Methodology: Boron Isotope Analysis

Boron isotopes natural materials

Compilation of δ11B ranges for various earth system materials and environmental conditions.

Boron has two naturally occurring isotopes 10B (19.9%) and 11B (80.1%). Due to a relatively large mass difference (10%) between the two isotopes and high volatility, the boron isotope ratio ranges from −70 to +60‰ in natural materials and has been used as a tracer for studying continental weathering, plate subduction processes, pH variability in the oceans and anthropogenic pollution. Boron isotopic ratios are conventionally expressed in delta notation (δ11B), which denotes the deviation of measured 11B/10B ratios from the standard in parts per thousand using the equation below:

Isobar boron isotopic ratio

Purification: Quantitative recovery of boron from the matrix is required for boron isotope measurements in carbonates and water. Low-blank separation of boron from the matrix is conducted by means of extraction chromatography using boron-specific chelating resin (Amberlite IRA-743) following the method of Giri et al., 2019.

B isotope measurement: Boron isotope measurements are performed with a Neptune Plus multi-collection inductively coupled plasma mass spectrometer (MC-ICP-MS) following the method in Giri et al., 2019.

References

Briand, C.; Plagnes, V.; Sebilo, M.; Louvat, P.; Chesnot, T.; Schneider, M.; Ribstein, P. and Marchet, P., 2013: Combination of nitrate (N, O) and boron isotopic ratios with microbiological indicators for the determination of nitrate sources in karstic groundwater. Environ. Chem., vol. 10, pp. 365–369. http://dx.doi.org/10.1071/EN13036.

Chalk, T.B.; Foster, G.L.; Wilson, P.A., 2019: Dynamic storage of CO2 in the Atlantic Ocean revealed by boron [CO32-] and pH record. Earth and Planetary Science Letters, vol. 510, pp. 1-11.

Giri, S.J.; Swart, P.K.; Pourmand, A., 2019: The influence of seawater calcium ions on coral calcification mechanisms: Constraints from boron and carbon isotopes and B/Ca ratios in Pocillopora damicornis. Earth and Planetary Sciences Letters, vol. 519, pp.130-140.

EPA-68-01-3201, 1976: Chemical technology and economics in environmental perspectives. Task II- Removal of Boron from wastewater. Environmental Protection Agency, Office of Toxic Substances, Washington, D.C. 20460