Mass closure on the chemical species in size-segregated atmospheric aerosol collected in an urban area of the Po Valley, Italy
A complete size segregated chemical characterisation was carried out\nfor aerosol samples collected in the urban area of Bologna over a\nperiod of one year, using five-stage low pressure Berner impactors.\nAn original dual-substrate technique was adopted to obtain samples\nsuitable for a complete chemical characterisation. Total mass, inorganic,\nand organic components were analysed as a function of size, and a\ndetailed characterisation of the water soluble organic compounds\nwas also performed by means of a previously developed methodology,\nbased on HPLC separation of organic compounds according to their\nacid character and functional group analysis by Proton Nuclear Magnetic\nResonance. Chemical mass closure of the collected samples was reached\nto within a few percent on average in the submicron aerosol range,\nwhile a higher unknown fraction in the coarse aerosol range was attributed\nto soil-derived species not analysed in this experiment. Comparison\nof the functional group analysis results with model results simulating\nwater soluble organic compound production by gas-to-particle conversion\nof anthropogenic VOCs showed that this pathway provides a minor contribution\nto the organic composition of the aerosol samples in the urban area\nof Bologna.