Removal of multi-contaminants from water by association of poplar and Brassica plants in a short-term growth chamber experiment

The plant association of Populus alba L. ‘Villafranca’, Brassica oleracea var. acephala sebellica (kale), and B. oleracea var. capitata ‘sonsma’ (cabbage) was exposed to Zn, Cd, and exogenous caffeine (13CFN)-contaminated water under growth chamber conditions. In the short term of treatment (15 days), poplar increased the root dry biomass (+ 25%) and decreased the chlorophyll content in new leaves (− 32%), compared to control. On the contrary, cabbage decreased the root dry biomass, enhancing the shoot dry biomass (+ 50%). Heavy metals were mainly concentrated in plant roots and in poplar reached the highest concentrations of 705 ± 232.6 and 338 ± 85.5 μg g−1 DW for Zn and Cd, respectively. The ability of poplar to accumulate more Zn and Cd than kale and cabbage in plant biomass was confirmed by heavy metal contents, following the order: poplar > kale = cabbage. However, poplar and Brassica sp. association was very useful for Zn and Cd decontaminations as reported by the bioconcentration factors (> 1). The concentration of 13CFN was below 2.4 ng g−1 FW in poplar and 7.4 ng g−1 FW in Brassica species, suggesting the caffeine uptake and degradation by plant association. Under our experimental conditions, the removal efficiency of the system was upper to 79%, indicating the capability of Populus-Brassica association to efficiently remove Zn, Cd, and 13CFN from mixed inorganic-organic–contaminated water in short term.