Spray-drift additives

The additive should not degrade under the high shear conditions in the spray tank. More recent developments in spray-drift additives have begun to address this challenge (Hazen, 1996). 

To solve this problem, modern pesticide formulations use a variety of additives (adjuvants) to improve the mass efficiency. Surfactants and polymeric rheology modifiers are used to reduce spray drift, surfactants are used to modify surface tension and reduce... 

The models chosen in FOCUSsw for estimating the different routes of entry are MACRO for estimating the contribution of drainage, PRZM for the contribution of runoff and erosion, and TOXSWA for the estimation of the final PEC in surface waters. An additional loading is defined as spray drift input. The calculation of the contribution of the spray drift is incorporated in the Graphical User Interface (GUI) for the surface water scenarios called SWASH (Surface WAter Scenario Help). This is a general software shell developed to ensure that the relevant FOCUS scenarios and input are defined consistently for all models [50]. 

Many modem sprayers are equipped with additional features designed to decrease spray-drift and improve deposition. Features include air assistance, where airflow, created by a fan placed on the sprayer, creates an air curtain behind the spray. The air is usually ducted via a flexible sleeve mounted on the boom. Fine drops leaving the nozzles are entrained in the air curtain and projected towards the crop (Miller and Hobson, 1991). 

The traditional formulation approach to reducing spray drift has been to increase the viscosity. The viscosity is usually increased by the use of polymers. Although there have been some advances via this route, there is still much room for improvement (Chappie el al., 1993). In particular, it has proved to be very difficult to combine all the desirable properties of the additive ... 

High-molecular weight polymers can have an effect on spray drift by increasing droplet size if the polymer is not physically degraded by mechanical action in the spray tank pumps. Newer non-polymeric drift control aids have also been developed that change the rheological properties of the tank mixture. Many additional types of adjuvants are used conunonly. Those presented above are... 

Another use of anti-drift additions to sprays is in the controlled direction of the spraying. In the control of johnson grass, redroot, pigweed, and hemp sesbania in soybeans sprays were directed across the rows to catch the higher weeds in June, July, and August. The anti-drift polymer at 0.1% in the spray balanced the increased effectiveness through the use of surfactants in the formulation. The Nalco-trol polymer consisted of a long chain polymer that thickened water and eliminated the production of spray droplets smaller than 200 microns. 

When land costs are too high, spray ponds often provide a viable alternative to cooling ponds. It is estimated that a spray pond requires only about 5 to 10 percent of the area of a cooling pond due to the more intimate air-water contact. In addition, drift losses and corrosion problems are less severe than in cooling towers. 

Covered-boom sprayers look similar to a large, bat-wing-type reel mower. Spray nozzles are enclosed so that spray is directed with little drift. In addition, many sprayers today are computerized. Computers control the amount of output depending on ground speed, sprayer height, wind speed and flow rate pressure. Computers also can perform such functions as tracking the number of hectares treated, the amount of product used and the day and time it was applied. The possibilities are many, but they all may not be practical or affordable (Walker, 1997). 

Herbicides and insecticides are usually diluted in a carrier so that these can be applied uniformly (Anon, 1985 Cox Scherm, 2001 Kapusta, 1984 Woolwine Reagan, 2001). Water almost exclusively was used for insecticides, but relatively large volumes (200 L/ha, 21 gal/A) are used requiring frequent time-consuming refilling of spray tanks. The introduction of rotary atomizing nozzles facilitated the application of very small volumes (2-3 L/ha or 0.2-0.3 gal/A), and has made it practical to use soybean oil as carrier. Additional benefits of this technology are reduced drift and evaporative losses and increased penetration that reduce effective application rates. 

Jumping to the end of the spectrum, there is a large, well-defined, sharp peak arriving at the Faraday plate at approximately 11.9 ms. This peak corresponds to the quasi-molecular product ion (MH+) produced from the ionization reaction M -I- H3O+ MH+ + H2O occurring in the liquid phase before the sample is electro-sprayed into the IMS. In addition to the ion peak at 11.9 ms, there is another sharp, well-defined ion peak at a drift time of about 8.9 ms. In IMS, as in mass spectrometry (MS), dibasic compounds with molecular weights greater than about 500 Da can contain two charges after ESI. Thus, the force exerted by the electric field on the... 

Atmospheric conditions should be defined in terms of temperature, humidity, and contaminants, as well as their corrosivity to the specific materials of construction being considered. In addition to the general atmospheric conditions, special conditions such as cooling tower drift or spray, spills, or releases of water or chemicals should not be overlooked and must be taken into account. 

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