Wednesday, November 15, 2006 - 2:00 PM

Fate and Transport of Phosphorus in Biosolids and Water Treatment Residuals Amended Soils under Anaerobic Conditions.

T. Borch, Y. Assefa Mulisa, J.A. Ippolito, N.C. Hansen, and J.M. Jones. Colorado State Univ, Dept of Soil and Crop Sciences, Fort Collins, CO 80523-1170

Phosphorus (P) controls eutrophication in most freshwater systems and can also be a threat to some marine ecosystems.  Phosphorus derived from agricultural practices has been targeted as a major source of water quality degradation.  Surface water receives most of P in surface flows rather than in groundwater, since phosphate bind strongly to most soils and sediments.  However, mobilization or leaching of P has been observed in anoxic water-logged soils and lake sediments and can be a source of dissolved inorganic P in ground waters, aquifers, lakes or coastal oceans.  Natural environments often experience dynamic flow conditions resulting in chemical concentration gradients of compounds such as phosphate, ferrous iron, and organic matter.  The redox potential and nature of Fe(III) (hydr)oxides may vary along an advective flow path and thus have a significant impact on P cycling.  Water treatment residuals (WTRs) have been extensively used in an attempt to increase P retention within agricultural soils and biosolids amended soils, however little is known about the fate of P in biosolids amended soils and the impact of WTRs under anaerobic conditions. Accordingly, this presentation will discuss the influence of anaerobic conditions and dynamic flow conditions on the fate and transport of P in biosolids amended soils from Colorado in the presence and absence of WTRs.  Temporal P-fractionation, Fe-speciation, CO2-production, NO3-, NH4+, pH and Eh were determined in batch and column experiments under aerobic and anaerobic conditions in the presence and absence of biosolids with and without co-amendments of WTRs.  Transport of phosphorus was studied in columns under advective flow conditions as a function of the above mentioned treatments.  This presentation will bring new insights to the intricate interactions of P, WTRs, biosolids and soils under anaerobic conditions and will help improve biosolids application strategies and P leaching predictions.