Phytoremediation of Co-Contaminated Soil using Plant-Bacteria Synergism

Abstract

Co-contaminated soils pose a particularly daunting challenge, as they simultaneously bear the burden of multiple pollutants such as heavy metals and petroleum hydrocarbons. Cadmium and total petroleum hydrocarbons co-contamination in agricultural soil is one such example, with unique remediation demands. To address this challenge, a meticulously designed experimental setup was employed, involving soil spiking with the two selected contaminants. Various treatment permutations were applied with Sorghum bicolor as the phytoremediator, combined with the bacterial strains Bacillus cereus and Serratia bozhouensis, and compost as an organic amendment. The contaminant removal efficiency along with the impact on various soil and plant parameters was observed for each treatment. The outcomes of this study were assessed through various statistical analyses, with Principal Component Analysis emerging as a particularly informative tool. The treatment, T4, which incorporated both organic compost and Serratia bozhouensis exhibited the highest levels of Cd (61%) and TPH removal (75%), indicating a synergistic effect in enhancing remediation efficiency. T5, involving Bacillus cereus and compost, demonstrated similar but slightly lower efficacy. The synergy between compost and bacterial strains demonstrated a promising avenue, merging bioaugmentation and biostimulation. Plant metrics, stress markers, and physiological indicators all experienced positive enhancements through organic amendment application, further accentuated by the inclusion of plant growth-promoting bacteria. T4 exhibited the highest biomass along with the highest levels of photosynthetic pigments. The content of stress markers, MDA and H2O2, and antioxidant enzymes, APX and GPX, were remarkably lower in T4 as well. T5 had similar plant growth characteristics as T5 but at slightly lower levels. Furthermore, T3 showed better plant growth characteristics than both T1 and T2. Additionally, observations highlighted the more dominant influence of Cd contamination on soil and plant parameters compared to TPH contamination. This study offers profound insights into the multifaceted dynamics of co contaminant remediation, exploring pathways towards sustainable soil restoration techniques. Keywords: Co-contamination, phytoremediation, cadmium, petroleum hydrocarbons, sorghum