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| Resource Library > chemistry > Forensic Chemistry |
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What is Forensic Chemistry (FC)?
FC is an investigation approach that uses multiple lines of evidence to reduce decision uncertainty when conventional analytical techniques do not adequately "tell the whole story." FC can be applied to remediation projects involving risks associated with contaminant loading, contaminant distribution, and potential sources of contamination.
Historically, site investigation and characterization data  />were generated using a single line of evidence based on "standard" analytical methods and was used to address all needs of the project-contaminant characterization, fate and transport, remedial selection and design, and human and ecological risk assessment.
This single line of evidence is often insufficient to reduce decision uncertainty to a tolerable level. FC often uses a combination of standard and more sophisticated or emerging technologies to analyze samples and provide information that single lines of evidence methods cannot provide.
Developing Lines of Evidence for Contamination
When developing additional lines of evidence, managers often look to strategic sampling design and collection techniques and newer, more "sophisticated" analytical methods to report and correlate data. Common additional lines of evidence include multiple sampling from different locations or depths, analysis of chemical species in addition to the main contaminants of concern, and evaluating contaminant ratios in different matrices.
 For example, the investigative tool called "chemical fingerprinting" looks for recurring patterns (e.g., chromatographic patterns that show relative concentrations of components), and can be used to identify sources of contaminants such as fuel-related petroleum products, PAHs, and PCBs.
To evaluate the progress of contaminant degradation processes, DNA testing and chemical fingerprinting add critical information after data on concentrations of target analytes are obtained using conventional analytical methods.
Using FC to Address Questions of Remedy Selection and Design
FC can be used to provide additional lines of evidence to more sufficiently establish site conditions prior to evaluating remedial designs. Additional data obtained from non-traditional investigation and analytical methods can enhance the results for the following remedial design processes:
- Identification and delineation of contaminant source(s)
- Environmental and human health risk assessments to determine minimum cleanup goals
- Natural degradation or attenuation mechanisms
- Contaminant transport pathways
- An alternative analysis of remediation technologies capable of reaching those goals
- An examination of the associated capital and O&M costs
Selecting the FC Approach
After a decision is made to employ FC, selecting the type or combination of FC approaches should be based on:
- Tolerable level of uncertainty desired
- High profile of the project site/decision
- Cost
- Schedule
- Accessibility of sampling locations
Sampling design and collection techniques can be critical components of an FC approach. For example, it may be necessary to collect samples outside the previously defined project site or area when establishing sources of contamination. This is especially true if there are several potential sources of contamination. Sampling time and frequency may be adjusted to reduce the effect of daytime operations or ambient conditions to the relative composition of contaminant vapor.
Newer or innovative analytical methods usually lack the same level of quality control that standard methods have. This becomes an important issue when there is a potential for litigation. Typical FC analytical methods involve the examination of ratios of constituents found in representative samples. Methods can involve radioisotope-to-stable isotope ratios as in the case of carbon dating, where the ratio of stable carbon-12 to radioactive carbon-14 is examined to determine when the assimilation of carbon into a piece of wood ceased, or it can involve ratios of stable isotopes to help determine the source of contamination.
Carbon Dating
Common FC Applications
- Biomarkers to identify or perform age-dating of chemical compounds/mixtures
- Radioisotope tracer analysis for fate and transport modeling of chemicals in groundwater
- Radioisotope dating for weathering of chemical mixtures
- Light/electron microscopy for determining the source of contaminated particulates
- Stable isotope analysis to determine the source of petroleum, oil, and lubricants (POL) or tar products
- Thin layer chromatography (TLC) for visually discerning gasoline/diesel grades
- Fingerprinting of complex products, such as petroleum fuels which, with biomarker determination, enables. determination of the source of a spill
- Evaluation of mixed plumes of the same organic contaminant based on isotopic fingerprints
- Contaminant loading, contaminant distribution, and potential sources of contamination
- Examination of DNA using rapid 16S rRNA gene-based detection methods for giving insight into microbiological populations present at sites contaminated with chlorinated hydrocarbons
What Support Can AFCEE/TDV Chemistry Provide?
Site managers and other stakeholders may be unfamiliar with FC methods for their remediation projects. AFCEE/TDV Chemistry can help alleviate this problem by offering technical support in:
- Evaluating the feasibility of using FC tools to reduce site uncertainty
- Project planning
- Selecting and implementing the right FC approach and interpreting the results
- Selecting the right team (which may involve contracting outside vendors of services and equipment)
- Using the results to delineate (in three dimensions) contaminant distributions, developing a CSM, and arriving at other remedy decisions
- Providing periodic training to Air Force project managers, technical staff, and AFCEE contractors to discuss FC tools and actual examples of the application of these tools to reduce site uncertainty and decision risk and improve remediation decisions
AFCEE/TDV Chemistry is your experienced partner, not only helping resolve issues with FC solutions, but providing support every step of the way to site closure.
Forensic Chemistry Tools and Resources
- Characterization and Monitoring Technology Tools--Problem Solver
- Field-Based Methods Available for Specific Classes of Environmental Contaminants
- Naval Facilities Engineering Command, NAVFAC, TechData Sheet, TDS-2091-ENV, December 2002.
- Jenkins, T. F., et al., 2005, Representative sampling for energetic compounds at military training ranges, Environmental Forensics, 6: 45-55.
- PCBs (Polychlorinated Biphenyls) in New York's Hudson River, Where Does the Buck Stop?
- Philip, R. P., et al., Monitored natural attenuation forum: The use of carbon isotope analysis at MNA sites, Remediation Journal, 17:3, 127-137.
- Löffler, F. E., et al., 16S rRNA Gene-Based Detection of Tetrachloroethene-Dechlorinating Desulfuromonas and Dehalococcoides Species, Applied and Environmental Microbiology, 66:4, 1369-1374, April 2000.
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