HA6 Fluorinated Chemicals
Room 18A/B, Level 4
8:00 AM - 12:00 PM, Thursday, 13 November 2003
Chair: Hoke, Robert ,
Co-chair: Field, Jennifer ,
(529) Determination of fluorotelomer sulfonates in AFFF-contaminated groundwater: active ingredient or degradation product?
Schultz, M1, Barofsky, D1, Field, J2, 1 Dept. of Chemistry, Oregon State University, Corvallis, OR, USA2 Dept. of Environmental & Molecular Toxicology, Oregon State University, Corvallis, OR, USA
ABSTRACT- Fluorinated alkyl substances are used as active ingredients in aqueous-film-forming-foams (AFFF), which are used to fight hydrocarbon-fuel fires. Fluoroalkyl surfactants in AFFF products separate the flames from fuel surface or oxygen source and prevent re-ignition by suppression of the flammable vapors. The largest consumer of AFFF in the United States is the military and fire-training activities conducted at military bases has led to groundwater contamination both by unspent fuels and AFFF chemicals. The fluorinated surfactants present in the AFFF formulations can be produced either by electrochemical fluorination or from fluorotelomer-based chemistry. Electrochemically-fluorinated surfactants are perfluorinated, branched, and contain both odd and even numbers of carbons. In contrast, fluorotelomers have a C2H4 spacer, are linear, and have only even number of carbons in the fluorocarbon chain. Groundwater samples collected from Tyndall AFB, Wurtsmith AFB, and NAS Fallon were analyzed for fluorotelomer sulfonates by LC ESI MS/MS. Fluorotelomer sulfonates were observed and quantified in groundwater from Tyndall AFB and Wurtsmith AFB, including a site where a KC-135 airplane crashed. The crash site had a one-time application of AFFF in October 1988, which is in contrast to fire-training sites on military bases that typically receive repeated AFFF applications. To better understand the origin of fluorotelomer sulfonates, negative FAB/MS in low and high resolution mode was used to analyze a telomer-based AFFF product sold on contract to the military. A high molecular chemical class was observed in low resolution mode and then high mass accuracy measurements were used to identify the class as fluorotelomer-based alkylthiosulfonates. Precursor-ion detection and product-ion fragmentation patterns acquired by LC ESI MS/MS confirmed this identification. In addition, LC ESI MS/MS analyses of the AFFF product indicated trace levels of telomer sulfonates. LC ESI MS/MS analyses indicated that none of the parent fluorotelomer-based alkylthiosulfonates were present in groundwater at any of the military sites. It has yet to be determined if the telomer sulfonates are from the original AFFF applied or a degradation product of the fluorotelomer-based alkylthiosulfonates.
Key words: groundwater, fluorosurfactants, AFFF