Permeable Reactive Barriers (Proceedings of the International Symposium held at Belfast, Northern Ireland, March 2004). IAHS Publ. 298, 2005, 3-11.

1 Institute of Geosciences, University of Kiel, Ohlshausenstrasse 40,D-24118 Kiel, Germany

2 Department of Chemistry, University of Rome "La Sapienza", P.le Aldo Moro 5, I-00185 Rome, Italy

Abstract Fe⁰ has been previously shown to have potential for the removal of arsenic (As) from groundwater. Several sets of coupled experimental columns were run to investigate if As can be removed together with 1,2-DCE(cis) by Fe⁰-PRBs under different geochemical situations. As was removed with half-life times of approximately 2 h to concentrations of mostly below 10 µg l^-1 throughout the whole experiment under oxidic and reduced conditions. In contrast, 1,2-DCE(cis) dechlorination decreased with time, independently of the input redox conditions. The reason for the inhibited dechlorination is assumed to be passivation by Si adsorption following the onset of microbial sulphide reduction (MSR). Precipitation of arsenic sulphides and sorption of As to iron sulphides seems to stabilize As removal.

Key words 1,2-DCE(cis); arsenic; inhibition; long-term performance; microbial sulphide reduction; permeable reactive barrier; XAS; VOC