specifically our objectives were to (1) evaluate the mechanisms of Cr(VI) reduction in harbor sediments; (2) evaluate whether bacteria can couple their growth on organic matter to Cr(VI) reduction and if so, whether there is a hierarchy in the use of electron acceptors by these bacteria; and (3) to determine the effects of Cr(VI) on metal- and sulfate-reducing activities and consequential precipitation of Cr. Batch culture and harbor sediment mesocosm experiments examining the effect of Cr(VI) on microbial diversity and processes were performed. The results indicate that Cr(VI) reduction occurs in surficial harbor sediments as a result of microbial activities, primarily those of facultative anaerobic metal-reducing bacteria. As a result, Cr accumulates in the surface sediments. Bacteria capable of using Cr(VI) as an electron acceptor for oxidation of organic matter in the absence of oxygen were isolated and characterized. Cr(VI), even at moderately low levels, dramatically impacts the microbial communities found in sediments.