In situ biodegradation: microbiological patterns in a contaminated aquifer

Area of Science:

• Environmental Microbiology
• Aquatic Geochemistry
• Bioremediation Science

Background:

• Conventional methods for detecting in situ biodegradation of organic pollutants in aquifers are limited.
• Buried coal tar sites present complex challenges for assessing natural attenuation of contaminants.
• Polyaromatic hydrocarbons (PAHs) are persistent organic pollutants requiring effective monitoring strategies.

Purpose of the Study:

• To develop and validate a comprehensive approach for proving in situ biodegradation of organic pollutants in aquifers.
• To analyze microbiological activity and distribution data to infer biodegradation processes.
• To demonstrate microbial adaptation and growth in response to PAH contamination.

Main Methods:

• Collected sediment samples at consistent depths from aquifer boreholes across a contaminant gradient.
• Analyzed a comprehensive dataset of microbiological activity and distribution.
• Assessed mineralization of naphthalene and phenanthrene.
• Quantified protozoa and bacterial populations to indicate growth.

Main Results:

• Demonstrated microbial adaptation to polyaromatic hydrocarbons (PAHs) through the mineralization of naphthalene and phenanthrene in contaminated zones.
• Observed enhanced numbers of protozoa and their bacterial prey exclusively in contaminated subsurface samples, indicating contaminant-stimulated bacterial growth.
• Provided convergent lines of indirect evidence supporting in situ biodegradation.

Conclusions:

• The comprehensive analysis of microbiological data effectively documents in situ biodegradation of aquifer contaminants.
• This indirect evidence-based approach overcomes limitations of conventional methods for proving biodegradation.
• The findings support the potential for natural attenuation of PAHs in contaminated aquifers.