Polycyclic aromatic hydrocarbons in soil and plant samples from the vicinity of an oil refinery

Soil samples, and samples of leaves of Plantago major (great plantain) and grass (mixed species) were collected from the vicinity of an oil refinery i n Zelzate, Belgium, and analysed for seven polycyclic aromatic hydrocarbons (PAHs). The samples from the site adjacent to the refinery (site 1) contai ned very high total PAM-concentrations: namely 300, 8 and 2 mug/g dry wt, f or soil, P. major and grass, respectively. Concentrations in samples from m ore remote sites (up to 4 km from the refinery) were a factor of 10-30 lowe r than those from site 1, but between them the differences were small. The PAM-profiles of the plant samples, in contrast with those of the soil sampl es, appeared to shift to higher contributions of gaseous PAHs with increasi ng distance from the refinery. This can be explained by particle-bound PAHs being deposited closer to the source than gaseous PAHs. It is suggested th at particle-bound deposition is relatively more important for deposition to soil than to plants, due to blow-off and wash-off of the compounds from th e leaves. The total PAM-concentrations in the leaves of P. major were highe r than those measured in the grass samples, probably due to differences in aerodynamic surface roughness, leaf orientation and/or leaf age. However, t he concentration ratios of P. major/grass were not constant for the differe nt sites, varying from 1.2 to 8.8. Therefore, it appears that a precise pre diction of PAM-concentrations for one plant species from known concentratio ns of another species is not possible. When errors in predicted concentrati ons need to be smaller than a factor of approximately 10, the sampling stra tegy has to be focussed on all species of interest. (C) 2000 Elsevier Scien ce B.V. All rights reserved.