Rhizoremediation of a Cadmium-polluted Soil using Pseudomonas aeruginosa and Eleusine indica

Abstract

Rhizoremediation involves the use of plants and plant growth promoting rhizobacteria (PGPR) for remediation of contaminated soil. This study evaluated the use of Pseudomonas aeruginosa and Eleusine indica to remediate cadmium-polluted soil. Soil samples were collected around the roots of E. indica and PGPR were isolated and evaluated for their capacity for plant growth promotion. P. aeruginosa was selected for Cd remediation experiment which was based on treatments T1 (control soil), T2 (soil + cadmium), T3 (soil + plant + Cd + Pseudomonas applied 2x monthly) T4 (Soil + Plant + Cd + Pseudomonas applied once). T5 (soil + plant + Cd + Pseudomonas applied 1x monthly) T6 (soil + plant + Cd) and T7 (soil and plant). Cd concentration in soil treatments was equivalent to 8 mg/kg and treatments were monitored for 2 months. Bacterial count, physicochemical parameters, nutrient analyses, and Cd removal were subsequently evaluated. T3 had higher bacterial count and pH values (p < 0.05) relative to other treatments and this could be due to the inoculum addition. Conversely, reduction in electrical conductivity, organic carbon and organic matter observed in T3 could be attributed to improved rhizospheric activities. Again, rhizoremediation was highest (P < 0.05) in T3 (90 %) and this suggests P aeruginosa made bio-absorption of Cd easier for E. indica relative to treatments that do not have the inoculum.  This study showed that E. indica together with P. aeruginosa are suitable candidates for phytoremediation of Cd contaminated soils.