Innovative utilization of plant-derived dissolved organic matter to promote polycyclic aromatic hydrocarbons removal in constructed wetlands: Unraveling the synergy among substrate adsorption, plant uptake, and microbial degradation

Dissolved organic matter (DOM) is a group of active compounds which can influence Polycyclic aromatic hydrocarbons (PAHs) migration or biodegradation, thus may help solve the challenge of inefficient removal of PAHs in constructed wetlands (CWs). CWs with plant derived DOM (PA-A) or fulvic acid addition were set up to explore their influence on CWs performance. Results demonstrated significantly enhanced removal of phenanthrene (PHE, 7.81 % ± 2.07 %), benzo[a]pyrene (BaP, 7.11 % ± 1.91 %), and benzo[k]fluoranthrene (BkF, 5.04 % ± 3.48 %) by DOM. With DOM addition, PAHs concentration in substrate decreased while the bioavailability increased. Notably, in the shallow substrate, PHE content decreased by 19.61%–23.53 %, and BaP bioavailability increased by 1.88–2.00 times. The active absorption and migration of PAHs in P.australis were enhanced, resulting in the total concentrations of PAHs reaching 1743.66 ng/g in the roots and 398.77 ng/g in the leaves in PA-A. Biodegradation was calculated as the primary pathway for PAHs removal by mass balance. Ochrobactrum, Xanthobacteraceae, Rhizobium and Burkholderiaceae relating to PAHs biodegradation were dominate strains. This study unraveled the synergy among substrate adsorption, plant uptake and microbial degradation during PAHs removal, and offered novel insights into the utilization of wetland plants.