Evaluation of a Proposed Drift Reduction Technology High-Speed Wind Tunnel Testing Protocol

The U.S. Environmental Protection Agency (EPA) has initiated the development of protocols for for measuring spray drift reduction technologies (DRTs) related to the application of agricultural protection chemicals. The DRT Program is an EPA-led initiative program to “achieve improved environmental and human health protection through drift reduction by accelerating the acceptance and use of improved and cost-effective application technologies.” The first step in implementing the DRT program is to develop a set of protocols, standard operating procedures, and data quality assurance steps so that the results from any trials or research conducted are scientifically valid and repeatable. A protocol for measuring spray droplet spectra via laser diffraction equipment in a high speed wind tunnel (air velocities >160 kph (100 mph)) was tested. Following the proposed protocol, five reference nozzles were evaluated with spray solutions of deionized water, water + 9 % isopropanol, and water + 0.25 % of a nonionic surfactant. Each of the nozzle and spray solution combinations were evaluated in 160, 193, and 225 kph (100, 120, and 140 mph) airstreams, as well as under static (0 kph) conditions. The results of these atomization studies showed that there were significant differences in droplet spectra between the spray solutions and from the different air velocities. Based on the time to complete the tests, the author suggest using a ±5 % standard deviation values as criteria for accepting atomization tests results.