Pollution Due to Trace Elements.
|Pollution Due to Trace Elements|
- Neutron activation analysis.
- X-ray fluorescence spectrometry.
- Atomic absorption spectrometry.
Essential Trace Elements.
- It should be present in all healthy tissues in all living things.
- The concentration of an essential trace element is fairly constant among various species.
- Its deficiency or depletion induces reproducible structural and physiological abnormalities.
- The deficiency symptoms or abnormalities disappear or reverse on replenishment that element.
- These biochemical changes due to deficiency can be cured when the deficiency is cured.
- Metals: V, Cr, Mn, Fe, Co, Cu, Mo, Zn, Na, K, Ca, Mg, and Sn.
- Non-metals: F, Cl, Br, I, H. C, N, O, Si, P, S, and Se.
Toxic Trace Elements.
Compounds of Mercury (Hg) and Their Uses.
Mercury, both in the metallic form (quicksilver) and as the sulfide (HgS) plays a prominent role in the following aspects.
- Mercuric oxide, salicylate, and chloride salts were used as antiseptics.
- Red mercuric sulfide, mercuric benzoate, mercurous acetate, and mercurous iodide were used for treating syphilis.
- Mercury chloride or calomel has been used as a laxative.
- Mercury is now mostly used as filling material for dental cavities as silver amalgam.
- Mercury is still used as a diuretic to a limited extent.
Industrial Uses of Mercury (Hg).
- Pharmaceutical industries.
- The plastics industry in the manufacture of vinyl chloride.
- Electrical and electronic industries in the manufacture of mercury vapor lamps and fluorescent tubes, batteries, electric switch gears, etc.
- Paper and pulp industry.
- The Chlor-alkali industry for the manufacture of Cl2, and NaOH.
Pollution Sources of Mercury (Hg).
Combustion of fossil fuels is the main source of air pollution by mercury and about 3000 tonnes of mercury is annually released into the atmosphere by this source.
The mercury contents of bituminous coal, anthracite coal, crude oil, and residual tars are in the range, 1-25 ppb; 1100-2700 ppb, 1900-21,000 ppb, and 520,000 ppb respectively.
Organomercurials used as fungicides for seed dressing in agriculture is also a widespread source of pollution.
- It is estimated that the mercury electrodes used in the Chlor alkali industry all over the world themselves disperse 1 million pounds of mercury into the environment.
- Natural weathering processes and submarine volcanism release about 5,000 tonnes of mercury annually into the oceans.
Control of Mercury Pollution.