Microbial Data to Support Monitored Natural Attenuation
When remediation by engineered methods is not practical (e.g., large dilute plumes or impacts located far from the source area), monitored natural attenuation (MNA) may be the most promising strategy to achieve remedial objectives. MNA relies on naturally occurring physical processes (dispersion, volatilization, and dilution), abiotic degradation, and biodegradation to reduce contaminant concentrations and risks over time. To evaluate the feasibility and performance of MNA as a site management strategy, a multiple-lines-of-evidence approach is recommended, collecting:
- Chemistry to demonstrate that contaminant concentrations are decreasing or stable with a statistical approach like the Mann-Kendall test.
- Geochemistry to compare electron acceptor concentrations (e.g., dissolved oxygen, nitrate, iron, sulfate, methane) as an indirect indicator of microbial activity.
- Microbiology to directly evaluate biodegradation as a component of MNA using molecular biological tools (MBTs).
