Reinhard Bachofen, Linda Birch, Thomas G. Chasteen(*), Peter Ferloni, Isabelle Flynn, Gaudenz Jud, and Harald Tahedl

Institute for Plant Biology and Microbiology, University of Z¸rich, Zollikerstrasse 107, CH-8008 Z¸rich, Switzerland and (*) Department of Chemistry, Sam Houston State University, Huntsville, Texas USA

Proceedings of the Third International Symposium on In Situ and On-Site Bioreclamation, San Diego, CA, USA, April 1995, published in "Bioremediation of Inorganics", R. E. Hinchee, J. L. Means and D. R. Burris eds.; Battelle Press, Columbus, OH, 1995; 103-108.

Abstract

Soil polluted by arsenium compounds (total As up to 2% of d.w.) by a tanning company 50 years ago was leached in percolation columns under various environmental conditions. Endogenous microorganisms slowly solubilized and partially volatilized the soil-bound As.

Methanobacterium thermoautotrophicm is resistant towards arsenate and a concentration of 100 micromolar has no effect on growth and methanogensis. Chemostat cultures (dilution ratio 0.25/hr) in a bioreactor coupled to a mass spectrometer fed with 50 micromolar arsenate transformed As depending on the phosphate concentration to methylated arsines with a yield of more than 30%.

Many phototrophic bacteria are highly resistant towards arsenate and other oxyanions up to 30 micromolar and arsenate reduction and methylation by this group of microorganisms is under investigation.

Total As was determined by AAS and ICP-AES. For the analysis of educts and products in the mixed culture from soil as well as the pure culture of M. thermoautotrophicm, ion chromatographic separation of the charged forms (arsenate, arsenite, monomethyl arsinic acid and dimethylarsinic acid) and gas chromatographic separation (capillary GC with gas phase chemiluminescence detection) of the volatile forms (arsine, mono-, di-, and trimethyl arsine) have been developed.

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