Add UK tier 1 drainage PEC calculations

1 files changed, 53 insertions, 0 deletions

diff --git a/pkg/R/PEC_sw_drainage_UK.R b/pkg/R/PEC_sw_drainage_UK.R
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+++ b/pkg/R/PEC_sw_drainage_UK.R
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+# Copyright (C) 2015  Johannes Ranke
+# Contact: jranke@uni-bremen.de
+# This file is part of the R package pfm
+
+# This program is free software: you can redistribute it and/or modify it under
+# the terms of the GNU General Public License as published by the Free Software
+# Foundation, either version 3 of the License, or (at your option) any later
+# version.
+
+# This program is distributed in the hope that it will be useful, but WITHOUT
+# ANY WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS
+# FOR A PARTICULAR PURPOSE.  See the GNU General Public License for more
+# details.
+
+# You should have received a copy of the GNU General Public License along with
+# this program. If not, see <http://www.gnu.org/licenses/>
+
+#' Calculate initial predicted environmental concentrations in surface water due to drainage using the UK method
+#'
+#' This implements the method specified in the UK data requirements handbook and was checked against the spreadsheet
+#' published on the CRC website
+#'
+#' @param rate Application rate in g/ha
+#' @param interception The fraction of the application rate that does not reach the soil
+#' @param Koc The sorption coefficient normalised to organic carbon in L/kg
+#' @return The predicted concentration in surface water in µg/L
+#' @export
+#' @author Johannes Ranke
+#' @examples
+#' PEC_sw_drainage_UK_ini(100)
+PEC_sw_drainage_UK_ini <- function(rate, interception = 0, Koc,
+                                   latest_application = NULL, soil_DT50 = NULL)
+{
+  percentage_lost <- SSLRC_mobility_classification(Koc)[[2]]
+  amount_available <- rate * (1 - interception) # g/ha
+
+  if (!missing(latest_application)) {
+    if (missing(soil_DT50)) stop("You need to supply a soil DT50 value")
+    k = log(2)/soil_DT50
+    as.Date(paste(latest_application, "1999"), "%d %B %Y")
+
+    lct <- Sys.getlocale("LC_TIME")
+    tmp <- Sys.setlocale("LC_TIME", "C")
+    latest <- as.Date(paste(latest_application, "1999"), "%d %b %Y")
+    tmp <- Sys.setlocale("LC_TIME", lct)
+    degradation_time <- as.numeric(difftime(as.Date("1999-10-01"), units = "days", latest))
+    amount_available <- amount_available * exp(-k * degradation_time)
+  } 
+
+  volume = 130000 # L/ha
+  PEC = 1e6 * (percentage_lost/100) * amount_available / volume
+  return(PEC)
+}