Enhancement of phytoremediation efficiency of Acacia mangium using earthworms in metal-contaminated soil in Bonoua, Ivory Coast

Abstract

In this paper, the impact of Pontoscolex corethrurus on Acacia mangium growth and its phytoremediation efficiency in metal-contaminated soils were studied in a greenhouse pot culture under four treatments: non contaminated soil-non inoculated, control (C); non contaminated soilinoculated (NcI); contaminated soil-non inoculated (CNi); contaminated soil-inoculated (CI). The results showed that A. mangium growth performance and its Pb, Ni and Cr uptake were significantly (P<0.05) increased under CI treatment. Under CNi treatment, A. mangium uptake more Ni and Cr content in root tissue than in shoot tissue. But for Pb, the greater content was noted in shoot tissue. A. mangium noninoculated preferentially promoted the phytoimmobilization process for Cr and Ni and the phytoextraction process for Pb. However, under CI treatment, the greater content of potential toxic elements (Cr, Ni and Pb) was observed in roots tissue and A. mangium inoculated promoted the phytoimmobilization process for Cr, Ni and Pb. In addition, the phytoextraction efficiency (PEE) of A. mangium increase (ranged 0.1% under CNi to 14% under CI treatment. This study indicates that earthworms can be used to enhance the phytoremediation efficiency of metal-tolerant plant species in contaminated soil.

Combined Effects of Earthworms and Plant Growth-Promoting Rhizobacteria (PGPR) on the Phytoremediation Efficiency of Acacia mangium in Polluted Dumpsite Soil in Bonoua, Côte d’Ivoire

“…The concentrations of Cd (81 mg kg À1 ), Cr (130 mg.kg À1 ), Pb (118 mg kg À1 ), and Ni (119 mg kg À1 ) in dumpsite soil are greater than limit values recommended for agricultural soil. However, previous studies performed in pot experiment with polluted soil and A. mangium 5 have revealed that only lead, chromium, and nickel concentrations in plant biomass were above the detection limit. Thus, cadmium was not detectable in plant biomass.…”

“…In fact, A.mangium can accumulate 93.5 mg kg À1 of copper (Cu) and 79 mg kg À1 of zinc (Zn) in its biomass, was able to tolerate high concentration of cadmium (Cd) [3], and can require 5 and 17 years to remove 79.8 kg ha À1 of Zn and 47 kg ha À1 of Cu, respectively [4]. So, the phytoremediation efficiency of A.mangium has been reported in numerous studies [5,6] in which it has been demonstrated that the success of phytoremediation may not solely depend on the plant itself but also on the interaction of plant roots with soil microorganism and soil fauna and the availability of heavy metals accumulated in soil [2,7], because the interaction between plants and beneficial rhizosphere bacteria can enhance biomass production and the tolerance of plants to heavy metals.…”

“…However, in recent studies, the action of earthworms, particularly Pontoscolex corethrurus to improve plant metal uptake during phytoremediation in contaminated soils, has been demonstrated [13][14][15][16][17]. Furthermore, the beneficial effects of P. corethrurus earthworms on A. mangium growth and its Pb, Ni, and Cr uptake have also been showed [5]. It was noted that in the presence of P. corethrurus, A. mangium promoted the phytoimmobilization process for Ni, Cr, and Pb, but its effectiveness depends on the nature of the plant, its behavior toward metals, rhizosphere function, and metal speciation in different soil compartments involved in the phytoremediation process [5].…”

Response of Acacia mangium to inoculation with symbiotic microorganisms in the remediation of metal-contaminated soil at Bonoua, Ivory Coast

“…The ability of the plant to accumulate metals from the soil and transfer metals from the roots to the shoots was estimated by the bioconcentration factor (BCF) and translocation factor (TF), respectively, as described by [14]. BCF is the ratio of the metal concentration in the shoots of plants to that in the soil.…”

“…Innumerous researches show that symbiotic microorganisms can increase plant resistance to metal(oid)s toxicity by different ways, including changes in the metal uptake by plants [14][15]. Arbuscular mycorrhizal fungi (AMF) and nitrogen-fixing bacteria have a widespread occurrence in ecosystems and have been the most common plant associated beneficial microbes used as inoculants in remediation processes of metalcontaminated soils [11; 15-21].…”