متفاوت PH اثر لجن فاضلاب بر غلظت فلزات سنگين در گياهان كاهو و اسفناج در خاك هاي با

EFFECT OF SEWAGE SLU DGE ON HEAVY METAL CONCENTRATION OF SPINACH AND LETTUCE IN SOILS WITH DIFFERENT PH

Land application of sewage sludge is considered beneficial as an inexpensive nutrient source. However, high concentration of heavy metals in sewage sludge may contaminate soil and human and animal food chains. The objective of this study was to evaluate the effect of sewage sludge on yield and uptake of heavy metals by spinach (Spinacia oleracea) and lettue (Lactuca sativa) in soils with different pH levels. The study was carried out in greenhouse using a factorial experiment design with a completely randomized layout, with three replications. The factors were: four levels of sewage sludge: 0 or control (So), 50(S1), 100(S2), 200 (S3) t ha-1, and one level of inorganic fertilizer (250 kg ha-1 ammonium phosphate and 250 kg ha-1 urea), four soils and two plants (spinach and lettuce). The highest spinach and lettuce yields were obtained in S3 in Rasht soil and S2 in Lahijan and Isfahan soils and 8i in Langaroud soil. 8ewage sludge significantly increased concentration of Fe, Zn, Cu, Pb, and Cd in plant roots and shoots, and the concentration of some of the metals in plants reached to toxic levels in Langaroud and Lahijan soils.