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EFFECT OF BIOSOLIDS APPLICATION ON SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY
Citation:
Ryan*, J A., G. M. Hettiarachchi**, K G. Scheckel*, AND R. L. Chaney. EFFECT OF BIOSOLIDS APPLICATION ON SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY. Presented at Sustainable Land Application Conference, Lake Buena Vista, FL, January 04 - 08, 2004.
Impact/Purpose:
To inform the public.
Description:
Addition of biosolids to soils increases the environmental loading of toxic metals (Cd, Zn, Cu, Ni, Pb, etc.) and alters the chemistry and phytoavailability of these metals. This alteration in phytoavailability associated with biosolids amended soil was recognized and utilized by the U.S. Environmental Protection Agency in development of regulations designed to protect human health and the environment from reasonably anticipated adverse effects of land application of sewage sludge. Identification of the forms of adsorbed metals in soil system coupled with an understanding of their persistence will provide resolution to the debate over the long-term implication of the Agencies decision. To this end adsorption/desorption isotherms for soils from long-term biosolids-field experiments and their inorganic fractions and inorganic fractions with Fe/Mn removed were obtained. Results showed that addition of biosolids increased Cd adsorption and the increased adsorption associated with biosolids application was not limited to the OM addition from biosolids, rather the biosolids application also increased the adsorptive properties of the inorganic fraction. Further, biosolids-amended soils exhibited a greater retention for Cd than the control soil. X-ray microprobe analysis and micro-X-ray adsorption spectroscopy were utilized to determine association and "mechanisms" of metals with biosolids Fe and Mn compounds. Results from the elemental mapping of possible Fe and Mn phases and association of metals of interest with Fe and Mn phases in the biosolids and biosolids-amended soils confirm the importance of the inorganic phases of biosolids in retention of metals. Thus, the alteration in soil metal chemistry and phytoavailability is of a persistent nature.