Vapor Intrusion In Buildings

1. Vapor Intrusion In Buildings Lauren Sauer Chem 4101 December 9, 2011 http://www.skcinc.com/VaporIntrusion/default.asp

2. Importance: Trichloroethylene (TCE) and tetrachloroethylene (PCE) are resistant to breakdown by biological processes, which causes them to accumulate in soil and groundwater. These chlorinated hydrocarbons are released into the air as vapors and find their way into the indoor air of overlying homes and buildings. Relatively low concentrations of these volatile compounds can cause major indoor problems and are a health risk. These compounds need to be able to be detected in the vapor form as evidence for land to be put on the Superfund National Priority List for bioremediation. By identifying the locations of these vapors, it will be easier to find their source, and investigate how the compounds are being disposed of. Hypothesis: Trichloroethylene and Tetrachloroethylene are a source of vapor intrusion because of their introduction into the environment by their improper disposal at industrial plants, whoutilize them for dry cleaning products, metal degreasing, pharmaceutical production, weapons manufacturing, and pesticide formation.

3. Analytes Trichloroethylene (TCE) MW: 131.39 g/mol Bpt: 86.7 °C Tetrachloroethylene (PCE) MW: 165.83 g/mol Bpt: 121 °C Limit of Detection: 1.5 ppb Concentrations of TCE and PCE found in a known contaminated fieldwere found to be in the 0.01–10 ppb range. If TCE levels meet or exceed 1.6 ppb, land may be considered for remediation.

4. Experimental Design • Air samples should be taken in buildings with suspected TCE or PCE contamination. • If samples come back positive, soil around surrounding possible contamination sites should be taken in order to pin point the pollution source. At this point land tested positive for TCE or PCE can be recognized and the locations sent to the EPA for possible remediation. • Once point source is indentified, TCE and PCEdisposal methods can be analyzed for possible faults.

5. Possible Analytical Techniques

6. GC-MS

7. Sample Collection and Preparation for GC-MS Indoor air samples: Samples can be collected using the Anderson Volatile Organic Compound Canister Sampler (VOCCS). Canisters are cleaned and evacuated with 30’’ Hg vacuum. An air sample is drawn into the canisters with a Viton Diaphragm pump. The flow rate is controlled by a mass flow controller. A programmable digital timer can be used to activate the pumps. Typical sample collection time is from 10 to 24 hours. Outdoor air samples: Ampoules containing suspected contaminated soil are sealed and allowed to sit for at least one week to allow vapors to accumulate. An ampoule is placed into a VOA vial. Once the VOA is capped, it is shaken in order to break the ampoule and allow the soil to disperse. The vial is then allowed to rest for 20 minutes in order for the soil to settle. The VOA is then opened and the gas collected.

8. Gas Chromatography • Possible instrument: Agilent 5975E GC/MSD The 7000 series has a triple quadruple system. This would increase resolution,but the instrument is also significantly more expensive. • Supelco Equity-5 capillary column (30 m long, 0.25 mm inner diameter, 0.25μm film) • Helium carrier gas with a constant column head pressure of 60 kPa • Temperature is programmed to 40 °C for 7 minutes, then ramped to 130 at 30 °C/min and held for one minute.

9. Mass Spectrometry • QuadripoleMS has greater resolution than a TOF instrument, but is more cost effective than a triple quad instrument. • Flame ionization is ideal because of its sensitivity to hydrocarbons and reproducibility.

10. Mass Spectrum Trichloroethylene Mass of molecular ion: 130 Tetrachloroethylene Mass of molecular ion: 164

11. Conclusion • TCE and PCE can be measured in the ppb with proper separation from other volatile organic compounds by GC-MS. • By identifying vapor intrusion locations, soil from local industrial manufacturers who use TCE and PCE can also be tested in order to find the origin of the analytes.It is then possible to study the methods employed to dispose of them. • Possible future studies: • Creating a calibration curve that correlates TCE and PCE in soil and in the air above the soil. By observing how the vapors are released into the air, finding their source of origin could be simplified. • Finding which factors increase the rate of TCE and PCE being released into the air from contaminated soil.

12. References • U.S. Public Health Service, U.S. Department of Health and Human Services, Atlanta, GA. Agency for Toxic Substances and Disease Registry. Toxicological Profile for Tetrachloroethylene (Update).1997. • Hanson, D. J; EPA moves on vapor intrusion. Chemical and Engineering News, 2011, 89, 32-34. • Air and Waste Management Associtation; Field Method Comparison between Passive Air Samplers and Continuous Monitors for VOCs and NO2 in El Paso, Texas. J. Air and Waste Manage. Assoc.2004, 54, 307- 319. • Http://orgchem.colorado.edu/hndbksupport/ms/inletsys.html • Van Winkle, Michael R.; Scheff, Peter A.; Volatile Organic Compounds, Polycyclic Aromatic Hydrocarbons and Elements in the Air of Ten Urban Homes. Indoor air, 2001, 11, 49-64. • Kim, Sun Kyu; Chang, Hungwei; Zellers, Edward T.; Microfabricated Gas Chromatograph for the Selective Determination of Trichloroethylene Vapor at Sub-Parts-Per-Billion Concentrations in Complex Mixture. Anal. Chem. 2011, 83, 7198-7206. • Aeppli, Christoph; Holmstrand, Henry; Andersson, Per; Gustafsson, Orjan. Direct Compound-Specific Stable Chlorine Isotope Analysis of Organic Compounds with Quadrupole GC/MS Using Standard Isotope Bracketing. Anal. Chem. 2010, 82, 420-426. • Bernstein, Anat; Shouakar-Stash, Orfan; Ebert, Karin; Laskov, Christine; Hunkeler, Daniel. Compound-Specific Chloring Isotope Analysis: A Comparison of Gas Chromatography/ Isotope Ratio Mass Spectrometry and Gas Chromatography/Quadripole Mass Spectrometry Methods in an Interlaboratory Study. Anal Chem. 2011, 83, 7624-7634. • Http://www.chem.com/catalogs/ (accessed Oct 24, 2011)