The evaporation and degradation of VX (O-ethyl S-[2-N,N-(diisopropylamino)ethyl] methylphosphonothioate) on silica sand and borosilicate glass were measured using vapor analysis and 31 P solid state magic angle spinning nuclear magnetic resonance (SSMAS NMR) spectroscopy. 31 P SSMAS NMR studies of VX degradation on crushed glass, air-dried sand, and oven-dried sand at a variety of temperatures showed that the final product was nontoxic ethyl methylphosphonic acid (EMPA), produced via the toxic diethyl dimethylpyrophosphonate intermediate. The reaction exhibited a lag time that depended upon the quantity of water and EMPA that were present in the initial sample of VX and was autocatalytic; EMPA was both the catalyst and product for the degradation of VX. 31 P SSMAS NMR studies of VX on moist sand at a variety of temperatures showed that the final product was nontoxic EMPA; observed intermediates were protonated VX, O-ethyl methylphosphonothioic acid, and toxic EA-2192 (S-[2-N,N-(diisopropylamino)ethyl methylphosphonothioic acid). The VX degradation mechanism differed on the moist and dry surfaces; the activation energies were 80 kJ/mol on moist sand and ∼46 kJ/mol on glass, air-dried, and oven-dried sand. The VX degradation rate was 5 to 9 times slower on moist sand than on air-dried sand. Analysis of the vapor emitted showed that the maximum vapor concentration coincided with the maximum surface area of the droplets, which was at ∼300 min. After four days, no further change in the concentration of vapor emitted was detected; approximately 9% of the incident VX drop on sand and ∼60% of the incident VX drop on glass had been recovered as VX vapor.

Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense. Washington Headquarters Services. Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway, Suite 1204. Arlington, VA 22202-4302. Respondents should be aware that notwithstanding any other provision of law. no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number. PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS. REPORT DATE (DD-MM-YYYY) XX-07-2008 REPORT TYPE PERFORMING ORGANIZATION NAME(S) AND ADDRESS(ES) SAIC, P.O. Box 68, Gunpowder, MD 21010-0068 DIR, ECBC, ATTN: RDCB-DRC-M, APG, MD 21010-5424 PERFORMING ORGANIZATION REPORT NUMBER ECBC-TR-699 SPONSORING / MONITORING AGENCY NAME(S) AND ADDRESS(ES)Defense Threat Reduction Agency, 8725 John J Kingman Road., Fort Belvoir, VA 22060-6201 SPONSOR/MONITOR'S ACRONYM(S) DTRA SPONSOR/MONITOR'S REPORT NUMBER(S) DISTRIBUTION / AVAILABILITY STATEMENTApproved for public release; distribution is unlimited. SUPPLEMENTARY NOTES ABSTRACTThe evaporation of sulfur mustard from sand was studied as a function of temperature, drop size and air flow rate, using the same instrumentation as prior studies on glass. The evaporation rate increased with higher temperature, drop size, and wind speed; and an empirical equation was determined that would allow for the calculation of the evaporation rate given the environmental conditions. SUBJECT TERMS

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Public reporting burden for this collection of information is estimated to average 1 hour per response, including the time for reviewing instructions, searching existing data sources, gathering and maintaining the data needed, and completing and reviewing this collection of information. Send comments regarding this burden estimate or any other aspect of this collection of information, including suggestions for reducing this burden to Department of Defense. Washington Headquarters Services. Directorate for Information Operations and Reports (0704-0188), 1215 Jefferson Davis Highway. Suite 1204. Arlington. VA 22202-4302 Respondents should be aware that notwithstanding any other provision of law, no person shall be subject to any penalty for failing to comply with a collection of information if it does not display a currently valid OMB control number PLEASE DO NOT RETURN YOUR FORM TO THE ABOVE ADDRESS, REPORT DATE (DD-MM-YYYY)