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PE5 User's Manual


Environmental Fate and Effects Division
Office of Pesticide Programs
U.S. Environmental Protection Agency

Tier 2 Screening Model Shell for Pesticide Aquatic Exposure Assessment

Version 5.0 (Nov. 15, 2006)

Table of Contents

Introduction to PE5

October 22, 2007

The program PE5.pl (PE5, PE Version 5.0, dated Nov. 15, 2006) is a graphical interface (shell) that facilitates placing chemical- and use-specific input values into the proper positions in PRZM input files and EXAMS chemical files. The official versions of PRZM (Version 3.12.2, May 12, 2005), EXAMS(Version, Apr. 25, 2005), and the PE crop scenarios associated with PRZM version 3.12.2 should be installed on the hard drive of your computer before running the PE5 shell. Input parameters for this program are selected using the latest guidance for environmental fate and transport models (USEPA, 2002). Once the inputs have been entered, the interface creates the necessary input and run files, calls up PRZM and EXAMS, runs the programs, creates the output files generated by the DOS programs, and generates two additional output files. The two output files consist of a time series file and a summary file that echoes the input data and reports annual maximum and 1-in-10-year estimates. The interface was created using Perl and Tk, publicly available programming, and requires Perl to run. This guidance document provides instructions for setting up the shell and models on your computer, for running the shell, and for retrieving the outputs. The shell program code can be viewed in any text editor.

PE5 (PE Version 5.0) was implemented in August 2007 along with PRZM Version 3.12.2, EXAMS Version, and the associated PE crop scenarios as a replacement for PE4 (PE Version 4.01, dated Aug 8, 2003; developed by Ian Kennedy) and its associated suite of models and scenarios. The PE5 program, which is used in Tier 2 screening-level aquatic exposure assessments, was developed in response to user recommendations for improving the program and for making it consistent with newer versions of PRZM (Carsel, 1997) and EXAMS (Burns, 2000). The main differences between the PE4 and PE5 shells are that PE5 includes a corrected hydrologic length (356.8 meters) for the standard pond, can correctly read scenarios formatted for PRZM v3.12.2 (including changes in curve number format), can accept a different application rate at each application interval for a single run, and can model simultaneous runs for multiple application dates at a constant application rate.

Using standard crop scenarios, the WQTT conducted an evaluation of the computer code and model predictions. The results show that PE5 correctly read the updated input formats and correctly generated PRZM input files with the data provided. PE5 was also found to function accurately when compared to command line operation.

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Installing PE5

  1. Install Perl

    1. Perl for Windows is available from ActiveState at http://www.activestate.com. Exit EPA Disclaimer

    2. Click on the link for ActivePerl (as of this writing it's under the drop down window for "language distributions") and follow the instructions for downloading the MSI file for Windows, "ActivePerl" or the appropriate file for your operating system.

    3. Once you have downloaded the appropriate file (e.g., ActivePerl-, double-click on it and follow the instructions to install Perl.

    4. After installation, restart your computer to be sure the path to the Perl interpreter is set correctly.

  2. Set up a C:\Models directory, install PRZM and EXAMS, and copy input files.

    The shell and models look in set folders to call up the programs and supporting files (standard scenarios, meteorological files, and EXAMS environment files). The official program versions and QA/QC'd files for PE5 must be present in these folders. For PE5 to function properly, set up your C:\models directory as follows:

    1. Create the folder C:\Models\PRZM3\ and place the PRZM executable (PRZM3122.exe) within the folder.

    2. Create the folder C:\Models\EXAMS\ and place the EXAMS executable (EXAMS.exe) and the file exams.daf within the folder.

    3. Create the folder C:\Models\Inputs\ with the following subfolders:

      PRZMenv (contains the PE crop scenarios (.txt))
      EXAMSenv (contains the index reservoir and pond environment files (.exv))
      Metfiles (contains the weather files (metfiles) (.dvf))

    4. Although not necessary, you may want to create a "Runs" folder as a way of collecting and organizing your model runs.

      1. You must save your inputs (using File/Save on the interface's menu) before you do a run. This is how you tell the interface in which directory to save your output files.

      2. You can have as many folders for runs as you like.

      3. It is strongly recommended that you use the "Runs" folder within C:\Models\ , as PRZM cannot handle long directory strings, which are often associated with folders located elsewhere on your hard drive.

      4. As long as the file exams.daf is placed in the C:\Models\EXAMS\ folder, it is not necessary to include it in the "Runs" folder or any other folders where runs are saved.

    5. The folder set up is illustrated below:

      Folder/subfolders Required files
      Drive C:  
      Models PE5.pl
      PRZM3 PRZM3122.exe
      EXAMS EXAMS.exe
      InputsPRZMenv [Standard scenarios]
      EXAMSenv ir298.exv
      Metfiles [Weather files (metfiles)]
      Runs (exams.daf)1

      1 The exams.daf file is required in folders where runs are saved only when it is not placed in the C:\Models\EXAMS\ folder.

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Running PE5

  1. Open the C:\Models folder and double-click on the PE5.pl icon. Alternately, you can create a link on your desktop or any other folder where it is convenient.

    1. A DOS command box labeled "C:\Perl\bin\perl.exe" will open and automatically minimize. You can restore this window to watch PRZM and EXAMS runs and see some other messages written by PE5.pl.

    2. The shell labeled "PE5" will open. All inputs and commands are done through this interface.

  2. Choose your PE crop scenario, metfile, and EXAMS environment from the drop down menus found on the upper left side of the screen.

    1. Click on the "PRZM scenario" button for a list of available PE crop scenarios (.txt). Move the cursor to highlight the desired scenario and click to select.

    2. Press the "… from scenario" button and click "OK" in the pop-up dialog box to select the metfile (.dvf) associated with your selected crop scenario.

      1. If the suggested metfile is not present in the metfile folder, the command box will return the message "Error: Couldn't open".

      2. Alternatively, you can click on the "Metfile" button, move the cursor to highlight the desired metfile, and click to select manually.

    3. Click on the "EXAMS environment" button for a list of available EXAMS environment (.exv) files.

      1. Select the index reservoir (ir298.exv) for drinking water assessments.

      2. Select the standard pond (pond298.exv) for ecological exposure assessments.

    4. Press the "Field Size" button for a list of field size options.

      1. Select "Reservoir" for the index reservoir.

      2. Select "EPA Pond" for the standard pond.

      3. Note: This button will display "Default" or "Pond" when PE5 is used to open a .pzr file saved with PE4. "Default" and "Pond" are not valid field sizes and must be changed before modeling with PE5.

    5. Click on the appropriate Runoff Flow option button.

      1. Select "Overall" for the index reservoir.

      2. Select "None" for the standard pond.

    6. Enter the output filename (without extension) using the file-naming convention that suits you best.

    7. Enter the chemical name, chemical properties, and fate and transport parameters in the appropriate boxes.

      1. Use the current Input Parameter Guidance to derive the inputs (USEPA, 2002).

      2. PRZM will use the value entered for Kd. If there is no value entered for Kd, then PRZM will be set to estimate a value for Kd based on the entered value of KOC. If there is no KOC value, PRZM will be told to make estimates based on solubility. The interface will pass any values entered for both Kd and KOC to EXAMS.

      3. Degradation rates are entered as half-lives, in days. The script converts half-lives to rates (rate = -ln(1/2)/t1/2), unless the entered value is zero, in which case the script sets the rate to zero.

    8. Click on the "CAM" button to select the appropriate chemical application method.

      1 = Surface applied (broadcast, not incorporated)
      2 = Foliar applied, linear application
      3 = (Not used: nonlinear foliar application)
      4 = Incorporated, uniform with depth (default incorporation CAM)
      5 = Incorporated, linearly increasing with depth
      6 = Incorporated, linearly decreasing with depth
      7 = Incorporated, T-Band granular application (use DRFT input variable to define fraction of chemical to be applied in top 2 cm, remainder of chemical will be uniformly incorporated between 2 cm and user defined depth)
      8 = Incorporated entirely into depth specified by user

    9. Input an incorporation depth (cm) of 2.0 cm or greater for CAM=4,5,6,7,8.

    10. Input the application rate (kg a.i./ha), application efficiency fraction, spray drift fraction, initial application date (DD-MM), and number of applications per year.

    11. Press the "Intervals…" button if more than one application occurs per year.

      1. Input the interval between applications (days) and any new application rate (kg a.i./ha) after the interval in the appropriate fields of the pop-up dialog box.

      2. Note that the application rate field may be left blank for any applications that are at the same rate as the initial application.

      3. Note that application rates must contain six or less characters (including the implied 0 for decimals) in order for PRZM to function properly (e.g., limit the application rate at 10.333 or 0.0875 kg a.i./ha).

    12. Click on the "IPSCND" button to select the post-harvest foliar pesticide disposition.

      1 = Surface applied
      2 = Completely removed
      3 = Left as is on foliage

    13. Press the "Set Hydrolysis..." button or go to the "Edit" menu and choose "Hydrolysis..." to bring up a dialog box for hydrolysis values. The script requires either one value or three in order to calculate parameters for EXAMS. You can enter either one pH-hydrolysis half-life pair at pH 7 or three pairs at varying pH values. If you enter one pair, EXAMS will assume hydrolysis rates do not change with pH.

    14. The "More PRZM Parameters..." button is available for PRZM records 17, 18 and 26. If you don't have chemical-specific inputs for these records (and, in most cases, these data are not available), they will be appropriately left to default (or no input) values.

      1. The foliage pesticide first-order decay and volatilization parameters, PLDKRT and PLVKRT, respectively, are rate constants with units of d-1, rather than half-lives.

      2. The foliar wash-off extraction coefficient, FEXTRC, is a rate constant with units of cm-1.

    15. Check the "Write Benthic pore water concentrations" box if you desire an output file (.out) that reports summary statistics for benthic pore water concentrations.

  3. Save your inputs before running PE5.

    1. The shell runs PRZM and EXAMS from the directory you last saved or opened a file from, and if you do not use the open or save commands, it will use a default value.

    2. Choose "Save" from the pull-down menu under "File." The dialog box will prompt you to select a name and a folder. Save the file in the "Runs" folder or any separate folder with a brief directory string. The shell gives the saved file a ".pzr" extension, although it will open text files with any extension.

  4. Press the "Run PRZM/EXAMS" button to run the shell once.

    1. The progress of the run can be followed in the command prompt window launched when you started the script. The following files will be generated in the C:\Models\Runs folder:

      przm3.inp, przm3.run - PRZM input and run files
      pz2ex.exa - EXAMS command file
      CPRZM31.cnc, CPRZM31.hyd, CPRZM31.msb - PRZM summary outputs
      Filename.zts - PRZM time-series outputs
      Filename_TS.out - EXAMS time-series outputs
      Filename.out - Standard Table 20 summary outputs

    2. You may want to cut and paste your files into a subdirectory for later documentation. Because PRZM calls up some of these files, the shell will overwrite them during the next run. As with any PRZM run, you should examine the input files closely to make sure the correct information was entered.

    3. Use your favorite spreadsheet to open your output file and examine the results. The output file is in tab-delimited format and may be easier to view in a spreadsheet than a text editor.

  5. Alternatively, rather than pressing the "Run PRZM/EXAMS" button to run PE5 once, you may click on the "MultiRun…" button to simultaneously model multiple initial application dates for use patterns of constant application rate.

    1. Type "DATE" in the first row of the pop-up dialog box.

    2. Enter initial application dates (DD-MM) in the rows beneath.

    3. Do not use this feature if application rates other than the initial application rate (or a blank entry) are entered in the "Intervals…" dialog box.

    4. You may wish to save your "batch" of initial application dates in a text editor before running PE5, as the shell does not save data entered into the "MultiRun…" dialog box.

    5. PE5.pl creates individual output files (.zts, _TS.out, and .out) tied to each initial application date and creates a summary file (_summary.txt) that allows for easy comparison of 1-in-10-year EECs for each model run.

    6. While PE5.pl has the potential to vary any PRZM input parameter or PE crop scenario with the MultiRun function, the initial date of application (DATE) is the only variable currently evaluated and approved for use in the Office of Pesticide Programs.

  6. To pull up a saved file for further work, click on "Open" in the pull-down menu under "File." Navigate to the appropriate folder using the dialog box and click on the appropriate file to open.

  7. The pull-down menu under "Edit" includes options to edit any of the specific PRZM parameters (PRZM env...) or to edit EXAMS command lines (EXAMS command). This option is not something that will be needed for most standard assessments, but is provided for those who may need to go beyond a routine assessment and are familiar with PRZM and EXAMS.

  8. Use the "Quit" button or the "Quit" command under the "File" menu to quit. While you could also close the shell by clicking on the "X" button in the upper right corner, the Quit command shuts down both the shell and the command prompt that was opened at the beginning.

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Burns, L.A. 2000. Exposure Analysis Modeling System (EXAMS). Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency; Athens, GA.

Carsel R.F., J.C.Imhoff, P.R.Hummel, J.M.Cheplick and J.S.Donigian, Jr. 1997. PRZM-3, A Model for Predicting Pesticide and Nitrogen Fate in Crop Root and Unsaturated Soil Zones: Users Manual for Release 3.0. Environmental Research Laboratory, Office of Research and Development, U.S. Environmental Protection Agency; Athens, GA.

USEPA. 2002. Guidance for Selecting Input Parameters in Modeling the Environmental Fate and Transport of Pesticides. U.S. Environmental Protection Agency, Office of Prevention, Pesticides and Toxic Substances, Office of Pesticide Programs, Environmental Fate and Effects Division; Feb. 28, 2002. Online at: http://www.epa.gov/oppefed1/models/water/input_guidance2_28_02.htm

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