Document ID: EPA-HQ-OPP-2005-0189-0003
Agency: epa
Document Type: Supporting & Related Material
Title: 
Posted Date: 2007-09-20T04:00Z

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<p>Office of Pesticide Programs (OPP) Conference Room 1126<br />
1801 S. Bell St. - Crystal Mall 2<br />
Arlington, VA  22202</p>

<p><strong>On this Page</strong></p>

<ul>
<li><a href="#attendees">Attendees</a></li>
<li><a href="#welcome">Welcome and Introductions</a></li>
<li><a href="#old">Old Action Items</a></li>
<li><a href="#brief">Brief Updates</a></li>
<li><a href="#presentations">Major Presentations</a></li>
<li><a href="#wrap">Wrap up</a></li>
</ul>

<hr />

<h2 id="attendees">Attendees</h2>

<table class="table zebra" summary="Attendees">
<thead>
<tr><th scope="col">Name</th><th scope="col">Association</th></tr>
</thead>
<tbody>
<tr><td>Marietta Echeverria</td><td>		OPP/EFED</td></tr>
<tr><td>Ron Parker</td><td> 			OPP/EFED</td></tr>
<tr><td>Betsy Behl</td><td>			OPP/EFED</td></tr>
<tr><td>Mark Corbin</td><td>			OPP/EFED</td></tr>
<tr><td>Dirk Young</td><td>			OPP/EFED</td></tr>
<tr><td>Mohamed Ruhman</td><td>		OPP/EFED</td></tr>
<tr><td>Nelson Thurman</td><td> 			OPP/EFED</td></tr>
<tr><td>James Hetrick</td><td>			OPP/EFED</td></tr>
<tr><td>Lucy Shanaman</td><td>			OPP/EFED</td></tr>
<tr><td>Bill Eckel</td><td>			OPP/EFED</td></tr>
<tr><td>Greg Orrick</td><td>			OPP/EFED</td></tr>
<tr><td>Norm Birchfield</td><td>			OPP/EFED</td></tr>
<tr><td>Faruque Kahn</td><td>			OPP/EFED</td></tr>
<tr><td>Cheryl Sutton</td><td>			OPP/EFED</td></tr>
<tr><td>Keara Moore</td><td>			OPP/EFED</td></tr>
<tr><td>Jonathan Angier</td><td>			OPP/EFED</td></tr>
<tr><td>Kathy Carr</td><td>			Monsanto</td></tr>
<tr><td>Mary Nett</td><td> 			WQC</td></tr>
<tr><td>Russell Jones</td><td> 			BayerCropScience</td></tr>
<tr><td>George Sabbagh</td><td>			BayerCropScience</td></tr>
<tr><td>Nasser Assaff</td><td>			Valent</td></tr>
<tr><td>Piyush Singh</td><td>			Dupont</td></tr>
<tr><td>Paul Hendley</td><td> 			Syngenta</td></tr>
<tr><td>Scott Jackson</td><td> 			BASF</td></tr>
<tr><td>Uwe Wanner</td><td>			Crompton</td></tr>
<tr><td>Wenlin Chen</td><td>			Syngenta</td></tr>
<tr><td>Greg Leyes</td><td>			ISKB</td></tr>
<tr><td>Marty Williams</td><td> 			Waterborne Environmental</td></tr>
<tr><td>Jenn Trask</td><td>			Waterborne Environmental</td></tr>
<tr><td>Cathleen Hapeman</td><td>		USDA/ARS</td></tr>
<tr><td>Garey Fox</td><td>			University of Mississippi</td></tr>
<tr><td>Micah Reynolds</td><td>			Toxcel</td></tr>
<tr><td>Carrie Graff</td><td>			USDA ARS</td></tr>
<tr><td>Dean Hively</td><td>			USDA ARS</td></tr>
<tr><td>Earl Hayter</td><td> 			EPA/ORD-NERL</td></tr>
<tr><td>Ian Kennedy</td><td> PMRA</td></tr>
</tbody>
</table>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="welcome">Welcome and Introductions</h2>

<p>The Exposure Modeling Work Group hosts quarterly meetings that are open to the public and provide a forum for cooperative exchange of facts and technical information on technical issues related to pesticide exposure modeling between EFED and stakeholders with similar technical expertise.  Marietta Echeverria (OPP/EFED) chaired the meeting in the capacity of co-chair of the EFED Water Quality Tech Team (WQTT). </p>

<p>This meeting includes presentations which focused on sediment and contaminant transport modeling, factors influencing erosion modeling, leaching modeling with the Root Zone Quality Model, and an evaluation of the effect of BMP on stream water phosphorus.  All FIFRA EMWG agendas, minutes and presentations can be found at: </p>
<p><a href="http://www.epa.gov/oppefed1/models/water/emwg_top.htm">http://www.epa.gov/oppefed1/models/water/emwg_top.htm</a></p>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="old">Old Action Items</h2>

<p><strong>NAFTA Guidance for Conducting Terrestrial Field Dissipation Studies will be added to the EPA website when complete and approved.</strong></p>

<p>Mark Corbin  reported that this document has been released as a final draft and posted on the web for comments at: </p>
<p><a href="http://idocket.rtpnc.epa.gov/edkreg/index.jsp">http://idocket.rptnc.epa.gov/edkreg/index.jsp</a> </p>

<p><strong>EFED will post a list of those developed specifically for the OP cumulative assessment. </strong></p>

<p>Mark Corbin reported that the national/regional scenarios have been separated from those created specifically for the cumulative assessment of the organophosphate (OP) pesticides. Both groups are posted on the OPP/EFED website at 
<a href="http://www.epa.gov/oppefed1/models/water/index.htm">
http://www.epa.gov/oppefed1/models/water/index.htm</a>. The scenarios are included in a zipped file that will automatically extract into the two separate groups.</p>

<p><strong>ORD will post revised PRZM 3.12.2 on the CEAM website.</strong></p>

<p>Jim Hetrick reported that the final revised version of PRZM3.12.2 has been posted on the ORD/CEAM website at: </p>

<p><a href="http://www.epa.gov/ceampubl/gwater/przm3/index.htm">http://www.epa.gov/ceampubl/gwater/przm3/index.htm</a>. This version is dated May 2005.</p>

<p><strong>Information on PRZM 3.12.2 revised volatilization feature will be included in the description of model changes.</strong></p>

<p>Jim Hetrick reported that a description of the changes to the volatilization routines in PRZM will be included in the EFED QA/QC write-up.</p>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="brief">Brief Updates</h2>

<ol>

<li><p><strong>PRZM3.12.2 Evaluation</strong></p>

<p>Jim Hetrick reported on finalizing the EFED QA/QC of the new version of PRZM 3.12.2 which is now on the ORD CEAM website. The QA/QC is largely complete and the final report mostly written. Completing the report as soon as possible is a high priority for EFED.</p>

</li>
<li><p><strong>EXPRESS</strong></p>

<p>Ron Parker reported on QA/QC of the EXPRESS PRZM/EXAMS shell. The Office of Research and Development (ORD) Center for Exposure Assessment Modeling (CEAM) is conducting an extensive review and QA/QC of the shell. EFED is conducting a similar review of all of the surface water modeling scenarios which will be included in EXPRESS. </p>

</li>
<li><p><strong>EFED's Modeling Scenarios </strong></p>

<p>Mark Corbin reported on EFED's effort to respond to public comments on PRZM surface water runoff modeling scenarios. The only comments were received from CLA. EFED sent a general response to the public docket in September 2004 and is now working on scenario-specific issues. This includes both the regional/national scenarios and the scenarios which were designed for use in the cumulative OP assessment only.</p>

<p>Corrected scenarios have been received back from the contractor and will now be reviewed in EFED before posting on the website. EFED is planning the release of the scenarios before the end of the year. </p>

</li>
<li><p><strong>Spray Drift Update</strong></p>

<p>Norm Birchfield reported that there is a new version of RegDisp which is linked to a new version of PE4, but that version has not been evaluated due to other work priorities. Work is also ongoing for the ground-spray model which would also be included in RegDisp. A version of RegDISP should go into QA/QC by the end of 2005 with approval following shortly after that.</p>

<p>Drift Reducing Technologies Project. An OPP/ORD group has been awarded about $300,000 to evaluate spray drift reducing technologies. This will allow evaluation of 2 - 4 different technical options. If some options are shown to reduce the amount of drift, it is possible that growers using these technologies would be allowed reduced buffers or other modifications would be made to pesticide labels to reflect reduced exposures.</p>

</li>
<li><p><strong>Carbamate Cumulative Assessment</strong></p>

<p>Nelson Thurman reported that the minutes and report of the February 15-18 Science Advisory Panel (SAP) meeting discussing the N-Methyl Carbamate Cumulative Assessment can be found at: </p>

<p><a href="http://www.epa.gov/scipoly/sap/2005/february/minutes.pdf">http://www.epa.gov/scipoly/sap/2005/february/minutes.pdf</a>.</p>

<p>The second SAP meeting on this subject will be held August 23-26 in Washington. Times and locations for this meeting are available on the SAP website.</p>

</li>
</ol>

<p class="pagetop"><a href="#content">Top of page</a></p>
<hr />

<h2 id="presentations">Major Presentations</h2>

<p>All of the following presentations will be posted on the EMWG website.</p>

<p><strong>Coupled Watershed - Instream Sediment and Contaminant Transport and Fate Modeling System (Earl Hayter, USEPA-ORD/NERL)</strong></p>

<p>Earl Hayter, of the USEPA Office of Research and Development, National Exposure Research Laboratory presented a coupled modeling system for simulating watershed and instream sediment and contaminant transport. The externally coupled modeling system consists of a watershed loading model and an instream hydrodynamic, sediment and toxicant fate and transport model.  The watershed loading model, the Hydrologic Simulation Program - FORTRAN (HSPF), simulates watershed hydrology and water quality for both conventional and organic pollutants.  The instream sediment fate and transport model, the Environmental Fluid Dynamics Code (EFDC), is a 3D model that simulates the transport of suspended sediment and contaminants.  Multiple size classes of sediments and associated depositions and resuspension processes and bed geomechanics are also simulated with EFDC.  The coupled modeling system has been applied to a 282 mi<sup>2</sup> watershed and stream network that contains both point and non-point sources of an organic pollutant of concern.  The data requirements for the coupled modeling system are extensive and include hydrological, meteorological, land use and soil data; hydraulic and geomorphic data; flow and spatially varying sediment data; settling and resuspension velocities; and chemical properties of the toxicant(s) being modeled.   </p>

<p><strong>Factors Influencing Erosion in PRZM Modeling (Mark Corbin, EPA/OPP-EFED)</strong></p>

<p>Mark Corbin, Senior Scientist of Environmental Fate and Effects Division of the Environmental Protection Agency presented the effects of some key parameters of PRZM and crop scenarios, which can potentially influence the estimated environmental concentrations (EECs). The objective of his presentation was to share the information with stakeholders regarding the Agency's ongoing internal investigation of the PRZM model and crop scenarios. The results of these investigations are critical in developing Agency's risk assessment and characterization approaches transparent, clear, consistent and reasonable (TCCR). The presentation consisted of</p>

	<ol>
	<li><p>the evaluation of relative importance of erosion and runoff in contributing 	sediment mass as a function of Koc,</p></li>
	<li><p>the evaluation using discrete C factors versus using an average value 	throughout the year on resulting EECs,</p></li>
	<li><p>an illustration of the importance of compartment thickness on pesticide flux 	in erosion and the non-equilibrium condition between runoff and erosion, and </p>	</li>
	<li><p>preliminary investigation on the effect on the resulting EECs using 	irrigation routine of selected scenarios for compounds with high and low Koc.</p>	</li>
	</ol>

<p> The Agency will continue to probe the above key areas. He emphasized that no changes have been made or implemented in the Agency's current risk assessment and characterization processes. If changes occur, they will be communicated with the stakeholders by posting them on the OPP website.</p>

<p><strong>Issues Associated with Estimating Slope Length Factor for GIS-based Sediment Erosion Modeling (Scott Jackson, BASF and Paul Hendley, Syngenta)</strong></p>

<p>Scott Jackson and Paul Hendley presented analyses done for the Pyrethroids Working Group (PWG) to parameterize the Universal Soil Loss Equation, in particular the LS (slope length - slope gradient factor).    (Part 1) They discussed a method used by the Bureau of Land Management, devised by Moore and Wilson, and available on the BLM website under Terrain and Geomorphic Modeling.  The results were compared to historical (1920-1970 Purdue University) data sets from run-off plots of fixed length (670 feet) in Iowa and New York.  For the NY plot, correlation (R<sup>2</sup>) between measured and predicted results increased from 0.2 to 0.67 as plot length decreased from 90-m to 10-m.  The DEM-based method was also compared to National Resource Inventory data for Wilson County, NC (site of the NC cotton PRZM scenario), which uses a 30-m LS factor.  Total soil loss predicted was similar: 2.25 to 3 tons/year for NRI and 2-2.5 tons/year for DEM.  Paired point erosion (by mapping unit ID) was not consistently greater or lesser for either approach.  In comparison to STATSGO data, the gridded approach has finer resolution.  (Part 2)  The NRI method for erosion was examined.  It supplies a population of LS measurements, split by crop and slope class.  There is a close relationship between slope length and slope steepness (R<sup>2</sup> = 0.91), and the slope length distribution is approximately log-normal.  The PWG concluded that the DEM method, while technically more attractive (the underlying SSURGO data better attach a particular soil ID to a crop with a county), was computationally too intense, and that the NRI approach was adequate for a coarse-level assessment.</p>

<p><strong>Uncalibrated Modeling of Conservative Tracer and Pesticide Leaching to Ground Water using the Root Zone Water Quality Model (RZWQM) (Garey Fox, University of Mississippi)</strong></p>

<p>Garey Fox of the University of Mississippi presented an evaluation of RZWQM, a leaching model using the Green-Ampt equation for infiltration and the Richards equation for redistribution.  Some advantages include its capacity to consider macropore flow and sub-daily precipitation and to modify half-life and sorption with depth.  A North Carolina soybean scenario and a Georgia peanut scenario were modeled "cold" and based on site-specific data.  PRZM modeling of the same data had been performed previously and the results were compared using the normalized objective function (NOF), a statistic assessing the difference between predicted and observed concentrations.  In the North Carolina scenario, RZWQM had better pore water NOFs than PRZM for most cases and for soil concentrations, the two models were generally equivalent at shallow depths but RZWQM improved over PRZM deeper in the soil profile.  In Georgia, PRZM had slightly better results for pore water herbicide concentrations.  The two models' results for soil concentrations were generally equivalent for bromide and a nematicide, but RZWQM was slightly better for the herbicide.  General trends showed that both models tended to overpredict leaching and that soil concentrations were more accurately predicted than pore water concentrations.</p>

<p><strong>Modeling Sediment and Nutrient Transport at Field and Watershed Scales (Carrie Graff, USDA/ARS-Environmental Quality Lab, Beltsville, MD)</strong></p>

<p>Carrie Graff, of the USDA/ARS Environmental Quality Laboratory (EQL), presented and compared four models that can be used to estimate sediment and nutrient loads transported from agricultural fields.  These are: </p>

	<ol>
	<li><p>HSPF (Hydrologic Analysis Software Support Program); </p></li>
	<li><p>SWAT (Soil, Water, Assessment Tool);</p></li>
	<li><p>AnnAGNPS (Annualized Agricultural Non-point Source Model); and </p></li>
	<li><p>REMM (Riparian Ecosystem Management Model).</p></li>
	</ol>

<p>Details of two of these models, AnnAGNPS and REMM, were provided.  These models have also been used together to evaluate the impact of nutrient and sediment transport into adjacent streams and wetlands.  AnnAGNPS provides a continuous simulation (in daily time steps) of runoff processes.  Unlike other models, AnnAGNPS retains discrete spatial characteristics by dividing the landscape into cells, each of which individually contributes to the stream at user-defined locations.  Runoff processes in AnnAGNPS are affected by weather, precipitation, soil moisture, runoff (determined by curve number), and tile drainage.  Estimates of sediment yields, nutrient yields, and pesticide yields can be obtained.  REMM requires inputs for daily weather data (e.g., ppt), soil characteristics (e.g., Manning's N), vegetation types (e.g., rooting depth), site description (e.g., slope), and upland inputs.  REMM provides information on depth to water table, water flux, sediment yield, N flux, P flux, and groundwater nutrient content.  Outputs obtained from REMM, used in conjunction with AnnAGNPS, are most sensitive to changes in precipitation, slope, and Manning's N, and are least sensitive to vegetation parameters.  Results from these models can be used to assess the impact of agricultural management practices on the transport of potential contaminants.</p>

<p><strong>Multivariate Analysis of Paired Watershed Data to Evaluate Agricultural BMP Effects on Stream Water P (W. Dean Hively, Ph.D. - USDA-ARS Environmental Quality Laboratory)</strong></p>

<p>Dean Hively, USDA-ARS, presented his Ph.D. work on the effects of BMPs on phosphorus (P) loading in a small watershed that supports New York City's water supply (Bishop <em>et al</em>., 2005).   The multi-agency NYC Watershed Agriculture Program was founded to implement BMPs to pursue a 40% reduction in annual P loads to NYC reservoirs, where summertime eutrophication has been found to be largely limited by P concentrations originating from non-point sources, such as dairy farms.  Dr. Hively compared matched event stream quality data from two small paired watersheds located in the Cannonsville Reservoir basin (a forested "non-farm watershed" that served as a control and a 160-hectare "farm watershed" that was 38% dairy farm pasture, 53% forest, 7% row crops, and 2% impermeable) collected from 1993 to 2000, to analyze the impact of implemented BMPs on dissolved and particulate P loading from the farm watershed rich with non-point sources.</p>

<p>The BMPs were implemented from 1995 to 1996, separating the matched data into 2 years of pre-treatment data (pre-BMP) and 4 years of post-treatment data (post-BMP) covering event loads of total dissolved phosphorus (TDP) and particulate phosphorus (PP) from 231 precipitation events.  Post-BMP "large storm flows" outnumbered pre-BMP "large storm flows" by 7 to 1, but were not found to skew the study results.  Dr. Hively used the following five multivariate analysis of covariance (ANCOVA) models in an effort to compare their strengths for this analysis.</p>

	<ol>
	<li><p><strong>Univariate matched loads model:</strong></p>

	<p>  ln(Pf) = a + b ln(Pnf) + f k + ε </p>

		<ul>
		<li><p>Pf = farm event P load</p></li>
		<li><p>Pnf = non-farm event P load</p></li>
		<li><p>k = 0 if PRE-BMP, k= 1 if POST-BMP</p></li>
		</ul>

	</li>
	<li><p><strong>Bivariate matched loads model:</strong></p>

	<p>  ln(Pf) = a + b ln(Pnf) + c ln(Qf/Qnf) +  f k + ε</p>

		<ul>
		<li><p>ln(Qf/Qnf) compensates for differences in matched event precipitation		</p></li>
		</ul>

	</li>
	<li><p><strong>Multivariate matched loads model:</strong></p>

	<p>  ln(Pf) = a + b ln(Pnf) + c ln(Qf/Qnf) +  d ln(QfPeak) + e ln(QRf) + f k + 	ε</p>

		<ul>
		<li><p>ln(QfPeak) and ln(QRf) represent effects of event magnitude on P 		loading processes </p></li>
		</ul>

	</li>
	<li><p><strong>Univariate single watershed model for TDP analysis:</strong></p>

	<p>  ln(Pf) = a + b ln(Qf) + f k + ε</p>

		<ul>
		<li><p>ln(Qf) accounts for event flow volume, allowing a comparison of farm P 		concentrations in the pre- and post-treatment periods</p></li>
		</ul>

	</li>
	<li><p><strong>Bivariate single watershed model for PP analysis:</strong></p>

	<p>  ln(Pf) = a + b ln(QfPeak) + c ln(QRf) + f k + ε</p>
	</li>

	</ol>

<p>Bivariate and multivariate models outperformed univariate models in each season of the year in comparison of adjusted R<sup>2</sup> and statistical power.  Calculation of percent load reduction was best performed by the multivariate matched loads model for PP year-round and for TDP in all seasons except winter, for which the bivariate matched loads model performed best.</p>

<p>Dr. Hively concluded that ANCOVA provided estimates of P load reductions with confidence intervals and that the use of multiple covariates substantially increased model precision, which allowed separation of data into seasons.  Implementation of farm BMPs was associated with overall reductions in event based loading of TDP (40%) and PP (29%).  The small watershed approach evaluated the net effect of BMP implementation on P loading processes on farms.  Farm P loading rates (252 kg TDP ha<sup>-1</sup> yr<sup>-1</sup> PRE-BMP, 164 kg ha<sup>-1</sup> yr<sup>-1</sup> POST-BMP) remained high in comparison to the control (18 and 23 kg ha<sup>-1</sup> yr<sup>-1</sup>).</p>

<p>Bishop, Hively, Stedinger, Bloomfield, Rafferty, and Lojpersberger.  2005.  Journal of Environmental Quality <strong>34(3)</strong>: 1087-1101.</p>

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<h2 id="wrap">Wrap up</h2>

<p><strong>Next Meeting</strong></p>
 
<p>The next meeting will be October 26th, 2005.</p>

<p>OPP Conference Room 1126<br />
1801 S. Bell St. - Crystal Mall 2<br />
Arlington, VA  22202</p>

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