الفهرس 
contentsOnly 14 pages are availabe for public view
 |  | from | 218 |  |  |
| | | from | 218 | | |
Abstract
1.1. Sources of heavy metals in the environment.
Although not common, some natural contemporary environments, unmodified by man, may contain unusual high concentrations of metals (Gleeson and Coope, 1967; Brewer and Spencer, 1969; Kovalskii and Lentunova, 1974). In addition, man’s modification of parts of his environment has initiated or accentuated localized heavy metal concentrations in some water bodies, soils and even the atmosphere (Ehrlich, 1978). Hence, the source of heavy metals in nature can be divided into two major categories, natural and artificial.
1.1.1. Natural metal sources.
The primary natural sources are magnetic and hydrothermal activity, and igneous rocks. Sediments, and metamorphic and sedimentary rocks are secondary sources. The weathering of rocks may release heavy metals into solution which may then be transported to new sites where they may be reprecipitated or absorbed. Sometimes, heavy metal-compounds may occur in locally high concentrations in host rock. Such rock is then called ore (Ehrlich, 1978).
1.1.2. Artificial metal sources.
The artificial source of heavy metals is usually associated with man-made pollution. Man has been responsible for.