title: Long-term phosphorus immobilization by a drinking water treatment residual.
abstract: Excessive soluble P in runoff is a common cause of eutrophication in fresh waters. Evidence indicates that drinking water treatment residuals (WTRs) can reduce soluble P concentrations in P-impacted soils in the short term (days to weeks). The long-term (years) stability of WTR-immobilized P has been inferred, but validating field data are scarce. This research was undertaken at two Michigan field sites with a history of heavy manure applications to study the longevity of alum-based WTR (Al-WTR) effects on P solubility over time (7.5 yr). At both sites, amendment with Al-WTR reduced water-soluble P (WSP) concentration by >or=60% as compared to the control plots, and the Al-WTR-immobilized P (WTR-P) remained stable 7.5 yr after Al-WTR application. Rainfall simulation techniques were utilized to investigate P losses in runoff and leachate from surface soils of the field sites at 7.5 yr after Al-WTR application. At both sites, amendment with Al-WTR reduced dissolved P and bioavailable P (BAP) by >50% as compared to the control plots, showing that WTR-immobilized P remained nonlabile even 7.5 yr after Al-WTR amendment. Thus, WTR-immobilized P would not be expected to dissolve into runoff and leachate to contaminate surface waters or groundwater. Even if WTR-P is lost via erosion to surface waters, the bioavailability of the immobilized P should be minimal and should have negligible effects on water quality. However, if the WTR particles are destroyed by extreme conditions, P loss to water could pose a eutrophication risk.
authors.affiliation: Soil and Water Sci. Dep., Univ. Florida, Gainesville, FL 32611-0510, USA.
authors.forename: Sampson
authors.initials: S
authors.lastname: Agyin-Birikorang
authors.forename: George A
authors.initials: GA
authors.lastname: O'Connor
authors.forename: Lee W
authors.initials: LW
authors.lastname: Jacobs
authors.forename: Konstantinos C
authors.initials: KC
authors.lastname: Makris
authors.forename: Scott R
authors.initials: SR
authors.lastname: Brinton
mesh_terms: D010758:Phosphorus / Q000737:chemistry*; D014881:Water Supply
chemical_list: D010758:Phosphorus