1. Dilutions Over Treated Fields
Ryan D. Sullivan
David A. Sullivan
Sullivan Environmental
1900 Elkin Street, Suite 200
Alexandria, VA 22308 1

2. BystanderExposuresAffected by 2 Fluxes:
pesticideflux and heat flux (dilutionpotential)
• Conc. = emission x dilution
• Emission flux of pesticides has been focus
• Heat flux modification by tarped surfaces during
critical nocturnal periods equally important
• 3 field studies in 2015 included off-field & on-field
comparative heat flux and turbulent intensity data - -
basis to refine dilution term
2

3. Total Benefits of TarpsShould Be Considered
• Retention of A.I. and daughter products is very important
• But the full tarp benefits need to also consider the
influence on mitigating worst-case dilution conditions
(nocturnal inversions)
• Differences between neutral and inversion stability can
be on the order of a 3x factor - - all else being equal
3

4. Why Do Some ApplicationsEliminate
AtmosphericInversionsOver the Field?
• Pre-application irrigation increases:
• Thermal conductivity = greater downward heat
storages
• Heat capacity
• Heat reservoir
• Tarped applications promote heat storage by minimizing
loss of heat by surface evaporation
• Black tarp also reduces loss of heat by reflected loss 4

5. Exampleof Tarp CoveredSurface
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6. Non-AgriculturalExampleof Heat IslandEffect
Example: shopping mall monitored by Sullivan
Environmental with warm asphalt/concrete
surfaces surrounded by grassy residential areas
and wooded areas. During this period with very
light wind speeds, counter flow was observed with
the low-level flow of the colder converging air
moving uphill, rather than the more common cold
air drainage. The nocturnal surface temperature
differential between the mall surface and the
natural grass covered surfaces in this example was
8 to 10 C. In this sense, a heat island is an “island”
of warm air surrounded by cooler air, i.e. an
“oasis” in reverse.
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7. Exampleof Heat IslandCausedby Warmer
SurfaceSurroundedby Cooler Surfaces
7
Surface Temperature at 11:13 P.M. hours on 4/26/2013
Wind flow from 160 degrees
(uphill in opposition to gravity flow)
Asphalt surface 15-18 F warmer
than natural surfacesGrassy surface

8. Latest Field Data: SupportsRefinementof Modeling
for Ag Applications
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Key Factors to Atmos. Stability
• Tarp color
• Irrigated vs. unirrigated
• Soil type
Difference between neutral and stable
conditions
Black
tarp
Unirrigated
ground
White
tarp

9. Off-fieldMinus On-fieldTemperatureDifferences
Study
Temperature Difference
(F) comment
bedded, black Tarp Florida
June 2015 -6
IR Thermometer, Sfc
Based
bedded, white tarp,
California, Sept 2015 -0.2
measured 1m above
surfaces
bare ground, California,
October 2015 +1.2
measured 1m above
surfaces
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10. Phasing In Of Comparative Heat
Flux and Turbulence Data
On-Field Prepared Ground Versus
Bare ground natural surface
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11. Co-Variance Monitoring
(sensible heat, water vapor, turbulent intensity)
11

12. Bedded Black Tarp: 70 % Increasein Dilution
Rates Over Treated Field
Day Night
Period Wind Directions On-Field Off-Field On-Field Off-Field n n
6/15/15 1700 - 6/19/15 0046 all 0.16 0.15 0.165 0.118 2521 2266
6/15/15 1700 - 6/18/15 1500 20-160 0.155 0.154 0.173 0.125 1583 1048
6/15/15 1700 - 6/18/15 1500 340-360 0.167 0.156 0.172 0.096 163 159
6/15/15 1700 - 6/18/15 1500 0-20 0.164 0.144 0.183 0.112 265 195
6/18/15 1600 - 6/19/15 0046 20-160 0.128 0.137 0.146 0.135 67 169
weighted average 0-20 & 340-360 → 0.165 0.149 0.178 0.105
6/15/15 1700 - 6/18/15 1500
Daytime Nighttime
12~70 percent increase in relative dilution
over treated field

13. Vertical DispersionDifferencesOn-Field
Versus Off-Field(bare ground)
0
0.5
1
1.5
2
2.5
3
3.5
0
0.05
0.1
0.15
0.2
0.25
0.3
10/17/2015 10/19/2015 10/21/2015 10/23/2015 10/25/2015 10/27/2015
WINDSPEED(MPS)
SIGMAPHI
Study SEC 2015A: Sigma Phi On-field and Off-field Compared
with Wind Speed
on_Sig_Phi on_Sig_Phi Off_Sig_Phi Off_Sig_Phi 2 per. Mov. Avg. (wnd_spd m/s Smp)
13

14. On-FieldSensible vs Latent Heat Flux Bare
GroundApplication
-30
20
70
120
170
10/17/2015 10/19/2015 10/21/2015 10/23/2015 10/25/2015 10/27/2015
W/M^2SMP
Study SEC2015A: Sensible and Latent Heat Flux On Applied Field
ONFIELD Hs W/m^2 Smp LE_kh_wpl W/m^2 Smp
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15. LatestFieldData:SupportsRefinementof ModelingforAg
Applications:On-fieldandComparativeOff-FieldDataCollection
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Covariance Heat Flux
Krypton Hygrometer
Latent heat flux
Wind and
temp.
profile
Real time
Air density

16. Other Advancements in Flux
Study Research
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17. AdvancedGISprocessingof fetch
(Sub-meter accuracy360 degree directions)
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18. Conclusions
• Realistic assessment of nocturnal bystander exposures needs
to consider applied surface / tarp influence on dilution
• Currently modeling moderate dilution (neutral) at night as
though extremely limited dispersion (stable inversion
conditions)
• Near-field issue - - if >>100 m buffer zones using standard
modeling methods - - expect minor differences
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19. Conclusions(Cont.)
• Potential future supplemental data for our flux studies to
maximize downstream benefits of emissions studies:
• Dual co-variance monitoring of sensible and latent
heat flux
• Flux plates to measure soil heat flux
• Net radiation measurements
• Support needed to fully delineate atmospheric dilution
differences - - meteorological research separate from flux
studies
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