Abstract: Composite pollution caused by unreasonable discharge of heavy metals and residual pesticides during industrial and agricultural production is prevalent in water and sediments. To explore the remediation potential of vetiver grass (Vetiveria zizanioides) on Cd-prometryn composite polluted water, a greenhouse hydroponic simulation experiment was conducted to investigate the uptake accumulation and removal characteristics of vetiver grass on single/ composite pollutants of Cd (initial mass concentration of 0.5 mg·L^-1) or prometryn (initial mass concentration of 1 mg·L^-1) in water. The results show that with the increase of incubation time, the concentrations of Cd²⁺ and prometryn in the water of the vetiver grass planted group were significantly lower than those without vetiver grass (P<0.05). After 30 days of incubation, the relative removal rate (R₀) of Cd²⁺ in the water was 55.95% under the single Cd contamination condition, which was significantly higher than the relative removal rate of 47.33% under the Cd-prometryn composite contamination condition (P<0.05). After 30 d of incubation, the water Cd²⁺ and prometryn R₀ were significantly higher in the single Cd or single prometryn contaminated treatment than in the combined Cd-prometryn contaminated treatment (P<0.05). Compared with the control, vetiver grass planting resulted in significantly shorter (P<0.05) half-life (t_1/2) and time required to remove 99% of prometryn (t_0.99) in single prometryn contaminated and Cd-prometryn composite contaminated water. Compared with the control, the half-life of prometryn and the time required to remove 99% of prometryn were significantly shorter and the degradation rate of prometryn was significantly higher in the wate of the vetiver grass planted group (P<0.05). Compared with the composite contaminated treatment, the prometryn in the water of the single prometryn contaminated treatment had significantly shorter half-life and shorter 99% removal time and significantly higher degradation rate (P<0.05). During the incubation period, Cd²⁺ uptake by vetiver grass was mainly enriched in the root, and the Cd²⁺ content of the root was significantly higher than that of the stem and leaves (P<0.05), and the transfer coefficients of both were less than 1. The maximum transfer coefficient of prometryn in vetiver grass was 1.90 in the single prometryn treatment, while the transfer coefficients of the Cd-prometryn treatment were less than 1. Vetiver grass is able to remove both Cd and prometryn from water, and the removal effect of single pollution is better than that of composite pollution, indicating that vetiver grass can be used to remediate Cd and pesticide pollution in single/composite pollution water, which provides the theoretical basis for screening the ideal plants for remediation of heavy metal and pesticide single/composite pollution in artificial wetland.

Key words: Vetiveria zizanioides, phytoremediation, cadmium, prometryn, composite pollution