Evaluation of the bioaccumulation and toxicity of platinum group elements to white mustard plants (Sinapis alba)

Road traffic is a significant source of platinum group elements (PGEs), which contaminate various environmental compartments along roadways. Platinum group elements released from automotive catalytic converters readily disperse into the surroundings and may pose a hazard, particularly in areas with high traffic intensity. To better understand the mechanisms of PGE action, environmental monitoring should be complemented by laboratory-based toxicity studies using living organisms. In this study, the bioaccumulation and toxicity of Pd, Pt, and their mixtures in Sinapis alba were assessed using acute toxicity tests. Root growth inhibition assays revealed a lower EC50 for Pd (4.75 mg·L –1 ) than for Pt (5.26 mg·L –1 ). At Pd and Pt concentrations of 1–10 mg L −1 in the test solutions, up to 6 times more Pt than Pd accumulated in white mustard tissues. Lower accumulated concentrations of Pd than Pt induced comparable inhibitory effects, suggesting higher toxicity of Pd. On the contrary, at low concentrations (500 ng·L –1 and 1000 ng·L –1 ) corresponding to environmental levels, both elements exhibited similar bioaccumulation behaviour, with bioaccumulation factors up to 100 times higher than for concentrations above 1 mg L −1 and had stimulatory effects on root growth. Both elements were predominantly accumulated in the roots, and their concentrations increased with exposure duration. A comparison of the bioaccumulation of individual PGEs versus their mixtures revealed a statistically significant difference only for Pt, and only at high concentrations.