THE CONTRIBUTION OF GAS-PHASE REACTIONS TO THE NITROARENE FRACTION OFMOLECULAR-WEIGHT 247 PRESENT IN CARBON PARTICLES SAMPLED IN AN URBAN AREA OF NORTHERN ITALY

The formation of 2-nitrofluoranthene and 2-nitropyrene by gas-phase at mospheric reactions has been investigated by analysing the nitroarene fraction with molecular weight 247 extracted from 34 high-volume sampl es collected during two different monitoring campaigns held in the cen tre of Milan. 2-Nitrofluoranthene, 2-nitropyrene and 1-nitropyrene wer e the only nitroarenes detected. The ratios 2-nitrofluoranthene/1-nitr opyrene and 2-nitrofluoranthene/2-nitropyrene combined with the day/ni ght variations of various photochemical indicators have been used to a ssess the relative contribution of different reactions leading to the formation of 2-nitroarenes with MW 247 in carbon particles. Daytime OH radical-initiated reactions were found to be mainly responsible for t heir formation but evidence was collected of nighttime formation.