Platinum group elements (PGEs) are a group of environmental pollutants that include platinum (Pt), palladium (Pd) and rhodium (Rh). PGEs have been found to be gradually accumulating in soil due to continuous emission from automotive catalytic converters, with elevated concentrations detected in the soil up to 50 m away from roads (Zereini et al. 2001). The accumulation of PGEs in the soil is an issue of concern due to potential impacts on terrestrial ecosystems in roadside environments, parkland and gardens.
To better understand the phytotoxicity of PGEs in soil, the objective of the present study was to investigate the toxicological effect of PGE on several common vegetables including carrot, spinach, cress, lettuce, radish and spring onion by means of seed germination testing. Seeds were soaked in solution spiked respectively with Pt, Pd, Rh, and a combination of all three PGEs under different concentrations (0.1, 0.5, 0.7, 1, 5 ppm) in 5 replicates. Germination rates were scored daily over 21 days and root elongation was measured after germination.
The results showed that reduced germination and/or root length were observed in vegetable tested. For affected species, a significant reduction of germinated seeds and/or reduction of root length (P<0.05) was found at different concentrations of Pt, Pd, Rh and PGEs. At lower concentration, Pd was found to have a stimulative effect on root elongation. Exposure to the combination of PGEs led to a significantly greater reduction (P<0.05) in germination rate and root elongation compared to individual elements, which increases concerns regarding the ecotoxicological effects of PGEs as they tend to occur together in the environment.