a18_HCO3_H2O() calculates the 18O/16O fractionation factor between bicarbonate ion HCO3(-) and water.

## Usage

a18_HCO3_H2O(temp)

## Arguments

temp

Temperature (°C).

## Value

Returns the 18O/16O fractionation factor.

## Details

$$\alpha^{18}_{HCO3(-)/H2O} = e^{2.59 \times \frac{1000}{T^{2}} + 0.00189}$$

The equation above and in the function is the uncorrected equation in Beck et al. (2005). They experimentally determined the fractionation factor using BaCO3 precipitation experiments. However, they applied the acid fractionation factor of calcite during the data processing and not that of BaCO3. The acid fractionation factor of BaCO3 is not known accurately, which may result in a bias of up to 1‰ in the calculated 1000lna values.

## References

Beck, W. C., Grossman, E. L., & Morse, J. W. (2005). Experimental studies of oxygen isotope fractionation in the carbonic acid system at 15°, 25°, and 40°C. Geochimica et Cosmochimica Acta, 69(14), 3493-3503. doi:10.1016/j.gca.2005.02.003