Natural colonizers effectively restore heavy metal polluted wasteland

Abstract

In India, ∼30% of total land is degraded due to pollution, salinization, and nutrient loss. Change in soil-quality at urban waste-dumping site prior and after cow-dung amendment was compared with control agriculture soil. The soil at waste-dumping site had elevated pH, EC, temperature and lowered OC and NPK concentrations when compared to control. Polymetallic pollution of Cr, Cd, Pb, and Ni beyond permissible limits was obtained. Cow-dung amendment restored soil physicochemical properties at the waste-dumping site, with increasing soil moisture, CEC and OC; however, a slight change in soil bulk-density and heavy-metal concentration post-amendment was noted. The seven natural colonizers present at the waste-dumping site accumulated more metals in roots than shoots. Datura innoxia had maximum bioaccumulation of Cr, Calotropis procera of Cd and Ni and Parthenium hysterophorus of Pb in roots. All these plants had Bioacccumulation factor (BAf_root )>1 and translocation factor (Tf) <1 for Cd and serve as its phytostabilizer except Calotropis procera which had BAf_root >1 and Tf >1 and is identified as a phytoextractor for Cd. Cow-dung amendment alone appeared to be insufficient and additionally the revegetation of natural colonizers is recommended for effective reduction in heavy metal load and improving overall soil health at wasteland. Such eco-restoration may also minimize risks to biodiversity in India.

Novelty statement

The novelty of the work lies in revegetation of natural colonizers at polluted wasteland to reduce heavy metal load and improve overall soil health. Calotropis procera, Datura innoxia, Parthenium hysterophorus, and S. nigrum showed maximum bioaccumulation of Cr, Cd, Pb, and Ni. The work confirms C. procera as non-edible, fast growing natural colonizer as potential phytoextractor for Cd and taken into consideration to effectively restore heavy metals polluted wasteland.

Keywords:

• Colonizers
• heavy metals
• phytoremediation
• restoration
• wasteland

Acknowledgments

LP thanks Victor Agarwal for editing the English text of a draft of this manuscript. The authors would like to thank Prof. S. Mallick, National Botanical Research Institute (NBRI), Lucknow for sample analysis.

Author contributions

Lakshmi Pathak: methodology, visualization, investigation, and writing – original draft preparation. Kavita Shah: conceptualization, supervision, data curation, reviewing and editing.

Ethical approval

Not applicable.

Disclosure statement

There is no conflict of interest among the authors. All authors have contributed equally to this work.

Data availability statement

The datasets used or analyzed during the study are available from the corresponding author on request.

Additional information

Funding

This research was financially supported by the University Grant Commission (UGC), Banaras Hindu University.