FORENSIC TOOLS FOR
Petroleum
Hydrocarbon
Releases
Dawn Zemo – Zemo & Associates LLC
S
ubsurface releases of petroleum Forensic interpretations
hydrocarbons (crude oils and regarding petroleum
refined products) are one of the releases must also incorporate
refined products can have utility for
most frequent causes of groundwater impacts of environmental weathering
soil samples, but are not as useful for
contamination in the United States, (by evaporation, biodegradation, or
dissolved-phase groundwater plumes.
and the subject of billions of dollars solubilization) and impacts of changes
spent in investigation, remediation, in crude oil sources or refinery
Gas Chromatogram
and litigation. Forensics is frequently processes because these factors
applied to petroleum hydrocarbon greatly influence the composition Pattern Matching
releases because of factors related to: of the mixture. All of these sources This tool has been used for many
1) the chemical complexity of petroleum; decades for product-type identification.
of variability differentiate forensic
2) its weathering in the environment; Its foundation is high-resolution gas
investigations of petroleum from those
and 3) frequent commingling of plumes. chromatography, which separates
focused on discrete constituents such as
constituents within a sample based
Many forensic tools are available for trichloroethene, perchlorate, or nitrate.
primarily on boiling point. This
petroleum investigations; several have
Presently, the most commonly used forensic technique relies primarily on
been used for decades and others are now
forensic tools for petroleum releases matching the boiling range (carbon
more widely used due to improvements
are: 1) chromatogram pattern matching; range) and the pattern of the peaks
in laboratory analytical capabilities.
2) analyses of discrete constituents or or “humps” on the chromatogram of
The best tools to apply to a particular families of constituents; 3) analyses the unknown to known standards (see
case depend on the questions posed, of additives or blending agents; figure below). The boiling ranges and
so clarity about the ultimate objective 4) biomarkers; and 5) stable isotopes. general chromatographic character of
of the forensic work is important All of these tools have wide
from the start. For example, a focus acceptance in the forensics
on product identification or source community, and the peer-
attribution is usually quite different reviewed literature provides many
from age-dating the release. Crude examples of their application.
0 0
oil and refined products are complex 0 10 20
Time (min)
30 0 10 20
Time (min)
30
mixtures of hundreds to thousands of Because most petroleum Unleaded Gasoline Diesel Fuel #2
constituents that can have widely varying constituents have low effective
physio-chemical properties, and some solubilities in water, the
forensic tools are better suited to certain dissolved phase of crude oil
constituents than others. In addition, and most products are similar
the sample media, which may be pure and limited to relatively few 0
0 10 20 30
0
0 10 20 30
petroleum product, soil, dissolved- constituents. Therefore, many Time (min)
JP-4
Time (min)
JP-5
phase constituents in groundwater, or of the classic forensic tools that
Example chromatograms for four fuels. Vertical axis is the
vapors, also must be considered. were developed for crude oil or detector response.
26 • July/August 2007 • Southwest Hydrology
Petroleum
Hydrocarbon
Releases
Dawn Zemo – Zemo & Associates LLC
S
ubsurface releases of petroleum Forensic interpretations
hydrocarbons (crude oils and regarding petroleum
refined products) are one of the releases must also incorporate
refined products can have utility for
most frequent causes of groundwater impacts of environmental weathering
soil samples, but are not as useful for
contamination in the United States, (by evaporation, biodegradation, or
dissolved-phase groundwater plumes.
and the subject of billions of dollars solubilization) and impacts of changes
spent in investigation, remediation, in crude oil sources or refinery
Gas Chromatogram
and litigation. Forensics is frequently processes because these factors
applied to petroleum hydrocarbon greatly influence the composition Pattern Matching
releases because of factors related to: of the mixture. All of these sources This tool has been used for many
1) the chemical complexity of petroleum; decades for product-type identification.
of variability differentiate forensic
2) its weathering in the environment; Its foundation is high-resolution gas
investigations of petroleum from those
and 3) frequent commingling of plumes. chromatography, which separates
focused on discrete constituents such as
constituents within a sample based
Many forensic tools are available for trichloroethene, perchlorate, or nitrate.
primarily on boiling point. This
petroleum investigations; several have
Presently, the most commonly used forensic technique relies primarily on
been used for decades and others are now
forensic tools for petroleum releases matching the boiling range (carbon
more widely used due to improvements
are: 1) chromatogram pattern matching; range) and the pattern of the peaks
in laboratory analytical capabilities.
2) analyses of discrete constituents or or “humps” on the chromatogram of
The best tools to apply to a particular families of constituents; 3) analyses the unknown to known standards (see
case depend on the questions posed, of additives or blending agents; figure below). The boiling ranges and
so clarity about the ultimate objective 4) biomarkers; and 5) stable isotopes. general chromatographic character of
of the forensic work is important All of these tools have wide
from the start. For example, a focus acceptance in the forensics
on product identification or source community, and the peer-
attribution is usually quite different reviewed literature provides many
from age-dating the release. Crude examples of their application.
0 0
oil and refined products are complex 0 10 20
Time (min)
30 0 10 20
Time (min)
30
mixtures of hundreds to thousands of Because most petroleum Unleaded Gasoline Diesel Fuel #2
constituents that can have widely varying constituents have low effective
physio-chemical properties, and some solubilities in water, the
forensic tools are better suited to certain dissolved phase of crude oil
constituents than others. In addition, and most products are similar
the sample media, which may be pure and limited to relatively few 0
0 10 20 30
0
0 10 20 30
petroleum product, soil, dissolved- constituents. Therefore, many Time (min)
JP-4
Time (min)
JP-5
phase constituents in groundwater, or of the classic forensic tools that
Example chromatograms for four fuels. Vertical axis is the
vapors, also must be considered. were developed for crude oil or detector response.
26 • July/August 2007 • Southwest Hydrology
