Integrated remediation approach for metal polluted soils using plants, nanomaterials and root-associated bacteria

Abstract

Soil is a major sink for heavy metals released into the environment. The remediation of Pb-polluted soils brings a techno-economical challenge for researchers and decision makers. Phytoremediation enhanced by PGPR or nanomaterials, individually, have been studied to remove contaminants such as heavy metals from soil, but association of both PGPR and nanomaterials in phytoremediation of Pb contaminated soil has remained scant.Association of plants, nanomaterials and plant growth promoting bacteria (PGPR) was investigated for the first time in this research to support remediation of Pb, while optimizing the quantity of used nanomaterials. Seedlings of S. bicolor were exposed to different regimes of TiO₂ NPs (0, 100, 250, 500 and 1000 mg/kg) and the PGPR, separately and in combination, to investigate the effects on plant growth, Pb uptake and accumulation and physiological response of the plant in contaminated soil. Greater accumulation of Pb in the roots compared to the shoots of S. bicolor was observed in all treatments. Application of PGPR enhanced Pb uptake by roots. Using TiO₂ NPs significantly increased accumulation capacity of S. bicolor for Pb with the greatest accumulation capacity of 1377.18 µg per pot achieved in the “PGPR + 500 mg/kg TiO₂ NPs” treatment (p < 0.05). Adverse effects of using high concentration of TiO₂ NPs i.e., 1000 mg/kg were found on plant growth and phytoremediation performance. Significant beneficial effect of integrated use of TiO₂ NPs and PGPR on plant photosynthesis was also found. Promoted physiological response like relative growth and production of chlorophyll content was found for plants treated with association of TiO₂ NPs and the PGPR. Co-application of TiO₂ NPs and PGPR could reduce the required amounts of TiO₂ NPs for successful phytoremediation of heavy metalloid polluted soils. Results of this study presented a promising novel technique by combined application of TiO₂ NPs and PGPR in phytoremediation of Pb contaminated soils. Intelligent uses of plants in accompany with nanomaterials and PGPR have great application prospects in dealing with soil remediation.

Graphical Abstract

Keywords:

• TiO2 NPs
• PGPR
• phytoremediation
• S. bicolor
• soil
• chlorophyll content

Acknowledgments

The authors would like to thank the University of Tehran for providing support for this work.

Correction Statement

This article has been republished with minor changes. These changes do not impact the academic content of the article.

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Funding

This research did not receive any specific grant from funding agencies in the public, commercial, or not-for-profit sectors.