Visual Characterization of VX Droplets on Plant Foliage

A method was developed for maintaining healthy plants in a chemical surety hood and for disseminating, observing, and evaluating VX [O-ethyl-S-(2-diisopropylaminoethyl) methyl phosphonothioate] droplet spread, absorption, and appearance on leaves. In separate experiments, 1 or 3 microL droplets were dispensed onto plant leaves using a high-precision syringe. Digital photographs of the droplets were taken at intervals, saved, and analyzed. Each image was electronically traced and converted to surface area (SA) using Image-Pro Insight software (Media Cybernetics; Rockville, MD). Droplets on foliage initially appeared as transparent areas and spread with time. After 1 h, the 1 and 3 microL droplets ceased to spread, the VX appeared fully absorbed into leaf tissue, and the leaf tissue within the spread area appeared dry and darkened. After 24 h, the affected leaf tissue appeared light tan and necrotic. Mean SAs of the affected tissues for 1 microL droplets were 132, 192, 163, 135, and 142 mm2 at 0.017, 0.05, 1, 4, and 24 h, respectively, and those for 3 microL droplets were 166, 301, 303, 278, and 274 mm2 at 0.05, 1, 4, 24, and 48 h, respectively. Using these results can accelerate field identification and characterization of VX to more effectively protect Warfighters.