Sl. Mcgeehan, ARSENIC SORPTION AND REDOX REACTIONS - RELEVANCE TO TRANSPORT AND REMEDIATION, Journal of environmental science and health. Part A: Environmental science and engineering, 31(9), 1996, pp. 2319-2336
Sorption and redox reactions strongly influence the toxicity, bioavail
ability, and potential mobility of arsenic (As) in soils. The objectiv
e of this paper is to describe the impact of soil flooding on the sorp
tion and oxidation state of As. Soils were flooded in a batch system,
and aqueous-phase measurements including Eh, pH, and dissolved Fe, Mn,
and As were recorded at the end of each flooding period. In addition,
aqueous- and solid-phase arsenite and arsenate were determined by ion
chromatography and x-ray absorption spectroscopy. Soil suspension Eh
decreased rapidly during the initial two days of flooding, thereby est
ablishing anaerobic conditions for the remainder of the flooding perio
d. Dissolved Fe and Mn levels increased, suggesting reductive dissolut
ion of Fe and Mn (hydr)oxides occurred. Dissolved As decreased rapidly
during the initial 24 h of the experiment, most likely the result of
sorption. Oxidation state measurements showed dissolved arsenate disap
peared with a concurrent increase in dissolved arsenite. Furthermore,
solid-phase arsenate declined with a concurrent increase in arsenite.
These aqueous and solid-phase observations indicate that arsenate is r
educed to arsenite in flooded soils although it is not clear whether t
his reduction occurs in solution or on the soil particles.