Anaerobic Degradation of Vinyl Chloride in Aquifer Microcosms
- Theo H. M. Smitsac,
- Antoine Assalad,
- Daniel Hunkelerb and
- Christof Holliger *a
- a Ecole Polytechnique Fédérale de Lausanne (EPFL), School of Architecture, Civil and Environmental Engineering, Laboratory for Environmental Biotechnology, CH C3 425 (Bâtiment CH), Station 6, CH-1015 Lausanne, Switzerland
c current address: Agroscope Changins-Wädenswil (ACW), Division of Plant Protection, Schloss, Postfach, CH-8820 Wädenswil, Switzerland
d current address: David Livingstone Center for Sustainability, Univ. of Strathclyde, Colville Bldg., 50 Richmond St., Glasgow, G1 1XN, UK. Assigned to Associate Editor Jose-Julio Ortega-Calvo
b Centre of Hydrogeology, Univ. of Neuchâtel, Rue Emile-Argand 11, CH-2007 Neuchâtel, Switzerland
The anaerobic degradation potential at a chloroethene-contaminated site was investigated by operating two anoxic column aquifer microcosms enriched in iron(III). One column was fed with vinyl chloride (VC) only (column A) and one with VC and acetate (column B). In column A, after about 600 pore volume exchanges (PVEs), VC started to disappear and reached almost zero VC recovery in the effluent after 1000 PVEs. No formation of ethene was observed. In column B, effluent VC was almost always only a fraction of influent VC. Formation of ethene was observed after 800 PVEs and started to become an important degradation product after 1550 PVEs. However, ethene was never observed in stoichiometric amounts compared with disappeared VC. The average stable isotope enrichment factor for VC disappearance in column A was determined to be -4.3‰. In column B, the isotope enrichment factor shifted from -10.7 to -18.5‰ concurrent with an increase in ethene production. Batch microcosms inoculated with column material showed similar isotope enrichment factors as the column microcosms. These results indicated that two degradation processes occurred, one in column A and two in parallel in column B with increasing importance of reductive dechlorination with time. This study suggests that in addition to reductive dechlorination, other degradation processes such as anaerobic oxidation should be taken into account when evaluating natural attenuation of VC and that isotope analysis can help to differentiate between different pathways of VC removal.Please view the pdf by using the Full Text (PDF) link under 'View' to the left.
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