الفهرس 
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Abstract
The aim of the present researchis to study the effect of adsorbents,activated harcoal and water hyacinth roots,on the removal efficiency of heavy metals, Pb, Fe, Cu and Cd,by using laser induced breakdown technique LIBS) under different depths, contact time and initial concentration. Synthetic stock solutions of heavy metals were prepared. The used depths were 20, 40, 60 and 80 cm. the contact times were 20, 40, 60, 80, 100 and 120 min. the concentrations of heavy metals used in this study were 100, 00, 300 and 400 mg/L. The obtained results revealed that, removal fficiency of charcoal for Pb,Fe and Cu when the initial concentration ncreased from (100 to 400) mg/L, the removal efficiency increases from 81.13 to 92.10) %, (70.33 to 73) % and (71.33 to 72.67) % respectively. While it deceased for Cd from (23.67 to 21.33) %. The obtained results evealed that, removal efficiency of dried roots of water hyacinthfor Pb, Fe and Cu when the initial concentration increased from (100 to 400)mg/L, the removal efficiency increases from (69.23 to 77.96 %),(54.54 to 55.67) % nd (44.89 to 46.84) % respectively. While it decreased for Cd from (11.44 o 11.24) %. The effect of charcoal on maximum removalefficiency of the tudied heavy metals was between 93 %, 74, 73.67 and 24.33 %for Pb, Fe, Cu and Cd in depth 80 cm respectively. In addition,water hyacinth also ffect on the maximum removal efficiency for the same heavy metals tudied and it was between 93 %, 74, 73.67 and 24.33 %for the same depth.LIBS technique is utilized to measure the effect of charcoal and water hyacinth on Removal efficiency of the studied heavy metals Pb,Cd.Removal efficiency increases with time and reaches a max60 to 80 min of contact timefor charcoal, contracting water hya 100 and120 min. It was found that the removal efficiency of c water hyacinth for following elements Fe,Cu, Pb and Cd are affinitial concentration. Statistical analysiswith ANOVA(F test) the datapresented not only reveals that all treatments have difference for all studied concentrations 100, 200, 300 and between removal efficiency means but also for all depths and ti Test shows that the data presented significant differences, tefficiency of all charcoal treatments contained a large value cthose of all water hyacinth treatments for Pb, Fe, Cu and Cd. heavy metals can be arranged due to their removal efficie following descending order Pb > Fe > Cu > Cd. Key words:LIBS, water hyacinth, charcoal, removal efficiency, heavy metals