Validation of Chlorine and Oxygen Isotope Ratio Analysis to Differentiate Perchlorate Sources and to Document Perchlorate Biodegradation

Abstract : Perchlorate in the envirotm1ent is derived from both synthetic and natural sources. Synthetic perchlorate salts have been widely used as oxidants by the military and aerospace industry. A variety of conm1ercial products also contain synthetic perchlorate. In addition to synthetic sources, natural perchlorate from both Chilean fetiilizers and indigenous sources represents a potentially large source of perchlorate in groundwater and drinking water in the U.S. The key objective of the isotopic techniques described-in this guidance manual is to provide evidence concerning the origin of perchlorate in soils and groundwater, and more specifically whether that perchlorate is synthetic or natural. Chlorine and oxygen isotopic analyses of perchlorate provide the primary direct approach whereby different sources of perchlorate can be distinguished from each other. Other isotopic. chemical and geochemical techniques that can be applied in conjunction with isotopic analyses of perchlorate to provide supporting data in forensic studies are also described.