contaminated_site_measurements
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GasmetTM FTIR application note Contaminated site measurements KEY WORDS • Remediation of contaminated sites • Volatile organic compounds (VOCs) • Chlorinated compounds OVERVIEW Remediation and cleaning of contaminated sites is necessary when old industrial areas are converted to residential or commercial use. Aromatic and Chlorinated volatile organic compounds (VOCs) and other toxic substances may have leaked into the ground, necessitating measurements in order to determine the identity of pollutant, extent of spill and the pollutant concentration in the ground. The Gasmet DX4040 portable multi-gas analyser can achieve this by sampling the headspace of boreholes drilled into the ground. As FTIR (Fourier Transform Infrared) gas analysis is non-destructive, the sample can be extracted from the borehole, circulated through the analyser, and returned to the hole so that equilibrium is formed between the ground and the air in the borehole. Simultaneous analysis of up to 25 gases with subppm detection limits and high accuracy make the DX4040 an ideal tool for this purpose. Additionally, when a gas that is not included in the 25 Figure 1 Contaminated ground site being measured Copyright Gasmet Technologies Oy 2012 PRODUCTS • DX4040 Portable FTIR Gas Analyzer component list is present, its infrared spectrum can be compared against a larger library with a laptop computer and the unknown gas can be identified. Alternatively, if only a survey measurement for the presence of certain pollutants is required, the analyser can be operated without returning the sample gas to the borehole. In this way the operator can cover a large number of test points in a short period of time. The measurements are continuous, real time results with time weighted averaging. Typical averaging periods are from 5 to 60 seconds and the instrument takes approximately two minutes to reach 90% of the target concentration (T90 < 120 seconds). The DX4040 gas analyzer results are displayed on a PDA via bluetooth wireless communication. No span calibrations are required and the DX4040 is fully operational after a simple zero in clean ambient air. Figure 2 Gasmet DX4040 portable gas anal

TYPICAL GASES MEASURED AT CONTAMINATED REMEDIATION SITES Compound name Benzene Toluene p-Xylene Trichloroethylene (TCE) 1,1-Dichloroethylene cis-Dichloroethylene Perchloroethylene (PCE) Dichloromethane (DCM) Chloroform Methane Ethyl Chloride * Limit of detection is calculated as 3 x standard deviation of baseline noise, 60 second averaging time. Other ranges and compounds available; please contact Gasmet Technologies for further details Figure 3 Sample spectrum from borehole and reference spectra for expected gases. Methane and cis*Dichloroethylene are present, whereas...