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The effect of mineral surface chemistry on the biodegradation of petroleum
Abstract
The implementation of intrinsic bioremediation for the cleanup of petroleum contaminated subsurface sites requires an understanding of how mineral surface and organic matter sorption affects contaminant bioavailability. This experiment quantified the biodegradation of a crude oil in soils with different characteristics including mineral surface chemistry, organic matter content, and surface area in order to determine the impact of soil chemistry on bioavailability and biodegradability of petroleum. Two soils used in this study were; a Vertisol, dominated by the permanenty-charged phyllosilicate smectite,; and, an aquifer sand, dominated by pH-dependent charged iron oxides (1.8% Fe). The Vertisol is 62% clay, has an organic matter content of 1.5% and an external surface area of 52 m 2/g. The aquifer sand is 85% sand. has a very low organic matter content (0.02%) and an external surface area of 8 m2/g. Biodegradation of the light crude oil was quantified in flasks containing soil slurries that varied in soil type while controlling for soil surface area, soil-to sollution ratio, oil loading, microbial inoculation and environmental conditions. Duplicate flasks at two different surface areas (186 M2 and 372 m') were extracted at 0, 7, 21, 36, and 56 days and analyzed for specific polycyclic aromatic hydrocarbons (PAHs), saturate hydrocarbons, gross composition of the extracted petroleum and heterotrophic plate counts. The results were compared to soil-free samples and uninoculated controls. A nutrient solution sorption study was performed to determine-nine the possible impact of nutrient sorption on the biodegradation of petroleum in the two soils. The overall extent of biodegradation was substantially greater in the sand treatments than in the Vertisol treatments after normalizing based on the amount of available surface area. The high surface area (372 M2) sand treatment degraded faster than the low surface area (186 M2) sand treatment whereas the opposite was true for the Vertisol. The observed differences in biodegradation between the two soils are the result of differences in organic contaminant bioavailability and microbial population dynamics. Differences in rnicropore structure, mineral surface sorption, and organic matter content are likely responsible for the differences in contaminant bioavailability and biodegradability.
Description
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Citation
Allan, Katherine Ann (1997). The effect of mineral surface chemistry on the biodegradation of petroleum. Master's thesis, Texas A&M University. Available electronically from https : / /hdl .handle .net /1969 .1 /ETD -TAMU -1997 -THESIS -A445.
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