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ALTERATION OF SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY ASSOCIATED WITH BIOSOLIDS APPLICATION (ABSTRACT)
Citation:
Ryan*, J A., K G. Scheckel*, AND G. M. Hettiarachchi**. ALTERATION OF SOIL METAL CHEMISTRY AND PHYTOAVAILABILITY ASSOCIATED WITH BIOSOLIDS APPLICATION (ABSTRACT).
Description:
Biosolids are a complex mixture which contain both inorganic and organic adsorbents. Thus, addition of biosolids to soil not only increases the environmental loading of toxic metals (Cd, Zn, Cu, Ni, Pb, etc.) it alters the phytoavailability of these metals. This reduction 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. The persistence of this reduced phytoavailability has become an issue of concern. Resolution can be accomplished by identification of the forms of metals in soil system coupled with an understanding of their persistence. 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 by equilibration of the samples with cadmium nitrate. The cadmium nitrate solution was replaced with a calcium nitrate solution to obtain desorbed Cd. 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 altered 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 absorption spectroscopy at GSECARS, Advanced Photon Source, Argonne, IL were utilized to determine association and "mechanisms" of metals with biosolid's 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.