Evaluation of the potentiality of Sesbania cannabina (Retz.) Poir. for phytoremediation of hexavalent chromium contaminated soil

Ibne Kamal, Abdul Kadir (2023). Evaluation of the potentiality of Sesbania cannabina (Retz.) Poir. for phytoremediation of hexavalent chromium contaminated soil. University of Birmingham. Ph.D.

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Abstract

Abstract
Heavy metals (HM) accumulation in the soil or sediment is of significant environmental concern because of their toxicity to living organisms. Hexavalent chromium [Cr(VI)] is considered one of the most toxic HM released in the natural environment due to anthropogenic activities and they are still discharged from many industrial processes (e.g., chromo-tanning in leather industries), especially in developing countries like Bangladesh due to continuing use of chromium-containing salts (e.g. Na2CrO4, K2Cr2O7, Cr(OH)SO4). These HM do not decompose or disintegrate thus, removing or converting them into a less harmful state will reduce bioavailability and toxicity. Using plants (phytoremediation) in the remediation of HM has many advantages over chemical methods because it is less costly and can change metal speciation without the addition of further potential contaminants. The prerequisite for being a phytoremediation species is that species need to be fast-growing, able to grow under broad environmental stress and non-edible. A native species in Bangladesh Sesbania cannabina (Retz.) Poir. fulfils these conditions. This research aims to assess the Cr(VI) phytoremediation capacity of Sesbania cannabina (Retz.) Poir. (commonly known as Dhaincha in Bangladesh).
Study 1 (Chapter 2) provides evidence of Cr(VI) contamination in riverbank sediment (the highest Cr(VI) was recorded at 31.67±2.87 ppm, December 2021) of the Dhaleshwari River, Bangladesh. In Study 2 (chapter 3), we optimised the conditions (seeds pre-treated with H2O2 (6% v/v) for 5 minutes and primed with 65°C water for 5 minutes can germinate well at 27.5 ± 2.5°C) for S. cannabina seed germination. In study 3 (chapter 4), we tested the effect of Cr(VI) concentration on seed germination and root radicle elongation, and we observed S. cannabina can germinate and grow in concentrations of up to 175 ppm Cr(VI) in a growth medium. In addition, we observed the effect of Cr(VI) on the root system of S. cannabina by using rhizobox in study 4 (chapter 5) and found that root growth in plants grown in 160 ppm contaminated soil was reduced by about 55±0.65% at 25 days and 35±0.25 % at 45 days and that the root system was destroyed ≥360 ppm. Finally, we studied (chapter 6) the phytoremediation (in soil) potential of S. cannabina under different concentrations of Cr(VI) and observed that the plant species can convert all the harmful Cr(VI) to less harmful Cr(III) when grown in ≤ 175 ppm Cr(VI) contaminated soil.
Collectively, the four studies mentioned above (chapters 2 to 5) suggest that S. cannabina is a suitable candidate for phytoremediation of Cr(VI) (≤ 175 ppm) contaminated soil because it can convert all Cr(VI) to Cr(III) and sequester chromium in the roots.

Type of Work:

Thesis (Doctorates > Ph.D.)

Award Type:

Doctorates > Ph.D.

Supervisor(s):