Evaporation of sulphur mustard (HD) from common matrices with comparison to nerve agents

Abstract

ABSTRACT The use of chemical warfare agents (CWAs) in terrorist attacks remains a potential threat. Therefore, an updated wide-ranging database that contains details on the fate of CWAs on environmental surfaces is required, especially for the persistent blister agent sulphur mustard (HD). For this purpose, long-period evaporation rates measurements of HD from various common urban matrices were conducted from our specialised laboratory-designed wind tunnel. Small HD droplets were dispersed on each matrix surface, and then placed in the evaporation chamber. Samples of the target material were collected by continuous sampling on SPE (solid-phase extraction) tubes and analysed by GC (gas-chromatography) analytical method. Profiles of the air vapour concentrations as a function of time (up to four orders of magnitude) and the total mass balances were calculated at two temperatures. The results indicated fast clearance of HD together with a nearly full mass balance from stainless steel and smooth surface tiles, as these matrices are relatively inert. On the other hand, asphalt blocks relatively conserve HD, exhibiting a slow-release mode of action over 7–11 days until matching the GPL (General Population Limit) for HD. The concentration profile of commercial sidewalk bricks showed a moderate decay that characterises a semi-conserving matrix. These findings were compared to the evaporation profiles of the nerve agents sarin (GB) and VX from the same surfaces at the same experimental conditions. We can conclude that HD contamination can cause a secondary risk by a slow release into the atmosphere, especially from surfaces exhibiting conserving characteristics.