Enviornment

Heavy metal contamination in south Indian banana fields

The News

  • Researchers from Mahatma Gandhi University, Kottayam have found high levels of heavy metal contamination in banana fields in 3 southern Indian states.

 

Highlights of the Report

  • The report assessed the level of nutrient and toxic heavy metals in banana fields.
  • The study covered three south Indian states, Kerala, Karnataka, and Tamilnadu.
  • It is found that heavy-metal contamination in green revolution fields is due to decade –long use of chemical fertilizers or plant protective chemicals.
  • 286 soil samples were used for sample analysis.

 

Important Results

  • The quantitative assessment of ten metals done in these soils included Calcium, Magnesium, Manganese, Zinc, Iron, Copper, Lead, Nickle, Chromium, and Cobalt.
  • The amount of Cu observed in many fields was higher than the previous reports.
  • The amount of Co observed in 25 fields was above its threshold levels expected for normal soils.
  • The amount of Pb observed in all the soils appeared quite normal.
  • The amount of Ni observed in 14 soil series exceeded the upper limit of contamination.
  • Calcium levels were reaching the threshold levels.
  • Cr was detected in all the samples.
  • Magnesium content was found to be unusually high of about 900 mg/Kg.
  • Normally magnesium content of soil in South Indian soil is known to be between 30 and 220 mg/Kg.

 

Causes of high contamination

  • Decade-long use of chemical fertilizers without proper soil testing.
  • Calcium is used to maintain the soil pH and over the years has accumulated in the soil.
  • Manganese is a major component of pesticide used against fungal diseases like Fusarium wilt gets accumulated in the soil if overused.
  • High Iron concentration is mainly due to the laterite-based soil of the Deccan Plateau.

 

About Heavy-Metals contamination

  • Heavy metals are metallic elements with an atomic number greater than 20.
  • They are trace elements having a density at least five times that of water.
  • Some of these elements are necessary for growth, development and functioning of living organisms
  • These include Copper, zinc, chromium, iron etc.
  • Those which are unnecessary include cadmium, lead, mercury.
  • However, beyond a certain limit all of them are toxic for plants, animals and humans.
  • These elements penetrate the body by inhalation, ingestion and skin absorption.
  • If heavy metals accumulate in body tissues faster than the body’s detoxification a gradual build-up of these toxins occurs.
  • Vegetables provide the trace elements and heavy metals.
  • Minor or trace elements are essential for good health if they come from an organic or plant source.
  • In contrast, if they come from an inorganic or metallic source, they become toxic.
  • Vegetables and fruits accumulate higher amounts of heavy metals because they absorb these metals in their leaves.
  • The excessive amount of these metals in food is associated with:
    • Cardiovascular, kidney, nervous, bone diseases
    • Decreasing immunological defences
    • Intrauterine growth retardation
    • Impaired psychosocial faculties
    • Disabilities associated with malnutrition
    • Upper gastrointestinal cancer

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