Beyond Chemical Compliance: A Critical Review Toward Microbiome‐Informed Ecological Exit Criteria for Bioremediated Soils

ABSTRACT

Chemical compliance remains the usual endpoint for closing contaminated‐soil remediation projects, although it does not establish recovery of soil function or the durability of the post‐treatment state. This critical review examines when microbiological evidence can contribute to ecological closure decisions. It proposes a five‐tier sequence covering chemical and exposure adequacy, residual matrix harm, land‐use‐critical soil function, reference‐based ecological trajectory, and advanced resolution of decision‐relevant ambiguity. Microbiome metrics are not treated as independent exit criteria. Their main decision value lies in detecting incomplete recovery, distinguishing stable from transient biological change, and resolving uncertainty after lower‐tier endpoints have been assessed. The framework separates hard blocking failures from soft contradictions and restricts high‐resolution molecular methods to predeclared escalation triggers. Two retrospective worked applications to published field studies illustrate that available site‐level datasets may satisfy only part of the required evidence package and do not validate the framework as a closure standard. Implementation requires site‐specific sampling design, informative reference states, cost‐proportionate escalation, regulatory agreement, and standardized reporting. The immediate proposal is an auditable decision process, not a universal microbiome threshold.