Carol A. Brevett

Kinetics of the degradation of sulfur mustard on ambient and moist concrete.

The rate of degradation of the chemical warfare agent sulfur mustard, bis(2-chloroethyl) sulfide, was measured on ambient and moist concrete using (13)C Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Three samples of concrete made by the same formulation, but differing in age and alkalinity were used. The sulfur mustard eventually degraded to thiodiglycol and 1,4-oxathiane via the intermediate sulfonium ions CH-TG, H-TG, H-2TG and O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on all of the concrete samples, and in addition formed 8-31% vinyl moieties on the newer, more alkaline concrete samples. This is the first observation of the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH on a solid substrate. The addition of 2-chloroethanol to concrete on which mustard had fully degraded to thiodiglycol and 1,4-oxathiane resulted in the formation of O(CH(2)CH(2))(2)S(+)CH(2)CH(2)OH, thus demonstrating the reversibility of sulfur mustard degradation pathways. The sulfur mustard degradation half-lives on ambient concrete at 22 degrees C ranged from 3.5 to 54 weeks. When the substrates were moistened, the degradation half-lives at 22 degrees C ranged from 75 to 350h. The degradation of sulfur mustard occurred more quickly at elevated temperatures and with added water. The non-volatile toxic sulfonium ions persisted for months to years on concrete at 22 degrees C and weeks to months on concrete at 35 degrees C, before decomposing to the relatively non-toxic compounds thiodiglycol and 1,4-oxathiane.

Degradation of the chemical warfare agents HD, GD, thickened GD, and VX on ambient and moist environmental substrates

The rates, products, and mechanisms of the degradation of the chemical warfare agents GD, thickened GD, HD and VX on environmental substrates were determined using Solid State Magic Angle Spinning Nuclear Magnetic Resonance (SSMAS NMR). Increases in temperature were found to increase the rates of the reactions. The addition of water affected b oth the rate of the reactions and the products formed. The alkalinity or acidity of the substrate was also observed to affect t he products formed and the mechanism of the reaction. The chemical warfare agents VX (O-ethyl S-(2-N,N-(diisopropylamino)ethyl) methylphosphonothio- late), sulfur mustard (bis(2-chloroethyl) sulfide, HD), So man (GD, pinacolyl methylphosphonofluoridate, O-1,2,2-trimethylpropyl methylphosphonofluoridate), an d thickened GD (TGD, which is GD with�3% polymeric thickener added) are of interest due to the possibility of use by terrorist organizations and in global conflicts. Sulfur mustard was used during WWI and WWII (1), and in the Iran-Iraq war of the 1980s (2). Sulfur mustard is known for persistence in the en vironment, especially at the bottom of the ocean (3,4). The terrorist organization Aum Shinrikyo used Sarin (GB) in the Tokyo subway in March, 1995, killing 13 civilians, and VX in 1994 to kill a disgruntled ex-member (5). The results discussed here are part of a series of experiments performed to determine the degradation rates of agents on the environmentally prevalent substrates concrete, sand, asphalt and soil, and to determine any chemical properties of the substrates that may influence the degradation rates of the agents. This article summarizes the agent-substrate inter actions observed to date by the authors and other researchers, and highlights the influence the substrate has on the observed agent reactivity.

Degradation of Sulfur Mustard on Moist Sand as Determined by 13C Solid‐State Magic Angle Spinning Nuclear Magnetic Resonance

Abstract The degradation of sulfur mustard, bis(2‐chloroethyl) sulfide, on three types of moist sand at 22°C and 35°C was followed using 13C solid state‐magic angle spinning nuclear magnetic resonance (SSMAS NMR). The sulfur mustard degraded completely on moist sand within 8 weeks at 22°C and 1 week at 35°C, whereas degradation on dry sand at 22°C required more than 6 weeks. The major product, the toxic sulfonium ion H‐2TG, and the minor product, nontoxic thiodiglycol, were detected on all sand samples. The intermediate chlorohydrin was detected on one sand at 22°C, and evidence for the intermediates CH‐TG and H‐TG was detected on this same sand at 35°C. The H‐2TG that was initially formed degraded to thiodiglycol; completion of this degradation would require months. The lack of reaction on the ambient substrates, plus the formation of sulfonium ions, similar to the products that were previously seen in water and on moist soil, suggested that the sand functioned as a support on which the reaction between sulfur mustard and water occurred.