Degradation and Fate of Mustard in Soil As Determined by ¹³C MAS NMR

Abstract

The environmental fate of chemical warfare agents is a current concern, and the notorious persistency of mustard in soil is well-known. The current study utilizes 13C MAS NMR as an in situ method to study the behavior of mustard, and the common simulants 2-chloroethyl methyl sulfide (CEMS) and 2-chloroethyl phenyl sulfide (CEPS), in a sandy loam soil. Spreading of these water-insoluble liquids and surface sorption on the dry soil particles is observable, as is the recoalescence of liquid droplets and/or hydrolysis in the presence of added water. The relative hydrolysis rates are in agreement with those observed in solution. CEMS, possessing the shortest aqueous half-life, hydrolyzes without droplet reformation. But mustard and CEPS, possessing much longer aqueous half-lives, do not substantially hydrolyze prior to droplet reformation. For mustard, this behavior is crucial to its longevity in soil. Hydrolysis of CEMS and CEPS in the sandy loam soil yields predominately their corresponding alcohols, with some ether formation for the latter. Mustard hydrolysis in the sandy loam soil results in the nearly exclusive formation of the branched sulfonium ion HOCH2CH2SCH2CH2S+(CH2CH2OH)2 (CH-TG). A simple model based on droplet size is presented to explain the persistency of mustard in soil.

Degradation of the blister agent sulfur mustard, bis(2-chloroethyl) sulfide, on concrete

“…The peak width data were consistent with the observations that less sulfur mustard was extracted as the surface areas and contact times increased. These results were in contrast to the results in soil, in which the peaks remained narrow throughout the reaction [4]. Thus, the peak widths observed in this work were 200 Hz wide, compared to the 20-50 Hz peak widths that were typically seen for non-adsorbed liquid droplets in the SSMAS experiment.…”

“…However, the sulfur mustard will eventually degrade to form sulfonium ions; these can be extracted with both acetonitrile and water, and hence may become bioavailable [4,17]. Therefore, sulfur mustard bound in a matrix must be regarded as a future source of toxic, extractable, potentially bioavailable sulfonium ions.…”

“…Wagner and MacIver [4] used 13 C SSMAS (solid state magic angle spinning) NMR to show that sulfur mustard persisted for several weeks on dry soil, but hydrolyzed and polymerized to form toxic CH-TG and H-2TG sulfonium ions within 1 week when water was added. Liquid chromatography followed by electrospray ionization mass spectrometry 0304 Similarly, when sulfur mustard was placed on MgO or CaO, the products thiodiglycol (TDG), CEVS and DVS were formed [5].…”

Degradation of Mustard on Concrete: GC/MSD and SSMAS

“…These results were in contrast to-the results in soil, in which the peaks remained narrow throughout the reaction. 3 Thus, the peak widths observed in this work were 200 Hz wide, compared to the 20 to 50 Hz peak widths that were typically seen for non-adsorbed liquid droplets in the SSMAS experiment.…”

“…The concrete samples were stored in 20-mL glass vials that were sealed with GC septum caps. After a specified exposure time at 21 'C the samples were crushed in the vial using pliers, and extracted once with 2-mL CDCI 3 . The extracts were analyzed using GC/MSD and liquids 'H NMR.…”