Facing the Challenge of Long-Term Sediment Contamination: Are Bioreactive Sediment Caps the Answer?
Texas Tech University Abstract: Sediment capping represent an efficient and well-established remediation practice to contain contamination and minimize risks. Capping placement alters the sediment environment, which contains a rich microbial community with biodegradation potential. Biotransformation of toxic compounds in benign products diminish the mass of pollutants and relaxes challenges of remediation design. However, little is known about biodegradation within sediment caps, and slow kinetic transformation rates make biological transformation difficult to discern.
This presentation describes the current body of knowledge on how sediment caps affect oxidative pollutants in the context of environmental parameters and benthic microbial community composition and behavior. Results from our laboratory demonstrate that microorganisms linked to naphthalene biodegradation (model contaminant) can be enriched under appropriate electron accepting conditions and within different model capping systems, and the extent to which biodegrading consortia are enriched depend upon both biogeochemistry and capping material type.
Under oxic conditions, biofilm formation, naphthalene decay and biomarker levels increased with activated carbon, and naphthalene exerted a strong selective pressure in all capping systems except those made from clay, which inhibited degradative activity. Activated carbon stimulated naphthalene biodegradation that would otherwise not occur under highly reducing conditions, and mineralization corresponded with enrichment of genera that biodegrade naphthalene. The presentation concludes with recommendations on how to design sediment caps to promote degradative bioactivity.