Fate of Nerve Agent Simulants on Concrete

The nerve agent VX (O-ethyl S-[2-(diisopropylamino)ethyl]methylphosphonothiolate) has been shown to decompose in contact with concrete surfaces. We have previously shown that 31P NMR can be employed to study 1) the adsorption of VX into concrete; 2) the decomposition kinetics; and 3) detect decomposition products. Recently reported results show a dramatic effect of the VX decomposition kinetics on droplet size, with 0.01 μL droplets reacting within a few hours in contrast to months observed for VX drop sizes on the order of several μL. The objective of this paper is to probe the effects of temperature, moisture, concrete source and droplet size on the rate of hydrolysis. In the present study, 31P NMR showed that the hydrolysis of nerve agent simulant DMMP (dimethyl methylphosphonate) on concrete increased with increasing temperature, amount of water added, and pH of the concrete used. No effect on hydrolysis rate as a function of droplet size in the 0.05 to 2.0 μL range was detected.