Bacterial release of arsenic ions and organoarsenic compounds from soil contaminated by chemical warfare agents

The objective of this paper was to investigate possible participation of microorganisms in the release of soluble arsenical compounds from organoarsenic warfare agents in contaminated soil. A number of bacterial strains were isolated with high resistance against As3+ and As5+ ions which are able to degrade the water insoluble compounds triphenylarsine (TP) and triphenylarsineoxide (TPO). These strains belong to different genera of bacteria. Release of arsenic ions and soluble organoarsenic compounds from soil by the activity of autochthonic soil bacteria and a mixture of the isolated pure cultures was demonstrated by percolation experiments with undisturbed soil samples (core drills) from the contaminated site. This release increased after addition of nutrients (mineral nitrogen and phosphorus, sodium acetate and ethanol) and is nearly independent of the percolation temperature (5 degrees C and 22 degrees C). These results show that bacteria play an important role in the release of arsenical compounds from organoarsenic warfare agent contaminated soil. This release is limited by shortage of water and, above all, of nutrients for the microorganisms in the sandy forest soil. These results are important both for the management and security and possibly for bioremediation of military waste sites containing similar contaminations. Furthermore, this is the first report on bacterial degradation of organoarsenic warfare compounds.