الفهرس 
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Abstract
The present work aims to study the effect of some heavy metals present in wastewater from (Shanawan drainage canal Menoufeya governorate, that used for irrigation at Kata-Elkheel field at Shanawan village, Menoufiya governorate), on alfalfa plant. It was found that the concentration of Fe, Mn, Cr and Co in wastewater used by some farmers for irrigation in Katta-Elkheel field exceeded the permissible limits according to F AO (1976). Samples were collected from three locations 1, 2, 3 at different distances from the beginning of the drain (50, 170, 350 m, respectively). In the present work, Co, Cr, Pb, Zn, Mn and Fe in wastewater irrigated soils and alfalfa plants exceeded the maximum permissible limits according to Kabata¬Pendias (2000) and Adriano (2001).
Growth and seed production of alfalfa in Katta-Elkheel field were negatively affected by irrigation with wastewater and the heavy metals accumulated in the soil. Shoot and root length, number of branches, number of leaves and number of produced seeds obviously decreased from area 1 to area 3 because of the increased accumulation of heavy metals. It could be also attributed to generation of free radicals and reactive oxygen species by heavy metals that pose constant oxidative damage by degenerating important cellular compounds.
Chromium (Cr) and Cobalt (Co) were chosen for further study on germination and growth of alfalfa. Assaying of some enzyme activities and metabolic changes were carried out to evaluate the extent of alfalfa plant tolerance to the accumulation of heavy metals. The study also included an attempt to reduce the accumulation of heavy metals in alfalfa plant to protect animal and human health. This was
metalloids, e.g., As, Se and Te have the physical properties of metals but chemically behave more like non metal elements.
There are 35 metals that concern us because of occupational or residential exposure; 23 of these are the heavy elements or ”heavy metals”: antimony, arsenic, bismuth, cadmium, cerium, chromium, cobalt, copper, gallium, gold, iron, lead, manganese, mercury, nickel, platinum, silver, tellurium, thallium, tin, uranium, vanadium, and zinc (Fujimakia, 1996). Interestingly, small amounts of these elements are common in our environment and diet and are actually necessary for good health, but large amounts of any of them may cause acute or chronic toxicity (poisoning).
Heavy metals toxicity can result in damaged or reduced mental and central nervous function, lower energy levels, and damage to blood composition, lungs, kidneys, liver, and other vital organs. Long-term exposure may result in slowly progressing physical, muscular, nephrotoxicity (e.g., mercuric chloride, cadmium chloride), learning difficulties; nervousness and emotional instability; and insomnia, nausea, lethargy and neurological degenerative processes that mimic Alzheimer’s disease (e.g., lead) Parkinson’s disease, muscular dystrophy, and multiple sclerosis. Allergies (e.g., beryllium, chromium) are not uncommon and repeated long-term contact with some metals or their compounds may even cause cancer (e.g., arsenic, hexavalent chromium). (IOSHIe, 1999). Breathing high levels of hexavalent chromium can damage and irritate nose, lungs, stomach, and intestine (ATSDR, 1993).
In small quantities, certain heavy metals are nutritionally essential for a healthy life. Some of these are referred to as the trace elements (e.g., iron, copper