Mass size distribution of particle-bound water

• Published in: Atmospheric environment (1994) 2017-09, Vol.165, p.46-56
• Main Authors: Canepari, S., Simonetti, G., Perrino, C.
• Format: Article
• Language: English
• Subjects: Atmospheric stability; Desert dust; Karl Fisher analysis; Particulate matter; Urban dust
• ISSN: 1352-2310; 1873-2844
• DOI: 10.1016/j.atmosenv.2017.06.034

The thermal-ramp Karl-Fisher method (tr-KF) for the determination of PM-bound water has been applied to size-segregated PM samples collected in areas subjected to different environmental conditions (protracted atmospheric stability, desert dust intrusion, urban atmosphere). This method, based on the use of a thermal ramp for the desorption of water from PM samples and the subsequent analysis by the coulometric KF technique, had been previously shown to differentiate water contributes retained with different strength and associated to different chemical components in the atmospheric aerosol. The application of the method to size-segregated samples has revealed that water showed a typical mass size distribution in each one of the three environmental situations that were taken into consideration. A very similar size distribution was shown by the chemical PM components that prevailed during each event: ammonium nitrate in the case of atmospheric stability, crustal species in the case of desert dust, road-dust components in the case of urban sites. The shape of the tr-KF curve varied according to the size of the collected particles. Considering the size ranges that better characterize the event (fine fraction for atmospheric stability, coarse fraction for dust intrusion, bi-modal distribution for urban dust), this shape is coherent with the typical tr-KF shape shown by water bound to the chemical species that predominate in the same PM size range (ammonium nitrate, crustal species, secondary/combustion species - road dust components). [Display omitted] •Mass size-distribution of PM-bound water was determined by coulometric KF technique.•The shape of the KF curve in each size range depends on PM chemical composition.•High water amounts were found in the fine size range of PM during stability events.•High water amounts were found in the coarse size range during desert dust events.•Water was bound to the chemical species typical of the event: NH4NO3, crustal species.