Post on 16-Dec-2015
transcript
http://www.pearl.alterra.nl
A spatially-distributed model ofpesticide leaching
Aaldrik Tiktak
http://www.pearl.alterra.nl
http://www.pearl.alterra.nl
Outline of presentation
• Why spatially distributed modelling?• What is GeoPEARL?• How is a GeoPEARL assessment carried
out?• Which are the main model outputs?• Selected Results and Examples• Questions?• Overview of the User Interface
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Why spatially distributed modelling in registration?
Explicit consideration of the variability of the leaching process:
• where are the vulnerable regions?• Are specific areas (e.g. drinking water
abstraction areas) sufficiently protected?
Leaching in the area of use
Leaching in drinking water abstraction areas
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Why spatially distributed modelling in registration?
Explicit calculation of ‘realistic worst-case conditions’:
• calculation of percentiles of the leaching concentration in space
• more realistic choice of standard scenario’s, no need for safety factors in registration
Position ofthe DutchStandardScenario
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What is GeoPEARL?
•GeoPEARL is a spatially-distributed model of pesticide leaching to the groundwater and surface waters in the Netherlands. The core of the GeoPEARL consists of PEARL itself.
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The PEARL model - a 1D-column
preci pitat ion
irrigati on
t ranspirati onevaporat ion of
intercepted water
soilevaporat ion throughfall
f luctuati nggroundwater
level
soil waterf luxes
ponding
water uptakeby plant roots
seepage
lateral
discharge toditches and
f ield-drai ns
un
sa
tura
ted
zo
ne
sa
tura
ted
zo
ne
depositi on
applicat ion
dissipation at thecrop canopy
volati lisation
wash-of f
convect iondispersiondif fusion
pestic ideuptake
leaching
t ransform ation
solid-liquidgas
partit ioning
SWAPhydrology
PEARLpesticide fate
cropcalendar
heatf low
inject ion
surface
run-off
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Position of column in landscape
field-ditches
water courses< 3m
water courses> 3 m
PEARL 1Dcolumn
Leaching into theregional
groundwater
Groundwater table
Drainage into localsurface waters
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Why a complex model??????
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The plot appraoch
•PEARL is run in a GIS context for a large number of unique combinations (plots) of soil, climate, land-use and hydrogeological units.
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Derivation of the unique combinations:
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• Lower boundary of SWAP is upper boundary of National Groundwater Model;
• Start with NAGROM and a simple unsaturated zone model;
• Adjust the boundary flux by running NAGROM and SWAP iteratively;
• Wait until convergence is reached.
Obtaining the lower boundary of SWAP:
• Lower boundary condition is a prescribed flux condition (so-called ‘Neumann condition’);
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Plots are represented by a single vertical column:
A plot
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Basic soil properties in GeoPEARL
Slightly acidicsandy soils (‘higher part’)
Clay soils with near neutral pH-values (‘lower part’)
Acidic peat soils
pH-KCl!!!!!
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How are GeoPEARL assessments carried out?
• GeoPEARL is run for 250-6405 plots, depending on spatial detail wanted;
• The model is run for the area of potential usage only. This area is assumed equivalent to the area of the crop(s) for which a registration is requested;
• For each plot and crop-type, the model is run for 26, 46 or 66 years (FOCUS procedure);
• For each plot the median leaching concentration in time is extracted and put into a map.
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To be specified by the user:
•Substance properties (start withstandard dossier)
•Application schedule
•Number of plots (i.e. spatial detail wanted)
•One or more crops for which a registration is requested
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More attention for relationship between soil properties and substance properties:• DT50 in top-soil specified as a function of clay
content, pH and organic matter content
• KF specified as a function of organic matter and pH:
eqsoxsoxeqclayclayeqsiltsilteqsandsandeqomomeqFeqF KcKmKmKmKmKK ,,,,,0,,,
H-Ka-pH
ac
H-Ka-H
ac,,aceq,.
101
10
ppba
pppbabaeqomom
omF,eq
MM
MM
KKmK
max,50,50max,50,50
H,.,50
,50
max,50,50min,50
min,50,50min,50,50
)HH()()(if
DTDTDTDT
ppfmmfmmfDT
DTDTDTDT
DTDTDTDT
plotplot
rprlllromomomr
plot
plot
plotplot
or as a function of other properties:
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More attention for relationship between soil properties and substance properties:
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The target variable produced by the model:
•The 90th percentile in space and the 50th percentile in time of the leaching concentration at 1 m depth at the area of (potential) usage
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Further model outputs:
•Maps and frequency diagrams of terms of the water balances
•Maps and frequency diagrams of terms of the substance balances, including the leaching, drainage and volatilisation fluxes
•Maps of percentiles and frequency diagrams of the leaching concentration in time
•Tables of balance terms
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Example 1: Comparison of leaching of two substances
High pH
Vulnerable sandy soils
Ordinary substance pH-dependent sorption
Opposite spatial patterns!
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Example 2: Comparison of drainage and leaching
Drainage fluxes are highest in clay and peat soils...
Leaching fluxes are highest in sandy soils...
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Some conclusions from previous examples:
• Drainage fluxes are generally higher than leaching fluxes.
• For ordinary substances, drainage dominates in the peat and clay soils and leaching in sandy soils.
• The leaching pattern can be quite different for non-ordinary substances (e.g. substances with pH-dependent sorption)
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GeoPEARL considers the area of potential usage:
• Pesticides are usually authorised for particular crops;
• The new decision tree therefore considers the area of potential usage, approximated by the area of crops for which a registration is requested
• GeoPEARL is distributed with a database of areas for 24 major crops
• All results are presented for the area of potential usage
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GeoPEARL crops are not hydrologically different
• During the derivation of the UC’s, only four crops were included (grass, mais, potatoes and forest);
• For each plot, the dominant crop is used. Hydrological parameters are assigned to these crops;
• The 24 GeoPEARL crops are used for pre-processing only; i.e. for calculating the area of use.
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Effect of area of use on pesticide authorisation (1)
Maize is grown on slightly acidic sandy soils
Potatoes are grownon light sandy claysoils and in ‘the Veenkolonien’
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Effect of area of use on pesticide authorisation (2)
Substance with pH-dependent sorption behaviour
Light sandy claysoils and ‘the Veenkolonien’
Slightly acidic sandy soils
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Effect of area of usage on authorisation (cntd.)
Unsafe in potatoes
Safe in maize
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Some conclusions from previous section:
• GeoPEARL explicitly considers the variation of the leaching process, so that it is now possible to evaluate the leaching for different crop types
• Consideration of the area of usage can have a strong effect on the authorisation decision
• It is extremely important to investigate the relationship between pesticide properties and soil properties
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GeoPEARL assessments versus assessment items
• A notifier may wish to register for several crops;
• For each crop, GeoPEARL must be run separately;
• Combination of crop and application scheme is an assessment item;
• The three items together form an assessment;
• The 90th percentile is calculated for the combination of the three crops, i.e. for the assessment.
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The GeoPEARL database
Project
Assessment
SubstanceAssessment
item
Model control(number of plotsto be includedin assessment)
Crop forwhich a
registrationis asked
AnnualApplication
scheme
Parents andmetabolites
Applicationevent
Repeatinterval
of application
Generalsubstanceproperties
Sorptionparameters
Transformationparameters
Crop relatedparameters
Diffusion relatedparameters
1:n
1:n1:11:1
1:1 1:1 1:1
1:n
1:n
1:11:1
1:11:11:1
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Reduction of computation time by using zones:
• To reduce the computation time, plots are taken together;
• Clusters of plots are called ‘zones’.
1 2 3 4 5
6 7 8 9 10
11 12 13 14 15
16 17 18 19 20
21 22 23 24 25
1 1 1 1
2 2 2
2 3 3
3 4 4 4 4
5 5 5
Plots Zones
Plot without relevant crop
Plot with relevant crop
SLICE
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Slicing is done on the basis of ‘vulnerability’
• The normal Arc/Info slice operation clusters neighbouring cells;
• We cluster plots with adjacent vulnerability indexes;
• This will give a more reliable estimation of the 90th percentile, because we sample in each class of the cumulative frequency distribution.
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The vulnerability index for ordinary substances:
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How many plots must be included in an assessment?
almost nodifference
these two aredifferent!
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More plots = more detail, but 250 plots is generally enough...
How many plots must be included in an assessment? (cntnd.)
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250 plots is generally enough...
250 versus 6405 plots
0.00001
0.0001
0.001
0.01
0.1
1
10
0.00001 0.0001 0.001 0.01 0.1 1 10
GeoPEARL_6405 (ug/L)
Geo
PE
AR
L_2
50
(ug
/L)
0.00001
0.0001
0.001
0.01
0.1
1
10
0.00001 0.0001 0.001 0.01 0.1 1 10
GeoPEARL_6405 (ug/L)
Geo
PE
AR
L_2
50
(ug
/L)
spring
autumn
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Some conclusions from previous section:
• The maximum number of zones is 6405 (which is equal to the number of plots);
• A first impression of the leaching pattern can be obtained with less plots (e.g. the 30 as used in this course);
• At least 250 plots are required for an accurate estimation of the 90th percentile. This is the minimum number for a final submission.
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Other uses of GeoPEARL
•GeoPEARL has been combined with a database on pesticide usage in order to calculate the actual pesticide loads into surface waters and groundwaters.
• Evaluation of policy plans...
•A European version of GeoPEARL (called EuroPEARL) has been developed
• EU registration in zones...
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EuroPEARL example: 80th percentile of the leaching concentration of FOCUS substance D
Hotspots occur everywhere in Europe
High leaching risk
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Possible scales…
Catchment
EU
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• A model is now available that can be used to assess the leaching into the groundwater and the drainage into surface waters at a regional-scale
• The model is operational for:• the Dutch registration procedure• evaluation of policy plans
Final remarks
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The Graphical User Interface
GeoPEARLUser
Interface
GeoPEARLUser
Interface
GeoPEARLexecutable
GeoPEARLexecutable
XYWinviewer
XYWinviewer
GeoPearldatabase
GeoPearldatabase
ReportReport
MapsMaps
PEARLmodel
PEARLmodel
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First install the program….
Download geopearl_1_1_1.exefrom the address
http://www.pearl.alterra.nl.
Archive this application
Logon with administrator rights
Run geopearl_1_1_1.exe to install GeoPEARL
Launch GeoPEARL to install Interbase
Logon with your own user name
Start using GeoPEARL; register at the PEARL website
If FOCUS PEARL 2.2.2 is installed:launch FOCUS PEARL as well
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To be specified by the user:
•Substance properties (start withstandard dossier)
•Application schedule
•Number of plots (i.e. spatial detail wanted)
•One or more crops for which a registration is requested
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Getting started with the User Interface
Add or edit a substance .Parameters must be given for parent substances and for metabol ites
Add or edit a substance .Parameters must be given for parent substances and for metabol ites
Add or edit app lication schemes.Each assessment item may have i ts own application scheme.
Add or edit app lication schemes.Each assessment item may have i ts own application scheme.
Use the wizard to generate assessments.An assessment consists o f a single substance and one or assessment items.
Use the wizard to generate assessments.An assessment consists o f a single substance and one or assessment items.
Review the input and correct where necessaryReview the input and correct where necessary
Select assessments for execution andpush the ca lcu late button to start the simulations
Select assessments for execution andpush the ca lcu late button to start the simulations
View reports, graphs and mapsView reports, graphs and maps
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GUI step 1: Main form
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GUI step 2: Edit substance properties
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GUI step 3: Edit application schedules
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GUI step 4: Run wizard, select substance and resolution
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GUI step 5: Run wizard, select crops and applications (i.e. add items)
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GUI step 6: Run GeoPEARL
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The model is running….
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GUI step 7: Select output - Assessment as a whole
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GUI step 7: View output - Assessment as a whole
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GUI step 8: Select output - Assessment item
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GUI step 8: View output - Assessment item
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GUI step 9: View report (assessment as a whole)
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GUI step 10: Analyse the output
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GUI step 10: Analyse the output