‘Time capsule’ mustard plants could help detect use of chemical weapons

Chemical weapons could be detected in contaminated white mustard plants up to 45 days after use a paper published in Proceedings of the Royal Society A has found.

The Chemical Weapons Convention prohibits the use of chemical weapons by its 190 member states. Making sure members comply with the convention requires that scientists can accurately detect the use of chemical warfare agents. Currently they carry out tests on soil from areas where use is suspected. However, many nerve agents composed of organophosphorus compounds leach from soil over time removing the evidence of use and making verifying the deployment of chemical weapons like sarin, soman and VX difficult.

Today a collaborative team of scientists from the University of Central Lancashire and the Defence Science and Technology Laboratory present a method to detect chemical weapon use by analysing the compounds present in white mustard plants. The plants, which grow wildly across the world, are pollutant tolerant and can absorb nerve agent chemicals through their roots. The plants retain compounds from the agents for longer than soil can and act as a sort of ‘time capsule’ protecting the evidence of chemical weapon use for at least 45 days.

The team of researchers grew white mustard plants in three different types of soil spiked with VX to see if the type of soil affected how long the plants retained traces of compounds from chemical weapon use. After 8 days, plants grown in sandy soil had absorbed more VX than those grown in loam or clay soils, however, by 16, 33, and 45 days after the seeds were sown, the amount of VX in the plants from the different soils had converged. The team say this shows that regardless of soil type  ‘evidence for the prior presence of VX in soil can be downloaded from the plant at least 45 days after application’.

As well as being useful for detecting chemical weapons use the team say their results show that the plants could also be used in the future as a sort of ‘green manure’ absorbing chemicals from soil in polluted sites.  The team even found some evidence that the plants may be able metabolise nerve agents, breaking them down into their less harmful degradation products and helping to reduce the  ‘toxic environmental legacy’ of chemical weapons from areas where they have been deployed.