The effect of heavy metals on the nutritional value of Alfalfa: comparison of nutrients and heavy metals of Alfalfa (Medicago sativa) in industrial and non-industrial areas.

Abstract

The aim of this study is to compare the nutritional value of Alfalfa and accumulation of heavy metals in the farms near and far from the industrial regions. Three regions were considered located at 2, 32 and 65km distances from an industrial region, and the nutrient content of the Alfalfa including crude protein, crude fiber, crude fat, nitrogen-free extract, and Ash as well as soil and plant heavy metals was determined. The results showed no significant difference in the value of nutrients in the three regions except nitrogen-free extract (mainly starch and sugars). A positive correlation was observed between nitrogen-free extract and lead, chromium, and arsenic (p ≤ 0.05). In addition, the highest accumulations of heavy metals such as arsenic, chromium, lead and cadmium were found in soil and Alfalfa produced at 2km distance from the industrial area. The lead and cadmium concentrations were higher than the maximum allowable agricultural soil concentration in the areas near industrial region; the accumulation of these metals in the Alfalfa was however lower than the cattle and plant risk levels. The distribution of heavy metals in the Alfalfa cultivated in these three areas (zinc > copper > lead > chromium > arsenic > cadmium) did not coincide with the average of these metals in the soils (lead > zinc > chromium > copper > cadmium > arsenic). The positive correlation was also recorded between electrical conductivity of agricultural soils and copper, lead, chromium and arsenic content of Alfalfa. The highest translocation factors of arsenic, chromium and lead elements were detected in industrial areas. For copper and zinc, the highest translocation factor was found in non- industrial areas. The results of this study can be applied as an important control program in different areas.