Drift Reduction Technologies Andrew Hewitt DRTs Systems that avoid - - PowerPoint PPT Presentation

Drift Reduction Technologies

Andrew Hewitt

DRTs

• Systems that avoid “Fines” being sprayed (nozzles, tank mixes)
• Systems that avoid “Fines” forming through evaporation (anti-

evaporants)

• Minimizing the effective spray release height (lower the boom or add

a shield/ shroud/ air curtain)

• Moving the droplets faster toward the target (optimized velocity/

trajectory/ electrostatic charge)

• Targeted spraying

(sensors, directional spraying etc)

Avoiding Spray Drift Exposure the “Easy” Way

• Don’t spray small droplets (<~100-150 µm)

Droplet Diameter (micrometers) Fall velocity (m/s) Drift distance Downwind (m) 10 0.003 1000 30 0.027 111 100 0.25 12 300 1.2 2.5 1000 5.0 0.6

Avoiding Spray Drift Exposure the “Hard” Way

• If there are some “Fines” in the spray, there can be some mass of the

applied spray that can move off-target under unfavourable conditions (physical and air shields can help reduce this, e.g. hoods)

• The movement and deposition of these “Fines” will depend on many

factors and variables associated with the particle size/ velocity/ shape spectrum, application technique, boom height, sprayer wake/ vortices, meteorological and atmospheric conditions, evaporation rate, canopy, barriers, electrostatic charge, etc.

0.5 1 1.5 50 100

Speed (m/s)

0.5 1 1.5 2 2.5 3 3.5 4 10 20

Height (m)

0.5 1 1.5 2 2.5 3 3.5 4 200 400 600

Droplet Size (VMD) (µm)

0.5 1 1.5 2 4 6 8

Wind Speed (m/s)

0.5 1 1.5 20 40 60

Temperature (deg C)

0.5 1 1.5 50 100 150

Relative Humidity (%)

0.5 1 1.5 0.05 0.1 0.15 0.2 Turbulence intensity *

0.5 1 1.5 0.1 0.2 0.3

Turbulence intensity

70 µm 216 µm

AgDRIFT Sensitivity analysis - effect of application parameters on spray drift deposition

Spray Dynamics

• Spray dynamics are affected by nozzle type, energy input (e.g. spray

pressure, rotation rate, air shear) and tank mix physical properties from the sum of all components of the tank mix, and are not always intuitive especially for non-Newtonian tank mixes

• Many DRAs improve the droplet size spectrum even with the better

nozzles by “fine-tuning” the “Fines”

Assuring good coverage is important

• Adjuvants can help with spread/ retention/ uptake as well as

improving the droplet size spectrum – i.e. dual benefits possible with

• ptimized systems and when paired with the best application system

(e.g. nozzle)

• Some adjuvants increase, and others reduce, spray angle with some

nozzle types. If an adjuvant reduces the spray angle, do we need to use it with a wider angle nozzle such as some of the newer 140 degree types?

Application for Efficacy without Losses Such as Drift is Complex – Modeling Helps

• Spray dynamics affect total spray performance and we cannot only consider efficacy

– we also need to avoid losses such as drift

• Good efficacy requires good coverage. This is affected by spray dynamics, sprayer

speed, tank mix physical properties, leaf/ target characteristics, weather, etc.

• What works well with one sprayer at one site may not work at another because

conditions vary, as do sensitive areas

• When we change formulation chemistry we can change not only droplet size but

also the spreading and uptake

• Formulation effects can vary widely with different nozzles, pressures, etc
• By using spray dynamics and coverage data on each nozzle and tank mix, as well as

levels of concern for drift risk assessment, we link with decades of modeling work to show spray performance both for coverage and for no-spray buffer zones, using regulatory approved models

Spray Calculators: The Database Component

• Spray dynamics is much more than just droplet size. We also measure/

calculate many factors that are then used by the models, using accepted protocols/ standards to link with AGDISP:

• Droplet density and air inclusions
• Droplet size/ velocity profile
• Droplet/ spray evaporation rates
• Drift potential
• Dynamic surface tension at temperatures and lifetime ages appropriate

to a) atomization and b) retention/ spreading/ sticking/ uptake

• For non-Newtonian liquids, viscosity parameters such as Trouton Ratio

Data Collection for Full Spray Dynamics

The Modeling Component

• AGDISP Aerial and Ground models to put the spray dynamics into spray

fate and drift context for each unique application scenario (e.g. for decision-making) and reasonable worst case scenarios (for risk assessment). Note: Ground Modeling is based on inputs from our work with regulators and industry to determine how to use the ground model with appropriate inputs such as droplet size Rosin-Rammler conversion; appropriate evaporation algorithms; nozzle model choice; etc.

• Spray coverage modeling based on our research of droplet fate
• L-Studio modeling for plant leaf and droplet interactions

Evergreen

• Our approach is evergreen because we add new data sets as new

formulations, nozzles etc are developed

• Ditto for linking each pesticide toxicity for specific sensitive areas to

show DRT performance in terms of actual no-spray buffer zone reduction

• Validation work has covered ground and aerial applications. We also

included an approach based on some regulatory preferences for drift potential based on sampling airborne drift flux in a wide wind tunnel

• A key aspect of the work is the fact that drift reduction technology

performance requires proof that a DRT does not adversely affect efficacy potential. The calculator shows this

DRT Testing

• Field studies
• Wind tunnel droplet size
• Wind tunnel drift potential
• Some registrants have conducted field studies to show the drift potential of

their product with specific recommended nozzle(s) and then negotiated with EPA to cover tank mix partners through a standard protocol of testing with a nozzle such as TTI/ AIXR/ etc and then running data through AGDISP and approving those adjuvants that don’t increase the no-spray buffer zone size (or requiring a DRA with some adjuvants in order to be allowed)

• Other approaches can use a range of nozzles and pressures appropriate to

the application type

Nozzle Type Exit orifice Type Nozzle System Pressure (bar) F M C VC XC UC Air induction Single Hypro ULD120-04 6.0 4.5 2.5 Hardi ISO Minidrift 025 6.0 4.0 2.0 TeeJet AIC11025 6.5 4.5 2.5 TeeJet AIXR11002 6.0 5.0 2.5 1.5 Twin TeeJet AI3070-02 4.0 2.0 1.5 Hardi ISO Minidrift Duo 025 6.0 4.0 2.0 Air induction - Anvil Single TeeJet TTI110015 7.0 3.5 Twin TeeJet AITTJ60-11003 7.0 4.0 2.5 1.5 Anvil Single TeeJet TT11001 6.0 2.5 TeeJet TT11004 4.5 1.5 Twin TeeJet TTJ60-110025 6.0 4.5 1.5 Flat fan Single Hardi ISO F-110 015 5.0 1.5 TeeJet TP11001 3.5 TeeJet XR8003 4.0 1.5 Twin TeeJet TJ60-6503 4.0 2.0 Hollow cone Single TeeJet TX-18 5.0 Pre-orifice flat fan Single Hardi ISO LD-110 025 5.0 2.0 Twin TeeJet DGTJ60-11002 4.0 2.5

Conclusions

• DRTs should be assessed in view of drift reduction (e.g. reducing Fines

and showing buffer zone reduction through AGDISP modeling….or expensive field studies) AND coverage on the target

• Spray calculators can support decisions for the huge numbers of

nozzles, application rates, products, driving speeds, spray pressures, etc., complementing risk assessment with spray coverage on different targets for different conditions of spray dynamics