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Zinc Speciation in Proximity to Phosphate Application Points in a Lead/Zinc Smelter–Contaminated Soil
Author(s) -
Baker Lucas R.,
Pierzynski Gary M.,
Hettiarachchi Ganga M.,
Scheckel Kirk G.,
Newville Matthew
Publication year - 2012
Publication title -
journal of environmental quality
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.888
H-Index - 171
eISSN - 1537-2537
pISSN - 0047-2425
DOI - 10.2134/jeq2012.0168
Subject(s) - environmental chemistry , chemistry , phosphate , zinc , soil water , contamination , phosphoric acid , polyphosphate , phosphorite , bioavailability , ferrihydrite , soil contamination , genetic algorithm , aqua regia , phosphorus , metal , geology , ecology , soil science , bioinformatics , organic chemistry , adsorption , biology
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.