4 files changed, 112 insertions, 0 deletions
diff --git a/pkg/NAMESPACE b/pkg/NAMESPACE
index 86b85da..00b0022 100644
--- a/pkg/NAMESPACE
+++ b/pkg/NAMESPACE
@@ -2,6 +2,7 @@
 
 S3method(plot,TOXSWA_cwa)
 export(PEC_soil)
+export(PEC_sw_drift)
 export(TOXSWA_cwa)
 export(geomean)
 export(read.TOXSWA_cwa)
diff --git a/pkg/R/PEC_sw_drift.R b/pkg/R/PEC_sw_drift.R
new file mode 100644
index 0000000..ce57f79
--- /dev/null
+++ b/pkg/R/PEC_sw_drift.R
@@ -0,0 +1,55 @@
+# 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 predicted environmental concentrations in surface water due to drift
+#'
+#' This is a basic, vectorised form of a simple calculation of a contaminant
+#' concentration in surface water based on complete, instantaneous mixing
+#' with input via spray drift.
+#'
+#' @param rate Application rate in units specified below
+#' @param applications Number of applications for selection of drift percentile
+#' @param drift_data Source of drift percentage data
+#' @param crop Crop name (use German names for JKI data), defaults to "Ackerbau"
+#' @param distances The distances in m for which to get PEC values
+#' @param water_depth Depth of the water body in cm
+#' @param rate_units Defaults to g/ha
+#' @param PEC_units Requested units for the calculated PEC. Only µg/L currently supported
+#' @return The predicted concentration in surface water
+#' @export
+#' @author Johannes Ranke
+#' @examples
+#' PEC_sw_drift(100)
+PEC_sw_drift <- function(rate, 
+                         applications = 1,
+                         water_depth = 30, 
+                         drift_data = "JKI",
+                         crop = "Ackerbau",
+                         distances = c(1, 5, 10, 20),
+                         rate_units = "g/ha",
+                         PEC_units = "\u00B5g/L")
+{
+  rate_units <- match.arg(rate_units)
+  PEC_units <- match.arg(PEC_units)
+  drift_data <- match.arg(drift_data)
+  water_volume <- 100 * 100 * (water_depth/100) * 1000   # in L (for 1 ha)
+  PEC_sw_overspray <- rate * 1e6 / water_volume          # in µg/L
+  dist_index <- as.character(distances)
+  PEC_sw_drift <- PEC_sw_overspray * pfm::drift_data_JKI[[applications]][dist_index, crop] / 100
+  names(PEC_sw_drift) <- paste(dist_index, "m")
+  return(PEC_sw_drift)
+}
diff --git a/pkg/man/PEC_sw_drift.Rd b/pkg/man/PEC_sw_drift.Rd
new file mode 100644
index 0000000..20299a5
--- /dev/null
+++ b/pkg/man/PEC_sw_drift.Rd
@@ -0,0 +1,42 @@
+% Generated by roxygen2 (4.1.0.9001): do not edit by hand
+% Please edit documentation in R/PEC_sw_drift.R
+\name{PEC_sw_drift}
+\alias{PEC_sw_drift}
+\title{Calculate predicted environmental concentrations in surface water due to drift}
+\usage{
+PEC_sw_drift(rate, applications = 1, water_depth = 30, drift_data = "JKI",
+  crop = "Ackerbau", distances = c(1, 5, 10, 20), rate_units = "g/ha",
+  PEC_units = "µg/L")
+}
+\arguments{
+\item{rate}{Application rate in units specified below}
+
+\item{applications}{Number of applications for selection of drift percentile}
+
+\item{water_depth}{Depth of the water body in cm}
+
+\item{drift_data}{Source of drift percentage data}
+
+\item{crop}{Crop name (use German names for JKI data), defaults to "Ackerbau"}
+
+\item{distances}{The distances in m for which to get PEC values}
+
+\item{rate_units}{Defaults to g/ha}
+
+\item{PEC_units}{Requested units for the calculated PEC. Only µg/L currently supported}
+}
+\value{
+The predicted concentration in surface water
+}
+\description{
+This is a basic, vectorised form of a simple calculation of a contaminant
+concentration in surface water based on complete, instantaneous mixing
+with input via spray drift.
+}
+\examples{
+PEC_sw_drift(100)
+}
+\author{
+Johannes Ranke
+}
+
diff --git a/pkg/tests/testthat/test_PEC_sw_drift.R b/pkg/tests/testthat/test_PEC_sw_drift.R
new file mode 100644
index 0000000..390df34
--- /dev/null
+++ b/pkg/tests/testthat/test_PEC_sw_drift.R
@@ -0,0 +1,14 @@
+library(pfm)
+context("Simple PEC surface water calculations with drift entry")
+
+test_that("PEC_sw_drift gives the same results as the CRD PEC calculator", {
+  # One application of 30 g/ha to field crops calculated with UK PEC calculator published by CRD
+  expect_equal(round(PEC_sw_drift(30), 3), c('1 m' = 0.277, '5 m' = 0.057, '10 m' = 0.029, '20 m' = 0.015))
+
+  # 7 applications of 30 g/ha to field crops calculated with UK PEC calculator, initial PEC
+  expect_equal(round(PEC_sw_drift(30, 7), 3), c('1 m' = 0.161, '5 m' = 0.033, '10 m' = 0.017, '20 m' = 0.008))
+
+  # 4 applications of 30 g/ha to late fruit crops calculated with UK PEC calculator published by CRD (uses different drift values from SANCO aquatic guidance)
+  #expect_equal(round(PEC_sw_drift(30, 4, crop = "Obstbau spät", distances = c(3, 20, 50)), 3), c('3 m' = 1.101, '20 m' = 0.080, '50 m' = 0.013))
+})
+