engleski

Physical and chemical characterisation of airborne particulates in the port city of Rijeka, Croatia

Based on the previous results on impact of maritime traffic to urban air quality in Rijeka, this paper is devoted to further characterization of physical and chemical properties of the 11 fractions of airborne particulates collected with 10-stage cascade impactor with nominal cut-off sizes of: 10, 5.6, 3.2, 1.8, 1.0, 0.56, 0.32, 0.18, 0.10 and 0.056 μm. Two sampling campaigns were undertaken: autumn (26.10. -10.12.2018.) and spring (26.03.-21.05.2019.) Eight 7-day samples were collected in each campaign. The overall average mass /concentration varied between 9.8 and 37.4 μg/m3, except for the first week of monitoring when the average was 157.2 μg/m3. Distribution of airborne fractions shows a bimodal curve, with two maxima: S4 (particle diameter range d =1.8-3.2 μm) and S8 (d=0.18-0.32 μm) fractions. Size distribution of particulates' mass concentrations differs for the first week: except secondary peak at S4, there is a primary one at S6 (d= 0.56-1.00 μm ) and tertiary at S10 (d= 0.56 –1.00 μm). Three peak mass distribution is characteristic for the desert dust. Sample with Saharan sand shows higher content of nanoparticles (d<0.1um), although the highest contribution of nanoparticles derived from domestic heating started at mid-November. Chemical analyses showed that multiple higher mass/concentrations of secondary inorganic aerosols (SIA) sulphate and ammonium were found in the fine fractions S6.-S9 ( d= 0.10-0.56 μm) of the sample with Saharan sand, thus indicating atmospheric gas chemistry as their sources. The same is valid for the water soluble organic compounds (WSOC), as a proxy of secondary organic aerosols (SOA) in the same fine fractions. Unlike sulphate and ammonium, maximum of nitrate is found in the coarse fraction S4-S6 ( d= 0.56-3.2 μm) suggesting a well known intrusion of HNO3 in marine aerosols.

Rijeka ; maritime traffic ; airborne particulates ; nonoparticles

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