Search USGS⌕ Search

Geology topics

Kinga M. Revesz

Publications and source records attributed to Kinga M. Revesz.

12 recordsLinked to original sources
USGS2014

Integration of stable carbon isotope, microbial community, dissolved hydrogen gas, and 2 H H 2 O tracer data to assess bioaugmentation for chlorinated ethene degradation in fractured rocks

An in situ bioaugmentation (BA) experiment was conducted to understand processes controlling microbial dechlorination of trichloroethene (TCE) in groundwater at the Naval Air Warfare Center (NAWC), West Trenton, NJ. In the BA experiment, an electron donor (emulsified vegetable oil and sodium lactate) and a chloro-respiring microbial consortium were injected into a well in fractured mudstone of Triassic age. Water enriched in 2 H was also injected as a tracer of the BA solution, to monitor advective transport processes. The changes in concentration and the δ 13 C of TCE, cis-dichloroethene (cis-DCE), and vinyl chloride (VC); the δ 2 H of water; changes in the abundance of the microbial communities; and the concentration of dissolved H2 gas compared to pre- test conditions, provided multiple lines of evidence that enhanced biodegradation occurred in the injection well and in two downgradient wells. For those wells where the biodegradation was stimulated intensively, the sum of the molar chlorinated ethene (CE) concentrations in post-BA water was higher than that of the sum of the pre-BA background molar CE concentrations. The concentration ratios of TCE/(cis-DCE + VC) indicated that the increase in molar CE concentration may result from additional TCE mobilized from the rock matrix in response to the oil injection or due to desorption/diffusion. The stable carbon isotope mass-balance calculations show that the weighted average 13 C isotope of the CEs was enriched for around a year compared to the background value in a two year monitoring period, an effective indication that dechlorination of VC was occurring. Insights gained from this study can be applied to efforts to use BA in other fractured rock systems. The study demonstrates that a BA approach can substantially enhance in situ bioremediation not only in fractures connected to the injection well, but also in the rock matrix around the well due to processes such as diffusion and desorption. Because the effect of the BA was intensive only in wells where an amendment was distributed during injection, it is necessary to adequately distribute the amendments throughout the fractured rock to achieve substantial bioremediation. The slowdown in BA effect after a year is due to some extend to the decrease abundant of appropriate microbes, but more likely the decreased concentration of electron donor.

New Jersey↗
USGS2014

Automated determination of the stable carbon isotopic composition (δ 13 C) of total dissolved inorganic carbon (DIC) and total nonpurgeable dissolved organic carbon (DOC) in aqueous samples: RSIL lab codes 1851 and 1852

The purposes of the Reston Stable Isotope Laboratory (RSIL) lab codes 1851 and 1852 are to determine the total carbon mass and the ratio of the stable isotopes of carbon (δ 13 C) for total dissolved inorganic carbon (DIC, lab code 1851) and total nonpurgeable dissolved organic carbon (DOC, lab code 1852) in aqueous samples. The analysis procedure is automated according to a method that utilizes a total carbon analyzer as a peripheral sample preparation device for analysis of carbon dioxide (CO 2 ) gas by a continuous-flow isotope ratio mass spectrometer (CF-IRMS). The carbon analyzer produces CO 2 and determines the carbon mass in parts per million (ppm) of DIC and DOC in each sample separately, and the CF-IRMS determines the carbon isotope ratio of the produced CO 2 . This configuration provides a fully automated analysis of total carbon mass and δ 13 C with no operator intervention, additional sample preparation, or other manual analysis. To determine the DIC, the carbon analyzer transfers a specified sample volume to a heated (70 °C) reaction vessel with a preprogrammed volume of 10% phosphoric acid (H 3 PO 4 ), which allows the carbonate and bicarbonate species in the sample to dissociate to CO 2 . The CO 2 from the reacted sample is subsequently purged with a flow of helium gas that sweeps the CO 2 through an infrared CO 2 detector and quantifies the CO 2 . The CO 2 is then carried through a high-temperature (650 °C) scrubber reactor, a series of water traps, and ultimately to the inlet of the mass spectrometer. For the analysis of total dissolved organic carbon, the carbon analyzer performs a second step on the sample in the heated reaction vessel during which a preprogrammed volume of sodium persulfate (Na 2 S 2 O 8 ) is added, and the hydroxyl radicals oxidize the organics to CO 2 . Samples containing 2 ppm to 30,000 ppm of carbon are analyzed. The precision of the carbon isotope analysis is within 0.3 per mill for DIC, and within 0.5 per mill for DOC.

Techniques and Methods↗
USGS2012

Heterogeneous redox conditions, arsenic mobility, and groundwater flow in a fractured-rock aquifer near a waste repository site in New Hampshire, USA

Anthropogenic sources of carbon from landfill or waste leachate can promote reductive dissolution of in situ arsenic (As) and enhance the mobility of As in groundwater. Groundwater from residential-supply wells in a fractured crystalline-rock aquifer adjacent to a Superfund site in Raymond, New Hampshire, USA, showed evidence of locally enhanced As mobilization in relatively reducing (mixed oxic-anoxic to anoxic) conditions as determined by redox classification and other lines of evidence. Redox classification was determined from geochemical indicators based on threshold concentrations of dissolved oxygen (DO), nitrate (NO 3- ), iron (Fe 2+ ), manganese (Mn 2+ ), and sulfate (SO 4 2- ). Redox conditions were evaluated also based on methane (CH 4 ), excess nitrogen gas (N 2 ) from denitrification, the oxidation state of dissolved As speciation (As(III) and As(V)), and several stable isotope ratios. Samples from the residential-supply wells primarily exhibit mixed redox conditions, as most have long open boreholes (typically 50–100 m) that receive water from multiple discrete fractures with contrasting groundwater chemistry and redox conditions. The methods employed in this study can be used at other sites to gauge redox conditions and the potential for As mobilization in complex fractured crystalline-rock aquifers where multiple lines of evidence are likely needed to understand As occurrence, mobility, and transport.

New Hampshire↗
USGS2012

Determination of the δ 2 H and δ 18 O of soil water and water in plant matter; RSIL lab code 1700

The purpose of the Reston Stable Isotope Laboratory lab code 1700 is to determine the δ 2 H/ 1 H), abbreviated as δ 2 H, and the δ 18 O/ 16 O), abbreviated as δ 18 O, of soil water and water in plant matter. This method is based on the observation that water and toluene form an azeotropic mixture at 84.1 °C. This temperature is substantially lower than the boiling points of water (100 °C) and toluene (110 °C), but water and toluene are immiscible at ambient temperature. The water content of a soil or plant is determined by weighing, drying, and reweighing a small amount of sample. Sufficient sample to collect 3 to 5 milliliters of water after distillation is loaded into a distillation flask. Sufficient toluene is added so that the sample is immersed throughout the entire distillation to minimize evaporation of water, which would affect the δ 2 H and δ 18 O values. The mixture of sample and toluene is heated in a flask to its boiling point (84.1 °C) so that water from the sample and toluene can distill together into a specially designed collection funnel. The temperature of 84.1 °C is maintained until the water has been quantitatively transferred to the collection funnel, at which time the temperature is raised to the boiling point of the remaining component (toluene, 110 °C). The collection funnel is maintained at ambient temperature so that the sample water and toluene can be separated physically. After separation, the sample water is purified by addition of paraffin wax to the container with the sample water, capping the container, and heating to approximately 60 °C to melt the wax. Trace amounts of toluene will dissolve in the wax, purifying the sample water for isotopic analysis. The isotopic composition of the purified water is then determined by equilibration with gaseous hydrogen or carbon dioxide, followed by dual-inlet isotope-ratio mass spectrometry. Because laser-absorption spectrometry is sensitive to organic compounds, such as trace toluene remaining in water samples, water samples should be analyzed for isotopic composition only by mass spectrometry and not by laser-absorption spectrometry.

Techniques and Methods↗
USGS2010

Chemical evolution of groundwater near a sinkhole lake, northern Florida: 2. Chemical patterns, mass-transfer modeling, and rates of chemical reactions

Chemical patterns along evolutionary groundwater flow paths in silicate and carbonate aquifers were interpreted using solute tracers, carbon and sulfur isotopes, and mass balance reaction modeling for a complex hydrologic system involving groundwater inflow to and outflow from a sinkhole lake in northern Florida. Rates of dominant reactions along defined flow paths were estimated from modeled mass transfer and ages obtained from CFC-modeled recharge dates. Groundwater upgradient from Lake Barco remains oxic as it moves downward, reacting with silicate minerals in a system open to carbon dioxide (CO 2 ), producing only small increases in dissolved species. Beneath and downgradient of Lake Barco the oxic groundwater mixes with lake water leakage in a highly reducing, silicate-carbonate mineral environment. A mixing model, developed for anoxic groundwater downgradient from the lake, accounted for the observed chemical and isotopic composition by combining different proportions of lake water leakage and infiltrating meteoric water. The evolution of major ion chemistry and the 13 C isotopic composition of dissolved carbon species in groundwater downgradient from the lake can be explained by the aerobic oxidation of organic matter in the lake, anaerobic microbial oxidation of organic carbon, and incongruent dissolution of smectite minerals to kaolinite. The dominant process for the generation of methane was by the CO 2 reduction pathway based on the isotopic composition of hydrogen (δ 2 H(CH 4 ) = −186 to −234‰) and carbon (δ 13 C(CH 4 ) = −65.7 to −72.3‰). Rates of microbial metabolism of organic matter, estimated from the mass transfer reaction models, ranged from 0.0047 to 0.039 mmol L −1 yr −1 for groundwater downgradient from the lake.

Water Resources Research↗
USGS2002

δ 13 C and δ 18 O isotopic composition of CaCO 3 measured by continuous flow isotope ratio mass spectrometry: statistical evaluation and verification by application to Devils Hole core DH-11 calcite

A new method was developed to analyze the stable carbon and oxygen isotope ratios of small samples (400 ± 20 µg) of calcium carbonate. This new method streamlines the classical phosphoric acid/calcium carbonate (H 3 PO 4 /CaCO 3 ) reaction method by making use of a recently available Thermoquest-Finnigan GasBench II preparation device and a Delta Plus XL continuous flow isotope ratio mass spectrometer. Conditions for which the H 3 PO 4 /CaCO 3 reaction produced reproducible and accurate results with minimal error had to be determined. When the acid/carbonate reaction temperature was kept at 26 °C and the reaction time was between 24 and 54 h, the precision of the carbon and oxygen isotope ratios for pooled samples from three reference standard materials was ≤0.1 and ≤0.2 per mill or ‰, respectively, although later analysis showed that materials from one specific standard required reaction time between 34 and 54 h for δ 18 O to achieve this level of precision. Aliquot screening methods were shown to further minimize the total error. The accuracy and precision of the new method were analyzed and confirmed by statistical analysis. The utility of the method was verified by analyzing calcite from Devils Hole, Nevada, for which isotope-ratio values had previously been obtained by the classical method. Devils Hole core DH-11 recently had been re-cut and re-sampled, and isotope-ratio values were obtained using the new method. The results were comparable with those obtained by the classical method with correlation = +0.96 for both isotope ratios. The consistency of the isotopic results is such that an alignment offset could be identified in the re-sampled core material, and two cutting errors that occurred during re-sampling then were confirmed independently. This result indicates that the new method is a viable alternative to the classical reaction method. In particular, the new method requires less sample material permitting finer resolution and allows automation of some processes resulting in considerable time savings.

Rapid Communications in Mass Spectrometry↗
USGS2002

Comparison of δ18O measurements in nitrate by different combustion techniques

Three different KNO 3 salts with δ 18 O values ranging from about −31 to +54‰ relative to VSMOW were used to compare three off-line, sealed glass tube combustion methods (widely used for isotope studies) with a more recently developed on-line carbon combustion technique. All methods yielded roughly similar isotope ratios for KNO 3 samples with δ 18 O values in the midpoint of the δ 18 O scale near that of the nitrate reference material IAEA-NO-3 (around +21 to +25‰). This reference material has been used previously for one-point interlaboratory and intertechnique calibrations. However, the isotope ratio scale factors by all of the off-line combustion techniques are compressed such that they are between 0.3 and 0.7 times that of the on-line combustion technique. The contraction of the δ 18 O scale in the off-line preparations apparently is caused by O isotope exchange between the sample and the glass combustion tubes. These results reinforce the need for nitrate reference materials with δ 18 O values far from that of atmospheric O 2 , to improve interlaboratory comparability.

Analytical Chemistry↗
USGS2001

Measurement of delta 13 C and delta 18 O Isotopic Ratios of CaCO 3 by a Thermoquest Finnigan GasBench II Delta Plus XL Continous Flow Isotope Ratio Mass Spectrometer with Application to Devils Hole Core DH-11 Calcite

A new method was developed to analyze the stable carbon and oxygen isotope ratios of small samples (400?20 ?g) of calcium carbonate. This new method streamlines the classical phosphoric acid - calcium carbonate (H3PO4 - CaCO3) reaction method by making use of a Thermoquest-Finnigan GasBench II preparation device and a Delta Plus XL continuous flow isotope ratio mass spectrometer. To obtain reproducible and accurate results, optimal conditions for the H3PO4 - CaCO3 reaction had to be determined. At the acid-carbonate reaction temperature suggested by the equipment manufacturer, the oxygen isotope ratio results were unsatisfactory (standard deviation () greater than 1.5 per mill), probably because of a secondary reaction. When the acid-carbonate reaction temperature was lowered to 26?C and the reaction time was increased to 24 hours, the precision of the carbon and oxygen isotope ratios for duplicate analyses improved to 0.1 and 0.2 per mill, respectively. The method was tested by analyzing calcite from Devils Hole, Nevada, which was formed by precipitation from ground water onto the walls of a sub-aqueous cavern during the last 500,000 years. Isotope-ratio values previously had been obtained by the classical method for Devils Hole core DH-11. The DH-11 core had been recently re-sampled, and isotope-ratio values were obtained using this new method. The results were comparable to those obtained by the classical method. The consistency of the isotopic results is such that an alignment offset could be identified in the re-sampled core material, a cutting error that was then independently confirmed. The reproducibility of the isotopic values is demonstrated by a correlation of approximately 0.96 for both isotopes, after correcting for an alignment offset. This result indicates that the new method is a viable alternative to the classical method. In particular, the new method requires less sample material permitting finer resolution and allows automation of some processes resulting in considerable timesavings.

Open-File 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↗
USGS1990

A method to extract soil water for stable isotope analysis

A method has been developed to extract soil water for determination of deuterium (D) and 18 O content. The principle of this method is based on the observation that water and toluene form an azeotropic mixture at 84.1°C, but are completely immiscible at ambient temperature. In a specially designed distillation apparatus, the soil water is distilled at 84.1°C with toluene and is separated quantitatively in the collecting funnel at ambient temperature. Traces of toluene are removed and the sample can be analyzed by mass spectrometry. Kerosene may be substituted for toluene. The accuracy of this technique is ± 2 and &#xB1; 0.2&#x2030; "> ± 0.2‰ , respectively, for δD and δ 18 O. Reduced accuracy is obtained at low water contents.

Journal of Hydrology↗