Fractional Characterisation of Bioavailable Arsenic in Poultry-Litter Amended Soil by Geochemical Mobility Analysis and XRD Technique

Abstract

Many farmers are using poultry litter as an organic fertilizer. Unfortunately, a significant
portion of this litter comes from commercial broiler operations that use feeds containing
arsenic (As) as an additive to control parasites and increase poultry weight. Most of the
ingested arsenic does not accumulate in the poultry meat but is excreted by the poultry.
As a result, nearly 90% of arsenic feed to poultry ends up in their waste. The presence of
As in the poultry litter used as fertilizer potentially accumulated in soils and cause soil
contamination. In this study, five steps of Tessier method were adopted for the
geochemical partitioning of As to identify the fractional forms that are liable to leach from
the soil matrix amended with poultry litter. Also, X-ray diffraction (XRD) was used to
determine As association with soil components among the fractional forms. The results
observed indicated higher fractions of arsenic in the exchangeable phase for all the
samples when compared to the residual. This suggests As can be released or desorbed as
it was not tightly bound to the soil matrix and thus, could be a source of soil contamination.
Furthermore, the XRD results indicated that the bulk chemistry of the soil samples is
dominated by quartz followed by aluminosilicates (comprise of orthoclase, muscovite, and
clinochlore) all of which could be the sorption sites or sinks for As. However, As can be
released from such sorption sites by desorption and dissolution of Fe oxides in response
to changes in physicochemical conditions of the soil environment and thus, possibly
influence the As mobility. Accordingly, the use of poultry litter as a fertilizer and source of
organic matter needs to be monitored and regulated periodically, to safeguard soil health
quality and by extension prevent total environmental pollution through dispersion