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This article in JEQ

  1. Vol. 36 No. 4, p. 1076-1085
     
    Received: Dec 14, 2006
    Published: July, 2007


    * Corresponding author(s): agyin@ufl.edu
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doi:10.2134/jeq2006.0535

Lability of Drinking Water Treatment Residuals (WTR) Immobilized Phosphorus

  1. Sampson Agyin-Birikorang * and
  2. George A. O'Connor
  1. Soil and Water Sci. Dep., Univ. of Florida, Gainesville, Fl 32611-0510

Abstract

Time constraints associated with conducting long-term (>20 yr) field experiments to test the stability of drinking water treatment residuals (WTR) sorbed phosphorus (P) inhibit improved understanding of the fate of sorbed P in soils when important soil properties (e.g., pH) change. We used artificially aged samples to evaluate aging and pH effects on lability of WTR-immobilized P. Artificial aging was achieved through incubation at elevated temperatures (46 or 70°C) for 4.5 yr, and through repeated wetting and drying for 2 yr. Using a modified isotopic (32P) dilution technique, coupled with a stepwise acidification procedure, we monitored changes in labile P concentrations over time. This technique enabled evaluation of the effect of pH on the lability of WTR-immobilized P. Within the pH range of 4 to 7, WTR amendment, coupled with artificial aging, ultimately reduced labile P concentrations by ≥75% relative to the control (no-WTR) samples. Soil samples with different physicochemical properties from two 7.5-yr-old, one-time WTR-amended field sites were utilized to validate the trends observed with the artificially aged samples. Despite the differences in physicochemical properties among the three (two field-aged and one artificially aged) soil samples, similar trends of aging and pH effects on lability of WTR-immobilized P were observed. Labile P concentrations of the WTR-amended field-aged samples of the two sites decreased 6 mo after WTR amendment and the reduction persisted for 7.5 yr, ultimately resulting in ≥70% reduction, compared to the control plots. We conclude that WTR application is capable of reducing labile P concentration in P-impacted soils, doing so for a long time, and that within the commonly encountered range of pH values for agricultural soils WTR-immobilized P should be stable.

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