Tuesday, November 6, 2007
231-1

Influence of Salt-Water Irrigation during Chelate-Facilitated Phytoremediation.

Intkhab Hazoor Wahla and M. B. Kirkham. Kansas State University, 2004 Throckmorton Hall, Department of Agronomy, Manhattan, KS 66506

Heavy metals in sewage sludge, applied to land, contaminate soil. Phytoremediation, the use of plants to clean up toxic heavy metals, can remove them. Chelating agents are added to soil to solubilize the metals for enhanced phytoextraction. Yet no studies report the effect of salinity on the bioavailability of heavy metals in sewage sludge during chelate-facilitated phytoremediation. The objective of this research was to determine the mobility and uptake of heavy metals in sewage sludge applied to the surface of soil columns (76 cm long;17 cm diameter; containing a very fine sandy loam soil) irrigated with tap water or with salt water (10,000 ėg/mL NaCl or about a third of the concentration of sea water). Barley (Hordeum vulgare L.), the most salt-tolerant of commercially important crops, grew in the columns. Three weeks after the barley was planted, half the columns were irrigated with the disodium salt of the chelating agent, EDTA (ethylenediamine tetraacetic acid ) (0.5 g/kg soil). Drainage water, soil, and plants are being monitored for heavy metals (Cd, Cu, Fe, Mn, Ni, Pb, Zn). Results to date show that plants with the chelate and irrigated with salt water started to wilt and die within 24 hours after the addition of the chelate. Roots in these columns also apparently were dying, because amount of drainage water from them increased compared to the other columns. Plants in the columns with the chelate and tap water also started to wilt, but the reduction in the growth was not as severe as in the columns with chelate and salt water. In columns with no chelate, plants irrigated with 10,000 ėg/mL NaCl grew as well as plants grown with tap water, which showed the high salt tolerance of barley.