Heavy metals have a density of 6.0 g/cm3 or more (much higher than the average particle density of soils which is 2.65 g/cm3) and occur naturally in rocks but concentrations are frequently elevated as a result of contamination. The most important heavy metals with regard to potential hazards and occurrence in contaminated soils are arsenic (As), cadmium (Cd), chromium (Cr), mercury (Hg), lead (Pb) and zinc (Zn).
Health effects of selected heavy metals
Arsenic (As). Arsenic is well-known as a poison and a carcinogen. It has an average concentration in the soil of 5 to 6 mg/kg. Its amount in the soil is related to rock type and industrial activity.
Chromium (Cr). It is required for carbohydrate and lipid metabolism and the utilization of amino acids. Its biological function is also closely associated with that of insulin and most Cr-stimulated reactions depend on insulin. However, excessive amounts can cause toxicity. Toxic levels are common in soils applied with sewage sludge.
Lead (Pb). This has been known to be toxic since the 2nd century BC in Greece. It is a widespread contaminant in soils. Lead poisoning is one of the most prevalent public health problems in many parts of the world. It was the first metal to be linked with failures in reproduction. It can cross the placenta easily. It also affects the brain, causing hyperactivity and deficiency in the fine motor functions, thus, it results in damage to the brain. The nervous systems of children are especially sensitive to Pb leading to retardation. It is also cardiotoxic and contributes to cardiomyopathy (disease of the heart muscle leading to the enlargement of the heart).
Mercury (Hg). This heavy metal is toxic even at low concentrations to a wide range of organisms including humans. The organic form of mercury can be particularly toxic, and the methyl-and ethyl-forms have been the cause of several major epidemics of poisoning in humans resulting from the ingestion of contaminated food, e.g. fish. Two major epidemics in Japan were caused by the release of methyl and other mercury compounds from an industrial site followed by the accumulation of the chemicals in edible fish. The poisoning became well-known as Minamata disease.
Nickel (Ni). Nickel occurs in the environment only at very low levels. Humans use nickel for many applications like the use of nickel as an ingredient of steel and other metal products. Foodstuffs have a low natural content of nickel but high amounts can occur in food crops grown in polluted soils. Humans may also be exposed to nickel by inhalation, drinking water, smoking, and eating contaminated food. Uptake of high quantities of nickel can cause cancer, respiratory failure, birth defects, allergies, and heart failure (www. Lenntech.com/periodic-chart-elements/Ni-en.htm)
References
Oliver, M.A. 1997. Soil and human health: a review. European Journal of Soil Science 48: 573-592.
Puschenreiter M., O Horak, W. Friesel, and W. Hartl. 2005. Low-cost agricultural measures to reduce heavy metal transfer into the food chain- a review. Plant Soil Environ 51: 1-11.
Susaya JP. 2007. MSc thesis. Institute of Tropical Ecology, Visayas State University, Baybay, Leyte, Philippines.
9 comments:
-This has been very helpfu to me in my CAPT research!
So thank you!
A good summary of heavy metals that may be introduced in the soil
Simple and simplified presentation with sound knowledge
I thank Akonuatta and Laxman Singh for visiting my blogsite and for leaving kind comments.
What a brelliant work! Thank u very much for this I am well pleased.
WONDERFUL PRESENTATION
Than you sir. The information was really helpful for my project. Thanks a lot again :)
I have bookmarked your blog, the articles are way better than other similar blogs.. thanks for a great blog!
glutenfreefitness
Hi Olivia Princess, thank you so much for your kind comment. I am glad that you found my blog useful.
Kind regards,
vic
Post a Comment