Assessment of arsenate bioavailability in iron-rich environments: development of a high-pressure liquid chromatography method of quanitification for arsenate sorbed by Fe3+-substituted chelating resins in arsenic-bearing ferrihydrite suspensions
Given that the mobility, bioavailability, and toxicity of arsenate in natural systems is often
controlled by the strong binding capacity of iron oxyhydroxides, the objective of this study was to
document the interactions of Dowex M4195 Fe3+-substituted chelating resins (a potential fieldbased
tool for the quantification of potential arsenate bioavailability) and arsenic-bearing
ferrihydrite (AFH) as a function of suspension pH, suspension concentration, and background
electrolyte concentration. In 0.5 g AFH/L (0.001 M NaNO3) suspensions, arsenate sorption to
the resins was proportional to the degree of acidification of the AFH suspensions by the resins.
H+-enhanced dissolution of ferrihydrite artificially increased the arsenate in solution, causing a
consistent overestimation of potential arsenate bioavailability. Resin-induced acidification was
decreased with increasing suspension concentration. Arsenate sorption to the resins in 0.5 g/L
suspensions at pH 8 decreased with increasing NaNO3 concentrations, reflecting the decreasing
activity of arsenate under these conditions. The results of this study indicate that the high buffer
capacity of natural soils would prevent acidification as a result of resin introduction. Thus,
Dowex M4195 Fe3+-substituted chelating resins should provide a reasonable assessment of
potential arsenate bioavailability from poorly-crystalline iron oxide minerals. Possibly more
importantly, Dowex M4195 Fe3+-substituted chelating resins appear to be a new choice of
passive equilibrium sampling device that should work well for the determination of bioavailable
arsenate concentrations in the field.
Advisor:Herbert, Bruce E.; Grossman, Ethan; Loeppert, Richard H.
School:Texas A&M University
School Location:USA - Texas
Source Type:Master's Thesis
Date of Publication:08/29/2005