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Model Report

FQPA Index Reservoir Screening Tool

Last Revision Date: 11/16/2009 View as PDF
General Information Back to Top
Model Abbreviated Name:

Model Extended Name:

FQPA Index Reservoir Screening Tool
Model Overview/Abstract:
FIRST is a screening model designed to estimate the pesticide concentrations found in water for use in drinking water exposure assessments. It provides high-end values on the concentrations that might be found in a small drinking water reservoir due to the use of pesticide. FIRST is a single-event model (one run-off event), but can account for spray drift from multiple applications. FIRST uses a Drinking Water Reservoir as a standard waterbody. The FIRST scenario includes a 427 acres field immediately adjacent to a 13 acres reservoir, 9 feet deep, with continuous flow (two turnovers per year). The pond receives a spray drift event from each application plus one runoff event. The runoff event moves a maximum of 8% of the applied pesticide into the pond. This amount can be reduced due to degradation on field and the effect of binding to soil. Spray drift is equal to 6.4% of the applied concentration from the ground spray application and 16% for aerial applications. FIRST also makes adjustments for the percent crop area using the highest percentage of crop cover of any large watershed in the US and assumes that the entire crop is being treated.

“Passing” a FIRST model screening assessment (estimated concentration is lower than laboratory effects data) is an indicator or acceptable risk. “Failing” a FIRST model screening assessment (estimated concentration is higher than laboratory effects data) is not an indicator of unacceptable risk, but that additional assessment work must be carried out.

Keywords: Water Quality Modeling, Pesticide Environmental Fate and, Transport Modeling, Pesticide Exposure Assessment, Drinking Water Exposure Assessment, Screening Model, EBDC, FQPA
Model Technical Contact Information:
Developer Contact Information
Ronald Parker, Ph.D.
U.S. Environmental Protection Agency
Office of Pesticide Programs
Phone: (703) 305-5505
Fax: (703) 305-6019
Model Homepage: http://www.epa.gov/oppefed1/models/water/#first

User Information Back to Top
Technical Requirements
Computer Hardware
Any PC
Compatible Operating Systems
Download Information
The FIRST model is available to be downloaded.
Using the Model
Basic Model Inputs
Application rate, number, interval and method; incorporation depth; spray drift data; buffer data; soil/water partition coefficient (Kd or Koc; degradation inputs to the model (aerobic aquatic metabolism, abiotic hydrolysis, direct aquatic photolysis)
Basic Model Outputs
Outputs from this model are the acute (peak daily) and chronic (average 365 day) pesticide concentrations in the index reservoir.
User Support
User's Guide Available?
The FIRST model User's Guide is available to be downloaded.

Model Science Back to Top
Problem Identification
FIRST is a FORTRAN based meta-model of the USEPA PRZM and EXAMS environmental fate and transport models. The user answers consecutive questions presented on the screen and output is both displayed on the screen and to a printable file.
Summary of Model Structure and Methods
FIRST simulates pesticide runoff, spray-drift, adsorption and degradation/dissipation from a treated, 428-hectare field to an adjacent 13-hectare drinking water reservoir. Pesticide in runoff from the field ranges from 8 percent to 0.008 percent of the applied pesticide depending on the fraction of the pesticide that is adsorbed to field soil and to reservoir bottom sediments. Model output concentrations are designed to exceed field-monitored values at most sites most of the time based on comparisons with measured data.

Model Evaluation
QA/QC, peer review and code verification through Environmental Fate and Effects Division, Office of Pesticide Programs

FIRST equations are curve-matching functions developed to mimic output of the linked PRZM/ EXAMS models. Biological degradation in the treated fields in the watershed and photolytic, hydrolytic and biological degradation in the reservoir follow a first order processes. Concentrations from runoff and from spray-drift are calculated separately and summed to give the final output concentration. FIRST simulates two complete turnovers of the reservoir during the year. Multiple-day, mean pesticide concentrations are arithmetic averages of the appropriate number of daily values beginning with the first day Sensitivity and uncertainty analyses unavailable

Key Limitations to Model Scope
FIRST predictions of pesticide concentrations in surface water are designed to be higher than most concentrations from field sampling as well as most concentrations predicted by other, more complex models most of the time.
Case Studies
Many FIRST applications can be seen at:http://cfpub.epa.gov/oppref/rereg/status.cfm?show=rereg

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