APPENDIX I - Europa



APPENDIX I

STEPS 1-2 IN FOCUS

USER MANUAL

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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 sediment-dwelling 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 105 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:

3 x DT50 in sediment/water systems < time between individual applications.

(combined water + sediment)

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:

masw = msw * K

musw = msw * (1-K)

msw: total mass of pesticide in surface water (mg/m²)

masw: mass available for sorption and (mg/m²)

musw: mass unavailable for sorption (mg/m²)

K: 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.

Scenario data

Step 1: input into surface water

|Crop |Distance crop-water |Drift |Runoff/drainage |

| |(m) |(% 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 |

Step 2: input into surface water via spray drift

|Crop |Distance |Number of application per season |

| |crop-water | |

| |(m) |1 |2 |3 |

|BBCH-code * |00 – 09 |10 – 19 |20 – 39 |40 – 89 |

|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 |0 |0.2 |0.5 |0.7 |

|(crop < 50 cm and > 50 cm) | | | | |

|no drift (incorporation /seed |0 |0 |0 |0 |

|treatment) | | | | |

* 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 |% of soil residue |

|North Europe, Oct. - Feb. |5 |

|North Europe, Mar. - May |2 |

|North Europe, June - Sep. |2 |

|South Europe, Oct. - Feb. |4 |

|South Europe, Mar. - May |4 |

|South Europe, June - Sep. |3 |

|No Runoff |0 |

Surface water definitions

|Parameter: |value |

|water depth (cm): |30 |

|sediment depth (cm): |5 |

|effective sediment depth for sorption (cm): |1 |

|sediment oc (%): |5 |

|sediment bulk density (kg/L): |0.8 |

|ratio of field to water body: |10 |

Input Parameters

Identification of the compound

|Parameter |Comment |

|Active ingredient |Enter name of active ingredient to be assessed |

|Compound for PEC calculation |Enter name of metabolite |

| |This field is only visible if metabolites are to be |

| |calculated. |

|Comment |Enter any text to distinguish between PEC calculations for|

| |the same substance |

Application pattern

|Parameter |Comment |

|Application rate of active substance (g/ha) |Enter maximum single application rate for active substance|

| |and crop type |

|Number of applications per season |Choose number of applications |

|Time between 2 applications(days) |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 |

|Crop interception |Choose the suitable crop interception from a list of 4 |

| |options |

| |This field is only visible if step 2 simulations are to be|

| |performed |

|Region and Season of Application |Choose from 6 options that define the loading to surface |

| |water |

| |This field is only visible if step 2 simulations are to be|

| |performed |

|Application/Crop type |Choose one from in total 17 options that determines the |

| |amount of spray drift |

Substance specific data

|Parameter |Comment |

|Water solubility (mg/L) |Enter water solubility |

|KOC/KOM of compound for PEC calculation |Enter sorption constant related to org carbon or org. matter |

|(L/kg) |The button it to switch between KOC and KOM |

|DT50 in the sediment/water system (days) |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) |

|DT50 for degradation in water phase (days) |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 |

|DT50 for degradation in sediment phase (days)| |

|DT50 in soil (days) |Select soil DT50 in soil |

| |This field is only visible if step 2 simulations are to be performed |

|Molecular mass of active substance (g/mole) |Enter molecular mass of active substance |

|Molecular mass of metabolite (g/mole) |This field is only visible if metabolites are to be calculated |

|Maximum % of metabolite observed in |Enter maximum amount observed in sediment + water (not just water) |

|sediment/water studies |This field is only visible if metabolites are to be calculated |

|Maximum % of metabolite observed in soil |Enter maximum amount observed in appropriate soil studies. This may |

|studies |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 |

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: equivalent rate of compound for runoff (g/ha)

EQ_RATE_DRIFT_TOT: equivalent rate of compound for drift (g/ha)

APP_RATE: application rate (g/ha)

M_PAR: molecular mass of the parent compound (g/mole)

M_COMP: molecular mass of the simulated compound /g/mole)

MAX_SOIL: maximum % of metabolite observed in soil studies

MAX_SEDWAT 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 = EQ_RATE_DRIFT * DRIFT_PERC / 1000

INPUT_DRIFT_S: input via single drift event (mg/m²)

EQ_RATE_DRIFT: equivalent rate of compound for drift (g/ha)

DRIFT_PERC: 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_S * NUM_APP

INPUT_DRIFT: input via drift (mg/m²)

INPUT_DRIFT_S: input via single drift event (mg/m²)

NUM_APP: 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 = EQ_RATE_RUNOFF_TOT * RUNOFF_PERC * RATIO / 1000

INPUT_RUNOFF_S: input via single runoff event (mg/m²)

EQ_RATE_RUNOFF_TOT: equivalent rate of compound for runoff (g/ha)

RUNOFF_PERC: runoff percentage (related to soil residue) (%)

RATIO: 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:

INPUT_RUNOFF = INPUT_RUNOFF_S * NUM_APP

INPUT_RUNOFF: input via RUNOFF (mg/m²)

INPUT_RUNOFF_S: input via single RUNOFF event (mg/m²)

NUM_APP: 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 = WAT_DEPTH / (WAT_DEPTH + (EFF_SED_DEPTH * DENS * OC * KOC/100) )

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

WAT_DEPTH: depth of the surface water (cm)

EFF_SED_DEPTH: effective sediment depth of the surface water (cm)

DENS sediment bulk density (kg/L)

OC: sediment organic carbon content (%)

KOC: 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: surface water concentration (µg/L)

PEC_SED: sediment concentration (µg/kg)

INPUT_RUNOFF: input via runoff (mg/m²)

INPUT_DRIFT: input via drift (mg/m²)

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

WAT_DEPTH: depth of the surface water (cm)

SED_DEPTH: sediment depth of the surface water (cm)

DENS sediment bulk density (kg/L)

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: Internal factor (-)

PEC_SW: surface water concentration (µg/L)

PEC_SED: sediment concentration (µg/kg)

INPUT_RUNOFF: input via runoff (mg/m²)

INPUT_DRIFT: input via drift (mg/m²)

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

WAT_DEPTH: depth of the surface water (cm)

SED_DEPTH: sediment depth of the surface water (cm)

DENS sediment bulk density (kg/L)

DT50: DT50 in sediment/water study (d)

DAY_NO: 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): time weighted averaged concentration in water on day 1 (µg/L)

TWA_SED(1): time weighted averaged concentration in sediment on day 1 (µg/kg)

PEC_SW(0): surface water concentration on day 0 (µg/L)

PEC_SED(0) sediment concentration on day 0 (µg/kg)

For the other simulation days the time weighed averaged concentrations are calculated according to the following equations:

day > 1

INT_FAC1(i) = (DAY_NO-1){1-EXP ( - LN(2)* (DAY_NO-1) / DT50) }

PEC_SW(1)*INT_FAC1(i)

-------------------------------------- +TWA_SW(1)

TWA_SW(i) = LN(2)* (DAY_NO-1)/ DT50 _

DAY_NO

PEC_SED(1 *INT_FAC1(i)

--------------------------------------- +TWA_SED(1)

TWA_SED(i) = LN(2) * (DAY_NO-1) / DT50 _

DAY_NO

INT_FAC1: Internal factor (d)

TWA_SW(i): time weighted averaged concentration in water on day i (µg/L)

TWA_SED(i): time weighted averaged concentration in sediment on day i (µg/kg)

PEC_SW(i): surface water concentration on day i (µg/L)

PEC_SED(i): sediment concentration on day i (µg/kg)

DT50: DT50 in sediment/water study (d)

DAY_NO: simulation day (d)

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: equivalent rate of compound for runoff (g/ha)

EQ_RATE_DRIFT: equivalent rate of compound for drift (g/ha)

APP_RATE : application rate (g/ha)

M_PAR: molecular mass of the parent compound (g/mole)

M_COMP: molecular mass of the simulated compound (g/mole)

MAX_SOIL: maximum % of metabolite observed in soil studies

MAX_SEDWAT 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 * (1 – CRP_INT)

EQ_RATE_RUNOFF_TOT: equivalent rate of compound for runoff (g/ha)

EQ_RATE_RUNOFF: equivalent rate of compound for runoff, crop interception considered (g/ha)

CRP_INT: 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 * LN(2) / DT50_SOIL)

INT_FAC3 = 1 - EXP ( - T_APP * 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: internal factor (-)

INT_FAC3: internal factor (-)

NUM: number of treatments per season (-)

T_APP: time between 2 applications (d)

DT50_SOIL: DT50 in soil (d)

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)

EQ_RATE_RUNOFF_FINAL: equivalent rate of compound for runoff after the final treatment (g/ha)

DT50_SOIL: DT50 in soil (d)

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 = EQ_RATE_DRIFT * DRIFT_PERC / 1000

INPUT_DRIFT_S: input via single drift event (mg/m²)

EQ_RATE_DRIFT: equivalent rate of compound for drift (g/ha)

DRIFT_PERC: 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 = EQ_RATE_RUNOFF_EV * RUNOFF_PERC * RATIO / 1000

INPUT_RUNOFF: input via runoff (mg/m²)

EQ_RATE_RUNOFF_EV: equivalent rate of compound for runoff (g/ha)

RUNOFF_PERC: runoff percentage (related to soil residue) (%)

RATIO: 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 = WAT_DEPTH / (WAT_DEPTH + (EFF_SED_DEPTH * DENS * OC * KOC/100) )

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

WAT_DEPTH: depth of the surface water (cm)

EFF_SED_DEPTH: effective sediment depth of the surface water (cm)

DENS sediment bulk density (kg/L)

OC: sediment organic carbon content (%)

KOC: sorption constant related to org carbon (L/kg)

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 via drift (mg/m²)

INPUT_RUNOFF_W: runoff input through water phase (mg/m²)

INPUT_RUNOFF_S: runoff input through sediment phase (mg/m²)

INPUT_DRIFT_S: input via single drift event (mg/m²)

NUM_APP: number of applications per season

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

INPUT_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: drift input as percentage of total input (%)

PERC_RUNOFF_W: runoff input through water phase as percentage of total input (%)

PERC_RUNOFF_S: runoff input through sediment phase as percentage of total input (%)

INPUT_DRIFT: input via drift (mg/m²)

INPUT_RUNOFF_W: runoff input through water phase (mg/m²)

INPUT_RUNOFF_S: runoff input through sediment phase (mg/m²)

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 into surface water on day iapp (mg/m²)

INPUT_SED(iapp): input into sediment on day iapp (mg/m²)

INPUT_DRIFT_S: 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 into surface water on day istorm (mg/m²)

INPUT_SED(istorm) : input into sediment on day istorm (mg/m²)

INPUT_RUNOFF: input via runoff (mg/m²)

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

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): compound mass in the surface water on day 0 (mg/m²)

MASS_SED (0) compound mass in the sediment on day 0 (mg/m²)

INPUT_DRIFT_S: 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)

MASS_SW_INT_UNAV(0): temporary compound mass in the surface water at the end of day 0 that is not available for sorption (mg/m²)

MASS_SW_INT(0): temporary compound mass in the surface water at the end of day 0 (mg/m²)

DIST_COEFF distribution coefficient (value = 1.5)

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): compound mass in the surface water at the end of day 0 (mg/m²)

MASS_SED (0): compound mass in the sediment at the end of day 0 (mg/m²)

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)

MASS_SW_INT_UNAV(0): temporary compound mass in the surface water at the end of day 0 that is not available for sorption (mg/m²)

MASS_SED_INT(0): temporary compound mass in the sediment at the end of day 0 (mg/m²)

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

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): temporary compound mass in the surface water on day i (mg/m²)

MASS_SW (i-1): compound mass in the surface water on day i-1 (mg/m²)

DT50_SW: DT50 in surface water (d)

INPUT_SW(i) Input into surface water on day i (mg/m²)

MASS_SED_INT(i): temporary compound mass in the sediment on day i (mg/m²)

MASS_SED (i-1) compound mass in the sediment on day i-1 (mg/m²)

DT50_SED DT50 in sediment (d)

INPUT_SED(i): 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): compound mass in the surface water on day i (mg/m²)

MASS_SED (i) compound mass in the sediment on day i (mg/m²)

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_SED_INT(i): temporary compound mass in the sediment on day i (mg/m²)

F_RUNOFF: fraction of compound entering in water phase via runoff (-)

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): surface water concentration on day i (µg/L)

PEC_SED(i): sediment concentration on day i (µg/kg)

MASS_SW_INT(i): temporary compound mass in the surface water on day i (mg/m²)

MASS_SED_INT(i): temporary compound mass in the sediment on day i (mg/m²)

WAT_DEPTH: depth of the surface water (cm)

SED_DEPTH: sediment depth (cm)

DENS 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): averaged concentration in surface water over 24 h (µg/L)

TWA_24_SED(i): averaged concentration in sediment over 24 h (µg/kg)

PEC_SW(i): surface water concentration on day i (µg/L)

PEC_SED(i): sediment concentration on day i (µg/kg)

PEC_SW(i-1): surface water concentration on day i –1 (µg/L)

PEC_SED(i-1): sediment concentration on day i –1 (µg/kg)

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

j: counter for the number of days after the absolute maximum

TWA_24_SW(imax): averaged concentration in surface water on the day imax (µg/L)

TWA_24_SED(imax): averaged concentration in sediment on the day imax (µg/kg)

TWA_SW(1): Time weighted average conc. in surface water over 1 day (µg/L)

TWA_SED(1): Time weighted average conc. in sediment over 1 day (µg/kg)

day > imax +1 (j > 1)

TWA_SW(j) = { [pic] TWA_SW_24(i) } / j

TWA_SED(j) = { [pic] TWA_SED_24(i) } / j

i: counter for the number of simulation days

j: counter for the number of days after the absolute maximum

imax: day for which the absolute maximum of the concentration in surface water (or sediment) was calculated

TWA_24_SW(i): averaged concentration in surface water on the day i (µg/L)

TWA_24_SED(i): averaged concentration in sediment on the day i (µg/kg)

TWA_SW(j): Time weighted average conc. in surface water over j days (µg/L)

TWA_SED(j): 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.

Working with STEPS 1-2 in FOCUS

File handling

[pic]

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).

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

[pic]

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 report-button.

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.

[pic]

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.

[pic]

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.

Creating a Report

[pic]

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.

[pic]

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.

Viewing scenario data

[pic]

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

Modifying the preferences

[pic]

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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[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.

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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:



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