Chronic petroleum discharges resulting from underground storage tank (UST) system failures may continue for months or years, whereas catastrophic releases result from structural failures or overfills that occur over shorter time periods. A forensic analytical framework is useful for distinguishing between chronic and catastrophic releases and identifying responsible parties. However, the forensic program must account for the petroleum type because identifying release modes relies on understanding the chemical evolution of petroleum through time within the context of site conditions. Here we discuss key petroleum components that aid in reconstructing the release and identifying potential responsible parties when subsurface conditions are known.

Many different environmental-forensic techniques are needed when investigating the spillage of gasoline to soil or groundwater. An important laboratory analytical technique is known as a PIANO analysis, which can identify hundreds of different hydrocarbons in gasoline. Through interpretation of these results, the origin and age of the gasoline can often be determined and, hence, responsibility for the release can may be identified.

The term "age dating" is defined as: estimating the time frame of a contaminant release to the environment.Because of the high costs of environmental cleanups, age-dating studies have now become an integral part of environmental investigations.Knowledge of the local geology, hydrology and geochemistry are required to perform these studies and, therefore, geologists are commonly involved.The "middle distillates" include products such as diesel fuel, heating oils, kerosene and jet fuels.Middle-distillate fuels are used throughout the world to power motors, heat residences, fuel jet engines and propel ships, among many other uses.Middle-distillate fuels are commonly stored in aboveground or underground tanks and these tanks are often unprotected and exposed to the elements.Because of corrosion, leaks from storage tanks are a severe environmental problem, especially in locations where groundwater is used for potable supplies.Numerous underground storage tanks (USTs) were installed in North America during the "boom" years following World War II and impacts from leakage are now being found in the subsurface.An understanding of the problems associated with leaking petroleum USTs has been known since the 1950s (Kehoe, 1960).However, action was not undertaken until the late 1970s and in some places, even much later.For example, the US state of New Jersey did not pass UST regulations until 1986 (State of New Jersey, 1986).The average non-leaking lifespan of unprotected steel USTs may be as little as 15 years (Robinson et al., 1988).The Canadian province of Nova Scotia requires that USTs older than 25 years be removed (Hankey-Masui, 1998).Thus, numerous leaking USTs existed over the years and many probably continue today.Because of costs, the number of people impacted and the large number of cases, releases of middle-distillate fuels from USTs are a serious problem in North America (Oudijk et al., 1999).In the US states of New Jersey and Maine, several leaks are reported daily to regulatory agencies (Pearson & Oudijk, 1993;McCaskill, 1999).Similar problems exist in Europe (Bennet, 1997).Remediation costs can be high and cases exist where buildings were removed, razed or structurally supported to complete a cleanup.It is not uncommon for costs to exceed US$500,000 and many cases costing over US$1 million exist.Costs are often borne by insurance policies, although carriers may subrogate and obtain contribution from previous carriers or others responsible.For this reason, carriers and law firms commonly request information on the time frames of releases.Because of costs, many cases are litigated and, www.intechopen.com

To say that the subject of age-dating distillate fuels released to the environment is under discussion in the scientific literature would border on trite. Today, it seems that this subject is very much in play, to borrow a recent quote from a colleague. Let us join the fray. Since publication of an empirical technique for age-dating middle-distillate fuel (diesel fuel) by Christensen and Larsen in 1993 (C&L), forensic experts and commercial laboratories have mademuch of the approach. Much confusion regarding the applicability of the C&L approach has resulted in a polarization within the environmental forensics community. However, as discussed in many articles published in this and other journals, there are numerous positives and negatives related to the C&L method. It is our opinion that the C&L method should be considered, but never exclusively relied upon. At present, from our viewpoint there are two regimens or ways of thinking with regard to age-dating distillate fuel releases, which are described here. The first regimenmight be termed the let it fly experts—those who apply the C&L approach widely and without discrimination. In the extreme are the interests who will age-date anything that comes into a laboratory. Single samples are their specialty. Such an approach effectively disregards the possibility of multiple different releases and is ignorant of site-environmental conditions. This group does not provide error ranges or any opinion on uncertainty. Age-dating of single samples, without consideration of any facet of petroleum degradation or site-specific conditions, does us all a great disservice. Unfortunately, many in the fields of engineering and science have been employing this approach, thereby abusing fundamentally accepted scientific principles. The second regimen might be termed the how are we going to work with this? thinkers. One must remember that there

Refiners have used numerous gasoline additives since the 1920s to increase automotive performance and correct deficiencies. The history of organometallic additives, in particular lead-, manganese- and iron-containing compounds is discussed. Some of these additives can be helpful to environmental investigators for fingerprinting and age-dating leaded-gasoline releases. Knowing their history, investigators can decipher these releases more efficiently.

Dendrochronological methods have been in use for more than 100 years, providing us a record of climate, human activities (archaeology), floods, fire, mudslides and other geological and biological events. More recently, dendrochemisty has been used to assess the time frames of the onset and existence of environmental contamination. This article assesses the scientific status of dendrochronology and dendrochemistry with respect to the admissibility of expert testimony and Daubert legal criteria. The purpose of this article is to identify the crucial scientific aspects of dendrochronology and dendrochemistry that address the Daubert criteria and Rule 702 as amended in 2000. To clarify terminology, dendrochronology is the precise and reliable assignment of the year of formation of tree rings. Dendroecology is the use of dendrochronology to understand ecological and environmental processes (Schweingruber, 1996). Dendrochemistry is a subdiscipline of dendrochronology that analyzes and interprets the wood chemistry of precisely dated tree rings. Forensic dendrochemistry applies dendrochemistry to resolve environmental disputes and generally deal with questions regarding the timing and/or the source of environmental incidents. One significant application of forensic dendrochemistry to expert testimony is to address issues of anthropogenic contamination. Forensic dendroecology is a similar term to forensic dendrochemistry, but forensic dendrochemistry will be used in this discussion as the latter term emphasizes the use of chemical detection methods. Because dendrochemistry is based on the foundation of dendrochronology, both the former specialty and the latter broader discipline will be discussed.

The age of heating-oil releases from underground storage tanks (USTs) can be estimated by investigating the petroleum chemistry, the on-site environmental conditions, the extent of contaminant migration, the condition of the UST, site history and several additional factors. The heating-oil chemistry, and in particular the degree of weathering, can be assessed through an examination of: compound depletion, the carbon range, the n-alkane depletion and the size of the unresolved complex mixture (UCM). Each release site can be assigned a weathering regime, such as very aggressive, aggressive, moderate, weak and very weak. These designations are based on the on-site geological, hydrological and biological conditions. A matrix was constructed which compares the weathering regimes to the stages of petroleum weathering and provides potential age ranges. The matrix is a method to lead the investigator towards the correct age, but is not the final say on that age. The age ranges then need to be compared to site-specific characteristics, such as the UST age, the UST condition, the extent of contaminant migration and other extenuating factors. The error range for this method is estimated at +/- 2 years; however, there are numerous limitations to the methods and instances will arise where the age can only be constrained.

Releases of no. 2 heating oil are a serious threat to groundwater resources throughout much of the world. Because of the significant remediation costs for heating-oil spills, insurance carriers and associated law firms often request information on release time frames. A semi-quantitative age-dating procedure is proposed that incorporates factors such as site history, petroleum composition and weathering, environmental conditions, extent of contamination and the condition of the underground tank. The procedure uses the principles of petroleum chemistry and compares them to the known site-specific environmental conditions. Each contamination case is specific unto itself and a universal approach, such as a mathematical equation, is not proper because it cannot incorporate all the needed parameters. Furthermore, the use of only petroleum chemistry as an age-dating criterion is inadequate. Accordingly, the investigator will need to evaluate all factors, such as environmental conditions, petroleum chemistry, underground tank condition, site history and the extent of contamination, and assess the importance of each, prior to providing an age-date opinion.

Methyl-tert-butyl ether (MTBE) is an oxygenate added to gasoline in the United States and elsewhere to boost the octane ratio and reduce tailpipe emissions. Because of its known usage time frame, the presence of MTBE can help estimate the age of gasoline releases to the environment. However, because of its ubiquity, its presence can no longer be used to fingerprint, or differentiate, gasoline plumes in groundwater. Compound-specific stable carbon isotope analysis has recently become a method for differentiating MTBE sources and plumes affecting groundwater. In the present study, groundwater samples were collected from 20 monitoring wells located at two gasoline service stations in central New Jersey in an attempt to differentiate the dissolved gasoline plumes and possibly identify their sources. The carbon isotope ratio (C-13/C-12 expressed as delta C-13) values for each sample were determined through gas chromatography-isotope ratio-mass spectrometry (GCIRMS), and the impacted area for each plume was delineated. As biological degradation of MTBE proceeds, delta C-13 becomes heavier; petroleum-degrading bacteria preferentially assimilate the lighter C-12 isotope, thereby enriching the residual MTBE in the heavier C-13 isotope. The isotopic composition of MTBE at different locations demonstrated the varying degree to which MTBE had been altered by biodegradation. The delta C-13 values can also provide insight into the type of release and the magnitude of biodegradation. Two types of leaks occurred at the sites: a shallow piping leak and deeper leak from a tank system. delta C-13 values in the vicinity of the shallow leak were heavier, revealing increased biodegradation in the soil, while delta C-13 values in the vicinity of the tank leak were lighter, revealing the lack of biological degradation in non-aqueous phase liquid (NAPL) trapped beneath the water table. An assessment is provided where the physical site characteristics responsible for petroleum weathering are considered in comparison with the measured delta C-13 values.

Environmental forensics seeks to determine the responsible parties for contamination from leaks or spills of petroleum or other toxic products. Dendrochemistry contributes to environmental forensics at the intersection of analytical chemistry, tree biology, and environmental responsibility. To be useful, dendrochemistry requires the rigorous application of analytical techniques as well as an understanding of tree biology. The choice of analytical technique is usually driven by tradeoffs among the selection of chemical elements or molecules of interest, sensitivity and discrimination, spatial resolution, ease of sample preparation, availability, sample destructiveness, and cost.One useful solid-state spectroscopic technique for dendrochemical analysis is energy dispersive X-ray fluorescence (EDXRF). This method provides essentially non-destructive, simultaneous detection of a number of elements with an adjustable spatial resolution, typically from 0.1 to 0.3 mm. The most commonly targeted elements are S and Cl as markers for fossil fuels. Cl for solvents, and Pb for leaded gasoline. Other metal elements may also be used as indicators of mining and smelting.For elements that are not normally present in appreciable amounts in wood, the mere presence of the element anywhere in the tree-ring record indicates exposure of the tree to an unusual chemical event or process. Dating the environmental exposure from dendrochemical analysis can be complicated by internal changes in tree chemistry due to wood infection, tree maturation, and wood maturation. Published by Elsevier GmbH.

∗Gil Oudijk is the owner of Triassic Technology, Inc., a consulting firm located in New Jersey specializing in forensic investigations of soil and groundwater contamination problems.

Dendroecology, or the use of ring patterns to assess the age of trees and environmental factors controlling their growth, is a well-developed method in climatologic studies. This method holds great potential as a forensic tool for age dating, contamination assessment, and characterization of releases. Moreover, the method is independent of the physical presence of contamination at the time of sampling because it is focused on the effect rather than the cause. This review is one of the very few articles published to date exploring the forensic applicability of dendroecology. This article is organized in two parts: Part I describes the method principles and proposes a practical procedure for forensic applications; Part II exemplifies and validates the method through six case studies of successful forensic application (related to petroleum products and chlorinated solvent spills).

Part of a forensic scientist's role is to provide an unbiased and objective opinion, often in some type of dispute resolution process such as a trial. The purpose of this article is to look into the role of bias in an expert's opinion and how it can have a deleterious impact on one's testimony. The writings of the 17th-century philosophers Francis Bacon and Rene Descartes are discussed and their findings on the bias problem explored. Examples of where bias can appear within the testimony of an environmental expert are also explored and ways to alleviate this problem are provided.

Several techniques are available to forensic researchers to age-date and fingerprint gasoline releases to the environment. These techniques include the use of isotopes, chemical ratios, and groundwater flow rates, among many others. A case study is presented which describes the use of these methods congruently to assess the time frame of a gasoline release and assess whether or not more than one release had occurred. The principles discussed herein can be used to estimate the age(s) of subsurface gasoline releases in the 50 United States and the U.S. Territories in the Caribbean.

Click to increase image sizeClick to decrease image size Acknowledgments The authors' thanks go to Häkan Grüdd of Stockholm University, Paul Krusic, Bob Morrisson and Ioana Petrisor of DPRA, Inc., Michael Obolensky and Michael Heinrich of Triassic Technology, Inc. and Kevin Smith. This work was funded through a client who wishes to remain anonymous.

The modern world provides us with many technological advances such as high-speed computers, transatlantic flights and tiny cell phones (which are constantly being lost, crushed or dropped down moni...

Numerous age-dating techniques are available to estimate the time frame of contaminant releases impacting groundwater. One method, historically used in the hydrology field to assess recharge ages and rates of groundwater flow, can be applied to estimating the age of contaminant releases. Chlorofluorocarbons (CFCs) and tritium are anthropogenic substances present in the atmosphere over the past half century. These atmospheric contaminants recharge the groundwater through precipitation and can be used as age markers. In cases where the recharge water is in contact with contaminants, the CFCs and tritium may be used to estimate the minimum age of the contaminant release. Three case studies from New Jersey are provided which describe the methods used to age date releases of chlorinated solvents and petroleum products.

Numerous age-dating techniques are available to estimate the time frame of contaminant releases to the environment. One method, historically used in the hydrology field to determine recharge ages of groundwater, can be applied to estimating the minimum age of contaminant discharges. Chlorofluorocarbons (CFCs) and tritium are anthropogenic substances present in the atmosphere over the past half century. These constituents recharge the groundwater through precipitation and can be used as an age marker. In cases where the recharge water is in contact with contaminants, the CFCs and tritium may be used to estimate the minimum age of the contaminant release.