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February 4, 2004 Arsenic Speciation and Reactivity in Poultry LitterY. Arai1, A. Lanzirotti2, S. Sutton2,3, J.A. Davis1, and D.L. Sparks4 Recent U.S. government action to lower the Maximum Concentration Levels of total arsenic (As) in drinking water (currently 10 parts per billion) has raised serious concerns about the agricultural use of As-containing biosolids such as poultry litter (PL). Microfocused (μ) Synchrotron X-ray Fluorescence (SXRF) and μ-X-ray Absorption Near Edge Structure Spectroscopic (XANES) analyses showed that As(III and V) was always concentrated in abundant needle-shaped microscopic particles (approximately 20 μm x 850 μm) that are associated with Ca, Cu and Fe, and to a lesser extent with S, Cl and Zn. Post-edge XANES features of litter particles are dissimilar to those of the organo As(V) compound in poultry feed (i.e. roxarsone), suggesting possible degradation/transformation of roxarsone in the litter and/or in poultry digestive tracts. Our research results raise concerns about long-term PL amendment effects on As contamination in surrounding soil-water environments.
A photomicrograph of one of 17 As-rich particles (approximately 20 x 850 μm) found in an approximately 200 mm2 area (Figure 1) shows the distinctive elongated particle morphology. The XRF analyses at the center of this particle (indicated by a black open square) show that elevated As levels are associated with Ca, Fe and Cu, and to a lesser extent with Zn, Ti, Cl, and S (Figure 1). A total of 17 similar particles were found in nearly half of the thin section (about 200 mm2). Elemental maps (Figure 2) generated from the region in the white open square in Figure 1 also show that the distribution of As is highly associated with Cl and Cu. Assuming no significant changes in the sample thickness and the density of the particle, the flux-normalized fluorescence counts in Figure 2 can be correlated to relative elemental concentrations for each element. It is possible that the formation of mixed metal-As, As-S precipitates and/or As sorption complexes on metal oxide precipitates were occurring in the litter and/or during poultry digestion. Our preliminary microfocused X-ray diffraction analyses at the NSLS showed no distinctive diffraction patterns on these particles, indicating the amorphous nature of the As-containing particles. The μ-XANES measurements were performed on the particle in Figure 1 (i.e. particle A in Figure 3b) and several additional As-containing particles (only particles B and C are shown in Figs 3a and 3b). They all produce similar XRF spectra as particle A (data not shown). Wide whiteline peaks are consistently observed in particles A-C (Figure 3a and 3b), indicating the presence of mixed As(III and V) oxidation states in these particles. Although the absorption energy position at ~11871 eV might indicate the presence of the orpiment-like As(III)-sulfide species, the exact As(V) species are difficult to elucidate based on the absorption edge LC fit, since the energy positions for different As(V) standards closely occur within 0.8 eV (Fig 3a). Post-edge XANES features of the particles (indicated by a dotted circle in Fig 3b) are dissimilar to those of the organo-As(V) compound in poultry feed, suggesting possible degradation/transformation of roxarsone in the litter and/or in poultry digestive tracts.
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The National Synchrotron Light Source at Brookhaven National Laboratory in New York, is a national user research
facility funded by the U.S. Department of Energy's Office of Basic Energy Science. The NSLS operates two electron
storage rings: an X-Ray ring and a Vacuum UltraViolet (VUV) ring which provide intense light spanning the electromagnetic
spectrum from the infrared through x-rays. Each year over 2300 scientists from universities, industries and government
labs perform research at the NSLS.
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In the last four decades, the poultry industry has become one of
the major livestock operations in the middle Atlantic states of the
U.S. While PL has been recycled on agricultural lands as an N
amendment, much of the trace metal(loid) input (total annual As
inputs between 20 and 50 metric tons) into the environments has been
neglected. The origin of As in PL is an organo-As(V) compound
(3-nitro-4-hydroxyphenylarsonic acid (roxarsone)) for coccidiosis
control in the poultry feed (approximately 25 - 50 mg of roxarsone
is mixed per kilogram of feed). Feed spillage and digested materials
have increased the mean total As concentration in PL to 14 - 76 mg
kg-1. At present, annual total metal(loid) inputs on agricultural
lands via PL amendments are not specifically regulated at either the
state or federal levels, and continuous PL amendment effects on As
contamination in Atlantic coastal plain soil/water environments
remain virtually unknown. To better understand the reactivity of As
from PL to surface and ground water, the As solid-state speciation
in the PL was investigated using SXRF and μ-XANES at beamline X26A
at the National Synchrotron Light Source and at the GeoSoilEnviro
Consortium for Advanced Radiation Sources at Argonne National
Laboratory’s Advanced Photon Source. 
