Contaminated surficial sediments represent a potential point of entry into the food web for environmental pollutants that are toxic to fish, wildlife, and humans. One approach for managing polluted sediments is in situ capping, the placement of clean fill material, such as sand, atop the polluted sediments. A cap stabilizes the underlying sediment and physically separates pollutants from benthic organisms that inhabit the sediment/water interface. Additionally, a sediment cap can be amended with sorbents to sequester hydrophobic organic chemicals. While the physical processes affecting contaminant transport in sediment caps are readily modeled, fate and transport processes mediated by sediment bacteria are location-specific and thus highly uncertain. Laboratory bench-scale tests were employed to aid in the design of a sediment cap in Onondaga Lake. Recognizing the importance of bacterial activity beneath the benthic zone for affecting the risks of contaminant exposure, anaerobic processes were emphasized. A combination of batch and column tests were used to determine whether (1) bacteria in sediments were capable of biotransforming methylated and chlorinated benzenes, (2) the ability to biotransform the contaminants of interest would be translated from the sediments to a sand cap, (3) the rate of biogenic gas production in sediments would threaten the integrity of a sand cap, and (4) the contribution of gas-phase contaminant transport to the overall transport of contaminants from the sediments was significant. The apparent anaerobic biotransformation of toluene in a sand cap was supported by detection of a genetic biomarker for anaerobic toluene degradation, the development of substantial biomass in the sand column, apparent anaerobic biotransformation of toluene in sediment slurries, and the concomitant reduction of iron in the sand column. The dissimilarity in bacterial community composition between sediment and sand cap samples suggests that contaminant biotransformation capability cannot be predicted from community analysis. For sediments that failed to demonstrate biotransformation potential, amending a sand column with organophilic clay proved effective at retarding transport of the contaminants of interest. This work advances methods for characterizing bacterial processes in sediments and demonstrates the potential for anaerobic biotransformation of organic contaminants in sand caps. / text

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Thesis (M.S.)--Youngstown State University, 2008. / Includes bibliographical references (leaves 36-40). Also available via the World Wide Web in PDF format.

The intrusive and expensive nature of soil cleanup technologies like excavation and incineration created a need to search for alternative remediation technologies. Rhizoremediation and its associated microorganisms has the potential to cleanup contaminated soil in a ‘non invasive’ and cost-effective manner. The literature cites many benefits of the technology if implemented correctly. However, there is still a lack of knowledge concerning the interaction of the plants and microorganisms that are responsible for degrading the organic pollutants. In this study, the potential for degrading Poly aromatic hydrocarbons (PAH’S) by rhizosphere bacteria was investigated. In addition, the hydrocarbon removal efficiencies of different plant rhizospheres were investigated. The metabolic and genetic profiles of soil bacteria in vegetated and non- vegetated soils were determined. The results of the removal efficiencies of different plant rhizospheres showed that the removal of hydrocarbons was more effective in soil vegetated by different plant species. By using co-occurring (different) plant species, hydrocarbons were removed faster than when monoplanted were used. The number of hydrocarbon degrading bacteria in the rhizosphere increased during rhizoremediation of PAH’s contaminated soil. Analysis of the functional and genetic diversity in PAH’s contaminated and non-contaminated rhizosphere and non-rhizosphere soil, using Biolog (physiological community level) and genetic diversity (polymerase chain reaction- denaturant gradient gel electrophoresis) was determined. The biolog did not revealed clear difference on substrate utilization profiles of the microbial communities in the rhizosphere and bulk soil. However, unlike the Biolog DGGE revealed slightly differences in both the metabolic and genetic profiles of the different soil samples. The study on the feasibility of seeding bacteria capable of colonizing and surviving on the rhizosphere showed that Pseudomonas putida successfully colonized the rhizosphere of Eleusine corocana. The number of P putida increased during rhizoremediation of PAH’s. These results suggest that bacteria with the ability to adhere and survive in the root zone can be engineered and seeded for rhizoremediation purposes. However, other factors such as the influence of soil type and organic matter content must be investigated to improve rhizoremediation technology. / Dissertation (MSc)--University of Pretoria, 2009. / Microbiology and Plant Pathology / unrestricted

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The biogeochemical behaviour of plutonium and americium was investigated in contaminated soils from the UK to help determine possible remediation and management options. Stimulating anoxic sediments from Aldermaston, through the addition of a carbon substrate (glucose), induced reducing conditions resulting in a negligible change in Pu mobility. This was despite a substantial shift in the bacterial profile from a diverse community to one dominated by fermentative Beta proteobacteria and Clostridia. The latter group also includes organisms associated with metal reduction, such as close relatives to Clostridium species, reported previously to facilitate the reduction of Pu(IV) to Pu(III). A sequential extraction was performed on soils from Aldermaston and the Esk Estuary to identify which selected fractions the Pu and Am are most strongly associated with. The majority of Pu was associated with the 'residual fraction': 63.8 – 85.5 % and 91.9 – 94.5 % in the Aldermaston and Esk Estuary soils respectively. Metals associated with this fraction are highly recalcitrant and are unlikely to be released into solution over a significant time span under most geological conditions. The Am was more evenly distributed with the 'organic fraction' being the most dominant. Degradation of organic matter under oxidising conditions may result in mobilization of metals associated with this fraction. The Aldermaston soil was also subjected to bioleaching using a sulfuric acid producing microbial community, which resulted in a maximum 0.18 % of Pu released into solution. However, up to 12.5% of Am was found in solution suggesting Am is more susceptible to mobilization than Pu. The potential for Pu mobilization through abiotic oxidative leaching was investigated using permanganate. Even when carbonate was added to act as a potential complexant for the Pu, less than 1% of the Pu was leached. Greater success was observed when leaching was attempted using citric acid; an estimated 25 – 30% of Pu was released into solution offering a potential route for remediation of Pu-contaminated soils. These data would suggest that the Pu is highly recalcitrant, and may exist in a small particulate form in the Aldermaston soils, possibly in the oxide form, and is unlikely to mobilize under natural biogeochemical conditions.

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Land contamination by petroleum hydrocarbons is a widespread and global environmental pollution issue from recovery and refining of crude oil and the ubiquitous use of hydrocarbons in industrial processes and applications. Sustainable treatment of hydrocarbon-contaminated industrial land was considered with reference to seven published works on contaminated railway land including the track ballast, crude oil wastes and contaminated refinery soils. A methodology was developed to assess the level hydrocarbon contamination of track ballast (Anderson et al., 2000) and in Anderson et al. (2002, 2003) solvent and surfactant cleaning of ballast was investigated and potential environmental impacts of the processes examined. Optimisation of ex situ bioremediation of diesel-contaminated soil (Cunningham & Philp, 2000) demonstrated the efficacy of the addition of microorganisms (bioaugmentation) to enhance diesel biodegradation rates at field pilot scale. This work motivated a further study that examined a novel aeration approach incorporating ventilator turbines (cowls) for soil biopiles (Li et al., 2004). An optimised ex situ bioremediation for crude oil wastes was developed in Kuyukina et al. (2003) which demonstrated the efficacy of bioaugmentation and the application of biosurfactants. The final study investigated the potential application of biosurfactants to in situ remediation (Kuyukina et al., 2005) in laboratory soil columns contaminated with crude oil. The collected works are informative to those seeking to remediate hydrocarbon-contaminated industrial land and the sustainability of the approaches was considered.