Determination of PAH in airborne particulate: comparison between off-line sampling techniques and an automatic analyser based on a photoelectric aerosol sensor.

The automatic analyser is based on a photoelectric aerosol sensor, with continuous sampling and an on-line detection system. Traditional sampling monitoring systems consist of collecting airborne particulate on filters; the sample is then extracted, purified and analysed. It is possible to identify each compound and to determine its relative abundance in the total particulate matter, on the other hand, this method requires great complexity of analysis. Continuous monitoring systems allow getting quicker results to compare with threshold levels. It is also possible to obtain an easier correlation with factors such as traffic flows or meteorological conditions. However, such systems cannot quantify single compounds, and data are expressed as total PAH. The comparison between the results shows a satisfactory linearity between the data obtained with the two methods. The difference of about one order of magnitude between the data obtained with photoelectric aerosol sensor (PAS) system and the sum of the concentrations of selected PAHs determined with off-line methods can be explained with the different selectivity of the two methods employed. This work has been developed in Aosta, the administrative centre of the Aosta Valley district.