VX Fate on Common Matrices: Evaporation versus Degradation

Abstract

A study of the volatilization rate of the nerve agent VX (O-ethyl S-2-(N,N-diisopropylamino)ethyl methylphosphonothiolate) from various urban matrices in a specially designed climatic chamber (model system) is described. The performance of the model system combined with the analytical procedure produced profiles of vapor concentration obtained from samples of VX dispersed as small droplets on the surfaces of the matrices. The results indicated that the bitumencontaining surfaces such as asphalt blocks and bitumen sheets conserve VX and slow-release part of it over a long period of time. No complete mass balance could be obtained for these surfaces. Influence of environmental and experimental parameters as well as the efficacy of decontamination procedure were also measured. From smooth surface tiles a fast release of VX was measured and almost a complete mass balance was obtained, which characterizes the behavior of inert surfaces. Experiments carried out on concrete blocks showed fast decay of the concentration profile along with a very poor reconstruction of the initial quantity of VX, implying that this matrix degraded VX actively due to its multiple basic catalytic sites. To complement this study, solid-state NMR measurements were compared to add data concerning agent-fate within the matrices.

Evaporation of the Nerve Agent GB From Common Matrices: A Model‐System Study

“…From the second day, lower GB air concentrations were measured at the higher temperature, probably due to enhanced adsorption or degradation processes at this temperature. The conserving character of the asphalt surface was demonstrated in VX evaporation experiments . The organic bitumen phase dissolves organic materials such as GB or VX and releases them gradually to air.…”

“…The evaporation data in all experiments was presented in the graphs as ln[GB] (ng L −1 ) versus time. The data was fitted to a bi‐exponential curve which gave appropriate results according to previous studies . Detailed results of all experiments (concentrations and mass balances) are summarized in the Supporting Information.…”

“…In recent years some data was published on the desorption characteristics of the persistent CWAs O ‐ethyl S ‐2‐( N , N ‐diisopropylamino)ethyl methylphosphonothiolate) (VX) and sulfur mustard (HD) from numerous surfaces using laboratory‐sized wind tunnel devices. The results showed that bitumen‐containing surfaces, such as asphalt blocks, conserve VX and slowly release it over a long period of weeks to months . On the other hand, the concentration profile for concrete blocks showed a fast decay along with a very low restoration of VX.…”

“…On the other hand, the concentration profile for concrete blocks showed a fast decay along with a very low restoration of VX. This may be a result of VX degradation by chemical active basic sites incorporated in this surface . Smooth tiles exhibited the characteristic behavior of inert surfaces, as they released VX quickly, while obtaining almost complete mass balance.…”

“…In addition, this information can support the choice of the decontamination technology for a specific scenario. In recent years some data was published on the desorption characteristics of the persistent CWAs O-ethyl S-2-(N,N-diisopropylamino)ethyl methylphosphonothiolate) (VX) [2][3][4] and sulfur mustard (HD) [5][6][7][8][9] from numerous surfaces using laboratory-sized wind tunnel devices. The results showed that bitumencontaining surfaces, such as asphalt blocks, conserve VX and slowly release it over a long period of weeks to months.…”