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Vapor Intrusion In Buildings. Lauren Sauer Chem 4101 December 9, 2011. http:// www.skcinc.com/VaporIntrusion/default.asp. 1. Importance: Trichloroethylene (TCE) and tetrachloroethylene (PCE) R esistant to breakdown by biological processes A ccumulate in soil and groundwater

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vapor intrusion in buildings
Vapor Intrusion In Buildings

Lauren Sauer

Chem 4101

December 9, 2011

http://www.skcinc.com/VaporIntrusion/default.asp

slide2

1

Importance:

Trichloroethylene (TCE) and tetrachloroethylene (PCE)

  • Resistant to breakdown by biological processes
  • Accumulate in soil and groundwater
  • Known endocrine disruptors and possible carcinogens
  • Utilized for dry cleaning products, metal degreasing, pharmaceutical production, and weapons manufacturing.
  • Find their way into the indoor air of overlying homes and buildings.

Hypothesis: Trichloroethylene and Tetrachloroethylene become sources of vapor intrusion because of their introduction into the environment by improper disposal at industrial plants.

2

slide3

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 field were 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.

experimental design
Experimental Design
  • Air samples are taken in buildings with suspected TCE or PCE vapor intrusion.
  • Air above soil is tested at industrial plants (who utilize TCE and PCE) near buildings with vapor intrusion.
  • Once point source is thought to be indentified, TCE and PCE disposal methods can be analyzed for possible faults.
  • Control: Air in a building and above soil that is not near any industrial manufacturing sites who use TCE or PCE.
  • Analytical Standards:
  • Sigma-Aldrich 5 mL analytical standard TCE, for environmental analysis (Fluka)  catalogue number: T1115
  • Sigma-Aldrich 5 mL analytical standard PCE for  catalogue number T1023
slide7

Sample Collection and Preparation for GC-MS

Indoor air samples:

5

Air sample drawn into canister with Viton Diaphragm pump

Anderson Volatile Organic Compound Canister is evacuated with 30’’ Hg vacuum

Outdoor air samples:

6

Ampoule placed in VOA vial and shaken to break ampoule and allow soil to disperse

Vial rests for 20 minutes allowing soil to settle

Ampoule filled with soil and hermetically sealed

VOA is opened and gas collected

Vapor accumulates for 2 weeks

gas chromatography
Gas Chromatography
  • Agilent 5975E GC/MS (q-MS)
  • The 7000 series has a triple quadruple system.
  • 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.

http://www.chem.agilent.com/en-US/Products/Instruments/ms/gc-ms/systems/5975egcmsd/pages/default.aspx

mass spectrometry
Mass Spectrometry

10

  • 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.
slide10

Mass Spectrum

Trichloroethylene

Mass of molecular ion: 130

Tetrachloroethylene

Mass of molecular ion: 164

slide11

Conclusion

  • With a 1.5 ppb LOD TCE and PCE should be able to be measured 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 be tested 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 factors that increase the rate of TCE and PCE released into the air from contaminated soil.
references
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)
  • http://www.chm.bris.ac.uk/ms/theory/quad-massspec.html / (acessed Dec 6, 2011)