Distribution, Source and Contamination Level of REEs and Heavy Metals in Agricultural Soils of Fez-Upstream, Morocco

Abstract

ABSTRACT Although a few geochemical studies of agricultural soils have been conducted in southern Mediterranean countries like Morocco, such studies examining urban and sub-urban agricultural soils are very rare. The objective is to enable evaluation of different soil contamination indexes, and to identify the anthropogenic and natural sources of potential ecological risks. A sampling of nine soil samples were collected and analyzed to determine concentrations of Major elements, Rare Earth Elements (REEs) and Heavy Metals from agricultural soils of Fez-Upstream, Morocco. The major outcomes were: the average total concentration of REEs is 95.23 µg/g lower than those of the Upper Continental Crust (UCC), at 146.37 µg/g, and world soils at 137.09 µg/g; the ratios of La/Yb, La/Sm and Gd/Yb show that soil samples are enriched by light REEs. Enrichment factor (EF) and geo-accumulation index (Igeo) indicate that there is no enrichment by REEs. EF range from minimal to moderate enrichment. Igeo indicate that soil samples are unpolluted to moderately polluted. The contamination factor and degree of contamination indicate respectively moderate contamination and a low degree of contamination. Otherwise, all sampling sites have PLI values above 1 that indicate obvious anthropogenic pollution due to human activities. The results indicated that REEs contents are reflected by the parent materials. Lastly, it is interesting to note that these obtained results represent the first national data for REEs in Moroccan soils.