Uptake and transformation of oxybenzone in the presence of tio₂: Impact of nanoparticles on the plant remediation of an organic uv filter

Oxybenzone (OBZ) present in the environment as an emerging contaminant may occur jointly with the nanoparticle TiO₂ due to the typical composition of many sunscreens. Thus, potential effects caused by TiO₂ must be considered when investigating the environmental fate of sunscreens and also when plant performance with regard to remediation of OBZ is scrutinized. Toxicity effects of OBZ and TiO₂ on plant development were evaluated by recording germination rates and root lengths of tomato and barley. Results showed that OBZ significantly inhibited germination rate of tomato seeds, while no effect was observed for germination of barley seeds. Interestingly, co-exposure with TiO₂ lowered the toxicity of OBZ on the tomato seedlings as there were no differences on germination rate and root length between co-exposure and control treatments. Moreover, growth inhibition tests with Lemna minor showed that addition of TiO₂ even enhanced plant growth by increasing the frond area. Furthermore, influence of TiO₂ (3 mg/L) on removal of OBZ (5 µM) by plants was examined with respect to the variations in uptake and metabolism of OBZ in a hairy root culture system. Co-exposure to TiO₂ amplified the accumulation of OBZ in plants, while transient slower transformation to OBZ metabolites was recognized when TiO₂ had been added. Therefore, it can be concluded that Ti nanoparticles may generally reduce the phytotoxicity of OBZ and increase the uptake of this compound in phytoremediation, while the interaction with the transformation capacity should be considered when applying phytoremediation for UV-filter contaminated water.