Multi-metal screening of candidate herbaceous plants for bioretention under preference uncertainty using SMAA–PROMETHEE II

Abstract

Aqueous-phase concentration reduction, accumulation in harvestable shoots, and root retention in bioretention systems may favor different plant species, whereas fixed criterion weights cannot represent uncertainty in management preferences. In pot experiments with four landscape herbaceous species, this study measured aqueous-phase concentration reduction and organ accumulation of Cd, Cu, Pb, and Zn in Poa annua, Lolium perenne, Axonopus compressus, and Festuca arundinacea. Four criteria were constructed: aqueous-phase concentration reduction, shoot accumulation, scenario-dependent root allocation, and a composite measure of cross-metal performance balance. The species were ranked using SMAA–PROMETHEE II with 100,000 sets of Dirichlet-distributed random weights. The species favored by aqueous-phase concentration reduction differed from those favored by tissue accumulation. Under the harvestable-shoot-accumulation scenario, L. perenne had a first-rank probability of 83.92%. Under the root-retention scenario, the first-rank probabilities of L. perenne and P. annua were 57.47% and 42.53%, respectively. Changes in preference thresholds and the structure of g4, as well as comparisons with equal-weight PROMETHEE II, TOPSIS, and VIKOR rankings, did not change the leading candidate, although probability distributions and lower ranks varied. The framework replaces a single fixed-weight ranking with a probabilistic account of candidate competition across management preferences and provides a transparent, reproducible basis for prioritizing subsequent validation and planting decisions under multi-metal exposure.