Evidence for the adsorption of nitrated polycyclic aromatic hydrocarbons by tree bark

It has been previously demonstrated that polycyclic aromatic hydrocarbons (PAH) are adsorbed onto tree bark and that bark may in fact be used as a passive sampler for these compounds. It is now demonstrated that by suitable modification of this methodology nitrated polycyclic aromatic hydrocarbons (nitro-PAH) may also be detected in bark. Bark samples were taken from urban locations in Sheffield, South Yorkshire, UK. After soxhlet extraction using dichloromethane, the nitro-PAH fraction was isolated by solid-phase extraction using amino and alumina cartridges in series. Nitro-PAH were detected by gas chromatography with electron capture detection and gas chromatography-mass spectrometry in the negative chemical ionisation mode. A comparison is made with nitro-PAH found in diesel particulate extracts. (C) 1997 Elsevier Science B.V.