Monitoring the Efficiency of Rhazya stricta L. Plants in Phytoremediation of Heavy Metal-Contaminated Soil.

Ehab Azab,Ahmad K Hegazy

doi:10.3390/plants9091057

Abstract

Heavy metal-contaminated soil constitutes many environmental concerns. The toxic nature of heavy metals poses serious threats to human health and the ecosystem. Decontamination of the polluted soil by phytoremediation is of fundamental importance. Vegetation is an appealing and cost-effective green technology for the large-scale phytoremediation of polluted soils. In this paper, a greenhouse experiment was carried out to test the potential of Rhazya stricta as a heavy metal phytoremediator in polluted soil. Plants were grown for three months in pots filled with soils treated with the heavy metals Cd, Pb, Cu, and Zn at rates of 10, 50, and 100 mg/kg. The bioaccumulation factor (BCF) and translocation factor (TF) were calculated to detect the ability of R. stricta to accumulate and transfer heavy metals from soil to plant organs. The results showed that under increasing levels of soil pollution, the bioconcentration of Cd and Zn heavy metals showed the highest values in plant roots followed by leaves, whereas in the case of Pb and Cu, roots showed the highest values followed by stems. Heavy metals accumulation was higher in roots than in stems and leaves. The BCF of Zn reached the highest values in roots and stems for 10 mg/kg soil treatment, followed by the BCFs of Cd, Cu, and Pb. The TF for the different heavy metal pollutants’ concentrations was less than unity, suggesting that the plants remediate pollutants by phytostabilization. The TF values ranged from higher to lower were in the order Zn > Cu > Cd > Pb. The rapid growth of R. stricta and its tolerance of heavy metals, as well as its ability to absorb and accumulate metals within the plant, recommends its use in the phytoremediation of slightly polluted soils in arid lands by limiting the heavy metals transport.

Highlights

Environmental contamination by heavy metals is becoming a critical problem of global concern.The toxic metals may remain in the environment for a long period and can eventually accumulate to levels that could cause major threats to human health [1].Heavy metals are considered to be non-degradable inorganic pollutants, which are released to the environment from both human and natural activities, causing ecosystem disturbance [2]
The obtained results indicated the ability of R. stricta plants to grow in heavy metal-contaminated soil without significant morphological changes
The heavy metal concentration in the roots of R. stricta was higher than that in stems and leaves under the tested Cd, Pb, Cu and Zn soil treatments. This may be due to the increase in the heavy metal concentration in the soil leading to an increase in the bioaccumulation in roots

Summary

Introduction

Environmental contamination by heavy metals is becoming a critical problem of global concern.The toxic metals may remain in the environment for a long period and can eventually accumulate to levels that could cause major threats to human health [1].Heavy metals are considered to be non-degradable inorganic pollutants, which are released to the environment from both human and natural activities, causing ecosystem disturbance [2]. Human activities, including mining, the use of fertilizers, pesticides and sludge as well as intensive asphaltic road construction across the natural landscape, are the main sources of heavy metal contamination of non-polluted soils, which in turn affects the food chain, leading to environmental and human health risks [4,5,6,7]. According to their importance to living organisms, heavy metals are classified into essential and nonessential metals. Among the essential metals are Fe, Ni, Cu, Mn, and Zn, Plants 2020, 9, 1057; doi:10.3390/plants9091057 www.mdpi.com/journal/plants

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Discussion

Conclusion