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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↗

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

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↗

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↗

USGS2018

IUPAC Periodic Table of the Elements and Isotopes (IPTEI) for the education community (IUPAC Technical Report)

The IUPAC (International Union of Pure and Applied Chemistry) Periodic Table of the Elements and Isotopes (IPTEI) was created to familiarize students, teachers, and non-professionals with the existence and importance of isotopes of the chemical elements. The IPTEI is modeled on the familiar Periodic Table of the Chemical Elements. The IPTEI is intended to hang on the walls of chemistry laboratories and classrooms. Each cell of the IPTEI provides the chemical name, symbol, atomic number, and standard atomic weight of an element. Color-coded pie charts in each element cell display the stable isotopes and the relatively long lived radioactive isotopes having characteristic terrestrial isotopic compositions that determine the standard atomic weight of each element. The background color scheme of cells categorizes the 118 elements into four groups: (1) white indicates the element has no standard atomic weight, (2) blue indicates the element has only one isotope that is used to determine its standard atomic weight, which is given as a single value with an uncertainty, (3) yellow indicates the element has two or more isotopes that are used to determine its standard atomic weight, which is given as a single value with an uncertainty, and (4) pink indicates the element has a well-documented variation in its atomic weight, and the standard atomic weight is expressed as an interval. An element-by-element review accompanies the IPTEI and includes a chart of all known stable and radioactive isotopes for each element. Practical applications of isotopic measurements and technologies are included for the following fields: forensic science, geochronology, Earth-system sciences, environmental science, and human health sciences, including medical diagnosis and treatment.

Pure and Applied Chemistry↗

USGS2013

Spatial, seasonal, and source variability in the stable oxygen and hydrogen isotopic composition of tap waters throughout the USA

To assess spatial, seasonal, and source variability in stable isotopic composition of human drinking waters throughout the entire USA, we have constructed a database of δ 18 O and δ 2 H of US tap waters. An additional purpose was to create a publicly available dataset useful for evaluating the forensic applicability of these isotopes for human tissue source geolocation. Samples were obtained at 349 sites, from diverse population centres, grouped by surface hydrologic units for regional comparisons. Samples were taken concurrently during two contrasting seasons, summer and winter. Source supply (surface, groundwater, mixed, and cistern) and system (public and private) types were noted. The isotopic composition of tap waters exhibits large spatial and regional variation within each season as well as signiﬁcant at-site differences between seasons at many locations, consistent with patterns found in environmental (river and precipitation) waters deriving from hydrologic processes inﬂuenced by geographic factors. However, anthropogenic factors, such as the population of a tap’s surrounding community and local availability from diverse sources, also inﬂuence the isotopic composition of tap waters. Even within a locale as small as a single metropolitan area, tap waters with greatly differing isotopic compositions can be found, so that tap water within a region may not exhibit the spatial or temporal coherence predicted for environmental water. Such heterogeneities can be confounding factors when attempting forensic inference of source water location, and they underscore the necessity of measurements, not just predictions, with which to characterize the isotopic composition of regional tap waters. Published 2013. This article is a U.S. Government work and is in the public domain in the USA.

Hydrological Processes↗

USGS2025

Near-surface geophysics: Environmental applications

The field of geophysics encompasses a broad and diverse compilation of methodologies that employs principles of physics to characterize properties of earth materials within the subsurface. While geophysical methods have a long history in resource exploration and studies of Earth’s interior, the subdiscipline of “near-surface geophysics” has evolved in recent decades for examination of the shallow, near-surface environment for a range of purposes ranging from archaeological or forensic investigations to assessment of geologic, hydrologic, biologic, and geochemical properties and processes. “Environmental geophysics” are near-surface geophysical studies and methods that focus on understanding natural systems (e.g., watershed hydrology, groundwater–surface water connections, biophysical processes) as well as research pertaining to anthropogenic impacts and land management, (e.g., contamination and remediation, saltwater intrusion, agricultural practices). This field can be further subdivided into subdisciplines focused on specific topics and applications, such as water resources and hydrology (hydrogeophysics) or biologic and microbial processes (biogeophysics). Studies in environmental geophysics span a range of scales, from pore-scale laboratory tests to watershed-scale or regional field experiments. Methods vary by the nature of physics employed, the specific measurement acquired, and how that data is ultimately processed and analyzed to produce interpretable results. There exists further diversity in the acquisition logistics, geometry, and timing of data collection. Geophysical data can be collected in boreholes (one-dimensional, 1-D, vertical profiles), along survey lines (two-dimensional, 2-D, cross-sections), or in dense sensor arrays or gridded profiles (three-dimensional, 3-D, models). Regarding the temporal aspect, studies can conduct one-time geophysical surveys to obtain detailed imaging of subsurface structure or use timelapse and continuous monitoring to investigate variations in subsurface properties over time. The cumulation of all possible permutations of these factors (method, acquisition geometry, survey design, and target application) results in an immense diversity among environmental geophysical studies. Nevertheless, this field remains unified in the pursuit of understanding natural and human-impacted near-surface environments through geophysical investigations. Here we highlight some key references within environmental geophysics. Resources on geophysical theory, acquisition logistics, processing and inversion workflows, and example case studies are categorized into the most common geophysical classes within Geophysical Methods. Lastly, example references for the dominant types of applications in environmental geophysical studies are catalogued in Environmental Applications.

Book chapter↗

USGS2024

Geographic distribution of feather δ34S in Europe

Geographic distribution models of environmentally stable isotopes (the so-called “isoscapes”) are widely employed in animal ecology, and wildlife forensics and conservation. However, the application of isoscapes is limited to elements and regions for which the spatial patterns have been estimated. Here, we focused on the ubiquitous yet less commonly used stable sulfur isotopes (δ 34 S). To predict the European δ 34 S isoscape, we used 242 feather samples from Eurasian Reed Warbler ( Acrocephalus scirpaceus ) formed at 69 European wetland sites. We quantified the relationships between sample δ 34 S and environmental covariates using a random forest regression model and applied the model to predict the geographic distribution of δ 34 S. We also quantified within-site variation in δ 34 S and complementarity with other isotopes on both individual and isoscape levels. The predicted feather δ 34 S isoscape shows only slight differences between the central and southern parts of Europe while the coastal regions were most enriched in 34 S. The most important covariates of δ 34 S were distance to coastline, surface elevation, and atmospheric concentrations of SO 2 gases. The absence of a systematic spatial pattern impedes the application of the δ 34 S isoscape, but high complementarity with other isoscapes advocates the combination of multiple isoscapes to increase the precision of animal tracing. Feather δ 34 S compositions showed considerable within-site variation with highest values in inland parts of Europe, likely attributed to wetland anaerobic conditions and redox sensitivity of sulfur. The complex European geography and topography as well as using δ 34 S samples from wetlands may contribute to the absence of a systematic spatial gradient of δ 34 S values in Europe. We thus encourage future studies to focus on the geographic distribution of δ 34 S using tissues from diverse taxa collected in various habitats over large land masses in the world (i.e., Africa, South America, or East Asia).

Ecosphere↗