C. Grassi1

L. Dallai

M. Guidi

S. Nottoli

TOGNOTTI, LEONARDO

V. Campigli

English

Archivio della Ricerca - Università di Pisa

  PM Characterization by Carbon Isotope  C. Grassi1, V. Campigli3, L. Dallai2, S. Nottoli2, L. Tognotti3, M. Guidi2  1 Department of Mechanical, Nuclear and Production Engineering, University of Pisa, 56126 Pisa (Italy) 2 Geoscience and Georesources Institute, IGG-CNR of Pisa, Via G. Moruzzi 1, Pisa-I 56124. 3 Department of Chemical Engineering, University of Pisa, 56126 Pisa (Italy)  Keywords: Carbonaceous Particles, Chemical Composition, Measurement, Urban Aerosol, Source Identification.    Isotopic characterization of PM can play an important role in the individuation of primary and secondary sources and also in the determination of the natural/biogenic or anthropogenic/combustion contribution to the measured concentration. As the matter of fact, a methodology to analyze the stable isotope of the carbonaceous fraction of PM10 has been developed.  The PM10 samples were collected during the PaTOS monitoring campaign Autumn 2005 – Spring 2006 in six sites located on the regional Tuscany territory: Arezzo Urban/Traffic (AR-UT), Lucca Urban/Background (LU-UB), Livorno Suburban /Background (LI-SB), Prato Urban/Traffic (PO-UT), Firenze Urban/Background (FI-UB) and Grosseto Urban/ Background (GR-UB). A Low Volume Sampler (LVS), Tecora TCR, was used with sampling head USEPA-cfr part.50 to collect 24 hr daily aerosols samples on QUARTZ fibre filters.  The PM organic matter on the quartz fibre filters is converted into a combustion apparatus, Thermo Finnigan, Elemental Analyser-EA1108 , into CO2. A mixed flow rate of helium and oxygen was used as carrier gas in the apparatus to send the CO2 trough the spectrometer, Thermo Finnigan-Delta Plus XP, for the determination of the isotope abundance. The hardware and software connected to the spectrometer allow to determine δ13C(‰) in relation to the PDB reference standard (“Pee Dee Belemite” CaCO3), applying the δ13C/δ12C ratio equation.  The PM10 concentrations, calculated as daily averaged values, show a significant variability from the urban to suburban sites varying from 50 µg/m3 (AR-UT) to 20 µg/m3 (LI-SB) as averaged concentration on the sampling period and from autumn 60 µg/m3 (LU-UB) and spring 25 µg/m3 (LU-UB) periods. Also the PM carbon content, on period average values, shows very different results from site to sites with a minimum in GR-UB of 20% up to the 60% of LU-UB.  In figure 1 the average values of the carbon content, expressed as weight percentage of the PM, versus the δ13C parameter were shown for each monitoring sites together with the two parameters variability. The analytical results in terms of δ13C’s values are comprised from – 28 and -23 and show significant variation from the traffic and background sites; in fact, in the background and suburban sites (LI-SB, FI-UB and GR-UB) the δ13C’s show a bigger variability than in the urban sites AR-UT, PO-UT, LU-UB, LI-UB were the results don’t vary significantly, and this could be well correlated with the constant emissions from traffic. On the contrary the background sites both urban or rural, depending on the meteorology and atmospheric processes, show a wider variability in the δ13C values relating to the changing in the contribution from the natural, secondary and anthropogenic source emissions.  -28-27-26-25-24-23-220 10 20 30 40 50 60 70 80 90 100PM CARBON CONTENT [wt%]d13C(‰)LU-UB-OctoberLU-UB-MarchAR-UT -NovemberLI-SB-JanuaryLI-SB-MarchPO-UT-MarchFI-UB-AprilFI-UB-MayGR-UB-July   Figure 1. δ13C [o/oo] versus PM carbon content [wt%] for the monitoring sites, Tuscany.  The lower negativities of the δ13C values of the PO-UT compared to the AR-UT could be explained by the presence of industrial source that are negligible in the AR-UT and that concurred as lower negative δ13C values [Widory et al., 2004]. The δ13C values confirm the indication determined for the identification of the emissions from non stationary combustion sources as traffic vehicles and the differences shown between urban and rural sites [Haung et al., 2006].  Huang L., J.R. Brook, W. Zhang, S.M. Li, L. Graham, D. Ernst, A. Chivulescu, G. Lu. Atmospheric Environment 40 (2006) 2690–2705. Widory David, Stephane Roy, Yvon Le Moullec, Ghislaine Goupil, Alain Cocherie, Catherine Guerrot, Atmospheric Environment 38 (2004) 953–961. Cite abstract as Author(s) (2007), Title, European Aerosol Conference 2007, Salzburg, Abstract T15A011

PM Characterization by Carbon Isotope

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PM Characterization by Carbon Isotope

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