Nerve agents environmental degradation

Environment. Detection of environmental degradation products of nerve agents directly from the surface of plant leaves using static secondary ion mass spectrometry (sims) has been demonstrated (97). Pinacolylmethylphosphonic acid (PMPA), isopropylmethylphosphonic acid (IMPA), and ethylmethylphosphonic acid (EMPA) were spiked from aqueous samples onto philodendron leaves prior to analysis by static sims. The minimum detection limits on philodendron leaves were estimated to be between 40 and 0.4 ng/mm for PMPA and IMPA and between 40 and 4 ng/mm for EMPA. Sims analyses of IMPA adsorbed on 10 different crop leaves were also performed in order to investigate general apphcabiflty of static sims for... 

Environment. Detection of environmental degradation products of nerve agents directly from the surface of plantleaves using static secondary ion mass spectrometry (sims) has been demonstrated. 

Once chemical agents are fully dispersed, they do not tend to persist in the environment because of their high chemical reactivity, particularly with water (hydrolysis). However, in extremely dry desert climates, they can persist for considerable periods of time (U.S. Army, 1988). The major environmental degradation products of nerve and mustard agents have recently been assessed and their persistence and toxicity evaluated. A potential hydrolysis product of VX (S-(2-diisopropylaminoethyl) methylphosphonothioic acid [EA-2192]) is a degradation product expected to display a high level of mammalian toxicity. Some mustard partial hydrolysis products are also toxic (Munro et al., 1999). 

All of the parent nerve agents are highly toxic to aquatic organisms (Munro et al, 1999). Acute ecotoxicity information was found only for the degradation product, MPA. The 48- to 96-h LC50 values of several thousand mg/1 for daphnids and fish indicates that MPA has low environmental toxicity. 

Under environmental conditions, CWAs (vesicant agents, sulfur mustard (H, HD and HT) and lewisite (L) nerve agents, GA, GB, GD and VX) can undergo multiple-degradation processes such as hydrolysis, oxidation, dehydration and photolysis. These baseline degradation reactions can vary in rate and completeness, depending upon reaction temperature and pH, as well as the presence of free radicals and catalysts. Knowledge of these baseline reaction parameters has formed the basis for many modern decontamination procedures. 

T.E. Rosso and PC. Bossle, Capillary ion electrophoresis screening of nerve agent degradation products in environmental samples using conductivity detection, J. Chromatogr. A, 814,125-134, 1998. 

Environmental Fate. The primary degradation mechanism for nerve agents in the environment is hydrolysis to the corresponding alkyl methylphosphonate, followed, for most of the agents, by slow hydrolysis to methyl phosphonic acid. The alkyl methylphosphonates may persist for years in the environment. Degradation or decomposition in soil may be faster than in water as a result of the variety of available processes and catalysts. 

Technical experts generally agree that sea-dumped CW should be left undisturbed, because any attempt to move them could result in an explosion or other rupture of the munitions, thereby spilling the contents into the environment. Organophosphorus nerve agents hydrolyze readily in sea water into essentially benign degradation products of low toxicity. The primary environmental and human health threats are posed... 

Determination of nerve agents and their degradation products in various environmental samples, such as aqueous, snow and soil, and even common office media samples, were performed using LC-ESI and p-LC-ESI with MS, MS/MS or a time-of-flight MS [80-83]. Micro-LC procedures enhance the sensitivity needed for LC-MS instrumentation. Even with ESI-MS, LC-MS methods still have issues obtaining sensitivities comparable to those for GC-MS. MS/MS interfaced with LC-ESI does enhance sensitivity, providing increased... 

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