When is poplar-based phytomanagement of TPH-contaminated soils feasible? A dynamic integration of degradation kinetics, tree growth, ecosystem services and life cycle assessment

The application of phytoremediation is often constrained by the difficulty of predicting when remediation targets will be reached and what benefits the system delivers in the meantime. Without time-explicit estimates of both attenuation and co-benefits, nature-based remediation options are frequently discarded in favour of conventional, more disruptive techniques, despite the greater environmental, economic, and social costs. This work presents a dynamic modelling framework for poplar-based phytomanagement of soils contaminated by total petroleum hydrocarbons (TPH). Rhizodegradation kinetics reported in the literature are coupled to a system dynamics model simulating poplar growth under contaminated conditions. Biomass development and contaminant attenuation are therefore represented as mutually dependent processes: root system development drives rhizosphere degradation, while contaminant-induced stress feeds back on plant growth. A further feature of the framework is the dynamic quantification of the provided ecosystem services. For instance, CO2 sequestration is computed from simulated above- and below-ground biomass accumulation and from litter-derived soil organic carbon inputs; air contaminant removal and stabilisation are tracked as cumulative mass over time; further regulating services, such as runoff avoidance, are linked to canopy and root development. This highlights the trade-offs between remediation time and the provision of benefits over longer time horizons. Moreover, the model outputs are integrated with a Life Cycle Assessment, weighing the environmental burdens of the phytomanagement system against the quantified benefits. This covers cuttings production in nurseries, establishment of the phytoremediation plantation, and its management until the legal pollution threshold is reached. Beyond this stage, different scenarios are modelled to describe possible subsequent uses of the area planted with poplars. The net economic impact of phytomanagement, combining environmental costs and benefits, can be eventually calculated across all the considered life cycle phases. The framework thus provides a decision-support tool for designing and screening phytomanagement projects, particularly relevant for urban and peri-urban brownfields. While feasibility remains the primary requirement for remediation, weighing life cycle impacts against co-benefits and risk reduction is what could drive a wider and more responsible application of nature-based remediation options.