From rhizosphere potential towards field reliability: a bottleneck-based conceptual framework for rhizoremediation of contaminated soils

Abstract Rhizoremediation exploits interactions among plant roots, root-associated microorganisms and soil processes to transform, remove or immobilize contaminants. Yet biological activity under controlled conditions often does not translate into reproducible performance in heterogeneous field soils. This critical narrative review examines this translation problem and organizes the literature around four broad, interacting bottleneck domains: contaminant accessibility, biological capacity, environmental expression and operational feasibility. These domains provide an evidence-informed conceptual structure rather than a quantitative classification of failure frequency. We further distinguish chemical change, risk reduction and ecological recovery as related but non-equivalent outcomes, showing why greater biomass, microbial abundance, enzyme activity or contaminant availability cannot alone establish remediation success. On this basis, we propose a conceptual decision framework linking site diagnosis to candidate intervention selection, realistic pilot validation and multidimensional monitoring. Intervention choice is treated as conditional: biostimulation may be appropriate where relevant indigenous functions are constrained; bioaugmentation may be considered where realized functional capacity remains insufficient; amendments may be appropriate where accessibility, soil chemistry, root-zone habitat or toxicity limits performance; and combined approaches may be required where constraints co-occur or shift over time. Future tools, including multi-omics, synthetic communities, predictive modelling and genetic engineering, should be judged by whether they reduce uncertainty and improve robustness under realistic conditions. Field-reliable rhizoremediation therefore depends on reproducible, durable and site-appropriate performance rather than biological potential alone.