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Abstract:

Application of sewage sludge rich in organic matter and nutrients such as nitrogen, phosphorus and potassium tend to improve crop yields. Nevertheless, this use is limited because of their heavy metal content. The objective of this work is to study the effect of sewage sludge on the accumulation of metallic trace elements in seeds and rapeseed oil. For this purpose, two different types of sludge by their metal composition were tested. Compared to the control, the supply of industrial sludge increases the metallic load of seeds and rapeseed oil. This increase is noted with the highest doses 50 and 100 t/ha. The same trend was observed during the two years of application. This effect is due to the richness of these slurries in chrome, cadmium and lead. This modification of the metal composition was accompanied by the decrease in the oil content. Analysis of the fatty acid composition of total lipids shows an increase in the percentage of oleic acid at the expense of linoleic and linolenic acids. On the other hand, the increase of 18: 1 at the expense of linoleic and linolenic acids may be the result of metal-induced alteration. For urban sludge, we noticed a variation in Cr, Co, Cu, Ni and Zn contents in the seeds depending on the doses. However, for Cd and Pb no variation was recorded. An increase in metal trace element levels was well reported at the seed level during the second amendment. We also detected a decrease in oil content with the contribution of industrial sludge. The composition of the total lipids in fatty acids shows an increase in the percentage of oleic acid (C18: 1) at the expense of linoleic (C18: 2) and linolenic (C18: 3) acids under the effect of heavy metals brought by the industrial sludge while no difference is recorded with urban sludge regardless of the dose. No significant differences in heavy metals were observed with the addition of the different doses of urban sludge even after two years of application. Urban sludge has no effect on oil content or fatty acid composition. However, we detected increases in most heavy metals, especially for high doses of industrial sewage sludge.