Members Area News Site Map Contact עברית
The Technion Center of Excellence in Exposure Science and Environmental Health
Join our mailing list
Name Email Affiliation

Degradation of VX Surrogate Profenofos on Surfaces via in Situ Photo-oxidation

L. Petrick, S. Sabach, Y. Dubowksi.

Environmental Science & Technologט
47(15) 8751-8758, 2013.

Surface degradation of profenofos (PF), a VX nerve gas surrogate, was investigated using in situ photo-oxidation that combines simple instrumentation and ambient gases (O2 and H2O) as a function of exposure conditions ([O3], [OH], UV light λ = 185 and/or 254 nm, relative humidity) and PF film surface density (0.38–3.8 g m–2). PF film 0.38 g m–2 fully degraded after 60 min of exposure to both 254 and 185 nm UV light in humidified air and high ozone. The observed pseudo-first-order surface reaction rate constant (kobs = 0.075 ± 0.004 min–1) and calculated hydroxyl concentration near the film surface ([OH]g = (9 ± 2) × 107 molecules cm–3) were used to determine the second-order rate constant for heterogeneous reaction of PF and OH (kOHPF = (5 ± 1) × 10–12 cm3 molec–1 s–1). PF degradation in the absence of 185 nm light or without humidity was lower (70% or 90% degradation, respectively). With denser PF films ranging from 2.3 to 3.8 g m–2, only 80% degradation was achieved until the PF droplet was redissolved in acetonitrile which allowed >95% PF degradation. Surface product analysis indicated limited formation of the nontoxic phosphoric acid ester but the formation of nonvolatile chemicals with increased hydrophilicity and addition of OH.