Efficacy of <i>Paspalum paspaloides</i> (Michx.) Scribn. for Removal of Lead (Pb II) From Oil Refinery Effluent Using Hybrid Flow‐Built Wetlands, Baiji, Salahaddin, Iraq

The efficacy of the Paspalum paspaloides was systematically assessed in outdoor experiments involving vertical (VF-CWs), horizontal (HF-CWs), and hybrid (HBF-CWs) flow-built wetlands to get rid of lead (Pb II) from Baiji Oil Refinery effluents, Baiji, Salahaddin, Iraq. In this paper, only HBF-CWs are highlighted. Generally, results showed that the resilience of the P. paspaloides to adverse environmental conditions was demonstrated through an impressive survival rate of 100% during the entire studied period (90 days). The mean concentration of Pb taken from the outlet samples of the triple HBF-CWs (planted with P. paspaloides) was (0.08 ± 0.06 mg/L) compared with the concentration of Pb in the raw refinery's effluent (untreated) of (6.38 ± 0.62 mg/L), which was much lower than the Pb irrigation safe limit of (5 mg/L) set by international guidelines. The triple HBF-CWs planted with P. paspaloides showed a high Pb percentage removal rate of (94.2%) with a removal capacity of (11.32 ± 1.2 mg/day/g). However, the highest accumulated Pb concentration was (7.81 mg/plant) in roots and (16.7 mg/plant) in shoots. The phytoextraction capability of P. paspaloides using bioaccumulation factor (BAF) and translocation factor (TF) was evaluated. The BAF values for roots and shoots were (97.63) and (208.75), respectively, whereas the TF value was (2.14), proposing that P. paspaloides has a good capacity for Pb phytostabilization, as revealed in elevated BAF (>1) and TF value (>1) in plant parts. Genetic engineering techniques to implant a more efficient accumulator gene into P. paspaloides have been suggested by the authors.