Accurate Modeling for Drift Reduction: General Overview and Regulatory Status April 11 th, 2014 Dan...
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Transcript of Accurate Modeling for Drift Reduction: General Overview and Regulatory Status April 11 th, 2014 Dan...
Accurate Modeling for Drift Reduction:General Overview and Regulatory
Status
April 11th, 2014
Dan Dyer
On Behalf of the CLA Spray Drift Issue Management Team
Spray Drift Regulation
• Spray drift is complex… Ground, aerial, orchard/airblast sprays Broad range of technologies of spray equipment Significant differences in geography/climate Conservative drift models (perceived drift issue)
• But can be well managed… Local applicators/growers understand appropriate
conditions for application and minimizing drift Training / certification / education Pesticide Label Restrictions – wind speed, buffers,
etc. Newer drift reducing technologies
Spray Drift Regulation
• Recently released spray drift guidance for use of AgDRIFT in human and ecological exposure/risk assessment EPA-HQ-OPP-2013-0676 “Consideration of Spray
Drift in Pesticide Risk Assessment”
• CLA supports development of appropriate drift assessment methodologies
• However, EPA guidance is too restrictive and is limited in ability to make higher tier refinements
Factors Influencing Spray Drift
• Spray Characteristics Droplet size
Chemical / Formulation / Adjuvants
• Equipment & Application Nozzle type, size, orientation Nozzle pressure Height of release
• Weather, etc. Air movement (direction and velocity) Temperature & humidity Air stability/inversions
Droplet Categorization - ASABE
Need to select droplet size to
maximize efficacy and minimize drift
Category Symbol Color Code
Approximate
Dv0.5 (VMD)
(microns)
Extremely Fine XF Purple ≈50
Very Fine VF Red <136
Fine F Orange 136-177
Medium M Yellow 177-218
Coarse C Blue 218-349
Very Coarse VC Green 349-428
Extremely Coarse
XC White 428-622
Ultra Coarse UC Black >622
From: ASABE Standard S-572.1
AgDRIFT to Calculate Buffers
• EPA 2014 guidance uses AgDRIFT to determine drift for terrestrial (plant/animal) and aquatic habitat
• AgDRIFT based on Spray Drift Task-force data 48 unique SDTF Deposition Datasets
Excellent quality & GLP Used older (1992-93) spray application technology
• Several conservative approaches result in unrealistic ground drift estimates
• Unable to refine drift estimation using drift reducing technologies (DRT) and best management practices
AgDRIFT – Overestimation of Drift
• AgDRIFT produces unreasonably conservative drift estimates when compared to existing drift data sets
Figure Courtesy J. Wright
Comparison Between AgDrift Outputs vs. Field DataAgDrift Assumes 20 Spray Swaths, 90th% tile
Distance (ft)
0 200 400 600 800 1000
% o
f A
ppli
ed
0.0
0.2
0.4
0.6
0.8
1.0
SDTF 1992SDTF 1993Wolf (PMRA)GanzelemierAgDrift (20 swaths)
Figure Courtesy J. Wright
AgDRIFT – Scale-up Overestimation
• SDTF Data is foundation for AgDRIFT, but use of multipliers to scale-up to a ‘typical’ field is much too conservative
• 90th %ile curves inappropriate
• Gross overestimate at far-field distance
Downwind distance (m)
1 2 5 10 20 40 120
Dep
osi
t (%
of
app
lied
)
0.001
0.01
0.1
1
10 1
1
1
1
1
1
1
1
2
2
2
2
2
33
33
3
5
5
5
5
5
6 66 6
6
7 7
7 7 7
8 88 8
8
9 9
9 9 9
10 1010
1010
44
4 44
2011 AAFC Data – Multiple Swaths
• Dr. Tom Wolf of Agriculture and Agri-Food Canada (AAFC) developed drift dataset as basis for PMRA buffer zone calculator
• No significant deposition after 4-5 swaths (~250-300 ft)
• In AgDRIFT, SDTF data was consolidated into two categories:
• Inappropriate to evaluate medium or coarser sprays
• Inadequate for current nozzle technology
AgDRIFT – Overestimation of DriftNozzle Trial “Data Lumping”
Very Fine to Fine
Fine to Medium/Coarse
Category Symbol Color Code
Approximate
Dv0.5 (VMD)
(microns)
Extremely Fine XF Purple ≈50
Very Fine VF Red <136
Fine F Orange 136-177
Medium M Yellow 177-218
Coarse C Blue 218-349
Very Coarse VC Green 349-428
Extremely Coarse
XC White 428-622
Ultra Coarse UC Black >622
Nozzle Types
11
Flat Fan Nozzles
Air Induction Nozzles
AgDRIFTWind Speed “Data Lumping”
12
1 10 1001E-3
0.01
0.1
1
10
Per
cent
of A
pplie
d (lo
g)
log - Down Field Distance (m)
8.4 8.8 11.6 12.8 20.5
Wind (mph)
AI11004
• Drift at distance, is influenced by data generated in high wind (25% of SDTF ground data with >20 mph wind!!)
• 90th percentile could be ‘off-label’
1 10 100
1E-3
0.01
0.1
1
10
Per
cent
of A
pplie
d
Down Field Distance (m) - log
90th Pct
50th Pct
Mean
Nozzle - 11004
Dr. T. Wolf AAFC '2000
• Summary• Mathematical model used in AgDRIFT to
describe the conservative 90th percentile drift curves are subjective, and overestimate drift• ‘Best fit’ curves in AgDRIFT never
intersect zero
• Lumping of data for trials with different nozzles (spray quality / droplet sizes), and wind speed produces excessive overestimates* of drift from ground sprays, and removes capability to refine model
AgDRIFT – Overestimation of Drift
* in some circumstances AgDRIFT can predict movement of more off-target material than the amount applied
Drift Overestimation – The Impact?
• AgDRIFT used to calculate proximity distances and buffers for FIFRA ecological and human health risk assessments, and Endangered Species Risk Assessments
• Appropriate for ‘screening’ assessment, but requires refinement options• Risk should be refined before buffer size is
determined (mitigation)
Large Action Areas(Endangered Species)
• Spray Drift – 360 degrees, wind blowing in all directions, simultaneously
• Threshold’ = EEC / LOC
• EEC from AgDrift
Significant overestimate of action area and potential
buffer distances
Drift Overestimation – Impact on Agriculture
• Impact on agriculture (example)
• ~600 feet of field or parts of field cannot be treated
Drift Overestimation –Impact on Agriculture
• ‘Freedom to operate’ for grower Possible need to remove land from production as more
buffers and larger buffers are required (value / cost?) Cost effectiveness of having to use ground applications
instead of aerial
• Resistance Development Cutting rates to meet buffer requirements No applications to certain parts of field Incomplete coverage due to coarser spray droplet
Spray Drift – A Pragmatic Solution
• Need to find appropriate balance between efficacy, drift and resistance management, to allow cost-effective pest control. Model refinement is necessary – reasonable
conservatism ‘Drift education’ / Best Management Practices are critical Automation is desirable to allow flexibility
REGDISP
• Model built on AGDISP (v. 8.26) • USFS made code available to Industry • the current EPA accepted version of AGDISP • desire to keep the mechanistic ground model
• No changes to existing AGDISP code existing • Better interface for AGDISP calculators• Enables parsing of data/ addition of data• Addresses issues with AgDRIFT described
19
Canada Drift Regulation
• Pest Management Regulatory Agency in Canada worked with Dr. Tom Wolf of Agriculture and Agri-Food Canada (AAFC) and developed their own dataset as basis for their buffer zone calculator
• Launched in 2011
REGDISP Data Sets
• Agricultural Agri Food Canada (AAFC) ‘2000• Agricultural Agri Food Canada (AAFC) ‘2004• Agricultural Agri Food Canada (AAFC) ‘2011• 49 unique AAFC Deposition Datasets
• Spray Drift Task Force ‘1992• Spray Drift Task Force ‘1993• 48 unique SDTF Deposition Datasets
• 97 unique deposition datasets
21
Canadian Field Study Design (‘00 and ‘04)
XR8001, XR8003, AI110025, AI11005, AI11004 Nozzles
Fine to V. Coarse sprays
60 and 90 cm boom heights
Wind speed = 3 to 12 m/s
Single pass, 18m (60 ft) spray boom
Data Fit Method
23
Log/Log Transform Data
1. Log Transform2. Simple Regression (y=mx+b)
10 1001E-4
1E-3
Fra
ctio
n of
App
lied
Distance (m)
0 20 40 60 80 100 120
0.000
0.001
0.002
0.003
0.004
0.005
0.006
Fra
ctio
n of
App
lied
Distance (m)
Since Deposition Data is highly non-linear
• Accurate description of data• Doesn’t assume drift is unlimited
Deposition Data Calculation Tab
24
1. Select Dataset2. Select Nozzle3. Boom Height4. Wind Speed5. Enter Rate6. Run
Use Existing Calculators (and Code)
25
Toolbox
Consideration of DRTs in Risk Assessment
• DRTs are proposed for use in reducing the size of required buffers Promote Best Management Practices (BMPs)
• Recommendations for specific Spray Quality or Droplet Size likely needed to ameliorate ESA restrictions – and maintain a viable product
• REGDISP facilitates consideration of specific field data or combinations of DRTs in determining a suitable action area or buffer distance
Pragmatic Approach to Spray Drift
• Use of REGDISP as conservative, yet realistic drift model No ‘infinite’ drift
Ability to refine ground spray drift estimates – spray quality, wind, DRTs, BMPs, etc.
Defines reasonable proximity/buffer distances to expedite FIFRA and endangered species risk assessments
• Education / Stewardship Promote Best Management Practices
CropLife, chemical producers, nozzle manufacturers, product distributors, retailers, etc.
Ag extension, federal/state agencies, universities
Continued research
Pragmatic Approach to Spray Drift
• Use of automation of spray technology e.g. GIS on conjunction with automated nozzle
switching allows precision application with respect to buffer areas
• Need to provide spray drift options that growers and applicators can use today to:• allow safe use of products (human and
ecological),• without unduly impacting growers’ ability to
effectively produce crops
Thank you