APPENDIX I
STEPS 1-2 IN FOCUS
USER MANUAL
Please Note:
This user manual was published together with all
available documentation on 15 May 2003.
Therefore, it may not contain the most recent information as the models and the shells may have changed
with time.
Make sure that you always have the most recent version available, which may be obtained from the web
site of JRC, Ispra, Italy:
http://viso.ei.jrc.it/focus/
1
1
Introduction
As described in the remit of the Surface Water scenarios working group, step 1 and 2 calculations
should represent “worst-case loadings” and “loadings based on sequential application patterns” respectively but should not be specific to any climate, crop, topography or soil type. With this in mind the
group developed two simple scenarios for calculating exposure in surface water and sediment and has
constructed a MICROSOFT Visual Basic application for the derivation of PEC values in water and
sediment.
The assumptions at both steps 1 and 2 are very conservative and are essentially based around drift values calculated from BBA (2000)1 and an estimation of the potential loading of pesticides to surface
water via run-off, erosion and/or drainage. This “run-off” loading represents any entry of pesticide
from the treated field to the associated water body at the edge of the field.
At Step 1, inputs of spray drift, run-off, erosion and/or drainage are evaluated as a single loading to the
water body and “worst-case” water and sediment concentrations are calculated. If inadequate safety
margins are obtained (Toxicity Exposure Ratios < trigger values), the registrant proceeds to Step 2. At
Step 2, loadings are refined as a series of individual applications, resulting in drift to the water body,
followed by a run-off/erosion/drainage event occurring four days after the last application. The amount
lost via run-off is determined by the crop interception, the region of use (Northern or Southern Europe)
and season of application. Again if inadequate safety margins are obtained (Toxicity Exposure Ratios <
trigger values), the registrant proceeds to Step 3. Step 3 requires the use of the deterministic models
PRZM, MACRO and TOXSWA.
Please notice that the interception percentages used by STEPS 1-2 in FOCUS are not the same as listed
in the FOCUS groundwater report (FOCUS (2000) “FOCUS groundwater scenarios in the EU plant
protection product review process” Report of the FOCUS Groundwater Scenarios Workgroup, EC
Document Reference Sanco/321/2000, 197pp) as more recent literature has been used to compile the
numbers.
The purpose of formalising Step 1 and Step 2 calculations is to harmonise the methods of calculation
and to avoid unnecessary, complex exposure assessments for plant protection products when large safety margins exist even with conservative scenarios.
Standard Assumptions
A set of assumptions for the water body dimensions common to step 1 and 2 were compiled to derive
the scenario. These are based upon existing concepts with the EU and Member States together with
expert judgement. They are as follows:
A water depth of 30cm overlying sediment of 5 cm depth was selected in order to comply with existing
risk assessment approaches within the EU and existing ecotoxicity testing requirements for sedimentdwelling organisms. The density of the sediment was selected to be 0.8 g.cm -3 and an organic carbon
content of 5%. The water body is assumed to have an area equivalent to one tenth of the field from
which it receives run-off or drainage water (a field :water ratio of 10). Assuming a 1 ha field, the 0.1
ha (1000 m2) water body will have a volume of 3 x 10 5 litres.
Step 1 Assumptions
At Step 1 inputs of spray drift, run-off, erosion and/or drainage are evaluated as a single loading to the
water body and “worst-case” surface water and sediment concentrations are calculated. The loading to
surface water is based upon the number of applications multiplied by the maximum single use rate unless:
1
BBA (2000), Bekanntmachung über die Abtrifteckwerte, die bei der Prüfung und Zulassung von
Pflanzenschutzmitteln herangezogen werden. (8. Mai 2000) in : Bundesanzeiger No.100, amtlicher Teil, vom 25. Mai 2000, S. 9879.
1
3 x DT50 in sediment/water systems <
(combined water + sediment)
time between individual applications.
In such a case the maximum individual application is used to derive the maximum PEC as there is no
potential for accumulation in the sediment/water system. All inputs are assumed to occur at the same
time but their initial distribution between the surface water and sediment compartments is dependent
upon the route of entry and sorption coefficient (Koc) of the compound. Drift inputs are loaded into
the water where they subsequently distributed between water and sediment according to the compound’s Koc. The ‘run-off’ entry is distributed between water and sediment at the time of loading according to the compound’s Koc and an effective sediment depth of 1 cm. In this way compounds of
high Koc are added directly to the sediment whereas compounds of low Koc are added to the water
column in the ‘run-off’ water.
Step 2 Assumptions
At Step 2 inputs of spray drift, run-off, erosion and/or drainage are evaluated as a series of individual
loadings comprising of drift events (number and timing as defined in step 1) followed by a loading representing a run-off, erosion and/or drainage event four days after the final application. This assumption
is similar to that developed by the United States EPA in their GENEEC model. Degradation is assumed to follow first-order kinetics in soil, surface water and sediment (an option of using different
degradation rates in surface water and sediment is included).
The fraction of each application reaching the adjacent water is both a function of method and number
of applications. Drift values for aerial applications are not dependant upon the number of applications.
Four days after the final application, a ‘run-off’ loading is added to the surface water and associated
sediment and is function of the residue remaining in soil (g/ha), region and season of application and
the Koc./Kom
The user selects from two regions (Northern EU and Southern EU according to the definitions given
for crop residue zones and three seasons (March to May, June to September and October to January).
If a product is used across both regions or two or more seasons then the step 2 calculation can be used
to evaluate the worst-case (according to the loadings defined in a look-up table) or to determine which
combinations require further evaluation at step 3.
The daily concentrations in surface water and sediment are calculated. The times of the maximum concentration in water and sediment and the actual concentrations 1, 2, 4, 7, 14, 21, 28, 42, 50 and 100
days after the peak in each phase (water and sediment) are reported. Then the time weighted average
concentrations following the maximum concentration are calculated and reported for the same time
periods. As in step 1, drift inputs are loaded into the water where they subsequently distributed between
water and sediment according to the compound’s Koc and an effective sediment depth of 1 cm. The
‘run-off’ entry is distributed between water and sediment at the time of loading according to the compound’s Koc. In this way compounds of high Koc are added directly to the sediment concentration
whereas compounds of low Koc are added in the run-off water.
The fraction of the pesticide that enters the water body via drift has to be partitioned between water and
sediment in the following days. As experimental data do not support a full partitioning within 24 hours,
an extended approach is followed for STEPS1-2:
The pesticide is distributed in surface water into two theoretical compartments, “available” for sorption
to sediment and “unavailable” for sorption to sediment according to the following equation:
The fraction of the pesticide that enters the water body via drift has to be partitioned between water and
sediment in the following days. As experimental data do not support a full partitioning within 24 hours,
an extended approach is followed for STEPS1-2:
The pesticide is distributed in surface water into two theoretical compartments, “available” for sorption
to sediment and “unavailable” for sorption to sediment according to the following equation:
2
masw = msw * K
musw = msw * (1-K)
msw:
masw:
musw:
K:
total mass of pesticide in surface water (mg/m²)
mass available for sorption and (mg/m²)
mass unavailable for sorption (mg/m²)
distribution coefficient (-), set to value of 2/3 for all compounds
After the occurrence of the runoff/drainage event it is assumed that full equilibrium between water and
sediment is established within 24 hours (K = 1)
Dependent on the application pattern and the degradation of the pesticide it may occur that the multiple
application pattern leads to lower concentrations in surface water than the respective single application.
Therefore, the program will always do a second run with the respective single application pattern if the
user has entered a multiple application pattern for their substance.
3
Scenario data
Step 1: input into surface water
Crop
Distance cropwater (m)
Drift
Runoff/drainage
(% of application)
(% of application)
cereals, spring
1
2.8
10
cereals, winter
1
2.8
10
citrus
3
15.7
10
cotton
1
2.8
10
field beans
1
2.8
10
grass / alfalfa
1
2.8
10
hops
3
19.3
10
legumes
1
2.8
10
maize
1
2.8
10
oil seed rape, spring
1
2.8
10
oil seed rape, winter
1
2.8
10
olives
3
15.7
10
pome / stone fruit, early applications
3
29.2
10
pome / stone fruit, late applications
3
15.7
10
potatoes
1
2.8
10
soybeans
1
2.8
10
sugar beet
1
2.8
10
sunflower
1
2.8
10
tobacco
1
2.8
10
vegetables, bulb
1
2.8
10
vegetables, fruiting
1
2.8
10
vegetables, leafy
1
2.8
10
vegetables, root
1
2.8
10
vines, early applications
3
2.7
10
vines, late applications
3
8.0
10
application, aerial
3
33.2
10
application, hand (crop < 50 cm)
1
2.8
10
application, hand (crop > 50 cm)
3
8.0
10
no drift (incorporation or seed treatment)
1
0
10
4
Step 2: input into surface water via spray drift
Crop
Distance
Number of application per season
crop-water
(m)
1
2
3
4
5
6
7
>7
cereals, spring
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
cereals, winter
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
citrus
3
15.7
12.1
11.0
10.1
9.7
9.2
9.1
8.7
cotton
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
field beans
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
grass / alfalfa
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
hops
3
19.3
17.7
15.9
15.4
15.1
14.9
14.6
13.5
legumes
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
maize
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
oil seed rape, spring
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
oil seed rape, winter
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
olives
3
15.7
12.1
11.0
10.1
9.7
9.2
9.1
8.7
pome / stone fruit, (early)
3
29.2
25.5
24.0
23.6
23.1
22.8
22.7
22.2
pome / stone fruit (late)
3
15.7
12.1
11.0
10.1
9.7
9.2
9.1
8.7
potatoes
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
soybeans
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
sugar beet
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
sunflower
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
tobacco
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
vegetables, bulb
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
vegetables, fruiting
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
vegetables, leafy
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
vegetables, root
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
vines, early applications
3
2.7
2.5
2.5
2.5
2.4
2.3
2.3
2.3
vines, late applications
3
8.0
7.1
6.9
6.6
6.6
6.4
6.2
6.2
application, aerial
3
33.2
33.2
33.2
33.2
33.2
33.2
33.2
33.2
application, hand (crop < 50 cm)
1
2.8
2.4
2.0
1.9
1.8
1.6
1.6
1.5
application, hand (crop > 50 cm)
3
8.0
7.1
6.9
6.6
6.6
6.4
6.2
6.2
no drift (incorporation /seed treatment)
1
0.0
0.0
0.0
0.0
0.0
0.0
0.0
0.0
5
Step 2: crop interception
crop
no interception
minimal
intermediate
crop cover
crop cover
00 – 09
10 – 19
20 – 39
cereals, spring and winter
0
0.25
0.5
0.7
citrus
0
0.7
0.7
0.7
cotton
0
0.3
0.6
0.75
field beans
0
0.25
0.4
0.7
grass / alfalfa
0
0.4
0.6
0.75
hops
0
0.2
0.5
0.7
legumes
0
0.25
0.5
0.7
maize
0
0.25
0.5
0.75
oil seed rape, spring and winter
0
0.4
0.7
0.75
olives
0
0.7
0.7
0.7
pome / stone fruit, early and late
0
0.2
0.4
0.7
potatoes
0
0.15
0.5
0.7
soybeans
0
0.2
0.5
0.75
sugar beet
0
0.2
0.7
0.75
sunflower
0
0.2
0.5
0.75
tobacco
0
0.2
0.7
0.75
vegetables, bulb
0
0.1
0.25
0.4
vegetables, fruiting
0
0.25
0.5
0.7
vegetables, leafy
0
0.25
0.4
0.7
vegetables, root
0
0.25
0.5
0.7
Vines, early and late
0
0.4
0.5
0.7
application, aerial
0
0.2
0.5
0.7
application, hand
(crop < 50 cm and > 50 cm)
0
0.2
0.5
0.7
no drift (incorporation /seed
treatment)
0
0
0
0
BBCH-code *
*
full canopy
40 – 89
NOTE: indicative, adapted coding, the BBCH-codes mentioned do not exactly match (BBCH,
1994).
Step 2: input into surface water via runoff/drainage
Region/season
North Europe, Oct. - Feb.
North Europe, Mar. - May
North Europe, June - Sep.
South Europe, Oct. - Feb.
South Europe, Mar. - May
South Europe, June - Sep.
No Runoff
% of soil residue
5
2
2
4
4
3
0
6
Surface water definitions
Parameter:
water depth (cm):
sediment depth (cm):
effective sediment depth for sorption (cm):
sediment oc (%):
sediment bulk density (kg/L):
ratio of field to water body:
value
30
5
1
5
0.8
10
7
Input Parameters
Identification of the compound
Parameter
Active ingredient
Comment
Enter name of active ingredient to be assessed
Enter name of metabolite
This field is only visible if metabolites are to
be calculated.
Enter any text to distinguish between PEC
calculations for the same substance
Compound for PEC calculation
Comment
Application pattern
Parameter
Application rate of active substance
(g/ha)
Number of applications per season
Time between 2 applications(days)
Crop interception
Region and Season of Application
Application/Crop type
Comment
Enter maximum single application rate for
active substance and crop type
Choose number of applications
Choose time between each of the applications
in days. Value ignored if only one application
per season.
This field is only visible if more than one
application per season is calculated
Choose the suitable crop interception from a
list of 4 options
This field is only visible if step 2 simulations
are to be performed
Choose from 6 options that define the loading
to surface water
This field is only visible if step 2 simulations
are to be performed
Choose one from in total 17 options that determines the amount of spray drift
Substance specific data
Parameter
Water solubility (mg/L)
KOC/KOM of compound for PEC
calculation (L/kg)
DT50 in the sediment/water system
(days)
DT50 for degradation in water
phase (days)
DT50 for degradation in sediment
phase (days)
DT50 in soil (days)
Molecular mass of active substance
(g/mole)
Molecular mass of metabolite
(g/mole)
Maximum % of metabolite observed in sediment/water studies
Comment
Enter water solubility
Enter sorption constant related to org carbon or org.
matter
The button it to switch between KOC and KOM
Enter value for DT50 for degradation in the whole sediment/water system not surface water (the number will
be used for step 1 simulations only)
Enter first-order half-life in water column and sediment
if calculated. Do not enter, for example, a dissipation
rate in water that accounts for both degradation and
adsorption. If specific rates cannot be calculated enter
the degradation rate for the whole system in both cells.
Justify selection as appropriate.
These fields are only visible if step 2 simulations are to
be performed
Select soil DT50 in soil
This field is only visible if step 2 simulations are to be
performed
Enter molecular mass of active substance
This field is only visible if metabolites are to be calculated
Enter maximum amount observed in sediment + water
(not just water)
This field is only visible if metabolites are to be calculated
8
Maximum % of metabolite observed in soil studies
Enter maximum amount observed in appropriate soil
studies. This may be value from aerobic studies at 20ºC
or 10ºC or anaerobic study depending upon use pattern.
This field is only visible if metabolites are to be calculated
9
MODEL Algorithms
STEP 1 calculations
Compound rate
For active ingredients simply the application rate” is taken as “equivalent rate of the compound”. If
metabolites are simulated the “equivalent rate of compound” is estimated based on the application rate
for the parent compound, the molecular masses, and the maximum fractions of the metabolite in soil
(for runoff/drainage) and water (for drift) according to following equations:
EQ_RATE_RUNOFF_TOT
=
APP_RATE * (M_COMP / M_PAR) * MAX_SOIL / 100
EQ_RATE_DRIFT
=
APP_RATE * (M_COMP / M_ PAR) * MAX_SEDWAT /100
EQ_RATE_RUNOFF_TOT:
EQ_RATE_DRIFT_TOT:
APP_RATE:
M_PAR:
M_COMP:
MAX_SOIL:
MAX_SEDWAT
equivalent rate of compound for runoff (g/ha)
equivalent rate of compound for drift (g/ha)
application rate (g/ha)
molecular mass of the parent compound (g/mole)
molecular mass of the simulated compound /g/mole)
maximum % of metabolite observed in soil studies
maximum % of metabolite observed in sediment/water studies
Input via drift
The input into the surface water via a single drift event is calculated based on crop dependent drift percentages:
INPUT_DRIFT_S
=
INPUT_DRIFT_S:
EQ_RATE_DRIFT:
DRIFT_PERC:
EQ_RATE_DRIFT * DRIFT_PERC / 1000
input via single drift event (mg/m²)
equivalent rate of compound for drift (g/ha)
drift percentage (%)
Usually, this single rate is taken even if multiple applications are to be simulated. However, if the interval between two applications is below three times the DT50 of the compound, the input will be accumulated dependent on the number of applications per season:
INPUT_DRIFT
=
INPUT_DRIFT:
INPUT_DRIFT_S:
NUM_APP:
INPUT_DRIFT_S * NUM_APP
input via drift (mg/m²)
input via single drift event (mg/m²)
number of applications per season
Input via runoff/drainage
For the calculation of the input via runoff/drainage the following equation is used:
INPUT_RUNOFF_S
=
INPUT_RUNOFF_S:
EQ_RATE_RUNOFF_TOT:
RUNOFF_PERC:
RATIO:
EQ_RATE_RUNOFF_TOT * RUNOFF_PERC * RATIO / 1000
input via single runoff event (mg/m²)
equivalent rate of compound for runoff (g/ha)
runoff percentage (related to soil residue) (%)
ratio of field to water body (-)
Usually, this single rate is taken even if multiple applications are to be simulated. However, if the interval between two applications is below three times the DT50 of the compound, the input will be accumulated dependent on the number of applications per season:
10
INPUT_RUNOFF
INPUT_RUNOFF:
INPUT_RUNOFF_S:
NUM_APP:
=
INPUT_RUNOFF_S * NUM_APP
input via RUNOFF (mg/m²)
input via single RUNOFF event (mg/m²)
number of applications per season
Fraction of compound entering in water phase via runoff
The fraction entering in the water phase via runoff/drainage is calculated dependent on the sorption
constant of the compound:
F_RUNOFF
=
F_RUNOFF:
WAT_DEPTH:
EFF_SED_DEPTH:
DENS
OC:
KOC:
WAT_DEPTH / (WAT_DEPTH + (EFF_SED_DEPTH * DENS * OC *
KOC/100) )
fraction of compound entering in water phase via runoff (-)
depth of the surface water (cm)
effective sediment depth of the surface water (cm)
sediment bulk density (kg/L)
sediment organic carbon content (%)
sorption constant related to organic carbon (L/kg)
Daily concentrations
At Step 1, inputs of spray drift and run-off, erosion and/or drainage are evaluated as a single loading to
the water body and “worst-case” water and sediment concentrations are calculated: No distribution
between water and sediment phase is considered for the first day.
day = 0
PEC_SW
=
INPUT_RUNOFF * F_RUNOFF * 100 + INPUT_DRIFT * 100
WAT_DEPTH
PEC_SED
=
INPUT_RUNOFF * (1 - F_RUNOFF) * 100
(SED_DEPTH* DENS)
PEC_SW:
PEC_SED:
INPUT_RUNOFF:
INPUT_DRIFT:
F_RUNOFF:
WAT_DEPTH:
SED_DEPTH:
DENS
surface water concentration (µg/L)
sediment concentration (µg/kg)
input via runoff (mg/m²)
input via drift (mg/m²)
fraction of compound entering in water phase via runoff (-)
depth of the surface water (cm)
sediment depth of the surface water (cm)
sediment bulk density (kg/L)
11
After the initial day degradation in water and sediment as well as distribution between the water and
sediment phase is considered for the estimation of concentrations:
day > 0
INT_FAC
=
EXP (-LN(2) *DAY_NO/ DT50)
PEC_SW
=
(INPUT_RUNOFF + INPUT_DRIFT)* F_RUNOFF * 100 * INT_FAC
WAT_DEPTH
PEC_SED
=
(INPUT_RUNOFF +INPUT_DRIFT)*(1 - F_RUNOFF) * 100 * INT_FAC
SED_DEPTH* DENS
INT_FAC:
PEC_SW:
PEC_SED:
INPUT_RUNOFF:
INPUT_DRIFT:
F_RUNOFF:
WAT_DEPTH:
SED_DEPTH:
DENS
DT50:
DAY_NO:
Internal factor (-)
surface water concentration (µg/L)
sediment concentration (µg/kg)
input via runoff (mg/m²)
input via drift (mg/m²)
fraction of compound entering in water phase via runoff (-)
depth of the surface water (cm)
sediment depth of the surface water (cm)
sediment bulk density (kg/L)
DT50 in sediment/water study (d)
simulation day (d)
Time weighted averaged concentrations (TWA)
For the first simulation day the time weighted averaged concentration is simply based on the arithmetic
mean of the concentrations on the first two simulation days:
day = 1
TWA_SW (1)
=
[ PEC_SW(0) + PEC_SW(1)] / 2
TWA_SED(1)
=
[ PEC_SED(0) + PEC_SED(1) ] / 2
TWA_SW(1):
TWA_SED(1):
PEC_SW(0):
PEC_SED(0)
time weighted averaged concentration in water on day 1 (µg/L)
time weighted averaged concentration in sediment on day 1 (µg/kg)
surface water concentration on day 0 (µg/L)
sediment concentration on day 0 (µg/kg)
12
For the other simulation days the time weighed averaged concentrations are calculated according to the
following equations:
day > 1
INT_FAC1(i)
TWA_SW(i)
=
=
(DAY_NO-1){1-EXP ( - LN(2)* (DAY_NO-1) / DT50) }
PEC_SW(1)*INT_FAC1(i)
-------------------------------------- +TWA_SW(1)
LN(2)* (DAY_NO-1)/ DT50
DAY_NO
_
PEC_SED(1 *INT_FAC1(i)
--------------------------------------- +TWA_SED(1)
LN(2) * (DAY_NO-1) / DT50
_
DAY_NO
TWA_SED(i)
=
INT_FAC1:
TWA_SW(i):
TWA_SED(i):
PEC_SW(i):
PEC_SED(i):
DT50:
DAY_NO:
Internal factor (d)
time weighted averaged concentration in water on day i (µg/L)
time weighted averaged concentration in sediment on day i (µg/kg)
surface water concentration on day i (µg/L)
sediment concentration on day i (µg/kg)
DT50 in sediment/water study (d)
simulation day (d)
13
STEP 2 calculations
Compound rate
For active ingredients simply the application rate” is taken as “equivalent rate of the compound”. If
metabolites are simulated the “equivalent rate of compound” is estimated based on the application rate
for the parent compound, the molecular masses, and the maximum fractions of the metabolite in soil
(for runoff/drainage) and water (for drift) according to following equations:
EQ_RATE_RUNOFF_TOT
=
APP_RATE * (M_COMP / M_PAR) * MAX_SOIL/100
EQ_RATE_DRIFT
=
APP_RATE * (M_COMP / M_PAR) * MAX_SEDWAT/100
EQ_RATE_RUNOFF_TOT:
EQ_RATE_DRIFT:
APP_RATE :
M_PAR:
M_COMP:
MAX_SOIL:
MAX_SEDWAT
equivalent rate of compound for runoff (g/ha)
equivalent rate of compound for drift (g/ha)
application rate (g/ha)
molecular mass of the parent compound (g/mole)
molecular mass of the simulated compound (g/mole)
maximum % of metabolite observed in soil studies
maximum % of metabolite observed in sediment/water studies
Crop interception
In opposite to step 1 crop interception is considered at step 2. Crop interception factors are available
dependent on crop and crop stage and will reduce the amount that is entering the system via the runoff/drainage event.
EQ_RATE_RUNOFF
=
EQ_RATE_RUNOFF_TOT:
EQ_RATE_RUNOFF:
CRP_INT:
EQ_RATE_RUNOFF_TOT * (1 – CRP_INT)
equivalent rate of compound for runoff (g/ha)
equivalent rate of compound for runoff, crop interception considered (g/ha)
crop interception factor (-)
Concentration in soil after the final treatment
The concentration in soil after the final treatment is based for the calculation of the mass entering the
water body via the runoff/drainage event
INT_FAC2
=
1 - EXP( -NUM
*
T_APP *
INT_FAC3
=
1 - EXP ( - T_APP * LN(2) / DT50_SOIL)
LN(2) / DT50_SOIL)
INT_FAC2
EQ_RATE_RUNOFF_FINAL
=
EQ_RATE_RUNOFF * ----------------INT_FAC3
EQ_RATE_RUNOFF:
equivalent rate of substance for runoff (g/ha)
EQ_RATE_RUNOFF_FINAL:
equivalent rate for runoff after the last treatment (g/ha)
INT_FAC2:
INT_FAC3:
NUM:
T_APP:
DT50_SOIL:
internal factor (-)
internal factor (-)
number of treatments per season (-)
time between 2 applications (d)
DT50 in soil (d)
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Concentration in soil at the time of the runoff/drainage-event
The runoff/drainage event will always occur 4 days after the final treatment. The previous calculated
rate will therefore be corrected due to degradation before the storm event:
EQ_RATE_RUNOFF_EV
=EQ_RATE_RUNOFF_FINAL * EXP(-4 * LN(2) / DT50_SOIL)
EQ_RATE_RUNOFF_EV:
equivalent rate of compound for runoff at the time of the runoff
event (g/ha)
equivalent rate of compound for runoff after the final treatment
(g/ha)
DT50 in soil (d)
EQ_RATE_RUNOFF_FINAL:
DT50_SOIL:
Input via drift
The input into the surface water via a single drift event is calculated based on crop dependent drift percentages:
INPUT_DRIFT_S
=
INPUT_DRIFT_S:
EQ_RATE_DRIFT:
DRIFT_PERC:
EQ_RATE_DRIFT * DRIFT_PERC / 1000
input via single drift event (mg/m²)
equivalent rate of compound for drift (g/ha)
drift percentage (%)
Input via runoff
Based on the runoff percentage for the specific situation the input into the surface water via the runoff/
drainage event is calculated as shown in the following equation:
INPUT_RUNOFF
=
INPUT_RUNOFF:
EQ_RATE_RUNOFF_EV:
RUNOFF_PERC:
RATIO:
EQ_RATE_RUNOFF_EV * RUNOFF_PERC * RATIO / 1000
input via runoff (mg/m²)
equivalent rate of compound for runoff (g/ha)
runoff percentage (related to soil residue) (%)
ratio of field to water body (-)
Fraction of compound entering in water phase via runoff
The fraction entering in the water phase via runoff/drainage is calculated dependent on the sorption
constant of the compound:
F_RUNOFF
=
F_RUNOFF:
WAT_DEPTH:
EFF_SED_DEPTH:
DENS
OC:
KOC:
WAT_DEPTH / (WAT_DEPTH + (EFF_SED_DEPTH * DENS *
OC * KOC/100) )
fraction of compound entering in water phase via runoff (-)
depth of the surface water (cm)
effective sediment depth of the surface water (cm)
sediment bulk density (kg/L)
sediment organic carbon content (%)
sorption constant related to org carbon (L/kg)
15
Total loading to water body
The total loading entering in the water phase is calculated in mg/m² and as percentage:
INPUT_DRIFT
=
INPUT_DRIFT_S * NUM_APP
INPUT_RUNOFF_W
=
INPUT_RUNOFF * F_RUNOFF
INPUT_RUNOFF_S
=
INPUT_RUNOFF * (1 - F_RUNOFF)
INPUT_DRIFT:
INPUT_RUNOFF_W:
INPUT_RUNOFF_S:
INPUT_DRIFT_S:
NUM_APP:
F_RUNOFF:
INPUT_RUNOFF:
input via drift (mg/m²)
runoff input through water phase (mg/m²)
runoff input through sediment phase (mg/m²)
input via single drift event (mg/m²)
number of applications per season
fraction of compound entering in water phase via runoff (-)
input via runoff (mg/m²)
PERC_DRIFT
=
INPUT_DRIFT * 100 / TOTAL_INPUT
PERC_RUNOFF_W
=
INPUT_RUNOFF_W * 100 / TOTAL_INPUT
PERC_RUNOFF_S
=
INPUT_RUNOFF_S * 100 / TOTAL_INPUT
PERC_DRIFT:
PERC_RUNOFF_W:
PERC_RUNOFF_S:
drift input as percentage of total input (%)
runoff input through water phase as percentage of total input (%)
runoff input through sediment phase as percentage of total input
(%)
input via drift (mg/m²)
runoff input through water phase (mg/m²)
runoff input through sediment phase (mg/m²)
INPUT_DRIFT:
INPUT_RUNOFF_W:
INPUT_RUNOFF_S:
Daily input into the surface water
At Step 2, loadings are refined as a series of individual applications, resulting in drift to the water body,
followed by a run-off/erosion/drainage event occurring four days after the last application. In opposite
to the drift input that fully enters the surface water without any distribution, the input via runoff/ drainage is immediately distributed between the water and sediment layer:
day iapp (day of application)
INPUT_SW(iapp)
=
INPUT_DRIFT_S
INPUT_SED(iapp)
=
0
INPUT_SW(iappi):
INPUT_SED(iapp):
INPUT_DRIFT_S:
input into surface water on day iapp (mg/m²)
input into sediment on day iapp (mg/m²)
input via single drift event (mg/m²)
day istorm (day of runoff event)
INPUT_SW(istorm)
=
INPUT_RUNOFF * F_RUNOFF
INPUT_SED(istorm)
=
INPUT_RUNOFF * (1 – F_RUNOFF)
INPUT_SW(istorm) :
INPUT_SED(istorm) :
INPUT_RUNOFF:
F_RUNOFF:
input into surface water on day istorm (mg/m²)
input into sediment on day istorm (mg/m²)
input via runoff (mg/m²)
fraction of compound entering in water phase via runoff (-)
16
Daily mass distribution in the system
On the first simulation day simply the input via a single drift event is taken to calculate the compound
mass in the water phase. No input is considered for the sediment phase.
day = 0
MASS_SW(0)
=
INPUT_DRIFT_S
MASS_SED(0)
=
0
MASS_SW (0):
MASS_SED (0)
INPUT_DRIFT_S:
compound mass in the surface water on day 0 (mg/m²)
compound mass in the sediment on day 0 (mg/m²)
input via single drift event (mg/m²)
At the end of day 0 (just before day 1) the distribution of the compound between the water and sediment layer is calculated for the first time (without considering degradation). The calculator assumes
that following a drift event, the pesticide is distributed in surface water into two theoretical compartments, "available" for sorption to sediment and "unavailable" for sorption to sediment.
First the fractions available for sorption and unavailable for sorption in surface water are calculated:
End of day = 0
MASS_SW_INT_AV(0)
=
MASS_SW_INT(0) / DIST_COEFF
MASS_SW_INT_UNAV(0)
=
MASS_SW_INT(0) - MASS_SW_INT_AV(0)
MASS_SW_INT_AV(0):
temporary compound mass in the surface water at the end of day 0
that is available for sorption (mg/m²)
temporary compound mass in the surface water at the end of day 0
that is not available for sorption (mg/m²)
temporary compound mass in the surface water at the end of day 0
(mg/m²)
distribution coefficient (value = 1.5)
MASS_SW_INT_UNAV(0):
MASS_SW_INT(0):
DIST_COEFF
Then, the mass distribution between water and sediment is estimated based on the intermediate results:
End of day = 0
MASS_SW(0)
=
MASS_SW_INT_UNAV(0)+(MASS_SW_INT_AV(0) +
MASS_SED_INT(0)) * F_RUNOFF
MASS_SED(0)
=
MASS_SW_INT(0) + MASS_SED_INT(0) - MASS_SW(0)
MASS_SW (0):
MASS_SED (0):
MASS_SW_INT_AV(0):
MASS_SW_INT_UNAV(0):
MASS_SED_INT(0):
F_RUNOFF:
compound mass in the surface water at the end of day 0 (mg/m²)
compound mass in the sediment at the end of day 0 (mg/m²)
temporary compound mass in the surface water at the end of day 0
that is available for sorption (mg/m²)
temporary compound mass in the surface water at the end of day 0
that is not available for sorption (mg/m²)
temporary compound mass in the sediment at the end of day 0
(mg/m²)
fraction of compound entering in water phase via runoff (-)
17
The daily concentrations for the following simulation days are calculated using a stepwise approach
based on the current compound masses in the system. First, a temporary mass of the compound in water and sediment is calculated considering only degradation and drift or runoff/drainage events:
day > 0
MASS_SW_INT(i)
=
MASS_SW (i-1) * EXP(-LN(2)/DT50_SW) + INPUT_SW(i)
MASS_SED_INT(i)
=
MASS_SED (i-1) * EXP(-LN(2)/DT50_SED) + INPUT_SED(i)
MASS_SW_INT(i):
MASS_SW (i-1):
DT50_SW:
INPUT_SW(i)
MASS_SED_INT(i):
MASS_SED (i-1)
DT50_SED
INPUT_SED(i):
temporary compound mass in the surface water on day i (mg/m²)
compound mass in the surface water on day i-1 (mg/m²)
DT50 in surface water (d)
Input into surface water on day i (mg/m²)
temporary compound mass in the sediment on day i (mg/m²)
compound mass in the sediment on day i-1 (mg/m²)
DT50 in sediment (d)
Input into sediment on day i (mg/m²)
The calculator assumes that following a drift event, the pesticide is distributed in surface water into two
theoretical compartments, “available” for sorption to sediment and “unavailable” for sorption to sediment.
MASS_SW_INT_AV(i)
=
MASS_SW_INT(i) / DIST_COEFF
MASS_SW_INT_UNAV(i)
=
MASS_SW_INT(i) - MASS_SW_INT_AV(i)

MASS_SW_INT_AV(i):
temporary compound mass in the surface water on day i that is
available for sorption(mg/m²)
MASS_SW_INT_UNAV(i):
temporary compound mass in the surface water on day i that is not
available for sorption(mg/m²)
MASS_SW_INT(i):
temporary compound mass in the surface water on day i (mg/m²)
DIST_COEFF:
distribution coefficient
(value = 1.5 before the runoff event,
value = 1 during and after the runoff-event)

Based on the compound fraction in water available for sorption the distribution of the compound between the water and sediment layer is considered:
MASS_SW(i)
=
MASS_SW_INT_UNAV(i)+(MASS_SW_INT_AV(i) +
MASS_SED_INT(i)) * F_RUNOFF
MASS_SED(i)
=
MASS_SW_INT(i) + MASS_SED_INT(i) - MASS_SW(i)
MASS_SW (i):
MASS_SED (i)
MASS_SW_INT_AV(i):
compound mass in the surface water on day i (mg/m²)
compound mass in the sediment on day i (mg/m²)
temporary compound mass in the surface water on day i
that is available for sorption(mg/m²)
MASS_SW_INT_UNAV(i):
temporary compound mass in the surface water on day i
that is not available for sorption(mg/m²)
MASS_SED_INT(i):
F_RUNOFF:
temporary compound mass in the sediment on day i (mg/m²)
fraction of compound entering in water phase via runoff (-)
18
Daily concentrations
The daily concentrations are calculated based on the masses in the system before the distribution between water and sediment is considered.
PEC_SW(i)
=
MASS_SW_INT * 100
WAT_DEPTH
PEC_SED(i)
=
MASS_SED_INT * 100
SED_DEPTH * DENS
PEC_SW(i):
PEC_SED(i):
MASS_SW_INT(i):
MASS_SED_INT(i):
WAT_DEPTH:
SED_DEPTH:
DENS
surface water concentration on day i (µg/L)
sediment concentration on day i (µg/kg)
temporary compound mass in the surface water on day i (mg/m²)
temporary compound mass in the sediment on day i (mg/m²)
depth of the surface water (cm)
sediment depth (cm)
sediment bulk density (kg/L)
Averaged concentrations over 24 hours
For the estimation of time weighted averaged concentration 1 day averaged concentrations are calculated in first step:
TWA_24_SW(i)
=
(PEC_SW(i-1) + PEC_SW(i) ) / 2
TWA_24_SED(i )
=
(PEC_SED(i-1) + PEC_SED(i) ) / 2
TWA_24_SW(i):
TWA_24_SED(i):
PEC_SW(i):
PEC_SED(i):
PEC_SW(i-1):
PEC_SED(i-1):
averaged concentration in surface water over 24 h (µg/L)
averaged concentration in sediment over 24 h (µg/kg)
surface water concentration on day i (µg/L)
sediment concentration on day i (µg/kg)
surface water concentration on day i –1 (µg/L)
sediment concentration on day i –1 (µg/kg)
19
Time weighted averaged concentrations (TWA)
As the default modus the time weighted averaged concentrations are always calculated beginning with
the time of the absolute maximum of the concentration (PEC) in surface water or in sediment (imax).
day = imax +1 ( j=1)
TWA_SW (j=1)
=
TWA_24_SW(imax)
TWA_SED (j=1)
=
TWA_24_SED(imax)
imax:
day for which the absolute maximum of the concentration in surface water (or sediment) was calculated
counter for the number of days after the absolute maximum
averaged concentration in surface water on the day imax (µg/L)
averaged concentration in sediment on the day imax (µg/kg)
Time weighted average conc. in surface water over 1 day (µg/L)
Time weighted average conc. in sediment over 1 day (µg/kg)
j:
TWA_24_SW(imax):
TWA_24_SED(imax):
TWA_SW(1):
TWA_SED(1):
day > imax +1 (j > 1)
TWA_SW(j)
=
{
imax  j

TWA_SW_24(i)
} /j
i  imax 1
TWA_SED(j)
=
{
imax  j

TWA_SED_24(i)
} /j
i  imax 1
i:
j:
imax:
TWA_24_SW(i):
TWA_24_SED(i):
TWA_SW(j):
TWA_SED(j):
counter for the number of simulation days
counter for the number of days after the absolute maximum
day for which the absolute maximum of the concentration in surface water (or sediment) was calculated
averaged concentration in surface water on the day i (µg/L)
averaged concentration in sediment on the day i (µg/kg)
Time weighted average conc. in surface water over j days (µg/L)
Time weighted average conc. in sediment over j days (µg/L)
If the user has selected the moving time frame for the estimation of the time weighted average concentrations, the system will analyse all possible windows and select the window that gives the highest concentration.
20
Working with STEPS 1-2 in FOCUS
File handling
Scenario Data
Substance Data
STEPS 1-2
in FOCUS
Reports
Diagrams
Figure 1: STEPS 1-2 in FOCUS: Input and Output data
All scenario data used by the program are read in from the file "scenario.txt". This file is read protected, but it can be viewed using STEPS 1-2 in FOCUS (click menu view - scenario data on the main
form),. However, there is no possibility to modify any scenario data.
The pesticide information is stored in the file “pesticide.txt” for all compounds. Also pesticide.txt is an
ASCII-file, the necessary pesticide input data is stored in lines (one line per substance) with one comment at the beginning. To edit the pesticide data file just use "edit" in the menu of the main form or
double click at the list box).
21
Results are written into Testfiles (RTF-format) and stored in the subdirectory “results”. The files names
are automatically set using the name of the compound together with the type of estimation (step 1 or
step 2). A second file will be written if step 2 simulations are performed, showing more detailed results
of the simulations. The file name is also automatically chosen by the name of the compound. The extension of this file is xls allowing direct loading into MICROSOFT Excel.
Running Simulations
Figure 2: STEPS 1-2 in FOCUS: Main form
After having called the program STEPS 1-2 in FOCUS automatically performs a calculation using the
currently selected compound. The results are always directly updated after having selected a new compound. The most important output data are presented on the main form. However, a full report summarising all input data and providing you with more detailed output is created after clicking at the reportbutton.
22
Editing Substance Specific Information
There is a special form that is used to view or edit all substance specific input data.
The form is loaded on the screen after double clicking at the box listing all active ingredients by using
the menu (View – Substance data or Edit).
As long as you are in the view modus (white background colour) you may go through the list stored in
the data base. In the view modus you may add, copy or delete records (=compounds). However, you
cannot modify any data. If you use “Add” a new (empty) data record will be created, “Copy” doubles
the current data record.
Figure 3: STEPS 1-2 in FOCUS: Viewing substance specific input data
If you switch to the edit modus (yellow background colour) you may change the values of the parameters. Please consider that you cannot move to a new substance as long as you stay in the edit modus.
Dependent on the selections chosen for the simulation-level (step 1 or step 2) and the type of compound (metabolite or active ingredient) the number of parameters visible on the form may change.
23
Figure 4: STEPS 1-2 in FOCUS: Editing substance specific input data
If you click at the “Help”-button an additional box will appear on the bottom of the form with some
information on how to set the correct input data.
When you leave the edit modus you are asked whether you would like to save the changes in a new
record or modify the existing record.
24
Creating a Report
Figure 5: STEPS 1-2 in FOCUS: Report
STEPS 1-2 in FOCUS will start creating a full report after clicking at the “REPORT”-button on the
main screen. The report appears on the screen, but it is also written into a file using the RTF-format
(file name = name of the compound + modus of the simulation + ".rtf") and stored in the subdirectory
“results”. Finally the report can be copied into the clipboard to paste into other applications.
25
Figure 6: STEPS 1-2 in FOCUS: Time series diagram
You may add a number of diagrams to the report. First, click at the diagram-button and then click at the
button "copy into the report". You can change the format of the diagram by using the 2 list boxes (decide between a graph representing the concentration either in sediment or in the water phase / choose
the time the TWA-concentration is based on). Finally, you may change the maximum time shown in
the graph (use the right mouse button to open a small box where you can enter the t-max value you
prefer).
When you do a simulation in step 2 modus the calculator creates an additional output file showing all
results of the simulation on a daily basis. The file name is also automatically chosen by STEPS 1-2 in
FOCUS using the name of the compound. The extension of this file is xls allowing direct loading into
MICROSOFT Excel.
26
Viewing scenario data
Figure 7: STEPS 1-2 in FOCUS: Scenario data
You can have a look on all scenario data STEPS 1-2 in FOCUS is using by calling the form “Scenarios
for surface water”. It is available from the menu on the main form (View – scenario data). The tables
can be copied into other applications via the clipboard
27
Modifying the preferences
Figure 8: STEPS 1-2 in FOCUS: preferences
If the user wants to use an individual period for the calculation of the time weighted average concentrations it can be considered in the preferences. Additionally, a moving time frame for the TWA (instead
of a fixed frame starting with the absolute maximum concentration) can be selected here.
References
BBCH (1994). Compendium of growth stage indication keys for mono- and dicotyledonous plants extended BBCH scale. Ed R Stauss. Published by BBA, BSA, IGZ, IVA, AgrEvo, BASF, Bayer
& Ciba, ISBN 3-9520749-0-X, Ciba-Geigy AG, Postfach, CH-4002 Basel, Switzerland.
BBA (2000), Bekanntmachung über die Abtrifteckwerte, die bei der Prüfung und Zulassung von
Pflanzenschutzmitteln herangezogen werden. (8. Mai 2000) in : Bundesanzeiger No.100,
amtlicher Teil, vom 25. Mai 2000, S. 9879.
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