| The mechanisms of the removal and accumulation of phenanthrene (PHE) and pyrene (PYR) by rock plant Pogonatherum paniceum were studied by pot experiments. Results showed that P. paniceum might effectively remove PHE and PYR from soils at their initial concentrations of 20 to 322 mg·kg-1. About 50.97%-86.77% of PHE or 46.45%-76.7% of PYR was removed from the soils respectively after 70-day plantation of P. paniceum; the average removal rates of PHE or PYR from the soils by P. paniceum were 63.56% and 58.6% higher than those of CK1 (with addition of 0.1% NaN3), and 46.09% and 42.92% higher than those of CK2 (without NaN3). P. paniceum did show ability to accumulate polycyclic aromatic hydrocarbons (PAHs) from the soils; the contents of PAHs in its root and shoot increased with the increase of PAHs concentrations in the soils. The bioconcentration factors (BCFs) for PAHs tended to decrease with increasing concentrations of these contaminants in soil. BCFs for PYR were higher than those for PHE, and BCFs for PHE (0.12-1.63) and PYR (1.03-5.61) in shoots were much lower than those in roots (0.21-3.08 and 1.31-10.11) at the same treatment. The mechanisms of phytoremediation processes by P. paniceum involve both biotic and abiotic factors. Contributions of each factor to the phytoremediation processes were estimated, which indicated that abiotic loss, plant accumulation, phytodegredation and microbial degradation accounted for 5.1%, 0.32%, 4.22% and 17.47% of the total removal of PHE, and 2.56%, 4.27%, 2.01% and 15.68% of PYR from soils, respectively. In contrast, 41.56% removal of PHE and 36.64% of PYR were attributed to plant-microbial interactions. Thus plant-microbial interactions are the main mechanisms for the remediation of soil PAHs pollution. |
