Forensic Analysis and Sorbent Collection Methods

MSRAS Soil Gas Sampling WorkshopIndianapolis, IN

August 21-22, 2006

Gina Plantz

NewFields Environmental Forensics Practice, LLCgplantz@newfields.com

781-264-4950

Why use Forensics?

Ability to differentiate between sources of contaminationBTEX (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

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 20-50 pptv

•Ability to differentiate background from soil gas impacts

•Ability to detect trace levels of target compounds in presence of high concentration samples

Ertel Sample Collected from SS3D

•Analysis by EPA TO-15:–TCE @ 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

Ertel Sample Collected from SS3D

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TIC: R10032.D\DATASIM.MS

EPA TO-15

Forensic TO-15

TCE, 42 ppbv on column (55,000 total)

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TIC: R10061.D\datasim.ms

TCEBenzene, 2.2 ppbv on column (22 total)

Ertel Sample Collected from P6

•Analysis by EPA TO-15:–PCE @ 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

Ertel Sample Collected from P6

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TIC: R10033.D\DATASIM.MS

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TIC: R10058.D\datasim.ms

PCE, 53 ppbv on column (11,000 total)

EPA TO-15

Forensic TO-15

PCE

C4

C5

C6

C7

T

N124TMB

MPX

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.))

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

Sample Volume needed to meet 10-6 Shallow Soil Gas Screening Criteria

(OSWER Draft VI Guidance, 2002)SAMPLE VOLUME TO ACHIEVE OSWER GUIDANCE TABLE 2C SUB-SLAB TARGET CONCENTRATION

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Acena

phth

ene

Aceto

nitril

e

Benza

ldehy

de

Benzo

(b)fl

uora

nthe

ne

Bis(2-

chlor

oeth

yl)et

her

Chloro

phen

ol; 2

-

Chrys

ene

Fluo

rene

HCH; alp

ha- (

alph

a-BHC)

HCH; gam

ma-

(Li

ndan

e)

Hexac

hloro

cyclo

pent

adien

e

Hexac

hloro

etha

ne

Met

hacr

ylonit

rile

Met

hylna

phth

alen

e; 2

-

Nitrob

enze

ne

Nitrop

ropa

ne; 2

-

Nitrot

oluen

e;o-

Propy

lben

zene

; n-

Pyren

e

Sa

mp

le V

olu

me

(L

)

Slide courtesy of Severn Trent Laboratories

EPA TO-17Will 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

www.skcinc.com

www.sensidyne.com

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

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