Sources and levels of metals in the upper Litani basin soils

Abstract

There are a number of factors that contribute to heavy me tal contamination in agricultural soils including deficient management of solid waste, waste water disc harge, irrigation with contaminated water, and use of fertilizers and pesticides. Th e aim of this study is to estimate the sources and the levels of metals in soils of the ULB (Upper Litani Basin) that receive all mentioned factors. Soil samples were coll ected during the dry season from 24 sites along the Litani River flow, and 12 sites irrigated by Canal 900 withdrawn from the Qaraoun Dam along river. Metals in soils were analyzed using EDXRF (energy dispersive X-ray fluorescence) technique. Da ta revealed the following average levels of some heavy metals in soils with high percentage of samples exceeding the international guidelines : Mn (593 mg/kg)—67%, Ni (98 mg/kg)—96%, Cr (143 mg/kg)—92%, Hg (3.6 mg/kg)—38%, Cd (2.8 mg/kg)—25% and As (17.6 mg/kg)—84%. In canal soils: Mn (683 mg/kg)—86%, Ni (156 mg/kg)—100%, Cr (203 mg/kg) —100%, Hg (2.3 mg/kg)—25%, Cd (3.3 mg/kg)—25% and As (19.5 mg/kg)—92%. The prime source of toxic metals was due to the agricultural runoffs, beside sewage and domestic waste water discharge. T hus, the prominent findings of high levels of toxic metals (Cr, Cd, Hg and As) in soils and consequent probability in plants might induce a major health threa t to consumers. Key words: Agricultural runoffs, contamination, metals , soils, Upper Litani Basin, Lebanon.