Plant-assisted rhizoremediation of decabromodiphenyl ether for e-waste recycling area soil of Taizhou, China

To develop an effective phytoremediation approach to purify soils polluted by decabromodiphenyl ether (BDE-209) in e-waste recycling area, pot experiments were conducted through greenhouse growth of seven plant species in BDE-209-polluted soils. The hygrocolous rice (Oryza sativa L.) cultivars (XiuS and HuangHZ) and the xerophyte ryegrass (Lolium perenne L.) were found to be as the most effective functional plants for facilitating BDE-209 dissipation, with the removal of 52.9, 41.9, and 38.7 % in field-contaminated soils (collected directly from field, with an average pollution concentration of 394.6 μg BDE-209 kg⁻¹ soil), as well as 21.7, 27.6, and 28.1 % in freshly spiked soils (an average pollution concentration of 4413.57 μg BDE-209 kg⁻¹ soil, with additional BDE-209 added to field-contaminated soils), respectively. Changes in soil phospholipid fatty acid (PLFA) profiles revealed that different selective enrichments of functional microbial groups (e.g., arbuscular mycorrhizal fungi and gram-positive bacteria) were induced due to plant growth under contrasting water management (flooded-drained sequentially, flooded only, and drained only, respectively). The abundance of available electron donors and acceptors and the activities of soil oxido-reductases were also correspondingly modified, with the activity of catalase, and the content of NO₃ ⁻ and Fe³⁺ increased generally toward most of the xerophyte treatments, while the activity of dehydrogenase and the content of dissolved organic carbon (DOC) and NH₄ ⁺ increased toward the hygrophyte treatments. This differentiated dissipation of BDE-209 in soils as function of plant species, pollution doses and time, and water-dependent redox condition. This study illustrates a possibility of phytoremediation for BDE-209-polluted soils by successive cultivation of rice followed by ryegrass coupling with suitable water management, possibly through dissipation pathway of microbial reductive debromination and subsequent aerobic oxidative cleavage of benzene ring.