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Forensic Analysis and Sorbent Collection Methods MSRAS Soil Gas Sampling Workshop Indianapolis, IN August 21-22, 2006 Gina Plantz NewFields Environmental.

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Presentation on theme: "Forensic Analysis and Sorbent Collection Methods MSRAS Soil Gas Sampling Workshop Indianapolis, IN August 21-22, 2006 Gina Plantz NewFields Environmental."— Presentation transcript:

1 Forensic Analysis and Sorbent Collection Methods MSRAS Soil Gas Sampling Workshop Indianapolis, IN August 21-22, 2006 Gina Plantz NewFields Environmental Forensics Practice, LLC

2 Why use Forensics?  Ability to differentiate between sources of contamination  BTEX (benzene, toluene, ethyl benzene and xylenes) compounds are commonly used to determine the hydrocarbon source(s) - BTEX is present in many different hydrocarbon sources and more information is needed for definitive chemical fingerprinting  Ability to differentiate VI impacts from background sources  Common practices to deal with discerning background: - Building survey and product inventory - Using indicator compounds detected by standard methodology (e.g. Benzene, MTBE, isooctane, isopentane for gasoline constituents) - Compound ratio analysis of compounds detected by standard methodology between sub-slab and IA

3 Forensic Approach Air method developed to “fingerprint” HC sources −Extended analyte list specific to hydrocarbons (93 compounds; PIANO, Thiophenes, Fuel Additives) −Analysis by GC/MS/FID −MS is run in simultaneous full SCAN and SIM modes −Reporting limits are pptv Ability to differentiate background from soil gas impacts Ability to detect trace levels of target compounds in presence of high concentration samples

4 Ertel Sample Collected from SS3D Analysis by EPA TO-15: – 55,000 ppbv – Large dilution needed for analysis, leading to majority of Non-detects for other targets Analysis by Forensic TO-15: – Ability to analyze sample without dilution leading to sub ppbv RLs for HCs

5 Ertel Sample Collected from SS3D EPA TO-15 Forensic TO-15 TCE, 42 ppbv on column (55,000 total) TCE Benzene, 2.2 ppbv on column (22 total)

6 Ertel Sample Collected from P6 Analysis by EPA TO-15: – 11,000 ppbv – Large dilution needed for analysis; few HCs detected leading and many non-detects for other targets Analysis by Forensic TO-15: – Ability to analyze sample without dilution leading to fingerprint pattern and sub ppbv RLs

7 Ertel Sample Collected from P6 PCE, 53 ppbv on column (11,000 total) EPA TO-15 Forensic TO-15 PCE C4 C5 C6 C7 T N 124TMB MPX

8 Why use sorbent media? Many states have compounds of concern which only focus specifically on VOCs 114 compounds in Table 2 of OSWER Guidance – VOCs, SVOCs, PCBs, Metals EPA TO-15 is only applicable for VOCs – Nothing heavier than Naphthalene Sorbent collection/analysis methods necessary for all SVOCs Sorbent types (PUF/XAD, Tenax, etc.))

9 What to look out for w/sorbent collection RLs are based upon the amount of sample volume collected Sample volumes needed to meet screening criteria may not be practical for many screening levels Sample duplicates are recommended at each point (TO-17) Sample breakthrough may occur at high flow rates or with high concentrations Recommended that tubes are placed in series when high concentration is expected Samples must be chilled <4 C

10 Sample Volume needed to meet Shallow Soil Gas Screening Criteria ( OSWER Draft VI Guidance, 2002) Slide courtesy of Severn Trent Laboratories

11 EPA TO-17  Will be demonstrated tomorrow  Samples collected on a sorbent tube with use of pump  Collect duplicate samples per sampling point  Analyzed by GC/MS  Holding time is 14 days from collection  Must be chilled <4 C

12 SVOC collection TO-13A: – PAHs and many other 8270 compounds; TO-4A: – Pesticides & PCBs (including congeners); PUF/XAD media for sample collection Modified versions: low flow pump Samples must be chilled <4 C Picture courtesy of GeoSyntec

13 Summary Forensic techniques for VI assessments are an emerging and powerful tool Forensic TO-15 showed the ability to report hydrocarbons to low ppbv RLs in presence of ppmv levels of chlorinated compounds Forensic TO-15 was able to fingerprint a potential hydrocarbon source where standard TO-15 was not able to detect many hydrocarbons due to elevated PCE and TCE Adsorptive media is needed for all SVOC collection Current methods for SVOC collection and analysis may not be practical for meeting action levels


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