Reference Corrections
In NEONiso: Tools to Calibrate and Work with NEON Atmospheric Isotope Data

knitr::opts_chunk$set(
  collapse = TRUE,
  comment = "#>"
)

library(NEONiso)

date: 2022-09-21

There are several instances across the atmospheric isotope measurements made by NEON where there appears to be a disconnect between the "known" isotope ratio (and in the case of CO2, the mixing ratio) of the reference materials used. NEONiso attempts to correct these to maximize data coverage, primarily through: a) analysis of time series plots of reference and measured values of validation gases, and/or b) consultation with NEON staff.

As of version 0.6.0, these corrections are only applied to carbon isotopes, as the water isotope calibration functions are still experimental and have known deficiencies.

The list of carbon isotope reference material corrections can be accessed using the 'carb' data object bundled with NEONiso:

#manually load data file:
carb <- readRDS("carb.rds")
print(carb[, -4], width = Inf, n = 27)

This table lists, in order, a) the site affected; b) the reference gas affected; c) the start and end dates to which the correction is applied; d) the suspect CO2 reference mole fraction; e) the corrected CO2 mole fraction; f) logical of whether files recently pulled from the NEON data portal are expected to have the CO2 values already corrected; f) the suspect d13C value; g) the corrected d13C value; h) the version of NEONiso where that entry was added to the table; and i) any additional notes regarding the correction.

Note that because this table may change over time, it is possible that calibrations performed by different versions of the code may change over time (though, hopefully for the better.) Please post any suspected missing values to the maintainer as issues on the GitHub repo.