Abstract
Mercury (Hg) contamination within the Oak Ridge Reservation has been an ongoing research. A comprehensive understanding of the potentials of predominant microorganisms in selected cleanup strategy is highly paramount. The use of sorbents has been proposed as a cleanup strategy; however, biological factors need to be evaluated as regards to the strategy. The goal of this study was to use microbes isolated from various contaminated sites and determine their effectiveness on sorbents to reduce total Hg (HgT). We isolated DNA from contaminated soils (SB 5-8, SB 14-8) and control soil (Hinds Creek) with little
or no Hg contamination. Pure cultures were obtained from soil samples using broad-spectrum nutrient broth, and natural medium formulated using extracts from the different soil samples. Selected colonies and total DNA from the soils were used for 16S rDNA sequencing. Some Hg reducers (Acinetobacter rhizosphaerae and Serratia marcescens) were isolated. S. marcescens was chosen due to its role in bioremediating and transforming Hg. Study of hg leachability in the contaminated soils showed that the amount of leachable Hg varied in magnitude among the three soils possibly due to seasonal changes. Sorbent was added to determine control in leachability after the soils have been incubated for 14 days in diH2O. S. marcescens was inoculated into the soils along with sorbents and incubated for 48 hrs at 25°C. Total Hg (HgT) concentrations were determined using cold vapor atomic fluorescence in accordance with EPA method 1631. A variable amount of methylators was found in each soil type. Organisms that grew on the nutrient agar grew poorly on the natural medium with variable colonies. However, S. marcescens grew on both media. S. marcescens showed high reduction of Hg2+ compared to the sorbent; however, when inoculated in the soil, the sorbent was found to absorb more HgT in solution.
