15 - Dehalogenation of environmental contaminants in the hydrologic system by sulfur nucleophiles

Jack E. Barbash, jbarbash@usgs.gov, U.S. Geological Survey, Tacoma, Washington 98402, United States

One mechanism by which environmental contaminants may undergo dehalogenation in the hydrologic system is through halogen displacement by naturally occurring nucleophiles. Some of the most powerful among these are sulfur nucleophiles, especially bisulfide, polysulfides, thiosulfate and sulfite—all of which are frequently encountered in oxygen-deficient natural waters. Extensive research over the past quarter century has examined these reactions for over 30 contaminants, including insecticides, fumigants, herbicides and pesticide adjuvants. These investigations provide a wealth of information about the effects of nucleophile structure, substrate structure, mineral surfaces, temperature, soil moisture and experimental methods on reaction rates and products. Another sulfur nucleophile responsible for some of these reactions is reduced glutathione, a co-enzyme employed by soil microorganisms for several purposes, including detoxifying halogenated contaminants. When it involves chloroacetanilide herbicides, this reaction produces sulfonic and oxanilic acid metabolites that have been detected in natural waters in many agricultural areas across the United States.

Sunday, March 25, 2012 10:35 AM
Special Symposium in Honor of Martin Reinhard (08:00 AM - 12:15 PM)
Location: Hilton San Diego Bayfront
Room: Cobalt 500