Geology Reports⌕ Search

Geology topics

Tyler B. Coplen

Publications and source records attributed to Tyler B. Coplen.

At least 109 records · Page 6Linked to original sources
USGS2006

Determination of the δ 15 N of total nitrogen in solids; RSIL lab code 2893

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 2893 is to determine the δ( 15 N/ 14 N), abbreviated as δ 15 N , of total nitrogen in solid samples. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total nitrogen in a solid sample into N 2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines relative difference in the isotope-amount ratios of stable nitrogen isotopes ( 15 N/ 14 N)of the product N 2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that contains an oxidant, where the combustion takes place in a helium atmosphere containing an excess of oxygen gas. Combustion products are transported by a helium carrier through a reduction tube to remove excess oxygen and convert all nitrous oxides into N 2 and through a drying tube to remove water. The gas-phase products, mainly CO 2 and N 2 , are separated by a gas chromatograph. The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan MAT (now Thermo Scientific) ConFlo II interface, which also is used to inject N 2 reference gas and helium for sample dilution. The IRMS is a Thermo Scientific Delta V Plus CF-IRMS. It has a universal triple collector, two wide cups with a narrow cup in the middle, capable of measuring mass/charge ( m/z ) 28, 29, 30, simultaneously. The ion beams from N 2 are as follows: m/z 28 = N 2 = 14 N 14 N; m/z 29 = N 2 = 14 N 15 N primarily; m/z 30 = NO = 14 N 16 O primarily, which is a sign of contamination or incomplete reduction.

Techniques and Methods↗
USGS2006

Determination of the δ 34 S of Total Sulfur in Solids: RSIL Lab Code 1800

The purpose of Reston Stable Isotope Laboratory Lab (RSIL) Code 1800 is to determine the δ( 34 S/ 32 S), abbreviated as δ 34 S, of total sulfur in a solid sample. A Carlo Erba NC 2500 elemental analyzer (EA) is used to convert total sulfur in a solid sample into SO 2 gas. The EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines the relative difference in stable sulfur isotope-amount ratio ( 34 S/ 32 S) of the product SO 2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in tin capsules and loaded into a Costech Zero-Blank Autosampler on the EA. Under computer control, samples are dropped into a heated tube reaction tube that combines both the oxidation and the reduction reactions. The combustion takes place in a He atmosphere that contains an excess of oxygen gas at the oxidation zone at the top of the reaction tube. Combustion products are transported by a He carrier through the reduction zone at the bottom of the reaction tube to remove excess oxygen and through a separate drying tube to remove any water. The gas-phase products, mainly CO 2 , N 2 , and SO 2 , are separated by a gas chromatograph (GC). The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Thermo-Finnigan ConFlo II interface, which also is used to inject SO 2 reference gas and He for sample dilution. The IRMS is a Thermo-Finnigan DeltaPlus CF-IRMS. It has a universal triple collector with two wide cups and a narrow cup in the middle. It is capable of measuring mass/charge ( m/z ) 64 and 66 simultaneously. The ion beams from SO 2 are as follows: m/z 64 = SO 2 = 32 S 16 O 16 O; and m/z 66 = SO 2 = 34 S 16 O 16 O primarily.

Techniques and Methods↗
USGS2006

Determination of the δ 34 S of low-concentration sulfate in water; RSIL lab code 1949

The purpose of the Reston Stable Isotope Laboratory (RSIL) lab code 1949 is to determine the δ( 34 S/ 32 S), abbreviated as δ 34 S, of dissolved sulfate having a concentration less than 20 milligrams per liter. Dissolved sulfate is collected on an anion-exchange resin in the field, eluted in the laboratory with 3 M KCl, and precipitated with BaCl 2 at pH 3 to 4 as BaSO 4 . The precipitated BaSO 4 is filtered and dried before introduction into an elemental analyzer (EA) Carlo Erba NC 2500. The EA is used to convert sulfur in a BaSO 4 solid sample into SO 2 gas, and the EA is connected to a continuous flow isotope-ratio mass spectrometer (CF-IRMS), which determines differences in the isotope-amount ratios of stable sulfur isotopes ( 34 S/ 32 S) of the product SO 2 gas. The combustion is quantitative; no isotopic fractionation is involved. Samples are placed in a tin capsule and loaded into the Costech Zero Blank Autosampler of the EA. Under computer control, samples are dropped into a heated reaction tube that combines the oxidation and reduction reactions. The combustion takes place in a helium atmosphere containing an excess of oxygen gas at the oxidation zone at the top of the reaction tube. Combustion products are transported by a helium carrier through the reduction zone at the bottom of the reaction tube to remove excess oxygen and through a separate drying tube to remove any water. The gas-phase products, mainly CO 2 , N 2 , and SO 2 , are separated by a gas chromatograph. The gas is then introduced into the isotope-ratio mass spectrometer (IRMS) through a Finnigan MAT (now Thermo Scientific) ConFlo II interface, which is also used to inject SO 2 reference gas and helium for sample dilution. The IRMS is a Thermo Scientific Delta V Plus CF-IRMS. It has a universal triple collector with two wide cups and a narrow cup in the middle. It is capable of measuring mass/charge ( m/z ) 64 and 66 simultaneously. The ion beams from SO 2 are as follows: m/z 64 = SO 2 = 32 S 16 O 16 O; m/z 66 = SO 2 = 34 S 16 O 16 O primarily.

Techniques and Methods↗
USGS2004

Using dual-bacterial denitrification to improve δ15N determinations of nitrates containing mass-independent 17O

The bacterial denitrification method for isotopic analysis of nitrate using N 2 O generated from Pseudomonas aureofaciens may overestimate δ 15 N values by as much as 1–2‰ for samples containing atmospheric nitrate because of mass-independent 17 O variations in such samples. By analyzing such samples for δ 15 N and δ 18 O using the denitrifier Pseudomonas chlororaphis , one obtains nearly correct δ 15 N values because oxygen in N 2 O generated by P. chlororaphis is primarily derived from H 2 O. The difference between the apparent δ 15 N value determined with P. aureofaciens and that determined with P. chlororaphis , assuming mass-dependent oxygen isotopic fractionation, reflects the amount of mass-independent 17 O in a nitrate sample. By interspersing nitrate isotopic reference materials having substantially different δ 18 O values with samples, one can normalize oxygen isotope ratios and determine the fractions of oxygen in N 2 O derived from the nitrate and from water with each denitrifier. This information can be used to improve δ 15 N values of nitrates having excess 17 O. The same analyses also yield estimates of the magnitude of 17 O excess in the nitrate (expressed as Δ 17 O) that may be useful in some environmental studies. The 1- σ uncertainties of δ 15 N, δ 18 O and Δ 17 O measurements are ±0.2, ±0.3 and ±5‰, respectively.

Rapid Communications in Mass Spectrometry↗
USGS2003

Two new organic reference materials for δ13C and δ15N measurements and a new value for the δ13C of NBS 22 oil

Analytical grade L-glutamic acid is chemically stable and has a C/N mole ratio of 5, which is close to that of many of natural biological materials, such as blood and animal tissue. Two L-glutamic acid reference materials with substantially different 13 C and 15 N abundances have been prepared for use as organic reference materials for C and N isotopic measurements. USGS40 is analytical grade L-glutamic acid and has a δ 13 C value of −26.24‰ relative to VPDB and a δ 15 N value of −4.52‰ relative to N 2 in air. USGS41 was prepared by dissolving analytical grade L-glutamic acid with L-glutamic acid enriched in 13 C and 15 N. USGS41 has a δ 13 C value of +37.76‰ and a δ 15 N value of +47.57‰. The δ 13 C and δ 15 N values of both materials were measured against the international reference materials NBS 19 calcium carbonate ( δ 13 C = +1.95‰), L-SVEC lithium carbonate ( δ 13 C = −46.48‰), IAEA-N-1 ammonium sulfate ( δ 15 N = 0.43‰), and USGS32 potassium nitrate ( δ 15 N = 180‰) by on-line combustion continuous-flow and off-line dual-inlet isotope-ratio mass spectrometry. Both USGS40 and USGS41 are isotopically homogeneous; reproducibility of δ 13 C is better than 0.13‰, and that of δ 15 N is better than 0.13‰ in 100-μg amounts. These two isotopic reference materials can be used for (i) calibrating local laboratory reference materials, and (ii) quantifying drift with time, mass-dependent fractionations, and isotope-ratio-scale contraction in the isotopic analysis of various biological materials. Isotopic results presented in this paper yield a δ 13 C value for NBS 22 oil of −29.91‰, in contrast to the commonly accepted value of −29.78‰ for which off-line blank corrections probably have not been quantified satisfactorily.

Rapid Communications in Mass Spectrometry↗
USGS2001

Distribution of oxygen-18 and deuteriun in river waters across the United States

Reconstruction of continental palaeoclimate and palaeohydrology is currently hampered by limited information about isotopic patterns in the modern hydrologic cycle. To remedy this situation and to provide baseline data for other isotope hydrology studies, more than 4800, depth- and width-integrated, stream samples from 391 selected sites within the USGS National Stream Quality Accounting Network (NASQAN) and Hydrologic Benchmark Network (HBN) were analysed for δ 18 O and δ 2 H ( http://water.usgs.gov/pubs/ofr/ofr00-160/pdf/ofr00-160.pdf ). Each site was sampled bimonthly or quarterly for 2·5 to 3 years between 1984 and 1987. The ability of this dataset to serve as a proxy for the isotopic composition of modern precipitation in the USA is supported by the excellent agreement between the river dataset and the isotopic compositions of adjacent precipitation monitoring sites, the strong spatial coherence of the distributions of δ 18 O and δ 2 H, the good correlations of the isotopic compositions with climatic parameters, and the good agreement between the ‘national’ meteoric water line (MWL) generated from unweighted analyses of samples from the 48 contiguous states of δ 2 H=8·11δ 18 O+8·99 ( r 2 =0·98) and the unweighted global MWL of sites from the Global Network for Isotopes in Precipitation (GNIP) of the International Atomic Energy Agency and the World Meteorological Organization (WMO) of δ 2 H=8·17δ 18 O+10·35. The national MWL is composed of water samples that arise in diverse local conditions where the local meteoric water lines (LMWLs) usually have much lower slopes. Adjacent sites often have similar LMWLs, allowing the datasets to be combined into regional MWLs. The slopes of regional MWLs probably reflect the humidity of the local air mass, which imparts a distinctive evaporative isotopic signature to rainfall and hence to stream samples. Deuterium excess values range from 6 to 15‰ in the eastern half of the USA, along the northwest coast and on the Colorado Plateau. In the rest of the USA, these values range from −2 to 6‰, with strong spatial correlations with regional aridity. The river samples have successfully integrated the spatial variability in the meteorological cycle and provide the best available dataset on the spatial distributions of δ 18 O and δ 2 H values of meteoric waters in the USA.

Hydrological Processes↗
USGS2000

Stable hydrogen and oxygen isotope ratios for selected sites of the U.S. Geological Survey's NASQAN and benchmark surface-water networks

Increasingly, hydrologic studies require information on the isotopic composition of natural waters. This report presents stable hydrogen (delta2H) and oxygen isotope ratios (delta18O) from 391 selected sites of the U.S. Geological Survey's National Stream Quality Accounting Network (NASQAN) and BENCHMARK surface water networks collected during the years 1984-1987. Depth-integrated samples were collected and analyzed from each site bimonthly or quarterly for about 3 years.

Open-File Report↗
USGS2000

Stable hydrogen and oxygen isotope ratios for selected sites of the National Oceanic and Atmospheric Administration's Atmospheric Integrated Research Monitoring Network (AIRMoN)

Increasingly, hydrologic studies require information on the isotopic composition of natural waters. This report presents stable hydrogen (δ 2 H) and oxygen isotope ratios (δ 18 0) of precipitation samples from seven selected sites of the National Oceanic and Atmospheric Administration's Atmospheric Integrated Research Monitoring Network (AIRMoN) collected during the years 1992-1994.

Delaware;Illinois;New York;Ohio;Pennsylvania;Tenne↗
USGS2000

A guide for the laboratory information management system (LIMS) for light stable isotopes--Versions 7 and 8

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program, the Laboratory Information Management System (LIMS) for Light Stable Isotopes, is presented herein. Major benefits of this system include (i) a dramatic improvement in quality assurance, (ii) an increase in laboratory efficiency, (iii) a reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) a decrease in errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for laboratories. LIMS for Light Stable Isotopes is available for both Microsoft Office 97 Professional and Microsoft Office 2000 Professional as versions 7 and 8, respectively. Both source code (mdb file) and precompiled executable files (mde) are available. Numerous improvements have been made for continuous flow isotopic analysis in this version (specifically 7.13 for Microsoft Access 97 and 8.13 for Microsoft Access 2000). It is much easier to import isotopic results from Finnigan ISODAT worksheets, even worksheets on which corrections for amount of sample (linearity corrections) have been added. The capability to determine blank corrections using isotope mass balance from analyses of elemental analyzer samples has been added. It is now possible to calculate and apply drift corrections to isotopic data based on the time of day of analysis. Whereas Finnigan ISODAT software is confined to using only a single peak for calculating delta values, LIMS now enables one to use the mean of two or more reference injections during a continuous flow analysis to calculate delta values. This is useful with Finnigan?s GasBench II online sample preparation system. Concentrations of carbon, nitrogen, and sulfur can be calculated based one or more isotopic reference materials analyzed with a group of samples. Both sample data and isotopic analysis data can now be exported to Excel files. A calculator for determining the amount of sample needed for isotopic analysis based on a previous amount of sample and continuous flow area is now an integral part of LIMS for Light Stable Isotopes. LIMS for Light Stable Isotopes can now assign an error code to Finnigan elemental analyzer analyses in which one of the electrometers has saturated due to analysis of too much sample material, giving rise to incorrect isotopic abundances. Information on downloading this report and downloading code and databases is provided at the Internet addresses: http://water.usgs.gov/software/geochemical.html or http://www.geogr.uni-jena.de/software/geochemical.html in the Eastern Hemisphere.

Open-File Report↗
USGS1998

A manual for a Laboratory Information Management System (LIMS) for light stable isotopes

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

Open-File Report↗
USGS1997

Unnatural isotopic composition of lithium reagents

Isotopic analysis of 39 lithium reagents from several manufacturers indicates that seven were artificially depleted in 6 Li significantly in excess of the variation found in terrestrial materials. The atomic weight of lithium in analyzed reagents ranged from 6.939 to 6.996, and δ 7 Li, reported relative to L-SVEC lithium carbonate, ranged from −11 to +3013‰. This investigation indicates that 6 Li-depleted reagents are now found on chemists' shelves, and the labels of these 6 Li-depleted reagents do not accurately reflect the atomic and (or) molecular weights of these reagents. In 1993, IUPAC issued the following statement: “Commercially available Li materials have atomic weights that range between 6.94 and 6.99; if a more accurate value is required, it must be determined for the specific material.” This statement has been found to be incorrect. In two of the 39 samples analyzed, the atomic weight of Li was in excess of 6.99.

Analytical Chemistry↗
USGS1997

A manual for a laboratory information management system (LIMS) for light stable isotopes

The reliability and accuracy of isotopic data can be improved by utilizing database software to (i) store information about samples, (ii) store the results of mass spectrometric isotope-ratio analyses of samples, (iii) calculate analytical results using standardized algorithms stored in a database, (iv) normalize stable isotopic data to international scales using isotopic reference materials, and (v) generate multi-sheet paper templates for convenient sample loading of automated mass-spectrometer sample preparation manifolds. Such a database program is presented herein. Major benefits of this system include (i) an increase in laboratory efficiency, (ii) reduction in the use of paper, (iii) reduction in workload due to the elimination or reduction of retyping of data by laboratory personnel, and (iv) decreased errors in data reported to sample submitters. Such a database provides a complete record of when and how often laboratory reference materials have been analyzed and provides a record of what correction factors have been used through time. It provides an audit trail for stable isotope laboratories. Since the original publication of the manual for LIMS for Light Stable Isotopes, the isotopes 3 H, 3 He, and 14 C, and the chlorofluorocarbons (CFCs), CFC-11, CFC-12, and CFC-113, have been added to this program.

Open-File Report↗
USGS1995

Methane production and consumption monitored by stable H and C isotope ratios at a crude oil spill site, Bemidji, Minnesota

Stable isotopic ratios of C and H in dissolved CH 4 and C in dissolved inorganic C in the ground water of a crude-oil spill near Bemidji, Minnesota, support the concept of CH 4 production by acetate fermentation with a contemporaneous increase in HCO 3 − concentration. Methane concentrations in the saturated zone decrease from 20.6 mg L −1 to less than 0.001 mg L −1 along the investigated flow path. Dissolved N 2 and Ar concentrations in the ground water below the oil plume are 25 times lower than background; this suggests that gas exsolution is removing dissolved CH 4 (along with other dissolved gases) from the ground water. Oxidation of dissolved CH 4 along the flow path seems to be minimal because no measurable change in isotopic composition of CH 4 occurs with distance from the oil body. However, CH 4 is partly oxidized to CO 2 as it diffuses upward from the ground water through a 5- to 7-m thick unsaturated zone; the δ 13 C of the remaining CH 4 increases, the δ 13 C of the CO 2 decreases, and the partial pressure of CO 2 increases. Calculations of C fluxes in the saturated and unsaturated zones originating from the degradation of the oil plume lead to a minimum estimated life expectancy of 110 years. This is a minimum estimate because the degradation of the oil body should slow down with time as its more volatile and reactive components are leached out and preferentially oxidized. The calculated life expectancy is an order of magnitude estimate because of the uncertainty in the average linear ground-water velocities and because of the factor of 2 uncertainty in the calculation of the effective CO 2 diffusion coefficient.

Minnesota↗
USGS1995

Interlaboratory comparison of reference materials for nitrogen-isotope-ratio measurements

Aliquots of seven different reference materials were distributed for an interlaboratory comparison of stable nitrogen-isotope-ratio measurements. Results from 15 laboratories were compiled and evaluated selectively to yield provisional values of 515N for each material, i, with respect to atmospheric N2 (o1SN,7air). The 515N values reported by the different laboratories are correlated in such a way that some of the major discrepancies may be removed by normalization (/. e., by altering the length of the ô N scale for each laboratory by an amount defined by local measurements of reference materials with extreme values).

Report↗
USGS1991

Caution on the use of Viton® or FETFE® O-rings in carbon dioxide sample containers for δ 18 0 analysis

After 10 days, 3-&mu;mol CO 2 samples in containers having glass stopcocks with Viton &reg; or FETFE O-rings were enriched in 18 O by 1.5% as a result of absorption by the elastomer; this amount of enrichment is &sim;20 times greater than the precision of &delta; 18 O measurements of most laboratories. No change in 13 C content was observed. Increasing the sample size to 100 &mu;mol resulted in an 18 O enrichment of 0.2% and did not affect the 13 C content. Caution needs to be exercised in selecting sample containers for CO 2 isotope-ratio samples of < 200 &mu;mol. If stopcocks are used in construction of containers for such samples, the use of all-glass stopcocks with Apiezon N &reg; hydrocarbon-based grease will eliminate the fractionation of oxygen isotopes.

Chemical Geology: Isotope Geoscience Section↗