19-12-2012, 01:07 PM
HEAVY METALS AND LIVING SYSTEMS
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HEAVY METALS:
Any toxic metal may be called heavy metal.
These include the transition metals, some metalloids, lanthanides, and actinides.
Any metal species may be considered as “contaminant”. Metals/metalloids include
lead (Pb)
cadmium (Cd),
mercury (Hg),
arsenic (As),
chromium (Cr),
copper (Cu),
selenium (Se),
nickel (Ni),
silver (Ag), and
zinc (Zn).
Heavy Metals and Living Organism:
Living organisms require varying amounts of heavy metals. Iron, cobalt, copper, manganese, molybdenum, and zinc are required by humans.
All metals are toxic at higher concentrations
Heavy metals disrupt metabolic functions in two ways:
They accumulate and thereby disrupt function in vital organs and glands.
They displace the vital nutritional minerals from their original place, thereb, hindering their biological function.
Plants experience oxidative stress upon exposure to heavy metals that leads to cellular damage and disturbance of cellular ionic homeostasis.
To minimize the detrimental effects of heavy metal exposure and their accumulation, plants exhibits detoxification mechanisms.
Heavy Metals and Environmental Pollution:
Metal concentration in soil typically ranges from less than one to as high as 100,000 mg/kg.
Irrespective of the origin of the metals in the soil, excessive levels of many metals can result in soil quality degradation, posing significant hazards to human, animal, and ecosystem health.
CONTAMINATION WITH VEGETABLES:
Vegetables are rich sources of vitamins, minerals, and fibers, and also have beneficial antioxidative effects.
Heavy metal contamination of food is one of the most important aspects of food quality assurance. Heavy metals are no-biodegradable and persistent environmental contaminants
HEAVY METALS AND POLYMERS:
Complexation, separation, and removal of metal ions have become increasingly attractive areas of research and have led to new technological developments.
Meta--chelating and ion exchange polymers were used in hydrometallurgical applications such as recovery of rare metal ions from seawater and removal of traces of radioactive metal ions from wastes.