title: Degradation kinetics of VX on concrete by secondary ion mass spectrometry.
abstract: At trace coverages on concrete surfaces, the nerve agent VX (O-ethyl S-2-diisopropylaminoethyl methyl phosphonothiolate) degrades by cleavage of the P-S and S-C bonds, as revealed by periodic secondary ion mass spectrometry (SIMS). The observed kinetics were (pseudo-) first-order, with a half-life of 2-3 h at room temperature. The rate increased with surface pH and temperature, with an apparent second-order constant of k(OH) = 0.64 M(-1) min(-1) at 25 degrees C and an activation energy of 50-60 kJ mol(-1). These values are consistent with a degradation mechanism of alkaline hydrolysis within the adventitious water film on the concrete surface. Degradation of bulk VX on concrete would proceed more slowly.
authors.affiliation: Battelle Salt Lake City Operations, West Valley City, UT 84120, USA.
authors.forename: John M
authors.initials: JM
authors.lastname: Williams
authors.forename: Brad
authors.initials: B
authors.lastname: Rowland
authors.forename: Mark T
authors.initials: MT
authors.lastname: Jeffery
authors.forename: Gary S
authors.initials: GS
authors.lastname: Groenewold
authors.forename: Anthony D
authors.initials: AD
authors.lastname: Appelhans
authors.forename: Garold L
authors.initials: GL
authors.lastname: Gresham
authors.forename: John E
authors.initials: JE
authors.lastname: Olson