Quantification of volatile organics in soil aging experiments using fourier transform infrared spectroscopy.
On-line Fourier transform infrared (FT-IR) spectroscopy was applied to monitor the concentration of halogenated volatile organic compounds in a sample-preparation process that simulates long-term, slow accumulation of contaminants in soils (i.e., aging). Artificial aging is conducted by circulating a supercritical fluid solution containing the contaminant(s) of interest through a packed soil column. Mid-infrared spectra of several volatile halocarbons were measured in supercritical Xe and CO(2) to evaluate possible interferences from the strong absorption of CO(2). Although some of the C-X bands were partially masked in supercritical CO(2), all of the compounds studied had distinct spectral features in the region 1400-700 cm(-1) and could be monitored in either solvent. Quantitative measurements of halogenated volatile organics in supercritical CO(2) were demonstrated with CCl(4). Excellent results were obtained over the range 7-280 mM. Representative artificial aging experiments were conducted on two test soils using CCl(4) as the contaminant. On-line (FT-IR) estimates of the aged soil concentrations were 1.3-4.4 times higher than off-line concentrations obtained by gas chromatography/mass spectrometry. The discrepancies were primarily ascribed to post-aging losses that occurred during depressurization and subsequent sample handling. FT-IR spectroscopy is shown to be a powerful tool for monitoring soil loading behavior and for developing artificial aging protocols.
Thompson
Christopher J
CJ
Pacific Northwest National Laboratory, P.O. Box 999, Richland, Washington 99352, USA. Chris.Thompson@pnl.gov
Riley
Robert G
RG
Amonette
James E
JE
Gassman
Paul L
PL
D002244:Carbon / Q000737:chemistry*; D002245:Carbon Dioxide; D002251:Carbon Tetrachloride / Q000737:chemistry; D004784:Environmental Monitoring / Q000295:instrumentation* / Q000379:methods*; D004785:Environmental Pollutants / Q000737:chemistry; D006846:Hydrocarbons, Halogenated / Q000737:chemistry; D016014:Linear Models; D011312:Pressure; D012987:Soil; D012997:Solvents; D017550:Spectroscopy, Fourier Transform Infrared / Q000295:instrumentation* / Q000379:methods*; D013696:Temperature; D013997:Time Factors
D004785:Environmental Pollutants; D006846:Hydrocarbons, Halogenated; D012987:Soil; D012997:Solvents; D002245:Carbon Dioxide; D002244:Carbon; D002251:Carbon Tetrachloride