Laserfiche WebLink
a� <br /> to <br /> Prior to sampling and analysis, the specific chemical components of concern at the site <br /> should be identified. These components commonly consist of the VOCs and SVOCs that <br /> have been identified as chemicals of concern (COCs) at the site. In addition, some <br /> regulatory agencies have specified which COCs must be included in the list of analytes. <br /> The tracer compound (isopropanol) should also be included. The analytical method used <br /> should be capable of quantifying these components at a concentration such that the <br /> subsurface vapor to indoor air exposure pathway can be adequately evaluated. Indoor air <br /> target levels for COCs can be used to identify the necessary analytical detection limits for <br /> soil vapor samples. Confer with the laboratory and applicable guidance to ensure that the <br /> necessary detection limits are met. <br /> A. VOCs/SVOCs <br /> Gas chromatography/mass spectrometer (GC/MS) methods are recommended for all <br /> VOC and SVOC analyses. Method TO-15 is highly recommended. Naphthalene must <br /> be analyzed, using TO-15, but the laboratory must be notified of this request prior to <br /> ordering the Summa®canisters from the laboratory. <br /> B. Fixed gases <br /> Method ASTM 1946, a gas chromatography/thermal conductivity detector (GC/TCD) <br /> method, is recommended for analysis of fixed gases, including 02, CO2, N2. For CH4, <br /> ASTM 1946 can also be used,with a flame ionization detector(FID) in place of a TCD. <br /> V. Data reporting <br /> Soil vapor concentrations are reported in units of ug/L, ug/m3, ppmv, and ppb . Unlike <br /> concentration units for groundwater, these units are not directly interchangeable. The <br /> molecular weight of the compound in question is a factor in the conversion from units of <br /> mass per unit volume to parts per million or parts per billion. The H&P Mobile <br /> Geochemistry website has a useful conversion spreadsheet: <br /> h=://www.handpmg.com/ <br /> Data are usually reported in table format, which is adequate for understanding and <br /> interpreting soil vapor concentrations over time and space. However, it is often useful to <br /> plot time series graphs of soil vapor concentrations to visualize changes in concentration <br /> over time, and depth profiles for multi-level soil vapor sampling probes in order to <br /> visualize changes in VOC concentrations and respiration/fixed gases over a given depth <br /> interval. Plotting data in visual formats often enhances the message that the text is <br /> providing. <br /> ETC Soil Vapor Sampling Technical Toolkit 23 <br /> Version 1.4, September 7,2005 <br />