The use of diffusive sampling for monitoring of benzene, toluene and xylene in ambient air (technical report)

A diffusive sampler, originally developed for workplace monitoring of organic vapours has been evaluated for its potential for monitoring ambient air quality, particularly for benzene, toluene and xylene. The diffusive sampling rate, which is different for workplace and ambient air applications because of the wide differences in concentration levels and times of exposure, has been determined accurately, and been shown to be similar to other independent estimates determined from field studies or by exposing samplers to standard test atmospheres. In each cast, the actual mass concentration of the aromatic hydrocarbons in ambient air or test atmosphere has been established by an independent calibrated method, usually using pumped sampling and the diffusive sampling rates of parallel diffusive samplers determined from these concentrations. The potential for using such samplers for monitoring ambient air has been demonstrated in two local studies, at car parks and in a street canyon, and in three area studies, at urban (Sheffield), regional (UK) and global (world) levels. In addition, the diffusive sampler has been evaluated alongside the UK VOCair measuring instruments in the UK fixed monitoring stations, where in view of the uncertainties involved, similar results were obtained. These studies also gave useful insight into the practicability of employing these devices, their use by untrained personnel and their ruggedness in transportation and use.