Boron Isotopes



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Natural boron contains two stable isotopes – boron-10 and boron-11. Their natural abundance in compounds makes approximately 19.3% at. And 80.79% at., respectively. Nuclear properties of boron-10 and boron-11 differ greatly. Their reactions with neutrons are of critical importance. This new volume on boron isotope geochemistry offers review chapters summarizing the cosmochemistry, high-temperature and low-temperature geochemistry, and marine chemistry of boron. It also covers theoretical aspects of B isotope fractionation, experiments and atomic modeling, as well as all aspects of boron isotope analyses in geologic materials using the full range of solutions and in-situ. The boron isotope ratio is used as tracer to study mass transfer processes in geologic environments, seawater pH, and anthropogenic emissions in the atmosphere. The NIST SRM 951 boric acid solution is certified for use as an isotopic RM (NIST, 1999) and used as ‘delta zero’ material.

U.S. Geological Survey Scientific Investigations Report 2007–5166

Natural boron contains 2 isotopes, 10B and 11B with about 19.8 at% 10B, of which only 10B is a neutron absorber. For electronic purposes (improving the electronic properties) or nuclear applications (improving the neutron absorption efficiency), modifying this ratio can be required.

By Paul M. Buszka, John Fitzpatrick, Lee R. Watson, and Robert T. Kay

ONLINE ONLY

This report is available below as a 46-page PDF for viewing and printing.

Boron Isotopes

Abstract

Concentrations of boron greater than the U.S. Environmental Protection Agency (USEPA) 900 µg/L removal action level (RAL) standard were detected in water sampled by the USEPA in 2004 from three domestic wells near Beverly Shores, Indiana. The RAL regulates only human-affected concentrations of a constituent. A lack of well logs and screened depth information precluded identification of whether water from sampled wells, and their boron sources, were from human-affected or natural sources in the surficial aquifer, or associated with a previously defined natural, confined aquifer source of boron from the subtill or basal sand aquifers. A geochemically-based classification of the source of boron in ground water could potentially determine the similarity of boron to known sources or mixtures between known sources, or classify whether the relative age of the ground water predated the potential sources of contamination. The U.S. Geological Survey (USGS), in cooperation with the USEPA, investigated the use of a geochemical method that applied boron stable isotopes, and concentrations of boron, tritium, and other constituents to distinguish between natural and human-affected sources of boron in ground water and thereby determine if the RAL was applicable to the situation.

Boron stable-isotope ratios and concentrations of boron in 17 ground-water samples and tritium concentrations in 9 ground-water samples collected in 2004 were used to identify geochemical differences between potential sources of boron in ground water near Beverly Shores, Indiana. Boron and d11B analyses for this investigation were made on unacidified samples to assure consistency of the result with unacidified analyses of d11 Stronghold crusader apk data. B values from other investigations. Potential sources of boron included surficial-aquifer water affected by coal-combustion products (CCP) or domestic-wastewater, upward discharge of ground water from confined aquifers, and unaffected water from the surficial aquifer that was distant from human-affected boron sources.

Boron concentrations in potential ground-water sources of boron were largest (15,700 to 24,400 µg/L) in samples of CCP-affected surficial aquifer water from four wells at a CCP landfill and smallest (27 to 63 µg/L) in three wells in the surficial aquifer that were distant from human-affected boron sources. Boron concentrations in water from the basal sand aquifer ranged from 656 µg/L to 1,800 µg/L. Boron concentrations in water from three domestic-wastewater-affected surficial aquifer wells ranged from 84 to 387 µg/L. Among the representative ground-water samples, boron concentrations from all four samples of CCP-affected surficial aquifer water and four of five samples of water from the basal sand aquifer had concentrations greater than the RAL. A comparison of boron concentrations in acid-preserved and unacidified samples indicated that boron concentrations reported for this investigation may be from about 11 to 16 percent less than would be reported in a standard analysis of an acidified sample.

The stable isotope boron-11 was most enriched in comparison to boron-10 in ground water from a confined aquifer, the basal sand aquifer (d11B, 24.6 to 34.0 per mil, five samples); it was most depleted in CCP-affected water from the surficial aquifer (d11B, 0.1 to 6.6 per mil, four samples). Domestic-wastewater-affected water from the surficial aquifer (d11B, 8.7 to 11.7 per mil, four samples) was enriched in boron-11, in comparison to individual samples of a borax detergent additive and a detergent with perborate bleach; it was intermediate in composition between basal sand aquifer water and CCP-affected water from the surficial aquifer. The similarity between a ground-water sample from the surficial aquifer and a hypothetical mixture of unaffected surficial aquifer and basal sand aquifer waters indicates the potential for long-term upward discharge of ground water into the surficial aquifer from one or more confined aquifers. Estimated d11B values for acidified samples were depleted by 1.9 to 2.8 per mil in comparison to unacidified samples from the four wells sampled; those differences were small in comparison to the differences between d11B values of representative sources of boron in ground water.

Tritium concentrations ranged from 7.0 to 10.3 tritium units in six samples from the surficial aquifer and were less than 0.8 tritium units in three samples from the basal sand aquifer. Water from wells in the surficial aquifer represents predominantly modern, post-1972 recharge and sources of boron and other constituents. Water from the basal sand aquifer is associated with pre-1952 recharge from sources not affected by local boron inputs.

Ground water from six wells (five domestic wells and one public-supply well) where the ground-water source was unknown had boron concentrations, boron isotope ratios, and tritium concentrations similar to water from the basal sand aquifer. Boron concentrations greater than the RAL were found in water from four of these six wells. The boron isotope and tritium data from these four wells indicate a natural source of boron in ground water; therefore, the RAL does not apply to boron concentrations in water from these wells. Water samples from two domestic wells where the ground-water source was unknown had boron concentrations less than the RAL and boron isotope ratios and tritium concentrations that were similar to domestic-wastewater-affected water from the surficial aquifer. The boron isotope ratio for a sample from one domestic well was similar to that of CCP-affected water from the surficial aquifer and detergent compositions; the boron concentration of that sample was less than the RAL. The classifications of differences among representative sources of boron in ground water and water samples from wells where the ground-water source was unknown generally agreed with distinctions based on strontium-87/strontium-86 ratios and concentrations of strontium, chloride, nitrate, and ammonia. This application of boron concentrations, boron isotope ratios, and tritium concentrations to classify differences in relation to potential sources of boron in ground water was able to distinguish between boron from natural sources and from human-affected sources that are subject to regulation.

Boron Isotopes Wikipedia

Contents

Abstract

Introduction

Background Information

Purpose and Scope

Description of the Study Area

Hydrogeologic Framework

Methods of Data Collection and Analysis

Well Selection

Surficial Aquifer Wells Distant from Human-Affected Boron Sources

Basal Sand Aquifer Wells Representing Natural Boron Sources

Coal-Combustion-Product-Affected Wells in the Surficial Aquifer

Domestic-Wastewater-Affected Wells in the Surficial Aquifer

Water Samples from Wells with an Unknown Ground-Water Source

Sampling Methods

Laboratory Analyses of Water Samples

Evaluation of Ground-Water and Boron Sources

Quality-Assurance Results

Boron and Boron Stable-Isotopes in Representative Ground-Water Sources

Tritium in Representative Ground-Water Sources

Evaluation of Ground-Water and Boron Sources for Wells with an Unknown Ground-Water Source

Comparison with Selected Water-Chemistry Constituents

Limitations of the Evaluation Method

Summary and Conclusions

Acknowledgments

References Cited

Figures

1–4. Maps showing:
1. Study area near Beverly Shores and surrounding area, northwestern Indiana.
2. Wells sampled in the study area near Beverly Shores, the Town of Pines, and the Indiana Dunes National Lakeshore,
northwestern Indiana, 2004.
3. Wells sampled and wetland areas in the study area near Beverly Shores, northwestern Indiana, 2004.
4. Unconsolidated aquifer systems in the Lake Michigan region and the study area near Beverly Shores, northwestern Indiana.
5. Diagrammatic hydrogeologic section showing aquifers and conceptual ground-water-flow directions in the western half of the
Indiana Dunes National Lakeshore near Beverly Shores, Indiana.
6. Map showing wells completed in the surficial aquifer and wells with an unknown ground-water source sampled near Beverly Shores,
northwestern Indiana, 2004, in relation to the water-table altitude in the surficial aquifer, October 1980.
Percent
7–11. Photographs showing:
7. Wells 3S and 3B in relation to a nearby home along a dune ridge, facing southeast at Beverly Shores, Indiana.
8. A flowing well developed in the basal sand aquifer at Beverly Shores, Indiana.
9. Well 9A with the Yard 520 landfill in the background, facing southwest at the Town of Pines, Indiana.
10. (A) View facing west of well 5W in the surficial aquifer at a National Park Service public facility, and (B) view facing southwest
of homes that are upgradient of well 5W along the Lake Michigan shore at Beverly Shores, Indiana.
11. An example of a suspected domestic-wastewater seep at Beverly Shores, Indiana.
12–17. Graphs showing:
12. The average monthly tritium concentration in precipitation in samples collected from Ottawa, Canada, 1953–2002, and from
Chicago, Illinois, 1962–1979.
13. Chemistry of water samples from wells in and near Beverly Shores, northwestern Indiana, 2004, in relation to boron isotope
composition and boron concentrations for representative sources of boron in ground water.
14. The average annual tritium concentration in precipitation, corrected for decay to July 2004, in samples collected from Ottawa,
Canada, 1953–2002, compared with tritium concentrations in ground-water samples in the study area near Beverly Shores,
northwestern Indiana, 2004.
15. Boron concentrations (A) greater than 400 micrograms per liter and (B) less than 200 micrograms per liter in relation to boron
isotope composition in water samples from representative sources of boron in ground water and from wells with an unknown
ground-water source near Beverly Shores, northwestern Indiana, 2004.
16. Tritium concentrations in water from wells with an unknown ground-water source that were (A) less than 1 tritium unit and
(B) greater than 5 tritium units in relation to boron isotope compositions in water samples from representative sources of boron
in ground water near Beverly Shores, northwestern Indiana, 2004.
17. Strontium concentrations in relation to strontium-87/strontium-86 isotope ratios in ground-water samples for
(A) representative ground-water sources near Beverly Shores, 2004, and slag-affected ground water in northwestern Indiana,
1997–99, and (B) water from wells with an unknown ground-water source near Beverly Shores, 2004.

Tables

1. Comparison of hydrogeologic framework of the study area near Beverly Shores, Indiana with those of previous investigations.
2. Selected characteristics of wells sampled for water chemistry near Beverly Shores and the Town of Pines, northwestern Indiana, 2004.
3. Analytical methods for ground-water samples collected near Beverly Shores, Indiana, 2004.
4. Determinations of field parameters for water samples collected from wells near Beverly Shores and the Town of Pines, northwestern
Indiana, 2004.
5. Water-chemistry determinations for samples collected from wells near Beverly Shores and the Town of Pines, northwestern Indiana,
2004.
6. Water-chemistry determinations for samples and sequential duplicates collected from wells near Beverly Shores and the Town of Pines,
northwestern Indiana, and for deionized water and an equipment blank, 2004.
7. Comparison of boron determinations from analyses of acidified and unacidified samples from wells near Beverly Shores and the Town of
Pines, northwestern Indiana, November 2004.
8. Boron and boron stable-isotope analyses of a borax detergent additive and a detergent with perborate bleach, 2004.
9. Ranges of boron isotope ratios in samples of representative ground-water sources of boron collected in the study area near Beverly
Shores, northwestern Indiana, 2004 and of detergent additive and detergent samples, 2004, as compared to selected published data.
10. Comparison of chemistry of domestic-wastewater-affected water samples to those from a hypothetical mixture of representative
compositions of water from the surficial aquifer and water affected by coal-combustion products.
11. Classifications of similarity to representative sources of boron in ground water and to ground-water source, based on boron isotope
compositions and boron and tritium concentrations.
12. Water-chemistry determinations for slag-affected samples collected from wells in northwestern Indiana, 1997 and 1999.

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Buszka, P.M., Fitzpatrick, J., Watson, L.R., and Kay, R.T., 2007, Evaluation of ground-water and boron sources by use of boron stable-isotope ratios, tritium, and selected water-chemistry constituents near Beverly Shores, northwestern Indiana, 2004: U.S. Geological Survey Scientific Investigations Report 2007–5166, 46 p.



Boron Isotope Notation

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Periodic Table--Boron

Boron has two naturally-occurring stable isotopes, 11B (80.1%) and 10B (19.9%). The mass difference results in a wide range of d11B values in natural waters, ranging from -16 to +59 ‰ (data from references within Vengosh et al., 1994). Isotopic fractionation of boron is controlled by the exchange reactions of the boron species B(OH)3 and B(OH)4 (Schwarcz et al., 1969). Boron isotopes are also fractionated during mineral crystalization (Oi et al., 1989), during H2O phase changes in hydrothermal systems (Spivack et al., 1990; Leeman et al., 1992), and during hydrothermal alteration of rock (Spivak, 1985). The latter effect (species preferential removal of the 10B(OH)4 ion onto clays results in solutions enriched in 11B(OH)3; Schwarcz et al., 1969) may be responsible for the large 11B enrichment in seawater relative to both oceanic crust (Spivack and Edmond, 1987) and continental crust (Spivack et al., 1987). All of these effects combine to produce B isotopic variations in hydrologic systems that can be very useful. Boron isotopic ratios have been used to trace the origin of water masses (Palmer and Sturchio, 1990), to track the evolution of brines (Vengosh et al., 1991 a, b; Moldovanyi et al., 1993), to determine the origin of evaporites (Swihart et al., 1986; Vengosh et al., 1992), and to examine hydrothermal flow systems (Leeman et al., 1992).

Boron Isotopes 10

Boron in groundwater might derive from leaching of country rocks, infiltration of meteoric salts, mixing with adjacent groundwaters, and contamination by anthropogenic sources. While boric acid and borate minerals are widely used in industrial applications, the main use of boron compounds (especially sodium perborate) is as a bleaching agent in detergents. This usage causes high concentrations of boron in wastewaters worldwide. Vengosh et al. (1994) note that each of these sources has a distinctive boron isotopic signature (eg., the d11B of seawater is 39‰ and that of average continental crust is 0 +/- 5 ‰).

In one study in Israel (Vengosh et al., 1994), raw and untreated sewage were found to have d11B values ranging from 5.3 to 12.9 ‰, overlapping the compositions of natural non-marine sodium borate minerals (-0.9 to 10.2 ‰). However, these values were significantly different from regional uncontaminated groundwater (~30 ‰) and seawater. Furthermore, groundwater contaminated by recharge of treated sewage had a high B/Cl ratio and a distinctive d11B signature of 7 to 25 ‰. Elemental B and d11B variations reflect both mixing with regional groundwater and the boron isotope fractionation caused by boron removal by adsorption onto clays. Therefore, boron isotopes have a high likelihood of being a very useful tracer in groundwater systems in which the role of clay and minerals can be clearly identified, as a tracer for anthropogenic boron and as a tracer for seawater contamination.

Source of text: This review was assembled by Carol Kendall, Eric Caldwell and Dan Snyder, primarily drawing from Vengosh et al. (1994) and Nimz (1998).

Boron Isotopes Atomic Number

References
Leeman, W. P., Vocke, R. D., and McKibben, M. A. (1992). 'Boron isotopic fractionations between coexisting vapor and liquid in natural geothermal systems.' In: Y. K. Kharaka and A. S. Maset (Eds.), Water-rock Interaction, Proceedings of the 7th International Symposium on Water-Rock Interaction. Balkema Publishers, Rotterdam, p. 1007.
Moldovanyi, E. P., Walter, L. M. and Land, L. S. (1993). 'Strontium, boron, oxygen, and hydrogen isotope geochemistry of brines from basal strata of the Gulf Coast sedimentary basin, USA.' Geochim. et Cosmochim. Acta, 57: 2083.
Nimz, G. J. (1998). 'Lithogenic and Cosmogenic Tracers in Catchment Hydrology.' In: C. Kendall and J. J. McDonnell (Eds.), Isotope Tracers in Catchment Hydrology. Elsevier, pp. 247-290.
Oi, T., Nomura, M., Musashi, M., Ossaka, T., Okamoto, M. and Kakihana, H. (1989). 'Boron isotopic compositions of some boron minerals.' Geochim. et Cosmochim. Acta, 53: 3189.
Palmer, M. R. and Sturchio, N. C. (1990). 'The boron isotope systematics of the Yellowstone National Park (Wyoming) hydrothermal system: A reconnaissance.' Geochim. et Cosmochim. Acta, 54: 2811.
Schwarcz, H. P., Agyei, E. K., McCullen, C. C. (1969). 'Boron isotopic fractionation during clay adsorption from seawater', Earth Planet Sci. Lett.6,1-5.
Spivack, A. J. (1985). 'Boron isotope marine geochemistry.' Conf. Int. Les Isotopes dans le Cycle Sedimentaire, Obernai. Cited in: J. Hoefs, 1987. Stable Isotope Geochemistry, Third Edition. Springer-Verlag, Berlin.
Spivack, A. J., Berndt, M. E. and Seyfried, W. E. (Jr.) (1990). 'Boron isotope fractionation during supercritical phase separation.' Geochim. et Cosmochim. Acta, 54: 2337.
Spivack, A. J. and Edmond, J. M. (1987). 'Boron isotope exhange between seawater and ocean crust.' Geochim. et Cosmochim. Acta, 51: 1003.
Spivack, A. J. , Palmer, M. R. and Edmond, J. M. (1987). 'The sedimenary cycle of boron isotopes.' Geochim. et Cosmochim. Acta, 51: 1939.
Swilhart, G. H., Moore, P. B. and Callis, E. L. (1986). 'Boron isotopic composition of marine and non-marine evaporite borates.'Geochim. et Cosmochim. Acta, 50: 1297.
Vengosh, A., Heumann, K. G., Juraske, S., and Kasher, R. (1994) 'Boron isotope application for tracing sources of contamination in groundwater', Environ. Sci., Technol., 28, 1968-1974.