Estimating temporal and spatial levels of PAHs in air using rain samples and SPME analysis: Feasibility evaluation in an urban scenario.

There is a growing interest in evaluating the role of concentration changes of contaminants in temporal and spatial gradients. This is often relevant for fast moving environmental phases such as air and water. In this paper, small volumes of rainwater were sampled as proxy for air concentrations of Polycyclic Aromatic Hydrocarbons (PAHs): rain was collected in three sampling sites (high traffic, restricted traffic and a low traffic zone) in Como. Solid phase micro extraction (SPME) was used for the extraction to reduce required sample volumes, allowing the acquisition of more samples in time. Rain samples highlighted a spatial and temporal variability along a traffic gradient in the Como city, especially for the most abundant PAH, e.g. phenanthrene. Air concentrations were then estimated from rain concentrations. The results show that this is a cheap and promising method, although requiring rainfall/snowfall conditions, that can be used to perform monitoring campaign of air concentrations at a higher temporal and spatial resolution than the adopted standard methods (e.g. high-volume air samplers). The results could be employed for evaluation of the exposure, emission profiles and calibration of fate models.