Abstract

Abstract The present chapter deals with the dynamics of arsenic (As) in a relative simple natural system consisting of hydrothermal spring outlets showing precipitation of iron (Fe) oxyhydroxides and carbonates. It was determined through a complete study comprising: (a) observation, (b) laboratory and field experimental partitioning studies and (c) geochemical modelling. The focus was on inorganically mediated geochemical processes, especially on the determination of the precipitation of mineral phases. Iron oxyhydroxides clearly show to control the fate of As through adsorption processes. Carbonates do not trap As, but play nevertheless an indirect role in the system. Their precipitation leads to the increase of pH causing desorption of As, which has been observed in the laboratory experiment. Field observations indicate, however, a stability of the As–Fe oxyhydroxide association. Arsenic remains linked to Fe oxyhydroxides in the travertine deposits associated to the springs as well as in the surrounding soils. The adsorption process appears very rapid, with around 90% of As being trapped within several minutes.

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