ABSTRACT
Subsurface contaminant fate determination requires multiple integrated lines of evidence. No single methodology is sufficient to build a robust case. Furthermore, integrated investigations are crucial for designing engineered solutions to instances of unsatisfactory environmental fate.
While many groups and organizations have proposed protocols and methods for documenting intrinsic bioremediation, no single protocol has been adopted as a universal standard. In an attempt to clarify the situation, the National Research Council developed guidance for determining the biodegradative fate of subsurface contaminants. 4 This guidance is in the form of three criteria to be met for demon strating intrinsic bioremediation. The criteria are documenting loss of the contaminants from the subsurface, demonstration of the potential for biodegradation at the site, and, finally, proof that subsurface contaminant degradation is occurring. The demonstration of these criteria can be complicated by site factors, including continuous recharge of contaminants from a subsurface reservoir, unknown mixtures of contaminants, and the general inaccessibility of the subsurface to thorough examination. These complications can require the implementation of alternate routes to satisfying a criterion.
64Although each criterion could be satisfied with a single line of evidence, the number and diversity of integrated lines of evidence satisfying the criteria is an indication of the robustness of the argument supporting the intrinsic bioremediation assertion. Ideally, these multiple lines of evidence should come from differing study approaches. Through the integration of field, laboratory, and modeling efforts, the biodegradative environmental fate of contaminants can be reasonably determined.
