Willow can be recommended as a strong candidate for the phytoremediation of cadmium and pyrene co-polluted soil under flooding condition

Soil cadmium (Cd) and pyrene (PYR) pollutions have gained worldwide attention due to their negative effects on the environment. Intermittent flooding in rain-rich areas may affect phytoremediation of Cd and PYR in soil. Therefore, a pot-culture experiment, with and without flooding, was conducted to study the effects of flooding on soil Cd and PYR phytoremediation. Concentrations of Cd, PYR, and nutrients in soils and plants, as well as plant physiological and biochemical responses, were examined. Under both flooding and non-flooding conditions, willow ( Salix × aureo-pendula CL ‘J1011’) demonstrated a better ability to remove soil Cd and PYR. Flooding led to higher Cd accumulation in roots than that in shoots. Conversely, non-flooding resulted in higher Cd accumulation in shoots than that in roots. The maximum concentrations of Cd in shoots were 11.02 and 14.07 mg kg –1 with and without flooding, respectively. The maximum dissipation rates of PYR in soil were 47.35% and 88.61% under flooding and non-flooding conditions, respectively. In addition, flooding significantly increased the photosynthetic pigment, photosynthetic fluorescence, and chlorophyll fluorescence parameters in leaves, compared with non-flooding treatment. Flooding also increased the concentrations of Mg, Mn, P, Fe, and K in roots and shoots. This study outlines an effective insight for the phytoremediation of Cd- and PYR-contaminated soil under flooding condition. Graphical abstract