The influence of sulfur and iron on dissolved arsenic concentrations in the shallow subsurface under changing redox conditions.

ABSTRACT: The chemical speciation of arsenic in sediments and porewaters of aquifers is the critical factor that determines whether dissolved arsenic accumulates to potentially toxic levels. Sequestration of arsenic in solid phases, which may occur by adsorption or precipitation processes, controls dissolved concentrations. We present synchrotron x-ray absorption spectra of arsenic in shallow aquifer sediments that indicate the local structure of realgar (AsS) as the primary arsenic-bearing phase in sulfate-reducing conditions at concentrations of 1-3 mmol.kg(-1), which has not previously been verified in sediments at low temperature. Spectroscopic evidence shows that arsenic does not substitute for iron or sulfur in iron sulfide minerals at the molecular scale. A general geochemical model derived f

SUBMITTER: O'Day PA 

PROVIDER: S-EPMC518762 | biostudies-literature | 2004 Sep

REPOSITORIES: biostudies-literature