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Diffstat (limited to 'pkg/R/GUS.R')
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diff --git a/pkg/R/GUS.R b/pkg/R/GUS.R new file mode 100644 index 0000000..2690f50 --- /dev/null +++ b/pkg/R/GUS.R @@ -0,0 +1,74 @@ +#' Groundwater ubiquity score based on Gustafson (1989) +#' +#' The groundwater ubiquity score GUS is calculated according to +#' the following equation +#' \deqn{GUS = \log_10 DT50_{soil} (4 - \log_10 K_{oc}}{GUS = log10 DT50soil * (4 - log10 Koc)} +#' +#' @references Gustafson, David I. (1989) Groundwater ubiquity score: a simple +#' method for assessing pesticide leachability. _Environmental +#' toxicology and chemistry_ *8*(4) 339–57. +#' @inheritParams endpoint +#' @param chent If a chent is given with appropriate information present in its +#' chyaml field, this information is used, with defaults specified below. +#' @param DT50 Half-life of the chemical in soil. Should be a field +#' half-life according to Gustafson (1989). However, leaching to the sub-soil +#' can not completely be excluded in field dissipation experiments and Gustafson +#' did not refer to any normalisation procedure, but says the field study should +#' be conducted under use conditions. +#' @param Koc The sorption constant normalised to organic carbon. Gustafson +#' does not mention the nonlinearity of the sorption constant commonly +#' found and usually described by Freundlich sorption, therefore it is +#' unclear at which reference concentration the Koc should be observed +#' (and if the reference concentration would be in soil or in porewater). +#' @param lab_field Should laboratory or field half-lives be used? This +#' defaults to lab in this implementation, in order to avoid +#' double-accounting for mobility. If comparability with the original GUS +#' values given by Gustafson (1989) is desired, non-normalised first-order +#' field half-lives obtained under actual use conditions should be used. +#' @param degradation_value Which of the available degradation values should +#' be used? +#' @param sorption_value Which of the available sorption values should be used? +#' Defaults to Kfoc as this is what is generally available from the European +#' pesticide peer review process. These values generally use a reference +#' concentration of 1 mg/L in porewater, that means they would be expected to +#' be Koc values at a concentration of 1 mg/L in the water phase. +#' @param degradation_aggregator Function for aggregating half-lives +#' @param sorption_aggregator Function for aggregation Koc values +#' @return A list with the DT50 and Koc used as well as the resulting score +#' of class GUS_result +#' @author Johannes Ranke +#' @export +GUS <- function(...) UseMethod("GUS") + +#' @rdname GUS +#' @export +GUS.numeric <- function(DT50, Koc) { + score <- log10(DT50) * (4 - log10(Koc)) + res <- list(DT50 = DT50, Koc = Koc, score = score) + class(res) <- "GUS_result" + return(res) +} + +#' @rdname GUS +#' @export +GUS.chent <- function(chent, lab_field = "laboratory", + aerobic = TRUE, + degradation_value = "DT50ref", + sorption_value = "Kfoc", + degradation_aggregator = geomean, + sorption_aggregator = geomean, + digits = 1) +{ + DT50 = soil_DT50(chent, lab_field = lab_field, redox = aerobic, + value = degradation_value, + aggregator = degradation_aggregator, signif = 5) + Koc = soil_Kfoc(chent, value = sorption_value, + aggregator = sorption_aggregator, signif = 5) + GUS.numeric(DT50, Koc) +} + +#' @export +print.GUS_result = function(x, ..., digits = 1) { + cat("GUS: ", round(x$score, digits = 1), "\n") + cat("calculated from DT50 ", x$DT50, " and Koc ", x$Koc, "\n") +} |