Uptake and translocation of benzo[a]pyrene (B[a]P) in two ornamental plants and dissipation in soil

Pot experiments were conducted to evaluate the phytoremediation of B[a]P contaminated soil using two ornamental plants (Tagetes patula and Mirabilis jalapa). The results showed that the dry biomass of two plants was increased at low B[a]P contaminated soil and then inhibited with increasing B[a]P concentrations. It exhibited a significantly positive linear relationship between B[a]P absorption in roots, stems, leaves and shoots of the tested plants and the concentration of B[a]P in soils (P<0.01). Meanwhile, the contents of B[a]P in different tissues of the plants increased with growing time. After planting T. patula and M. jalapa, plant-promoted biodegradation of B[a]P was account for 79.5-99.8% and 71.1-99.9%, respectively, whereas the amount of B[a]P dissipation enhancement was only 0.2-20.5% and 0.1-28.9%, respectively. Moreover, low bioaccumulation factor (BF) and translocation factor (TF) values indicated that T. patula and M. jalapa took up B[a]P from contaminated soil and transferred them to the aerial parts with low efficiency. The B[a]P removal rates in rhizosphere soils at different growing stages of T. patula and M. jalapa were 2.7-26.8% and 0.4%-33.9%, respectively, higher than those of non-rhizopshere soils. Therefore, the presence of T. patula and M. jalapa roots was effective in promoting the phytoremediation of B[a]P contaminated soils.