Bioaugmentation and Bioaugmentation – Assisted Phytoremediation of Heavy Metals Contaminated Soil By a Synergistic Effect of Cyanobacteria Inoculation, Biochar, and Purtolaca Oleracea

Abstract In recent decades, soil contamination with heavy metals has become an environmental crisis due to their long-term stability and adverse biological effects. Therefore, bioremediation is an eco-friendly technology to remediate contaminated soil, that its efficiency requires further research. This study was conducted to comparatively investigate two strategies, including bioaugmentation by using Oscillatoria sp and bioaugmentation assisted phytoremediation by using Oscillatoria sp - portulaca oleracea for the bioremediation of heavy metal (Cr (III), Cr (VI), Fe, Al, and Zn) contaminated soil at 180 days. To facilitate the remediation process, various quantities of biochar (0, 0.5, 2, and 5% (w/w)) were used in the experiments. The results of the bioaugmentation showed a significant improvement in chlorophyll a , nitrogen, organic carbon contents of soil and decrease all heavy metal bioavailability and EC of soil. The remediation efficiency test using plants proved the success of remediation treatments. Moreover, the findings of bioaugmentation-assisted phytoremediation displayed an improvement in soil fertility and a substantial reduction in the bioavailable fraction of heavy metals, especially in soil amended with 5% biochar. Cyanobacteria inoculation and biochar amendment dramatically enhanced the root lengths and shoot heights of portulaca oleracea while it significantly decreased their heavy metal accumulation compared to the control. For all heavy metals, TF and BAC (except Zn) values ​​were found to be less than 1.0 at all treatments, illustrated the successful phytoextraction by the P. In conclusion, cyanobacteria inoculation along with biochar addition enhanced the TI quantities while diminished BAC and BCF values, suggesting the feasibility their applying in heavy metal contaminated soil for the facilitation of phytoremediation and their ability in pollutant immobilization .