Get absorbance peaks and indices
abs_parm.RdTakes a dataframe of absorbance data and calculates optical properties for each sample. If data was collected at greater than 1 nm intervals, data will be interpolated to 1 nm intervals.
Arguments
- abs_data
a dataframe containing the absorbance data, where each column is a sample
- waves
optional, a vector of wavelengths in nm to extract from the absorbance data
- meta
the metadata table for the sample run, should include DOC data in mg/L
- keep_all
a logical, TRUE will return all samples even those without DOC data, FALSE will only return samples with DOC data
- cuvle
the length of the cuvette in cm
Details
Absorbance indices based on Hansen et al. 2016. Measurements are defined as follows:
SUVA254, SUVA280, SUVA350, SUVA370: SUVA at 254, 280, 350, and 370 nm. Units of \(\text{L mgC}^{-1} \text{m}^{-1}\). Typically higher values are associated with greater aromatic content.
SVA412, SVA440, SVA480, SVA510, SVA532, SVA555: SVA at 412, 440, 480, 510, 532, 555 nm. Units of \(\text{L mgC}^{-1} \text{m}^{-1}\). Typically higher values are associated with greater aromatic content.
S275_295: Spectral slope between 275 to 295 nm.
S350_400: Spectral slope between 350 to 400 nm.
Spectral slopes are found with a nonlinear fit of an exponential function to the absorption spectrum, typically higher values are associated with lower molecular weight materials and/or lower aromaticity.
SR: Spectral slope S275_295 divided by spectral slope S350_400, negatively correlated to DOM molecular weight and generally increases on irradiation.
References
Hansen, A. M., Kraus, T. E. C., Pellerin, B. A., Fleck, J. A., Downing, B. D., & Bergamaschi, B. A. (2016). Optical properties of dissolved organic matter (DOM): Effects of biological and photolytic degradation. Limnology and Oceanography, 61(3), 1015–1032. https://doi.org/10.1002/lno.10270