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 mu M) 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.