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Impacts on plant growth from heavy metal contamination�Dr Nicola D Cannon (Nicky)�Professor of Agriculture�Specialism in agronomy

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Overview of the presentation

Factors that influence plant growth

Risks to plant growth from warfare

Challenges of heavy metals

Options for remediation

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Plant stresses

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Cause and effect diagram for physical impacts of warfare on soil (Broomandi et al. 2020)

    • Altering the physical characteristics of the terrain
    • Altering the hydrological behaviour of surface & underground water systems

The disturbance or removal of soil material for the avoiding attempts from offensive operations

    • Cratering and bombturbation
    • Soil removal causing a hollow
    • Mixing of soil horizons and transforming topography

Bombs and shells

    • Soil perturbation
    • Contamination by metal & plastic fragments and residues of explosives

Buried anti-tank and anti-personnel mines

    • Compaction making soil more vulnerable to erosion and runoff
    • Liquification causing issues such as mud formation

Warfare traffic including manoeuvres of heavy wheeled & tracked vehicles

    • Increased susceptibility to erosion starting on steep and burnt surfaces
    • Limitations on water infiltration
    • Runoff and erosion

Instigation of fires in crops or forests

Plus heavy metal contamination

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Heavy metals in the soil and the impacts for plant growth

  • Heavy metals do not degrade through biological or physical processes
  • Some heavy metals are essential for plants growth (Cu, Fe, Mn, Ni, Zn) but can become toxic in high quantities
  • Non-essential heavy metals eg Pb, Cd, As, Hg are toxic and can impact physiological and biochemical plant processes
  • Excess heavy metals can be removed with some success by soil incineration, excavation and landfill, soil washing, solidification, electric field application and phytoremidation.

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Kumar et al. 2019

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Impact of heavy metals on human health��Mitra et al. 2022

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Plus:

Biproducts of war

Modified from:

Kushwaha et al. (2015)

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How PAH and Metal(loid)s impact plant growth

A range of responses to direct toxic effects to inhibited plant metabolism including:

  • Thicker roots
  • Reduced root elongation
  • Thicker cortex, epidermis or endoderm

Works by reducing:

  • Reducing root absorptive surface
  • Decreased soil resource uptake

Delerue et al. 2022

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Crude oil pollution in maize and cowpea

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Adesina & Adelasoye (2014)

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Uptake, translocation and sequestration of heavy metals in plants

Yan et al (2020)

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Rylote & Bruce 2019

A range of Hydrocarbons from explosives

The impact of Russia’s war against Ukraine on the state of the country’s soil Analysis results 2023

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Hou et al. (2022)

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Grifoni et al. (2020)

How this is expressed in maize? Reduced yield but uneven impacts on plant tissues

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Hoque et al. (2021)

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Options for bioremediation

  • Understand different crop tolerance for pollutants
  • Grow heavy metal tolerant crops
  • Plants which can bioaccumulate heavy metals
  • Plant growth promoting bacteria (predominately still in the lab.)

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Plant growth promoting bacteria�Wang et al. (2022)

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Wu et al. (2022)

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Actions required

  1. Assess known risks
  2. Test soils for heavy metal contamination
  3. Look for good geospatial links between contamination and soil tests
  4. Consider environmental conditions (soil types, climatic conditions)
  5. Evaluate extent of remediation required
  6. Determine the cropping opportunities
  7. Evaluate crop products

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Checking plant health in the field

  • Soil testing
  • Ideally start monitoring from emergence
  • Fly frequently
  • Ground truth observations and check against known problem areas
  • GPS mark challenging areas in field to consider/avoid cultivation

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References

Adesina, G.O. & Adelasoye, K.A. (2014). Effect of crude oil pollution on heavy metal contents, microbial population in soil, and maize and cowpea growth. Agricultural Science 5(1). DOI:10.4236/as.2014.51004

Broomandi et al. (2020). Soil Contamination in Areas Impacted by Military Activities: A Critical Review. Sustainability 12.

Delerue et al. (2022). Biomass partitioning of plants under soil pollution stress. Communications Biology 5, 365.

Grifoni et al. (2020). The effect of residual hydrocarbons in soil following oil spillages on the growth of Zea mays plants. Environmental Pollution 265. https://doi.org/10.1016/j.envpol.2020.114950

Hou et al. (2020). Metal contamination and bioremediation of agricultural soils for food safety and sustainability. Nature Review: Earth & Environment 1, 366-381.

Hoque et al. (2021). Melatonin Modulates Plant Tolerance to Heavy Metal Stress: Morphological Responses to Molecular Mechanisms. International Journal of Molecular Sciences. 22(21):11445. doi:10.3390/ijms222111445

Kumar et al. (2019). Hazardous heavy metals contamination of vegetables and food chain: Role of sustainable remediation approaches - A review. Environmental Research 179.

Mitra et al. (2022). Impact of heavy metals on the environment and human health: Novel therapeutic insights to counter the toxicity. Journal of King Saud University – Science. https://doi.org/10.1016/j.jksus.2022.101865

Prabhat Kumar Rai, Sang Soo Lee, Ming Zhang, Yiu Fai Tsang, Ki-Hyun Kim. (2019). Heavy metals in food crops: Health risks, fate, mechanisms, and management. Environment International 125, 365-385. https://doi.org/10.1016/j.envint.2019.01.067

Rylote & Bruce (2019). Right on target: using plants and microbes to remediate explosives. International Journal of Phytoremediation, 21:11, 1051-1064, DOI: 10.1080/15226514.2019.1606783

Wang et al. (2022). Plant growth-promoting bacteria in metal contaminated soil: Current mechanisms on remediation mechanisms. Frontiers in Microbiology, 13.

Wu et al. (2022). Improved phytoremediation of heavy metal contaminated soils by Miscanthus floridulus under a varied rhizosphere ecological characteristic. Science of the Total Environment 808, https://doi.org/10.1016/j.scitotenv.2021.151995

Yan et al. (2020). Phytoremediation: A Promising Approach for Revegetation of Heavy Metal-Polluted Land. Frontiers Plant Science 11.

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