Insight into the uptake, fate and toxic effects of pharmaceutical compounds in two wetland plant species through hydroponics studies

Constructed wetland (CW) is a cost-effective and sustainable treatment method for diverse types of wastewaters. Plants play a cardinal role in attenuating organics, nutrients, and micropollutants with synergistic action of substrate and microbes. However, the uptake and fate of the emerging contaminants in the plants and the relation between plant and pollutant uptake characteristics are poorly understood. In this study, we investigated the removal, uptake, and fate of three different pharmaceutical compounds (namely atenolol (ATL), carbamazepine (CBZ), and diclofenac (DCF)) in two tropical plant species – Canna indica and Chrysopogon zizanioides under hydroponic conditions. C. indica demonstrated significantly higher specific uptake potential (10.72–14.16 mg/g of biomass Dry Weight (DW)) of target pollutants than C. zizanioides (5.27–7.57 mg/g of biomass DW). Notably, the accumulated pollutant concentrations in the plants were relatively low (<1%), with a larger fraction getting metabolized (43.9–81.8%). Metabolites such as atenololic acid (ATL), seven transformation products of CBZ, and six metabolites of DCF were observed in the plant tissues. The study also identified that plant characteristics such as lipid content, root and shoot biomass, transpiration rate influence the pollutant uptake, translocation, and accumulation. It was observed that anionic compound (DCF) gets accumulated in the root portion, whereas cationic (ATL)/ neutral (CBZ) compounds are amassed in the aerial parts of plants. Moreover, significant changes were observed in the physiological features of plants between treatments with different pollutants. DCF was observed to be deleterious for plant growth due to its higher reactive oxygen species (ROS) generation ability and lipophilicity. Conclusively, C. indica was found to be a potential candidate for the removal of selected pharmaceutical compounds.