Steve Jones, Ph.D.Jones Environmental, Inc.Santa Fe Springs, CA

Speciation of C5 – C12 Aliphatic Hydrocarbons and C6 – C12 Aromatic Hydrocarbons Using EPA 8260B for

Vapor Intrusion Risk Assessment Evaluations

Outline• Regulations• TPH Toxicity Criteria – MADEP/DTSC• GC/MS Advantages• Hydrocarbon Types• Mass Spec Interpretation of Hydrocarbons• Spectrum Plot of Different Hydrocarbons• Oxidative Degradation of Hydrocarbons• Compounds in TPH Results that are NOT Hydrocarbons• Conclusions

Regulations• MDEQ – “Method for the Determination of Air-Phase

Petroleum Hydrocarbons (APH)”, Massachusetts Department of Environmental Protection, Office of Research and Standards, Bureau of Waste Site Cleanup. December 2009, Table 7, page 33.

• DTSC – “Evaluating Health Risk from TPH”, June 16, 2009, section 5.0, page 8.

• DTSC – “Preliminary Endangerment Assessment Guidance Manual, January 1994 (Interim Final – Revised October 2013), section 2.5.2.3 5), Table 2-6 “TPH Toxicity Criteria”, page 45.

Regulations – Table 2-6 TPH Toxicity Criteria

# 0.03 mg/kg/day may be used instead of 0.004 if naphthalenes and methylnaphthalenes have been analyzed and evaluated individually

^ Value is for C9 – C32

* Not developed due to low volatility of the COPCs in this hydrocarbon range. Although inhalation exposure to C17+TPH may occur via TPH bound to airborne dust HERD does not recommend performing a quantitative evaluation of inhalation exposure for C17+ not be performed because of the significant uncertainty involved.

Regulations – Risk Assessment• DTSC/HERD recommends the use of the following six

groups of hydrocarbons for which chemical surrogates for toxicity have been selected.• C5 – C8 (aliphatics)• C6 – C8 (aromatics)• C9 – C18 (aliphatics – Reported as C9+)• C9 – C16 (aromatics – Reported as C9+)• C19+ (aromatics)• C17+ (aromatics)

• If the analytical method used during the site investigation did not provide speciation into aromatics and aliphatics then an assumption of a composition of 50% aromatics and 50% aliphaticscan be made for most sites.

GC/MS Advantages• Identification of each component – Fingerprint Technique

• No second column confirmations required

• Identification of unknowns – NIST Library searches

• Selecting individual compounds

• Simplified chromatographic patterns

• Screening techniques for organic compounds

Hydrocarbon Types• Aliphatic/Alkanes/Saturated Hydrocarbons

• Olefins/Alkenes/Unsaturated Hydrocarbons

• Aromatics/Benzene Ring Compounds

• Naphthenic/Cyclic HydrocarbonsPyrene Benzene

Cyclohexane

Mass Spec Interpretation of Hydrocarbonsn-Hexane

H = 1amu C = 12 amu O = 16 amu N = 14 amu F = 19 amu Cl = 35 & 37 amuS = 32 amu Br = 79 & 81 amu

C4 C5 C6

C7 C8 C9

Oxidative Degradation of Hydrocarbons• R-CH2-CH3 : Alkane

• R-CH2-CH2-OH : Primary Alcohol

• R-CHOH-CH3 : Secondary Alcohol

• R-CH2-CHO : Aldehyde

• R-CO-CH3 : Ketone

• R-CH2COOH : Organic Acid

Substantially Weathered Hydrocarbon Pattern

Conclusions• A simple, easy to use way to calculate different

hydrocarbon compounds using already existing EPA 8260B methodology.

• The same methodology can be used to eliminate/identify degraded hydrocarbons, natural products, and heteroatom compounds in soil gas samples.

Thank you!