Standard Terminology used in Environmental Forensics with Special Emphasis on U.S. Regulations and Standards.
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Triassic Technology has developed two new methods to help investigators assess the time frame of environmental releases. An age-dating investigation is defined as a study to estimate or assess the time frame of a contaminant release to the environment. Many different techniques have been used by forensic scientists over the years. Each method has its own pluses and minuses and some may be used on particular sites, while others may not. To provide the investigator with some more options, we have developed two new methods.

The Tritium Method
Since the 1950s, oceanographers and hydrologists have used the presence of the radioisotope, tritium (3H), to assess the age of water. 3H is derived from the explosion of hydrogen bombs, which first began in 1953. The hydrogen bombs allowed 3H to be spread, essentially uniformly, throughout the planet’s atmosphere. Because historical 3H concentrations in the atmosphere are known and the radioactive decay rate of 3H (half-life) is constant, the time frame since a certain water sample left the atmosphere can be calculated. Because ground water is essentially all derived from precipitation, we can then calculate the age of ground waters within the earth. If that ground water is contaminated, say from a gasoline tank leak, the age of the leak will be, at a minimum, the age of the ground water. 

These techniques have been used by other researchers for several decades. However, Triassic Technology was the first to apply these techniques to contaminated sites and environmental age-dating. These age-dating techniques are discussed at length in the articles cited below:

Oudijk, G., 2007, Environmental Age Dating: The Use of Atmospheric Contaminants: In Introduction to Environmental Forensics, Second Edition, Murphy, B. L. and Morrison, R. D. (Eds.), CRC Press, Sand Diego, CA.
Oudijk, G., 2006, Use of atmospheric contaminants to estimate the minimum age of contaminant releases impacting ground water: Background and theory: Proceedings of the Gas Technology Institute Environmental Conference & Exhibition: Energy and the Environment: Lake Buena Vista, FL.
Oudijk, G. 2005, The use of atmospheric contaminants to estimate the minimum age of environmental releases impacting ground water: Environmental Forensics 6 (4): 345-354.
Oudijk, G. and Knaebel, C., 2004, Quand l’eau joue les mouchards:, Environnement Magazine, Dossier No 1627, p. 48. 
Oudijk, G., 2003, Estimating the minimum age of a chlorinated solvent plume in ground water with chlorofluorocarbon (CFC) and tritium methodologies - A case study: Environmental Forensics 4 (1): 81-88.
Oudijk, G. and Schmitt, L. M., 2000, Age dating of a chlorinated solvent plume in groundwater: in Tracers and Modelling in Hydrogeology, Proceedings of the TraM’2000 Conference, Liège, Belgium, IAHS Publ. No. 262, p. 255-261.

The Tree-Ring Method
Trees develop annual rings, which represent their growth during the growing season. Trees uptakes soil water, and sometimes ground water, through their root system and this water, known as sap, can travel up through the rings. The outermost rings normally contain the greatest amount of sap. Accordingly, if the root system encounters impacted soil or ground water, the contaminants will be taken into the tree and is often fixed within the woods. Therefore, the rings will provide an historical record of past contamination in the vicinity of the tree.
To perform such an investigation, cores are collected from trees in the vicinity of a known release. The rings are closely counted, measured and then graphed to see if an anomalies exist. The sample is then analyzed for a variety of elements. In particular, we are looking for elements such as sulfur and chloride, which are markers of fossil fuels, and lead, which was an additive in gasoline. Based on chemical anomalies in the sample, we can assess when the contaminants reached the tree.

These techniques have been used to age date archeological sites and assess past climates for close to one hundred years. However, Triassic Technology was the first to apply these techniques to environmental age dating and, in particular, the assessment of petroleum release time frames. These age-dating techniques are discussed at length in the articles cited below:

Smith, K. T., Balouet, J. C. and Oudijk, G., 2007, Elemental line scanning of cores using EDXRF and LIBS: from fundamental research to environmental forensics applications: Dendrochronoligia (in press).
Balouet, J. C., Oudijk, G., Smith, K. T., Petrisor, I., Grudd, H. and Stocklassa, B., 2007, Dendroecology and environmental forensics: From fundamentals to case studies: Environmental Forensics 8 (1/2): 1-17.
Balouet, J. C. and Oudijk, G., 2006, The use of dendroecological methods to estimate the time frame of environmental releases: Environmental Claims Journal 18: 1-18.
Oudijk, G., 2005, Applications of dendroecology to age date soil and ground-water contamination: Proceedings of the Southeast Asia Environmental Forensics Conference, September 19-21, 2005, Taipei, Taiwan, p. 19.1-19.4.

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