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diff --git a/R/TSCF.R b/R/TSCF.R new file mode 100644 index 0000000..bfb4c42 --- /dev/null +++ b/R/TSCF.R @@ -0,0 +1,31 @@ +#' Estimation of the transpiration stream concentration factor +#' +#' The FOCUS groundwater guidance (FOCUS 2014, p. 41) states that a reliable measured +#' log Kow for neutral pH must be available in order to apply the Briggs +#' equation. It is not clarified when it can be regarded reliable, but the +#' equation is stated to be produced for non-ionic compounds, suggesting that +#' the compound should not be ionogenic (weak acid/base) +#' or ionic. +#' +#' The Dettenmaier equation is given to show that other views on the subject exist. +#' @references FOCUS (2014) Generic Guidance for Tier 1 FOCUS Ground Water Assessments. +#' Version 2.2, May 2014 +#' Dettenmaier EM, Doucette WJ and Bugbee B (2009) Chemical hydrophobicity and uptake +#' by plant roots. Environ. Sci. Technol 43, 324 - 329 +#' @param log_Kow The decadic logarithm of the octanol-water partition constant +#' @param method Short name of the estimation method. +#' @export +#' @examples +#' plot(TSCF, -1, 5, xlab = "log Kow", ylab = "TSCF", ylim = c(0, 1.1)) +#' TSCF_2 <- function(x) TSCF(x, method = "dettenmaier09") +#' curve(TSCF_2, -1, 5, add = TRUE, lty = 2) +#' legend("topright", lty = 1:2, bty = "n", +#' legend = c("Briggs et al. (1982)", "Dettenmaier et al. (2009)")) +TSCF <- function(log_Kow, method = c("briggs82", "dettenmaier09")) { + method <- match.arg(method) + TSCF <- switch(method, + briggs82 = 0.784 * exp(- (log_Kow - 1.78)^2 / 2.44), + dettenmaier09 = 11 /( 11 + 2.6^log_Kow) + ) + return(TSCF) +} |