JournalofASTMInternational,Vol.7,No.6 PaperIDJAI102775 Availableonlineatwww.astm.org Bradley K. Fritz,1 W. Clint Hoffmann,1 Norman B. Birchfield,2 Jay Ellenberger,3 Faruque Khan,4 W. E. Bagley,5 Jonathan W. Thornburg,6 and Andrew Hewitt7 Evaluation of Spray Drift Using Low-Speed Wind Tunnel Measurements and Dispersion Modeling ABSTRACT: The EPA’s proposed test plan for the validation testing of pesticide spray drift reduction technologies(cid:1)DRTs(cid:2)forrowandfieldcrops,focusingontheevaluationofgroundapplicationsystemsusing thelow-speedwindtunnelmeasurementsanddispersionmodeling,wasevaluated.Relativedriftreduction potentialforagivenDRTtestedinalow-speedwindtunnelisderivedfromairbornedropletsizemeasure- ments and airborne and deposited liquid volume measurements downwind from the spray nozzle. Mea- surements of droplet size and deposition data were made in a low-speed wind tunnel using standard referencenozzles.Ablankemulsifiableconcentrationspraywasappliedattwodifferentwindspeeds.The wind tunnel dispersion (cid:1)WTDISP(cid:2) model was used to evaluate the drift potentials of each spray using the dropletsizeandsprayfluxmeasuredinthewindtunnel.Thespecificobjectiveswere(cid:1)1(cid:2)theevaluationof model accuracy by comparison of modeled downwind deposition to that measured in the wind tunnel, (cid:1)2(cid:2) the evaluation of drift reduction potential of the spray nozzles relative to a reference nozzle, and (cid:1)3(cid:2) the determinationoflow-speedwindtunneldatacollectionrequirementsformodelinputtooptimizetheevalu- ationprocess.Themodeleddepositiondatadidnotcomparewelltothemeasureddepositiondata,butthis wasexpectedasthemodelwasnotmeanttobeusedforthispurpose.Thetestednozzleswereratedusing the International Standards Organization drift classification standard. The drift ratings generally showed trendsoflargerdropletproducingnozzleshavinggreaterdriftreductionratings.Anexaminationofseveral scenariosusingreducedmodelinputrequirements,whichwoulddecreasethelow-speedwindtunneldata collectiontime,didnotshowanyconclusiveresults.Theysuggestthatfurthertestingandrefinementofthe datacollectionprocessandtheWTDISPmodelmaysupportwideruseofthissystemfortheassessment ofDRTs. KEYWORDS:drift,DRT,driftreductiontechnology,spraydropletsizing Introduction Spray drift is defined as “…the physical movement of pesticide droplets or particles through the air at the time of pesticide application or soon thereafter from the target site to any non- or off-target site” (cid:3)1(cid:4). Industry, research agencies, and applicators are making great efforts to identify and develop alternative materials, methods and equipment to reduce drift and minimize adverse effects on off-target entities.With an increasing number of these new and alternative technologies, there is a growing need to determine if and to what effect they reduce spray drift. Sayles et al. (cid:3)2(cid:4) proposed the development of a testing program for measuring drift reduction technologies (cid:1)DRTs(cid:2), with Kosusko et al. (cid:3)3(cid:4) providing details on additional programoperationalframework.ThegoalofthisEPA-ledinitiativeisto“achieveimprovedenvironmental and human health protection through drift reduction by accelerating the acceptance and use of improved and cost-effective application technologies (cid:3)4(cid:4).” The basic operational framework falls into three different testing regimes: High-speed wind tunnel testing for aerial application technologies, low-speed wind tunnel testing for ground application technolo- gies, and full scale field testing for all types of application technologies.The development of a draft set of ManuscriptreceivedOctober9,2009;acceptedforpublicationMay19,2010;publishedonlineJune2010. 1USDA-ARS,2771F&BRd.,CollegeStation,TX77845. 2USEPA,MailCode8105R,1200PennsylvaniaAve.NW,Washington,DC20460. 3USEPA,OPP,ArielRiosBuilding(cid:1)MC7506P(cid:2),1200PennsylvaniaAve.NW,Washington,DC20460. 4USEPA,OPP,ArielRiosBuilding(cid:1)MC7506P(cid:2),1200PennsylvaniaAve.NW,Washington,DC20460. 5WilburEllis,265I-35SDevine,TX78016. 6RTI International, Center for Aerosol Technology, 3040 Cornwallis Road, Bldg. 11, Room 406, Research Triangle Park, NC 27709. 7LincolnVenturesLtd.,P.O.Box133,Lincoln,Christchurch7640,NewZealand. Copyright©2010byASTMInternational,100BarrHarborDrive,POBoxC700,WestConshohocken,PA19428-2959. Report Documentation Page Form Approved OMB No. 0704-0188 Public reporting burden for the collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing the collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden, to Washington Headquarters Services, Directorate for Information Operations and Reports, 1215 Jefferson Davis Highway, Suite 1204, Arlington VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to a penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. 1. REPORT DATE 3. DATES COVERED OCT 2009 2. REPORT TYPE 00-00-2009 to 00-00-2009 4. TITLE AND SUBTITLE 5a. CONTRACT NUMBER Evaluation of Spray Drift Using Low-Speed Wind Tunnel Measurements 5b. GRANT NUMBER and Dispersion Modeling 5c. PROGRAM ELEMENT NUMBER 6. AUTHOR(S) 5d. PROJECT NUMBER 5e. TASK NUMBER 5f. WORK UNIT NUMBER 7. PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) 8. PERFORMING ORGANIZATION U.S. Department of Agriculture,USDA-ARS,2771 F&B Rd,College REPORT NUMBER Station,TX,77845 9. SPONSORING/MONITORING AGENCY NAME(S) AND ADDRESS(ES) 10. SPONSOR/MONITOR’S ACRONYM(S) 11. SPONSOR/MONITOR’S REPORT NUMBER(S) 12. DISTRIBUTION/AVAILABILITY STATEMENT Approved for public release; distribution unlimited 13. SUPPLEMENTARY NOTES 14. ABSTRACT The EPA?s proposed test plan for the validation testing of pesticide spray drift reduction technologies DRTs for row and field crops, focusing on the evaluation of ground application systems using the low-speed wind tunnel measurements and dispersion modeling, was evaluated. Relative drift reduction potential for a given DRT tested in a low-speed wind tunnel is derived from airborne droplet size measurements and airborne and deposited liquid volume measurements downwind from the spray nozzle. Measurements of droplet size and deposition data were made in a low-speed wind tunnel using standard reference nozzles. A blank emulsifiable concentration spray was applied at two different wind speeds. The wind tunnel dispersion WTDISP model was used to evaluate the drift potentials of each spray using the droplet size and spray flux measured in the wind tunnel. The specific objectives were 1 the evaluation of model accuracy by comparison of modeled downwind deposition to that measured in the wind tunnel, 2 the evaluation of drift reduction potential of the spray nozzles relative to a reference nozzle, and 3 the determination of low-speed wind tunnel data collection requirements for model input to optimize the evaluation process. The modeled deposition data did not compare well to the measured deposition data, but this was expected as the model was not meant to be used for this purpose. The tested nozzles were rated using the International Standards Organization drift classification standard. The drift ratings generally showed trends of larger droplet producing nozzles having greater drift reduction ratings. An examination of several scenarios using reduced model input requirements, which would decrease the low-speed wind tunnel data collection time, did not show any conclusive results. They suggest that further testing and refinement of the data collection process and the WTDISP model may support wider use of this system for the assessment of DRTs. 15. SUBJECT TERMS 16. SECURITY CLASSIFICATION OF: 17. LIMITATION OF 18. NUMBER 19a. NAME OF ABSTRACT OF PAGES RESPONSIBLE PERSON a. REPORT b. ABSTRACT c. THIS PAGE Same as 14 unclassified unclassified unclassified Report (SAR) Standard Form 298 (Rev. 8-98) Prescribed by ANSI Std Z39-18 2 JOURNAL OFASTM INTERNATIONAL FIG.1—WTDISP input screen. protocols, standard operating procedures, and data quality assurance steps to ensure scientific validity and repeatability was completed for all three testing regimes (cid:3)5(cid:4). Initial testing of both the high-speed and low-speed wind tunnel testing protocols was undertaken by Fritz et al. (cid:3)6(cid:4) and Hoffmann et al. (cid:3)7(cid:4). Both ofthesestudiesfocusedondropletsizing(cid:1)forthelow-andhigh-speedtestings(cid:2)andflux(cid:1)forthelow-speed testing(cid:2) measurements across a set, or modified set, of American Society of Agricultural and Biological Engineers (cid:1)ASABE(cid:2) reference nozzles (cid:3)8(cid:4). The high-speed tunnel testing showed a separation in spray droplet distribution of the nozzles corresponding to their associated droplet size classifications, with smaller droplets for the nozzles in the finer size classifications and larger droplets with increasingly coarse size classifications (cid:3)7(cid:4). The low-speed tunnel testing measured spray concentration and droplet size at a location 2 m downwind of the spray nozzle, finding that droplet size and total spray flux 2 m downwind were generally greater for the coarser nozzles (cid:3)6(cid:4). Thestatedmeasureofdriftreductionforbothtestingprotocolsisderivedfromthemodeleddownwind deposition from 0 to 60 m.Agricultural dispersion (cid:1)AGDISP(cid:2) (cid:3)9(cid:4) is the preferred model for use with the high-speed wind tunnel data, while both AGDISP and wind tunnel dispersion (cid:1)WTDISP(cid:2) models are mentionedinthelow-speedwindtunnelprotocolaspotentialmodelstotranslatethemeasureddropletsize and flux data into downwind deposition estimates. However, AGDISP is primarily an aerial application model and is not currently structured to use this type of data. Hewitt (cid:3)10(cid:4) and Connell et al. (cid:3)11(cid:4) explored the development and use of WTDISP to estimate downwind deposition using spray droplet size and flux data measured in a low-speed wind tunnel from a series of nozzles, and they found good relative com- parisonbetweenWTDISPmodeledresultsandthosemeasuredduringfieldstudiesusingthesamenozzles. The objective of this work is to evaluate a WTDISPmodel for predicting downwind spray movement from droplet size and spray flux data measured in a low-speed wind tunnel under multiple wind speed conditions.ThisdepositionpredictedbytheWTDISPmodelwillbecomparedtothereported(cid:3)6(cid:4)in-tunnel deposition (cid:1)2–5 m downwind of the spray nozzle(cid:2) and used to compare the tested nozzles using a drift reduction rating scheme. Methods WTDISPis a dispersion model designed to integrate spray flux measurements made in a wind tunnel and then predict downwind deposition and drift that would be expected in a field application using the equip- ment tested in the wind tunnel. By using the model, it is hoped that researchers can limit the number of field trials, which can be very expensive to conduct. Downwind deposition values were modeled using WTDISPfollowing the input procedures and guidelines outlined in the user manual and on-screen menus. The input screen (cid:1)Fig. 1(cid:2) shows all of the inputs required by the model to predict downwind drift. The specificinputsrequiredaresprayfluxanddropletsizemeasured2mdownwindfromthespraytechnology FRITZ ETAL. ON EVALUATION OF SPRAY DRIFT WITH MODELING 3 TABLE1—Airspeed,temperature,andrelativehumiditymeansandstandarddeviationsforfluxanddepositionmeasurementsat1m/s airspeed. Airspeed(cid:2)s.d. Temperature(cid:2)s.d. RelativeHumidity(cid:2)s.d. Nozzle (cid:1)m/s(cid:2) (cid:1)°C(cid:2) (cid:1)%(cid:2) 8001 1.0(cid:2)0.06 26.5(cid:2)0.29 70.7(cid:2)0.58 8003 1.1(cid:2)0.06 28.0(cid:2)0.29 68.7(cid:2)2.52 8006 1.1(cid:2)0.06 29.6(cid:2)0.66 63.0(cid:2)2.00 8008 1.1(cid:2)0.06 26.3(cid:2)0.00 68.3(cid:2)1.53 6510 1.1(cid:2)0.06 26.6(cid:2)0.29 68.7(cid:2)1.53 being tested (cid:1)i.e., nozzle, adjuvant, etc.(cid:2). The spray flux and droplet size measured 0.1, 0.2, 0.3, 0.4, 0.5, 0.6,and0.7mabovethewindtunnelfloor.Theenvironmentalconditionssuchastemperature,windspeed, and relative humidity must also be input into WTDISP. The procedure for determining and measuring these input values is discussed in the sections that follow. Wind Tunnel Dispersion Modeling Inputs Spray flux and droplet size at 2 m downwind of the nozzle spray flux data inputs were based on the data set collected by Fritz et al. (cid:3)6(cid:4).This data set included droplet size and monofilament deposition (cid:1)(cid:1)L/cm2(cid:2) ofsprayat0.1,0.2,0.3,0.4,0.5,0.6,and0.7mforaselectionofnozzlesthatrepresentamodifiedversion of the ASABE S572.1 (cid:3)8(cid:4) reference nozzles. WTDISP requires flux in units of L/min/cm2 and only has inputcapacityforsixheights.The0.7mheightfromtheFritz(cid:3)6(cid:4)datasetwasdroppedforthisworkasthe measured monofilament concentrations at this height were minimal. The treatment of the time component of the required flux input will be discussed later. The measured monofilament deposition values reported by Fritz et al. (cid:3)6(cid:4) were corrected for the collection efficiency of the monofilament sampler following the method reported by Fritz and Hoffmann (cid:3)12(cid:4) using the measured droplet size distributions and reported airspeeds and environmental conditions. The measured data were also corrected for recovery losses. The percent recovery was determined by spiking ten clean samples of monofilament with a known volume of spray material.The samples were then processed following the study (cid:3)6(cid:4) protocols.The measured amount of spray material was then compared to the amount used to spike the samples. The average recovery rate was 90 %. Collection efficiencies and measured and adjusted string concentration data for the 1 and 2.5 m/sairspeedtrialsarereportedinTables10and11intheAppendix,respectively.Thedropletsizesateach of the heights under the two airspeeds as reported by Fritz et al. (cid:3)6(cid:4) are shown in Tables 12 and 13 in the Appendix. The WTDISP droplet size input interface allows a user to either import (cid:1)from a text file(cid:2) the droplet sizedataortoinputthedatabinbybin.ThedatafromFritzetal.(cid:3)6(cid:4)werenotinaformforimporting,and the bin by bin option was found to be very time consuming given the number of modeling runs that were required.To more efficiently enter this data, theAGDISPdroplet size entry interface was used as a further exploration of simplified and extended data input options in this study. The AGDISP model droplet size input interface has a user-defined option that allows for parametric droplet size entry using only the D V0.5 and the relative span (cid:1)RS(cid:2) (cid:1)D −D /D , where D represents the droplet diameter at which 0.X V0.9 V0.1 V0.5 V0.X faction of the spray is contained in smaller droplets(cid:2), which are used to interpolate the full droplet spectrum based on typical distributions for flat fan agricultural nozzles with Newtonian tank mixes.While this procedure does slightly modify the measured droplet spectrum curve, the cumulative impact on the overall downwind deposition is minimal. The calculated RS values for the Fritz et al. (cid:3)6(cid:4) data set (cid:1)Tables 12 and 13 in theAppendix(cid:2) and the reported D values were used to generate the required droplet size V0.5 distributions using this interface. The distribution data were then copied (cid:1)in text form(cid:2) directly from the AGDISPinput file to the WTDISPinput file in the appropriate location for each height, which could then be read and opened by WTDISP. Environmental Data The environmental conditions (cid:1)temperature, wind speed, and relative humidity(cid:2) were input based on the values measured and reported by Fritz et al. (cid:3)6(cid:4) and as shown in Tables 1 and 2. The non-volatile fraction 4 JOURNAL OFASTM INTERNATIONAL TABLE2—Airspeed,temperature,andrelativehumiditymeansandstandarddeviationsforfluxanddepositionmeasurementsat2.5m/s airspeed. Airspeed(cid:2)s.d. Temperature(cid:2)s.d. RelativeHumidity(cid:2)s.d. Nozzle (cid:1)m/s(cid:2) (cid:1)°C(cid:2) (cid:1)%(cid:2) 8001 2.4(cid:2)0.15 27.9(cid:2)1.55 66.0(cid:2)1.00 8003 2.5(cid:2)0.15 26.4(cid:2)0.17 66.0(cid:2)0.00 8006 2.4(cid:2)0.10 26.6(cid:2)0.29 66.0(cid:2)0.00 8008 2.4(cid:2)0.10 28.5(cid:2)0.29 64.7(cid:2)1.53 6510 2.4(cid:2)0.21 29.9(cid:2)0.29 60.7(cid:2)0.58 was set to one in order to remove the effects of evaporation and looking solely at the drift as related to droplet size of the spray as generated by the nozzles. Wind Tunnel Dispersion Modeling of Fritz et al. [6] Data Using the previously discussed results, all appropriate data were input into WTDISP for each nozzle and airspeed combination tested. There were several adjustments that were made to make WTDISP accom- modate the measured data formats. As discussed earlier, WTDISPlooks for a flux at 2 m downwind of the nozzle in units of L/cm2/min as well as a spray interval in seconds. The model multiplies the entered flux by the spray interval (cid:1)converted to minutes(cid:2) to calculate a total flux value in L/cm2.The values measured in the 2008 study (cid:3)6(cid:4) were in units of (cid:1)L/cm2 and corresponded to a spray interval of 10 s. To return modeled estimates of downwind deposition that are representative of the actual spray interval and measured spray plume char- acteristics, the measured monofilament deposition data were entered for each height (cid:1)in units of (cid:1)L/cm2(cid:2) and the spray interval was entered as 60 s. This results in the monofilament concentrations being multi- plied by 1 (cid:1)1 min=60 s(cid:2). Output results are converted to the spray flux data in units of (cid:1)L/cm2 using a factor of 1(cid:3)10−6 (cid:1)convert from litre to microlitre(cid:2). Themodeleddepositionestimatesarerelativeinpositiontotheinputfluxlocations.Thefluxlocations measured during the low-speed wind tunnel data collection trials were 2 m downwind of the spray nozzle. The mylar fallout deposition measurements were made at 2, 3, 4, and 5 m downwind of the spray nozzles. The 2 m flux locations and the 2 m downwind deposition locations coincided in the Fritz et al. study (cid:3)6(cid:4). When the spray flux and droplet size data were input into WTDISP, the model was designed so that these data represented the spray cloud profile that was leaving the edge of a field boundary. Therefore, the modeled deposition at 0 m would correspond to that measured at 2 m downwind from the actual spray nozzle, and likewise the modeled deposition at 3 m would correspond to that measured at 5 m. Optimization of the Number of Flux Entries Required As reported by Fritz et al. (cid:3)6(cid:4), the low speed wind tunnel collection requirements for droplet size and flux data required for WTDISP modeling assessment were an intensive process requiring, under the present sampling protocols, ten times greater time requirement compared to the high-speed wind tunnel testing protocols (cid:3)7(cid:4). Given this difference, one of the objectives of this work was to explore the possibility of reducing the required number of heights at which droplet sizing and flux measurements must be collected while maintaining the relative downwind deposition and drift reduction ratings between the different nozzles and wind speeds. Initially, the monofilament deposition data measured at each height for each nozzle operating in each airspeed were plotted to examine the spray plume pattern with the height in the tunnel (cid:1)Figs. 2 and 3 for 1 and 2.5 m/s airspeeds, respectively(cid:2). Note that the plots are of the measured data and the measured data correctedforsamplercollectionefficiencyastheplotsaretogiveageneralindicationoftheplumeprofile. Whilethemonofilamentdepositionforallnozzlesatbothairspeedstendedtobesimilaratthetoplocation, there tended to be more separation between nozzles in the middle and lower locations with increased flux from the smaller droplet producing nozzles toward the bottom of the tunnel. It is expected that measuring thedropletsizeandfluxatthemiddleheightonlywilllikelynotshowaseparationbetweenthetreatments (cid:1)nozzles(cid:2), and this was tested. For this work, three alternative scenarios and the full data set were com- pared. The first, referred to as Scenario 1 (cid:1)S1(cid:2), used only the 0.1, 0.3, and 0.6 m droplet size and FRITZ ETAL. ON EVALUATION OF SPRAY DRIFT WITH MODELING 5 FIG.2—Flux data by height of tunnel floor for each nozzle operated in a 1 m/s airstream. monofilament deposition data. The second, Scenario 2 (cid:1)S2(cid:2), used only the 0.2 and 0.5 m droplet size and monofilament deposition data. The third and final, Scenario 3 (cid:1)S3(cid:2), used only the 0.3 m droplet size and fluxdata.Thefulldatasetusingallsixheightsofmeasureddropletsizeandmonofilamentdepositiondata is referred to as full protocol (cid:1)FP(cid:2). FIG.3—Flux data by height of tunnel floor for each nozzle operated in a 2.5 m/s airstream. 6 JOURNAL OFASTM INTERNATIONAL TABLE3—WindtunnelmeasuredversusWTDISPmodeleddepositionforairspeedof1m/s. Deposition (cid:1)(cid:1)L/cm2(cid:2) Distance Nozzle (cid:1)m(cid:2) Measured WTDISPModeled 8001 2 0.819 0.028 3 0.589 0.173 4 0.262 0.032 5 0.090 0.006 8003 2 0.711 0.026 3 0.389 0.018 4 0.183 0.0046 5 0.063 0.0002 8006 2 0.539 0.019 3 0.192 0.074 4 0.130 0.019 5 0.025 0.005 8008 2 0.381 0.019 3 0.075 0.126 4 0.123 0.021 5 0.029 0.004 6510 2 0.261 0.002 3 0.063 0.048 4 0.123 0.006 5 0.031 0.001 Usingadatafilethatincorporatesallsixmeasurementheights(cid:1)FP(cid:2),newfilesweremadeandmodified to represent each indicated scenario. This was accomplished by entering a zero value for both height and flux for the locations in each scenario that were not being used and saving the data file under a new name. For example, for S1 for the 8001 nozzle at 1 m/s, the FPinput data were modified by changing the spray fluxandtheheightvaluesat0.2,0.4,and0.5tozero.Allmodelingscenarioswererun,andtheresultswere compared. Drift Reduction Ratings According to the proposed DRT evaluation protocols, the measure of performance for a given DRT is basedonmodeleddepositionfrom0to61m(cid:1)0–200ft(cid:2)downwind.Themeasurementsforeachtechnology evaluated are compared to similar data collected for a reference system operating under the same condi- tions. The reference system for this work was defined as the nozzle, which defines the fine/medium boundary in theASABE spray nozzle classification standard (cid:3)8(cid:4). This nozzle is the 11003 flat fan, which asdiscussedbyFritzetal.(cid:3)6(cid:4)wasreplacedwiththe80°versionofthisnozzle,orthe8003flatfannozzle, which has a similar droplet spectrum and flowrate as the 11003 (cid:3)6(cid:4). The nozzles selected were not meant toenhancethecurrentstandardorformthebasisforastandardbutwereratherselectedusingthestandard such that the nozzles would separate in terms of droplet size produced and therefore drift values measured and modeled. Based on the modeled data, a drift reduction rating in the form of a percent reduction from the reference system was calculated based on data corresponding to a deposition of 10 m downwind and total integrated deposition from 0 to 61 m downwind. While the integrated deposition will likely be more consistent than the single point source data, the 10 m distance data are included as an exploratory measure and for possible comparison with future field collected data. Results Wind Tunnel Measured versus Modeled Deposition Results WTDISP is not appropriate for comparison of modeled and measured ground deposition as stated by the developer(cid:3)13(cid:4)andasevidencedbytheresultsshowninTables3and4.However,Hewitt(cid:3)10(cid:4)andConnell FRITZ ETAL. ON EVALUATION OF SPRAY DRIFT WITH MODELING 7 TABLE4—WindtunnelmeasuredversusWTDISPmodeleddepositionforairspeedof2.5m/s. Deposition (cid:1)(cid:1)L/cm2(cid:2) Distance Nozzle (cid:1)m(cid:2) Measured WTDISPModeled 8001 2 0.908 0.0004 3 0.439 0.444 4 0.260 0.072 5 0.173 0.010 8003 2 0.472 0.0001 3 0.210 0.244 4 0.197 0.047 5 0.101 0.007 8006 2 0.248 0.0001 3 0.068 0.068 4 0.037 0.019 5 0.018 0.005 8008 2 0.333 0.000 3 0.118 0.005 4 0.083 0.0007 5 0.038 0.0001 6510 2 0.078 0.000 3 0.029 0.0001 4 0.006 0.0004 5 0.002 0.0001 et al. (cid:3)11(cid:4) suggested and continued to research options for the use of WTDISP for absolute rather than relative performance data through additional description of the spray source and sprayer speed using laser measurements of flux in wind tunnels. The measured deposition values for the present study have been adjusted for the recovery of 93 % following the methods listed previously. The modeled and measured results at 3 m tend to be similar, while the modeled results tended to be much lower than those measured at the other distance.WTDISPmodels the flux movement as if it were in anopenambientenvironment,andthemeasureddatacorrespondtoanenclosedtunnelenvironmentwithin which the plume dispersion is limited to the enclosed area. Wind Tunnel Dispersion Modeling Results Thenumericaldepositiondata,asmodeledbyWTDISP,foreachnozzleoperatingundereachairspeedand for each input scenario are shown in Table 5. TABLE5—Modeleddepositionat10mdownwindandintegratedfrom0to60mdownwindforeachscenarioforeachnozzleoperating under1and2.5m/sairspeeds. Deposition@10m IntegratedDeposition0–60m (cid:1)(cid:1)L/cm2(cid:2) (cid:1)(cid:1)L/cm2(cid:2) Nozzle FP S1 S2 S3 FP S1 S2 S3 1m/s 8001 3.0(cid:3)10−04 1.5(cid:3)10−04 4.7(cid:3)10−04 1.9(cid:3)10−03 0.01700 0.01800 0.01740 0.00940 8003 1.0(cid:3)10−05 6.6(cid:3)10−04 9.1(cid:3)10−04 1.1(cid:3)10−03 0.00870 0.01290 0.00980 0.00390 8006 2.5(cid:3)10−04 3.1(cid:3)10−04 3.5(cid:3)10−04 5.1(cid:3)10−04 0.01100 0.00900 0.00990 0.00500 8008 2.7(cid:3)10−04 2.5(cid:3)10−04 9.7(cid:3)10−06 3.0(cid:3)10−05 0.00660 0.00600 0.00880 0.00600 6510 8.0(cid:3)10−05 8.7(cid:3)10−05 5.4(cid:3)10−04 6.5(cid:3)10−04 0.00520 0.00530 0.00320 0.00340 2.5m/s 8001 4.1(cid:3)10−04 7.6(cid:3)10−04 2.6(cid:3)10−03 3.4(cid:3)10−03 0.02400 0.02830 0.01100 0.00780 8003 4.2(cid:3)10−04 3.1(cid:3)10−04 8.4(cid:3)10−04 2.0(cid:3)10−03 0.01400 0.01290 0.00980 0.00390 8006 6.3(cid:3)10−04 3.1(cid:3)10−04 3.5(cid:3)10−04 5.1(cid:3)10−04 0.00470 0.00520 0.00220 0.00100 8008 4.7(cid:3)10−06 3.8(cid:3)10−07 9.7(cid:3)10−06 3.0(cid:3)10−05 0.01200 0.01390 0.00490 0.00220 6510 1.8(cid:3)10−05 8.7(cid:3)10−06 3.9(cid:3)10−06 7.1(cid:3)10−06 0.00280 0.00320 0.00140 0.00050 8 JOURNAL OFASTM INTERNATIONAL TABLE6—Modeleddepositionat10mdownwindandintegratedfrom0to60mdownwindforeachscenarioforeachnozzleoperating under1and2.5m/sairspeedexpressedasmillionthspercentagesofapplied. Deposition@10m IntegratedDeposition0–60m (cid:1)MillionthPercentofApplied(cid:2) (cid:1)MillionthPercentofApplied(cid:2) Nozzle FP S1 S2 S3 FP S1 S2 S3 1m/s 8001 0.3830 0.1946 0.6004 2.4835 21.7022 22.9788 22.2129 12.0001 8003 0.0050 0.3279 0.4526 0.5605 4.3500 6.4500 4.9000 1.9500 8006 0.0833 0.1022 0.1177 0.1688 3.6667 3.0000 3.3000 1.6667 8008 0.0600 0.0560 0.0022 0.0066 1.4667 1.3333 1.9556 1.3333 6510 0.0160 0.0173 0.1072 0.1291 1.0400 1.0600 0.6400 0.6800 2.5m/s 8001 0.5281 0.9676 3.3273 4.3447 30.6384 36.1278 14.0426 9.9575 8003 0.2079 0.1563 0.4183 0.9773 7.0000 6.4500 4.9000 1.9500 8006 0.2116 0.1022 0.1177 0.1688 1.5667 1.7333 0.7333 0.3333 8008 0.0010 0.0001 0.0022 0.0066 2.6667 3.0889 1.0889 0.4889 6510 0.0036 0.0017 0.0008 0.0014 0.5600 0.6400 0.2800 0.1000 Thesedatawerethenconvertedtoapercentageofthetotalvolumeapplied(cid:1)Table6(cid:2).Thetotalvolume applied was calculated based on a 10 s spray time and the measured nozzle flowrate (cid:1)0.47, 1.2, 1.8, 2.7, and 3.0 L/min for the 8001, 8003, 8006, 8008, and 6510 nozzles, respectively (cid:3)6(cid:4) (cid:2). As the calculated percentages were numerically small, the data were expressed as millionth percentages of applied. Using these data, a percent reduction in drift from that modeled for the 8003 reference nozzle was determined(cid:1)Table7(cid:2).Notethatthemodeleddepositionvaluesusingthefluxanddropletsizedataatallsix heights for the 8003 nozzle (cid:1)for both the 10 and the 0–60 m integrated values(cid:2) did not follow expected trends as seen in the other nozzles (cid:1)i.e., the values would be expected to fall between the 8001 and the 8006values(cid:2).However,whenlookingatthemodeledresultsusingthealternativescenarios(cid:1)S1–S3(cid:2),these trends did hold. The modeling inputs and results were analyzed a number of times for the 8003 FP data, but no discernable reason for this inconsistency was found.As this data represent the reference point, the determined reductions and ratings are affected. The percent reduction within each scenario, wind speed, and deposition data sets was determined by comparison to the corresponding data for the 8003 nozzle. For example,thepercentreductioninmodeleddepositionat10musingallsixfluxheightsforthe8006nozzle operating in a 1 m/s airstream was calculated based on the modeled deposition at 10 m using all six flux heights for the 8003 nozzle under the same airspeed. There was also no consistency in the drift reduction percentages for either the 10 or the 0–60 m integrated deposition data in terms of reductions at the three scenarios versus the FP data. Overall, these data were more consistent, in terms of maintaining similar reduction levels across the different flux measurements scenarios, at the 2.5 m/s wind speed. The reduction percentages were then used to provide each nozzle/airspeed combination with a DRT rating. One potential method for ranking the effectiveness of these nozzles in reducing drift as compared to the reference nozzle is a drift classification scheme developed by the International Standards Organi- TABLE7—Driftreductionpercentagesforeachnozzleoperatingundereachairspeedascomparedtothe8003referencenozzleresults. PercentReductioninDriftComparedto8003ReferenceNozzle Deposition@10m IntegratedDeposition0–60m Nozzle FP S1 S2 S3 FP S1 S2 S3 1m/s 8001 (cid:4)7559.6 40.6 (cid:4)32.7 (cid:4)343.0 (cid:4)398.9 (cid:4)256.3 (cid:4)353.3 (cid:4)515.4 8003 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8006 (cid:4)1566.7 68.8 74.0 69.9 15.7 53.5 32.7 14.5 8008 (cid:4)1100.0 82.9 99.5 98.8 66.3 79.3 60.1 31.6 6510 (cid:4)220.0 94.7 76.3 77.0 76.1 83.6 86.9 65.1 2.5m/s 8001 (cid:4)154.0 (cid:4)519.0 (cid:4)695.4 (cid:4)344.6 (cid:4)337.7 (cid:4)460.1 (cid:4)186.6 (cid:4)410.6 8003 0.0 0.0 0.0 0.0 0.0 0.0 0.0 0.0 8006 (cid:4)1.8 34.6 71.9 82.7 77.6 73.1 85.0 82.9 8008 99.5 99.9 99.5 99.3 61.9 52.1 77.8 74.9 6510 98.3 98.9 99.8 99.9 92.0 90.1 94.3 94.9