Evaluate parent kinetics using the NAFTA guidance

The function fits the SFO, IORE and DFOP models using mmkin and returns an object of class nafta that has methods for printing and plotting.

nafta(ds, title = NA, quiet = FALSE, …)

Arguments

ds	A dataframe that must contain one variable called "time" with the time values specified by the time argument, one column called "name" with the grouping of the observed values, and finally one column of observed values called "value".
title	Optional title of the dataset
quiet	Should the evaluation text be shown?
…	Further arguments passed to mmkin.

Value

An list of class nafta. The list element named "mmkin" is the mmkin object containing the fits of the three models. The list element named "title" contains the title of the dataset used. The list element "data" contains the dataset used in the fits.

Source

NAFTA (2011) Guidance for evaluating and calculating degradation kinetics in environmental media. NAFTA Technical Working Group on Pesticides https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/guidance-evaluating-and-calculating-degradation accessed 2019-02-22

US EPA (2015) Standard Operating Procedure for Using the NAFTA Guidance to Calculate Representative Half-life Values and Characterizing Pesticide Degradation https://www.epa.gov/pesticide-science-and-assessing-pesticide-risks/standard-operating-procedure-using-nafta-guidance

Examples

  nafta_evaluation <- nafta(NAFTA_SOP_Appendix_D, cores = 1)
#> Warning: Calculation of the Jacobian failed for the cost function of the untransformed model.
#> No t-test results will be available
#> The SFO model is rejected as S_SFO is equal or higher than the critical value S_c
#> The representative half-life of the IORE model is longer than the one corresponding
#> to the terminal degradation rate found with the DFOP model.
#> The representative half-life obtained from the DFOP model may be used
  print(nafta_evaluation)
#> Sums of squares:
#>       SFO      IORE      DFOP 
#> 1378.6832  615.7730  517.8836 
#> 
#> Critical sum of squares for checking the SFO model:
#> [1] 717.4598
#> 
#> Parameters:
#> $SFO
#>               Estimate   Pr(>t)    Lower    Upper
#> parent_0       83.7558 8.08e-15 76.92822 90.58328
#> k_parent_sink   0.0017 7.45e-05  0.00111  0.00262
#> 
#> $IORE
#>                     Estimate Pr(>t)    Lower    Upper
#> parent_0            9.69e+01     NA 8.75e+01 1.06e+02
#> k__iore_parent_sink 8.40e-14     NA 1.09e-19 6.47e-08
#> N_parent            6.68e+00     NA 3.54e+00 9.83e+00
#> 
#> $DFOP
#>          Estimate   Pr(>t)    Lower    Upper
#> parent_0 9.76e+01 4.44e-13 8.88e+01 1.06e+02
#> k1       4.24e-02 3.55e-02 1.41e-02 1.27e-01
#> k2       8.24e-04 2.06e-02 3.17e-04 2.14e-03
#> g        2.88e-01 1.31e-04 1.78e-01 4.30e-01
#> 
#> 
#> DTx values:
#>      DT50    DT90 DT50_rep
#> SFO   407    1352      407
#> IORE  541 5192060  1562966
#> DFOP  429    2383      841
#> 
#> Representative half-life:
#> [1] 841.4096
  plot(nafta_evaluation)