title: Zinc speciation in proximity to phosphate application points in a lead/zinc smelter-contaminated soil.
abstract: The use of P to immobilize Pb in contaminated soils has been well documented. However, the influence of P on Zn speciation in soils has not been extensively examined, and these two metals often occur as co-contaminants. We hypothesized that additions of P to a Pb/Zn-contaminated soil would induce Zn phosphate mineral formation and fluid P sources would be more effective than granular P amendments. A combination of different synchrotron-based techniques, namely, spatially resolved micro-X-ray fluorescence (μ-XRF), micro-extended X-ray absorption fine structure spectroscopy (μ-EXAFS), and micro-X-ray diffraction (μ-XRD), were used to speciate Zn at two incubation times in the proximity of application points (0 to 4 mm) for fluid and granular P amendments in a Pb/Zn smelter-contaminated soil. Phosphate rock (PR), triple super phosphate (TSP), monoammonium phosphate (MAP), and fluid ammonium polyphosphate induced Zn phosphate formation. Ammonium polyphosphate was more effective at greater distances (up to 3.7 mm) from the point of P application. Phosphoric acid increased the presence of soluble Zn species because of increased acidity. Soluble Zn has implications with respect to Zn bioavailability, which may negatively impact vegetation and other sensitive organisms. Although additions of P immobilize Pb, this practice needs close monitoring due to potential increases in Zn solubility in a Pb/Zn smelter-contaminated soil.
authors.affiliation: Department of Agronomy, Kansas State University, Manhattan, KS, USA.
authors.forename: Lucas R
authors.initials: LR
authors.lastname: Baker
authors.forename: Gary M
authors.initials: GM
authors.lastname: Pierzynski
authors.forename: Ganga M
authors.initials: GM
authors.lastname: Hettiarachchi
authors.forename: Kirk G
authors.initials: KG
authors.lastname: Scheckel
authors.forename: Matthew
authors.initials: M
authors.lastname: Newville
mesh_terms: D004784:Environmental Monitoring; D019652:Extraction and Processing Industry; D007220:Industrial Waste / Q000032:analysis*; D007854:Lead / Q000737:chemistry*; D010710:Phosphates / Q000737:chemistry*; D012987:Soil / Q000737:chemistry; D012989:Soil Pollutants / Q000737:chemistry*; D014961:X-Ray Diffraction; D015032:Zinc / Q000737:chemistry*
chemical_list: D007220:Industrial Waste; D010710:Phosphates; D012987:Soil; D012989:Soil Pollutants; D007854:Lead; D015032:Zinc