Effectiveness and mechanism of plant purification of nutrients and perfluoroalkyl acids in simulated river water under microplastic stress

Pontederia cordata, Canna indica, Myriophyllum verticillatum, and Vallisneria natans were selected to investigate the effect and mechanism of plant removal of total nitrogen (TN), total phosphorus (TP), perfluorooctanoic acid (PFOA), and perfluorooctane sulfonate (PFOS) from simulated river water under microplastic stress through hydroponic experiments. The results showed that the four plants had good ability to remove TN, TP, PFOA, and PFOS from simulated river water under microplastic stress. The removal of TN, TP, PFOA, and PFOS by plants under microplastic stress ranged from 57.1% to 80.0%, 48.5% to 67.6%, 42.0% to 68.5%, and 48.0% to 85.3%, respectively. The best removal of TN and TP was achieved by P. cordata with 80.0% and 67.6%, respectively, while PFOA and PFOS were removed by P. cordata at a rate of 42.0% and 48.0%, respectively. M. verticillatum showed the most significant removal of PFOA and PFOS. The uptake of PFOS by plants was better than that of PFOA. Perfluorooctane sulfonate (PFOS) tended to accumulate in plant roots more than PFOA in P. cordata and C. indica. Microplastic stress resulted in a decrease in plant removal of TN, TP, PFOA, and PFOS by 3.9%∼5.3%, 5.4%∼6.9%, 4.9%∼7.2%, and 2.7%∼7.2%, respectively.