This is a reimplementation of the calculation described in the Exposit 3.02 spreadsheet file, in the worksheet "Konzept Drainage". Although there are four groups of compounds ("Gefährdungsgruppen"), only one distinction is made in the calculations, between compounds with low mobility (group 1) and compounds with modest to high mobility (groups 2, 3 and 4). In this implementation, the group is derived only from the Koc, if not given explicitly. For details, see the discussion of the function arguments below.

PEC_sw_exposit_drainage(
rate,
interception = 0,
Koc = NA,
mobility = c(NA, "low", "high"),
DT50 = Inf,
t_drainage = 3,
V_ditch = 30,
V_drainage = c(spring = 10, autumn = 100),
dilution = 2
)

## Arguments

rate The application rate in g/ha The fraction intercepted by the crop The sorption coefficient to soil organic carbon used to determine the mobility. A trigger value of 550 L/kg is used in order to decide if Koc >> 500. Overrides what is determined from the Koc. The soil half-life in days The time between application and the drainage event, where degradation occurs, in days The volume of the ditch is assumed to be 1 m * 100 m * 30 cm = 30 m3 The drainage volume, equivalent to 1 mm precipitation on 1 ha for spring/summer or 10 mm for autumn/winter/early spring. The dilution factor

## Value

A list containing the following components

perc_runoff

The runoff percentages for dissolved and bound substance

runoff

A matrix containing dissolved and bound input for the different distances

PEC_sw_runoff

A matrix containing PEC values for dissolved and bound substance for the different distances. If the rate was given in g/ha, the PECsw are in microg/L.

perc_runoff_exposit for runoff loss percentages and perc_runoff_reduction_exposit for runoff reduction percentages used
  PEC_sw_exposit_drainage(500, Koc = 150)#> $perc_drainage_total #> spring autumn #> 0.2 1.0 #> #>$perc_peak
#>