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TOTAL ORGANIC CARBON DETERMINATIONS IN NATURAL AND CONTAMINATED AQUIFER MATERIALS
Citation:
Powell, R. TOTAL ORGANIC CARBON DETERMINATIONS IN NATURAL AND CONTAMINATED AQUIFER MATERIALS. U.S. Environmental Protection Agency, Washington, D.C., EPA/600/D-90/159 (NTIS PB91129205), 1990.
Description:
Quantifying the total organic carbon (TOC) content of soils and aquifer materials is essential for understanding subsurface chemistry during environmental site characterization. ontaminant fate and transport, microbial ecology, and effective treatment methodology are all influenced by the quantity of both naturally occurring and anthropogenic organic carbon present. nfortunately, the determination both in natural and contaminated settings is complicated by many factors. hese include the system chemistry and heterogeneity, sampling methodology, and analytical limitations. ccurate determination becomes increasingly difficult as th total carbon (TC:TOC ratio increases, due to carbonate components of the TC and the difficulty of removing them with affecting the TOC. nterlaboratory data shows variations of 39% between laboratories analyzing the same sample, even with appropriate pretreatment. urther errors occur, enhanced by the limited sample sizes used in most instruments, when widely dispersed or heterogeneously distributed carbon particles are present. dditional complexity is introduced when the sample is form the saturated zone and contaminated with volatile organic (VOCs). his is illustrated by data from the aviation gasoline and JP-4 jet field spills at the Traverse City Coast Guard Air Station bioremediation projects. arbonate removal is impossible in this case and requires a separate determination, doubling the TOC measurement inaccuracy. his, combined with volatile losses during handling and potential transport of unreacted volatile through the instrument, resulting in observed coefficients of variation of 52%, with values 73% lower than a gas chromatographic (GC) method. tandardizing TOC determinations of subsurface materials,from both the saturated and unsaturated zones, must be accomplished for consistent interlaboratory results. tandard reference aquifer materials, from both the saturated and unsaturated zones, must be accomplished for consistent interlaboratory results. tandard reference aquifer materials are necessary. ttempts to increase sample integrity, from filed collection to analysis, particularly with volatile contaminants present, are needed. n instrument design prototype that should be useful for water-saturated, volatile contaminated aquifer materials is presented. ooperation between filed investigators, analysts, and instrument manufacturers will be required to improve data quality and usefulness.
