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USGS2009

Use of dendrochronology and dendrochemistry in environmental forensics: Does it meet the Daubert criteria?

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. ?? Taylor & Francis Group, LLC.

Environmental Forensics↗

USGS2011

Applications of selective ion exchange for perchlorate removal, recovery, and environmental forensics

Perchlorate (ClO4-) is a widespread contaminant found in drinking water and groundwater that has caused far-reaching ramifications ranging from public health issues to potential liabilities arising from environmental clean-up requirements. The chapter summarizes recent developments in highly selective and regenerable ion exchange technologies for removing ClO4- from contaminated water. The technologies rely on a unique, highly specific resin to trap ClO4-. The resin is then regenerated and ClO4- is either destroyed or recovered—leading to significant cost reduction and waste minimization. The ability to recover trace quantities of pure ClO4- from contaminated media also allows unambiguous identification of the sources of its contamination through stable isotope ratio analysis of chlorine and oxygen atoms. We provide detailed descriptions of the techniques for extracting, purifying, and crystallizing trade amounts of ClO4- and characterizing its isotopic composition for fingerprinting in the environment.

Book chapter↗

USGS2021

Isotopic composition of natural and synthetic chlorate (δ18O, Δ17O, δ37Cl, 36Cl/Cl): Methods and initial results

Natural chlorate (ClO 3 − ) is widely distributed in terrestrial and extraterrestrial environments. To improve understanding of the origins and distribution of ClO 3 − , we developed and tested methods to determine the multi-dimensional isotopic compositions (δ 18 O, Δ 17 O, δ 37 Cl, 36 Cl/Cl) of ClO 3 − and then applied the methods to samples of natural nitrate-rich caliche-type salt deposits in the Atacama Desert, Chile, and Death Valley, USA. Tests with reagents and artificial mixed samples indicate stable-isotope ratios were minimally affected by the purification processes. Chlorate extracted from Atacama samples had δ 18 O = +7.0 to +11.1‰, Δ 17 O = +5.7 to +6.4‰, δ 37 Cl = −1.4 to +1.3‰, and 36 Cl/Cl = 48 × 10 −15 to 104 × 10 −15 . Chlorate from Death Valley samples had δ 18 O = −6.9 to +1.6‰, Δ 17 O = +0.4 to +2.6‰, δ 37 Cl = +0.8 to +1.0‰, and 36 Cl/Cl = 14 × 10 −15 to 44 × 10 −15 . Positive Δ 17 O values of natural ClO 3 − indicate that its production involved reaction with O 3 , while its Cl isotopic composition is consistent with a tropospheric or near-surface source of Cl. The Δ 17 O and δ 18 O values of natural ClO 3 − are positively correlated, as are those of ClO 4 − and NO 3 − from the same localities, possibly indicating variation in the relative contributions of O 3 as a source of O in the formation of the oxyanions. Additional isotopic analyses of ClO 3 − could provide stronger constraints on its production mechanisms and/or post-formational alterations, with applications for environmental forensics, global biogeochemical cycling of Cl, and the origins of oxyanions detected on Mars.

Chemosphere↗

USGS2002

Forensic applications of nitrogen and oxygen isotopes in tracing nitrate sources in urban environments

Ground and surface waters in urban areas are susceptible to nitrate contamination from septic systems, leaking sewer lines, and fertilizer applications. Source identification is a primary step toward a successful remediation plan in affected areas. In this respect, nitrogen and oxygen isotope ratios of nitrate, in conjunction with hydrologic data and water chemistry, have proven valuable in urban studies from Austin, Texas, and Tacoma, Washington. In Austin, stream water was sampled during stremflow and baseflow conditions to assess surface and subsurface sources of nitrate, respectively. In Tacoma, well waters were sampled in adjacent sewered and un-sewered areas to determine if locally high nitrate concentrations were caused by septic systems in the un-sewered areas. In both studies, sewage was identified as a nitrate source and mixing between sewage and other sources of nitrate was apparent. In addition to source identification, combined nitrogen and oxygen isotopes were important in determining the significance of denitrification, which can complicate source assessment by reducing nitrate concentrations and increasing ??15N values. The two studies illustrate the value of nitrogen and oxygen isotopes of nitrate for forensic applications in urban areas. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

Environmental Forensics↗

USGS2007

Forensic fingerprinting of oil-spill hydrocarbons in a methanogenic environment-Mandan, ND and Bemidji, MN

In recent decades forensic fingerprinting of oil-spill hydrocarbons has emerged as an important tool for correlating oils and for evaluating their source and character. Two long-term hydrocarbon spills, an off-road diesel spill (Mandan, ND) and a crude oil spill (Bemidji, MN) experiencing methanogenic biodegradation were previously shown to be undergoing an unexpected progression of homologous n-alkane and n-alkylated cyclohexane loss. Both exhibited degradative losses proceeding from the high-molecular-weight end of the distributions, along with transitory concentration increases of lower-molecular-weight homologs. Particularly in the case of the diesel fuel spill, these methanogenic degradative patterns can result in series distributions that mimic lower cut refinery fuels or admixture with lower cut fuels. Forensic fingerprinting in this long-term spill must therefore rely on more recalcitrant series, such as polycyclic aromatic hydrocarbon or drimane sesquiterpane profiles, to prove if the spilled oil is single-sourced or whether there is verifiable admixture with other extraneous refinery fuels. Degradation processes impacting n-alkanes and n-alkylated ring compounds, which make these compounds unsuitable for fingerprinting, nevertheless are of interest in understanding methanogenic biodegradation.

Environmental Forensics↗

USGS2013

Petroleum fingerprinting with organic markers

Petroleum fingerprinting is an invaluable tool in forensic geochemistry. This article summarizes applications of fingerprinting in several oil spills and natural oil seepages that we have studied during the last 25 years. It shows how each unique chemical fingerprint can be used to correlate or differentiate oils. Fingerprints can provide information about processes in the environment that impact oils such as weathering and microbial degradation. They can be used to evaluate organic matter that contributed to oils, and classify oils with regard to the geological framework of their source, such as evaluating geological facies, age, lithology, and depositional environment.

Environmental Forensics↗

USGS2002

Low-maturity Kulthieth Formation coal: A possible source of polycyclic aromatic hydrocarbons in benthic sediment of the northern Gulf of Alaska

The successful application of forensic geology to contamination studies involving natural systems requires identification of appropriate endmembers and an understanding of the geologic setting and processes affecting the systems. Studies attempting to delineate the background, or natural, source for hydrocarbon contamination in Gulf of Alaska (GOA) benthic sediments have invoked a number of potential sources, including seep oils, source rocks, and coal. Oil seeps have subsequently been questioned as significant sources of hydrocarbons present in benthic sediments of the GOA in part because the pattern of relative polycyclic aromatic hydrocarbon (PAH) abundance characteristic of benthic GOA sediments is inconsistent with patterns typical of weathered seep oils. Likewise, native coal has been dismissed in part because ratios of labile hydrocarbons to total organic carbon (e.g. PAH:TOC) for Bering River coal field (BRCF) sources are too low - i.e. the coals are over mature - to be consistent with GOA sediments. We present evidence here that native coal may have been prematurely dismissed, because BRCF coals do not adequately represent the geochemical signatures of coals elsewhere in the Kulthieth Formation. Contrary to previous thought, Kulthieth Formation coals east of the BRCF have much higher PAH: TOC ratios, and the patterns of labile hydrocarbons in these low thermal maturity coals suggest a possible genetic relationship between Kulthieth Formation coals and nearby oil seeps on the Sullivan anticline. Analyses of low-maturity Kulthieth Formation coal indicate the low maturity coal is a significant source of PAH. Source apportionment models that neglect this source will underestimate the contribution of native coals to the regional background hydrocarbon signature. ?? Published by Elsevier Science Ltd. on behalf of AEHS.

Environmental Forensics↗

USGS2002

Alkylcyclohexanes in environmental geochemistry

The n-alkylated cyclohexanes (CHs) are a homologous series of hydrocarbon compounds that are commonly present in crude oil and refinery products such as diesel fuel. These compounds exhibit specific distribution patterns for different fuel types, providing useful fingerprints for characterizing petroleum products, especially after degradation of n-alkanes has occurred. However, there are no published data to show how these compounds are altered in the environment after long-term spillage of petroleum products. This paper presents two case studies of oil spills that demonstrate the changing distribution patterns resulting from long-term anaerobic microbial degradation. These spills are the 1979 crude-oil spill in Bemidji, Minnesota, and a chronic diesel-fuel spillage from 1953-1991 at Mandan, North Dakota. The alkyl CHs in both spilled oil products are affected by similar biodegradative processes in which the compounds undergo a consistent pattern of loss from the high molecular weight end of the homolog distribution. Degradation results in a measurable increase in the concentrations of the homologs in the lower molecular weight range, a gradual lowering in carbon number of the homolog maximum, and a gradual decrease of the total homolog range from the high molecular weight end. This pattern is the opposite of low-end loss expected with weathering and aerobic biodegradation. The enhancement of the low molecular mass alkyl CH homologs, if not recognized as a degradative pathway of diesel fuel in an anaerobic environment, can potentially be misinterpreted in fuel-oil fingerprinting as deriving from lower distillation-range fuels or admixture of diesel with other fuels.

Environmental Forensics↗

USGS2006

Differentiation of commercial fuels based on polar components using negative electrospray ionization/mass spectrometry

Polar components in fuels may enable differentiation between fuel types or commercial fuel sources. A range of commercial fuels from numerous sources were analyzed by flow injection analysis/electrospray ionization/mass spectrometry without extensive sample preparation, separation, or chromatography. This technique enabled screening for unique polar components at parts per million levels in commercial hydrocarbon products, including a range of products from a variety of commercial sources and locations. Because these polar compounds are unique in different fuels, their presence may provide source information on hydrocarbons released into the environment. This analysis was then applied to mixtures of various products, as might be found in accidental releases into the environment.

Environmental Forensics↗

USGS2007

Profiling refined hydrocarbon fuels using polar components

Identification of a fuel released into the environment can be difficult due to biodegradation or weathering. Negative electrospray ionization/mass spectrometry was used to screen for unique polar components in a wide variety of commercial hydrocarbon products and mixtures. These fuels produced unique and relatively simple spectra. When applied to hydrocarbon samples from a large, long-term fuel spill in a relatively cool climate in which the alkane, isoprenoid, and alkylcyclohexane portions had begun to biodegrade or weather, the polar components in these samples had changed little over time. This technique provided rapid fuel identification on hydrocarbons released into the environment, without sample preparation, fractionation, or chromatography.

Environmental Forensics↗

USGS2008

Compound-specific isotope analysis: Questioning the origins of a trichloroethene plume

Stable carbon isotope ratios of trichloroethene (TCE), cis-1,2- dichloroethene, and trans-1,2-dichloroethene were determined by use of gas chromatography-combustion-isotope ratio mass spectroscopy to determine whether compound-specific stable carbon isotopes could be used to help understand the origin and history of a TCE groundwater plume in Fort Worth, TX. Calculated ??13C values for total chlorinated ethenes in groundwater samples, which can approximate the ??13C of a spilled solvent if all degradation products are accounted for, were useful for determining whether separate lobes of the plume resulted from different sources. Most notably, values for one lobe, where tetrachloroethene (PCE) has been detected periodically, were outside the range for manufactured TCE but within the range for manufactured PCE, whereas values for a separate lobe, which is downgradient of reported TCE spills, were within the range for manufactured TCE. Copyright ?? Taylor & Francis Group, LLC.

Environmental Forensics↗

USGS2003

Insecticide residues on weathered passerine carcass feet

Nine brown-headed cowbirds ( Molothrus ater ) were exposed to turf sprayed with either EarthCare® (25% diazinon; 4.77 L a.i./ha) or Ortho-Klor® (12.6% chlorpyrifos; 5.21 L a.i./ha). Birds were euthanized and one foot from each bird was weathered outdoors for up to 28 days and the other foot was kept frozen until residue analysis. When compared to the unweathered feet, feet weathered for 28 days retained 43% and 37% of the diazinon and chlorpyrifos, respectively. Insecticide residues were below the level of detection (1.0 ppm) on control feet. Weathered feet may be used for determining organophosphorus insecticide exposure to birds.

Environmental Forensics↗

USGS2025

Determination of provenance soil type using inductively coupled plasma mass spectrometry (ICP-MS) analyses of Pinus ponderosa ash

This study demonstrates the feasibility of determining soil provenance from tree ash composition using elemental analysis and chemometric techniques. To date, no published studies have applied chemometric approaches to classify ash for provenance determination following forest fires. In this work, Pinus ponderosa ash was analyzed to distinguish samples based on soil type and geographic location. Pinus ponderosa , a widely distributed pine species in the western United States where wildfires are prevalent, was selected as a model system. Needles were collected from trees grown in five distinct soil types across northern Arizona and Colorado, then dry-ashed under controlled conditions. Classification was performed using three preprocessing techniques and five machine learning algorithms, including hierarchical modeling structures to optimize separation. Partial least squares discriminant analysis (PLS-DA) following a Box-Cox transformation yielded the highest classification accuracy, achieving a prediction kappa value of 0.98 for soil type identification. However, classification performance decreased when distinguishing both soil type and geographic location, indicating that additional variability may influence predictive accuracy in broader applications. These findings highlight the potential of inductively coupled plasma mass spectrometry (ICP-MS) and machine learning for post-wildfire forensic analysis and environmental monitoring.

Applied Spectroscopy↗

USGS2020

Variation of lead isotopic composition and atomic weight in terrestrial materials (IUPAC Technical Report)

The isotopic composition and atomic weight of lead are variable in terrestrial materials because its three heaviest stable isotopes are stable end-products of the radioactive decay of uranium ( 238 U to 206 Pb; 235 U to 207 Pb) and thorium ( 232 Th to 208 Pb). The lightest stable isotope, 204 Pb, is primordial. These variations in isotope ratios and atomic weights provide useful information in many areas of science, including geochronology, archaeology, environmental studies, and forensic science. While elemental lead can serve as an abundant and homogeneous isotopic reference, deviations from the isotope ratios in other lead occurrences limit the accuracy with which a standard atomic weight can be given for lead. In a comprehensive review of several hundred publications and analyses of more than 8000 samples, published isotope data indicate that the lowest reported lead atomic weight of a normal terrestrial materials is 206.1462 ± 0.0028 ( k = 2), determined for a growth of the phosphate mineral monazite around a garnet relic from an Archean high-grade metamorphic terrain in north-western Scotland, which contains mostly 206 Pb and almost no 204 Pb. The highest published lead atomic weight is 207.9351 ± 0.0005 ( k = 2) for monazite from a micro-inclusion in a garnet relic, also from a high-grade metamorphic terrain in north-western Scotland, which contains almost pure radiogenic 208 Pb. When expressed as an interval, the lead atomic weight is [206.14, 207.94]. It is proposed that a value of 207.2 be adopted for the single lead atomic-weight value for education, commerce, and industry, corresponding to previously published conventional atomic-weight values.

Pure and Applied Chemistry↗

USGS2014

Response to heavy, non-floating oil spilled in a Great Lakes river environment: a multiple-lines-of-evidence approach for submerged oil assessment and recovery

The Enbridge Line 6B pipeline release of diluted bitumen into the Kalamazoo River downstream of Marshall, MI in July 2010 is one of the largest freshwater oil spills in North American history. The unprecedented scale of impact and massive quantity of oil released required the development and implementation of new approaches for detection and recovery. At the onset of cleanup, conventional recovery techniques were employed for the initially floating oil and were successful. However, volatilization of the lighter diluent, along with mixing of the oil with sediment during flooded, turbulent river conditions caused the oil to sink and collect in natural deposition areas in the river. For more than three years after the spill, recovery of submerged oil has remained the predominant operational focus of the response. The recovery complexities for submerged oil mixed with sediment in depositional areas and long-term oil sheening along approximately 38 miles of the Kalamazoo River led to the development of a multiple-lines-of-evidence approach comprising six major components: geomorphic mapping, field assessments of submerged oil (poling), systematic tracking and mapping of oil sheen, hydrodynamic and sediment transport modeling, forensic oil chemistry, and net environmental benefit analysis. The Federal On-Scene Coordinator (FOSC) considered this information in determining the appropriate course of action for each impacted segment of the river. New sources of heavy crude oils like diluted bitumen and increasing transportation of those oils require changes in the way emergency personnel respond to oil spills in the Great Lakes and other freshwater ecosystems. Strategies to recover heavy oils must consider that the oils may suspend or sink in the water column, mix with fine-grained sediment, and accumulate in depositional areas. Early understanding of the potential fate and behavior of diluted bitumen spills when combined with timely, strong conventional recovery methods can significantly influence response success.

Michigan↗

USGS2014

Dendrochemical patterns of calcium, zinc, and potassium related to internal factors detected by energy dispersive X-ray fluorescence (EDXRF)

Energy dispersive X-ray fluorescence (EDXRF) provides highly sensitive and precise spatial resolution of cation content in individual annual growth rings in trees. The sensitivity and precision have prompted successful applications to forensic dendrochemistry and the timing of environmental releases of contaminants. These applications have highlighted the need to distinguish dendrochemical effects of internal processes from environmental contamination. Calcium, potassium, and zinc are three marker cations that illustrate the influence of these processes. We found changes in cation chemistry in tree rings potentially due to biomineralization, development of cracks or checks, heartwood/sapwood differentiation, intra-annual processes, and compartmentalization of infection. Distinguishing internal from external processes that affect dendrochemistry will enhance the value of EDXRF for both physiological and forensic investigations.

Chemosphere↗

USGS2007

Oxygen and chlorine isotopic fractionation during perchlorate biodegradation: Laboratory results and implications for forensics and natural attenuation studies

Perchlorate is a widespread environmental contaminant having both anthropogenic and natural sources. Stable isotope ratios of O and Cl in a given sample of perchlorate may be used to distinguish its source(s). Isotopic ratios may also be useful for identifying the extent of biodegradation of perchlorate, which is critical for assessing natural attenuation of this contaminant in groundwater. For this approach to be useful, however, the kinetic isotopic fractionations of O and Cl during perchlorate biodegradation must first be determined as a function of environmental variables such as temperature and bacterial species. A laboratory study was performed in which the O and Cl isotope ratios of perchlorate were monitored as a function of degradation by two separate bacterial strains ( Azospira suillum JPLRND and Dechlorospirillum sp. FBR2) at both 10 °C and 22 °C with acetate as the electron donor. Perchlorate was completely reduced by both strains within 280 h at 22 °C and 615 h at 10 °C. Measured values of isotopic fractionation factors were ε 18 O = −36.6 to −29.0‰ and ε 37 Cl = −14.5 to −11.5‰, and these showed no apparent systematic variation with either temperature or bacterial strain. An experiment using 18 O-enriched water (δ 18 O = +198‰) gave results indistinguishable from those observed in the isotopically normal water (δ 18 O = −8.1‰) used in the other experiments, indicating negligible isotope exchange between perchlorate and water during biodegradation. The fractionation factor ratio ε 18 O/ε 37 Cl was nearly invariant in all experiments at 2.50 ± 0.04. These data indicate that isotope ratio analysis will be useful for documenting perchlorate biodegradation in soils and groundwater. The establishment of a microbial fractionation factor ratio (ε 18 O/ε 37 Cl) also has significant implications for forensic studies.

Environmental Science & Technology↗

USGS2012

Stable isotope deltas: Tiny, yet robust signatures in nature

Although most of them are relatively small, stable isotope deltas of naturally occurring substances are robust and enable workers in anthropology, atmospheric sciences, biology, chemistry, environmental sciences, food and drug authentication, forensic science, geochemistry, geology, oceanography, and paleoclimatology to study a variety of topics. Two fundamental processes explain the stable isotope deltas measured in most terrestrial systems: isotopic fractionation and isotope mixing. Isotopic fractionation is the result of equilibrium or kinetic physicochemical processes that fractionate isotopes because of small differences in physical or chemical properties of molecular species having different isotopes. It is shown that the mixing of radioactive and stable isotope end members can be modelled to provide information on many natural processes, including 14C abundances in the modern atmosphere and the stable hydrogen and oxygen isotopic compositions of the oceans during glacial and interglacial times. The calculation of mixing fractions using isotope balance equations with isotope deltas can be substantially in error when substances with high concentrations of heavy isotopes (e.g. 13C, 2H, and 18O ) are mixed. In such cases, calculations using mole fractions are preferred as they produce accurate mixing fractions. Isotope deltas are dimensionless quantities. In the International System of Units (SI), these quantities have the unit 1 and the usual list of prefixes is not applicable. To overcome traditional limitations with expressing orders of magnitude differences in isotope deltas, we propose the term urey (symbol Ur), after Harold C. Urey, for the unit 1. In such a manner, an isotope delta value expressed traditionally as−25 per mil can be written as−25 mUr (or−2.5 cUr or−0.25 dUr; the use of any SI prefix is possible). Likewise, very small isotopic differences often expressed in per meg ‘units’ are easily included (e.g. either+0.015 ‰ or+15 per meg can be written as+15 μUr.

Isotopes in Environmental and Health Studies↗