ABSTRACT
On the site of a former pulp mill the arsenic content of groundwater was found to be up to 2 mg/L. High costs for decontamination and remediation were estimated, due to the fact that area is still in industrial use. A long term pollution potential in the case of adopting pump and treat measures was calculated. As the early site investigations gave evidence for immobilization of arsenic in the aquifer within close range of the hot spot, detailed laboratory and field measurements were carried out 1999/2000. The goal was to understand the principles of dissolution and precipitation of arsenic in sulfate reducing environments as a basis for a MNA-concept. The interactions between arsenic sulfur and iron under the influence of organic matter (sulfate reducing conditions) is complex. Both the soluble arsenic-sulfur species and the arsenic solid phases that are formed were not known. However, experience in the remediation of groundwater contaminations by acid mine water had shown that arsenic can be immobilized under sulfate reducing conditions by iron-bearing reaction walls (Blowes & Ptacek 1996; Köber et al. 2005; Wilopo et al. 2008).
