Evaluation of a proposed drift reduction technology high-speed wind tunnel testing protocol

Authors: Hoffmann, Wesley; Fritz, Bradley - Brad; Lan, Yubin

Submitted to: Journal of ASTM International
Publication Type: Peer Reviewed Journal
Publication Acceptance Date: 2/13/2009
Publication Date: 3/1/2009
Citation: Hoffmann, W.C., Fritz, B.K., Lan, Y. 2009. Evaluation of a proposed drift reduction technology high-speed wind tunnel testing protocol. Journal of ASTM International. 6:doi:10.1520/JAI102122.

Interpretive Summary: Drift associated with spray application of crop production and protection products is a continual concern for the spray application industry. As such, an increasing number of drift-reducing technologies are being developed and marketed for use with agricultural chemicals in aerial application treatments. With this growing market, there is a need to scientifically quantify and rate the effectiveness of these products in order to inform end users. Protocols for testing drift reduction technologies in high speed wind tunnels were evaluated. The results of these protocol evaluation studies revealed significant differences in droplet spectra between the spray solutions and from different air velocities. The implementation of these testing protocols will result in an improved and more equitable science-based evaluation program for drift reducing technologies.

Technical Abstract: 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, water + 0.25% of a nonionic surfactant, and water + 9% isopropanol. 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 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 ±5% standard deviation values as criteria for accepting atomization tests results.