Developing a Remediation Strategy for Phosphorus Immobilization: Effect of Co-blending, Al-residual and Ca-Mg Amendments in a Manure-Impacted Spodosol

Abstract

A remediation strategy called “co-blending” was developed for rapid phosphorus (P) immobilization. Immobilization was achieved through the combination of an Al-based water treatment residual (Al-WTR) with Ca-Mg-based materials (Slag and magnesium oxide) for use in incubation and leaching experiments. Al-WTR was co-blended with Slag and MgO as “Al-WTR+Slag” and “Al-WTR+MgO,” respectively. Sequential extraction was used to delineate P species into operationally defined fractions: soluble or exchangeable, Al-Fe, and Ca-Mg-bound pools. Results from soils used in the incubation experiment showed that Al-amended material tended to sequester P bound (∼26%) to the Al-Fe pool. On the other hand, Ca-Mg-based materials tended to sorb (∼70%) of P greatly associated to the Ca-Mg pool. Amendments were applied at 2% or 20 g kg⁻¹ as Al-WTR, MgO, and Slag and at 1%+1% or 10 g kg⁻¹+10 g kg⁻¹ as co-blended Al-WTR+MgO and Al-WTR+Slag, respectively, on mass basis. Results from leaching data suggest that treatment effects on pH are significant at (p < 0.0001) and also significant (p < 0.01) with weeks of leaching. A similar significant (p < 0.0001) trend was observed for effects of treatment on redox potential (Eh). However, treatment effects on weeks of leaching were not significant. Cumulative soluble P (mg) of leachate showed linear reduction (96%) from the control (without amendments) using a regression model. Potential co-blended material selected was Al-WTR+Slag (1%+1%) due to less P in leachates, moderate effect on pH, and fewer amounts of Al-WTR and Slag used compared with 2% Al-WTR and Slag, respectively. In addition, the RMSE of Al-WTR+Slag data fitted to a regression model was the least. Results suggested that the metal cations Al, Ca, and Mg tended to bind different forms of total P at any given pH. Through co-blending, less soluble P may be lost to the environment than using sorption materials independently.

Keywords:

• co-blending
• manure-impacted soil
• drinking water treatment residual
• remediation
• immobilization
• Ca-Mg-based materials

Acknowledgements

The authors would like to thank the drinking water treatment facility at Bradenton, Florida, Martin Marietta Magnesia Specialties LLC, MD, and Holcim (US) Inc., Alabama, for the supply of Al-WTR, MgO, and slag, respectively. In addition, M.K. Miyittah would like to thank Dr. S.G.K. Adiku, Leighton C. Walker, and Stephen Narh (University of Florida, Gainesville) for helpful discussions.

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