Dynamics of cadmium and sulfamethoxazole removal by Chrysopogon zizanioides under individual and combined pollution conditions under exogenous phosphate addition

Reducing phosphorus loads is key to water eutrophication control and has become a current research focus. Cadmium (Cd) and sulfamethoxazole (SMX) are typical pollutants in wetland environments and are commonly co-occur. Vetiver (Chrysopogon zizanioides (L.) Roberty) is a perennial herbaceous plant widely used in phytoremediation and other fields due to strong stress resistance and pollutant tolerance. However, the impact of vetiver on Cd and SMX removal when the pollutants are present alone and in combination in phosphorus-rich environments remains unclear. This study used greenhouse pot experiments to simulate wetland conditions, examining pollutant dynamics in vetiver roots, shoots, soil, and water under varying phosphorus levels, and Cd and SMX contamination. At 400 mg·L⁻¹ phosphorus, vetiver significantly enhanced the removal of Cd and SMX, both singly and combined. Cd removal rates were higher under single (1.48 %) and combined (1.59 %) pollution. Cd accumulation in shoots was higher under combined pollution (14.72 ± 0.24 μg). SMX degradation rate constants were higher under single (1.91) and combined (1.86) pollution. By day 42, SMX levels were below detection limits in the wetland environment. Compared to the control, phosphorus significantly enhanced vetiver shoot growth, promoted Cd²⁺ translocation to shoots, and partially facilitated SMX translocation and degradation.