elimination through permeability barrier, enzymatic reduction, and capturing and
sequestering in the cell active efflux pumps (Nies 1999; Bruins et al. 2000). There
are many cases in which different microbes are used in association with plants which
enhance the uptake and availability of heavy metals in soil and to plants (shown in
Table 14.2).
14.6 Earthworm-Assisted Remediation
of Contaminated Soil
Earthworms are the prevailing groups of macroinvertebrates of soil in numerous
terrestrial ecosystems comprising almost 80% of the biomass of soil. They are
known as key ecosystem engineers as they help in modifying and maintaining the
soil habitat. They play a key role in decomposition of organic matter, nutrient
cycling, and improving soil condition (Lemtiri et al. 2016). Earthworms slightly
decrease the pH of soil by the secreting fulvic and humic acids through their gut
microflora which increase the nutrient and heavy metal availability to soils (Drake
and Horn 2007). They promote the plant growth by enhancing the accessibility of
nutrients and microbes in the rhizosphere. The increased uptake of nutrients results
in increased biomass, shoot length, and root length (Varghese and Prabha 2014).
Earthworms excrete most of the ingested materials as vermicasts which are mucuscoated granular aggregates. The vermicasts are rich in nutrients like nitrogen,
phosphorus, potassium, magnesium, and calcium and have low carbon:nitrogen
ratio and good moisture holding capacity (Sharma et al. 2017). The dual action of
earthworms and improved soil properties result in enhanced metal uptake of heavy
metals (Kaur et al. 2017). The applications of earthworm by-products are also
reported to have positive impact on plant growth parameters and metal uptake.
Various reports of using earthworms and vermicompost for assisted
phytoremediation are mentioned in Table 14.3.
14.7 Conclusion
Heavy metal pollution is one of the leading causes of major environmental issues
due to their persistence in the environment and their nondegradable character.
Bioaccumulation of these metals in the food chain and their toxicity points a serious
threat for living organisms. The pronounced effects of the heavy metals have
attracted attention worldwide to get effective solutions for remediating contaminated
soils. Many physiological, chemical, and biological approaches have been figured.
Phytoremediation is considered as one of the safe, eco-friendly, innovative strategy.
Assisted phytoremediation with plant growth-promoting microbes, earthworms,
fungi, etc. enhances the efficiency of the remedial technology. Ample amount of
work has been done on various plant growth regulators and earthworms that show
14 PGPR and Earthworm-Assisted Phytoremediation of Heavy Metals
235
sequestering in the cell active efflux pumps (Nies 1999; Bruins et al. 2000). There
are many cases in which different microbes are used in association with plants which
enhance the uptake and availability of heavy metals in soil and to plants (shown in
Table 14.2).
14.6 Earthworm-Assisted Remediation
of Contaminated Soil
Earthworms are the prevailing groups of macroinvertebrates of soil in numerous
terrestrial ecosystems comprising almost 80% of the biomass of soil. They are
known as key ecosystem engineers as they help in modifying and maintaining the
soil habitat. They play a key role in decomposition of organic matter, nutrient
cycling, and improving soil condition (Lemtiri et al. 2016). Earthworms slightly
decrease the pH of soil by the secreting fulvic and humic acids through their gut
microflora which increase the nutrient and heavy metal availability to soils (Drake
and Horn 2007). They promote the plant growth by enhancing the accessibility of
nutrients and microbes in the rhizosphere. The increased uptake of nutrients results
in increased biomass, shoot length, and root length (Varghese and Prabha 2014).
Earthworms excrete most of the ingested materials as vermicasts which are mucuscoated granular aggregates. The vermicasts are rich in nutrients like nitrogen,
phosphorus, potassium, magnesium, and calcium and have low carbon:nitrogen
ratio and good moisture holding capacity (Sharma et al. 2017). The dual action of
earthworms and improved soil properties result in enhanced metal uptake of heavy
metals (Kaur et al. 2017). The applications of earthworm by-products are also
reported to have positive impact on plant growth parameters and metal uptake.
Various reports of using earthworms and vermicompost for assisted
phytoremediation are mentioned in Table 14.3.
14.7 Conclusion
Heavy metal pollution is one of the leading causes of major environmental issues
due to their persistence in the environment and their nondegradable character.
Bioaccumulation of these metals in the food chain and their toxicity points a serious
threat for living organisms. The pronounced effects of the heavy metals have
attracted attention worldwide to get effective solutions for remediating contaminated
soils. Many physiological, chemical, and biological approaches have been figured.
Phytoremediation is considered as one of the safe, eco-friendly, innovative strategy.
Assisted phytoremediation with plant growth-promoting microbes, earthworms,
fungi, etc. enhances the efficiency of the remedial technology. Ample amount of
work has been done on various plant growth regulators and earthworms that show
14 PGPR and Earthworm-Assisted Phytoremediation of Heavy Metals
235