A PIXE and ICP-MS Analysis of Metallic Atmospheric Contaminants in Tree Bark Tissues, A Basis for Biomonitoring Uses∗

The qualitative and quantitative metallic content of tree barks of Argania spinosa (L.) Skeels were studied. Argania spinosa is an endemic species in Morocco. This tree is adapted to semi-arid climates and exposed to specific conditions of relative humidity, temperature, wind, and particle transport. Three sites were sampled in Morocco: the large town of Rabat, the harbor of Agadir, and Ait Baha, a countryside location exposed to continuous desert wind. The methodologies included (1) in situ microanalysis with proton-induced X-ray emission (PIXE) and (2) trace element determinations by mass spectrometry with inductively coupled plasma (ICP-MS) associated with extraction procedures. Both methods allowed detection of elements coming from different bark compartments. The profile of airborne contaminants in the barks was typical of the sampling sites. The level of lead in barks sampled in Rabat reached 100 ng cm−2, or higher, while it varied between 3 and 35 ng cm−2 in Ait Baha. The in situ study of the micro...