ZINC...

Introduction
More than 50 chemical elements are found in the human body which is required for growth, repair & regulation of vital function they are

a) Major minerals – calcium, phosphorous, sodium potassium& magnesium.

b) Trace elements – There are elements required by the body in quantities less than few milligrams per day Ex – Iron, iodine, fluorine, zinc, copper, cobalt, chromium, manganese,
molydecem, selenium nickel, silicon &
vanidicem.

c) Trace elements no known function – lead
mercury barium, alceminicem.
Zinc has catalytic, structural & regulatory actions.
Zinc is metal present in all cells. It is co-factor for more than 300 enzymes, and it is necessary for wide variety of biological functions. It is also component of more than 100 transcriptions factors. Zinc is required for synthesis of DNA, normal growth, gene expression, gene
regulation, cell division, immunity. Deficiency of
zinc may lead to many diseases more than 2 billion (2.5) in developing world are deficient of zinc.
Zinc deficiency can be causative factor for increase in the infection leading to death of children about 80000 children all over world die due to zinc deficiency. Zinc is one of the most important essential trace element zinc & its requirement for growth. Zinc deficiency is common in developing countries.
Zinc is the heaviest member of the first row
transition series of elements, consisting of Sc, Ti, V, Cr, Mn, Fe, Co, Ni, Cu and Zn, and belongs to group 12 of the periodic table, along with Cd and Hg, The chemistry of Zn is most similar to that of Cd. including sphalerite ZnS, also widely processes, like most other first-row transition metals, shows compatibility during early fractionation and thus
becomes enriched in mafic relative to felsic rocks.
The principal Zn carrier in mafic rocks is magnetite, while biotite is generally the most
important in granite contents of some
igneous rock types.
The distribution of Zn in sedimentary rocks is
primarily controlled by the abundance of
ferromagnesian silicates, detrital oxides, e.g.,
magnetite, and clay minerals, Carbonate rocks.
Zinc is readily adsorbed onto ferric oxides, although when Fe is absent it is often associated with carbonate and silicate phases. It has a greater affinity for organic matter and high values of Zn occur in oil shale.
Zinc is used in geochemical prospecting as a pathfinder for various types of Zn mineralisation, and is normally accompanied by Cd.
Zinc in association with Cd, Pb, etc. strongly suggests the presence of Sedex or VHMS mineralisation. Because of its strong chalcophile character, Cd may be used to validate a questionable Zn anomaly.
The Zn content in soil depends on the nature of parent rocks, texture, organic matter and pH, The different forms of Zn in soil may include:

(1) water soluble.
(2) exchangeable and extractable from soil surfaces.
(3) occluded by soil hydrous oxides;
(4) precipitates;
(5) immobilised in living organisms and biological residues.
(6) constituents in the
lattice of primary and secondary minerals.
Several soil profile studies have shown that extractable Zn generally decreases with depth, while total Zn is uniformly distributed throughout the profile. Extractable Zn usually correlates positively with total Zn, organic matter, clay content and cation exchange capacity. An inverse correlation has been observed between the amount of extractable Zn and free CaCO3, soil pH
Since Zn is easily adsorbed by mineral and organic components in most soil types, it normally accumulates in the surface horizons.

ZINC IN SOIL
The subsoil of Zn distribution map shows low values over northern Europe, especially the Netherlands, Poland, northern Germany, central Finland and southern Sweden.
Zn and Pb may indicate Zn-pollution of the
topsoil by liquid manure spreading.

ZINC IN STREAM WATER
High Zn concentrations in stream water are found in countries bordering the Baltic
Sea, on Precambrian Shield in southern Sweden, partly south-eastern Norway, On Variscan terrains high Zn in stream water occurs in Brittany, in northern
Portugal, central and southern Spain.

ZINC IMPORTANCE

1. Zinc plays essential role in human metabolism.
2. Zinc maintains gastrointestinal system of the body.
3. Zinc improves childhood growth.
4. Zinc act important role in appetite regulation.