Assessing environmental contamination from a pentachlorophenol fire: screening soils for octachlorodibenzo- [formula omitted]-dioxin

Abstract

Evaluation of environmental contamination caused by pentachlorophenol (PCP) fires is extremely costly and time consuming because elaborate measurements of polychlorinated dibenzodioxin and furan (PCDD/F) isomers are required. Large geographic areas may potentially be affected greatly increasing the number of samples required for adequate investigation. Our laboratory has developed a rapid gas chromatography procedure for measurement of soil-bound octachlorodibenzo- p -dioxin (OCDD), a probe for PCP combustion products. Congener profile analyses of PCP combustion samples in our laboratory and others have revealed that OCDD is the principal PCDD/F product and, thus, a useful marker for these substances. For the screening procedure, composited soil samples are sieved and Soxhlet extracted with hexane. Quantitative analysis of OCDD in soil extracts is accomplished by capillary gas-liquid chromatography (GLC) using on- column injection and a 63Ni electron capture detector. Recoveries were >99% (at 20 ug/kg) and, without supplemental sample cleanup, the method detection limit was 6 ug/kg, adequate for detection of OCDD above expected background levels. OCDD levels determined by this method agreed with those measured by gas chromatography-mass spectrometry (GC-MS). The OCDD screening procedure was used to investigate contamination from a recent industrial fire in northern California that consumed an estimated 4,500 kg of PCP and was predicted to impact an area of about 2,000 km 2. For this incident a weighted, stratified sampling scheme was used to locate sampling points in communities in the path of the plume. Environmental sampling was stratified on ground level exposure concentration (or deposition) contours predicted by atmospheric dispersion modeling conducted by Systems Applications Inc. (San Rafael, CA). The number of samples collected in each contour was determined by the predicted degree of deposition as well as population. The combined application of soil screening for OCDD and sampling based on human exposure potential provides a rapid means for evaluating PCDD/F contamination caused by PCP fires.