1,721,034 research outputs found
Brown carbon and thermal-optical analysis: A correction based onoptical multi-wavelength apportionment of atmospheric aerosols
No full textThermo-optical analysis is widely adopted for the quantitative determination of total, TC, organic, OC and
elemental, EC, Carbon in aerosol samples collected on quartz fibre filters. Nevertheless, the methodology
presents several issues in particular about the artefacts related to the formation of pyrolytic carbon. It is
usually neglected the uncertainty due to the possible presence of brown carbon (BrC) in the sample
under analysis, i.e. the optically active fraction of OC produced by biomass burning and with characteristics
intermediate between OC and EC. We introduce here a novel correction to the standard thermooptical
protocol based on the determination of the fraction of the sample absorbance due to the
(possible) presence of BrC. This is achievable thanks to the coupled use of the Multi Wavelength
Absorbance Analyser (MWAA) of the University of Genoa and a standard Sunset Inc. EC/OC analyser. Our
correction provides a firmer OC/EC separation as well as an operative quantification of the BrC mass. The
methodology has been validated against independent determination of the levoglucosan content in the
same filters sent to the Sunset analysis. Corrections up to 23% in the OC and EC values, determined via the
standard and new thermo-optical analysis, have been found in a set of PM10 (i.e. Particulate Matter with
aerodynamic diameter less than 10 mm) samples collected wintertime at a mountain site in Northern
Italy
PMF5.0 vs. CMB8.2: An inter-comparison study based on the new European SPECIEUROPE database
No full textReceptor Models are tools widely adopted in source apportionment studies. We describe here an experiment in
which we integrated two different approaches, i.e. Positive Matrix Factorization (PMF) and Chemical Mass
Balance (CMB) to apportion a set of PM10 (i.e. Particulate Matter with aerodynamic diameter lower than 10 μm)
concentration values. The study was performed in the city of Genoa (Italy): a sampling campaign was carried out
collecting daily PM10 samples for about two months in an urban background site. PM10 was collected on Quartz
fiber filters by a low-volume sampler. A quite complete speciation of PM samples was obtained via Energy
Dispersive-X Ray Fluorescence (ED-XRF, for elements), Ionic Chromatography (IC, for major ions and levoglucosan),
thermo-optical Analysis (TOT, for organic and elemental carbon). The chemical analyses provided the
input database for source apportionment by both PMF and CMB. Source profiles were directly calculated from
the input data by PMF while in the CMB runs they were first calculated by averaging the profiles of similar
sources collected in the European database SPECIEUROPE. Differences between the two receptor models
emerged in particular with PM10 sources linked to very local processes. For this reason, PMF source profiles
were adopted in refined CMB runs thus testing a new hybrid approach. Finally, PMF and the “tuned” CMB
showed a better agreement even if some discrepancies could not completely been resolved. In this work, we
compared the results coming from the last available PMF and CMB versions applied on a set of PM10 samples.
Input profiles used in CMB analysis were obtained by averaging the profiles of the new European SPECIEUROPE
database. The main differences between PMF and CMB results were linked to very local processes: we obtained
the best solution by integrating the two different approaches with the implementation of some output PMF
profiles to CMB runs
Developing air quality forecast and evaluation in the city of Genoa and in the Liguria Region (Italy)
No full textEvaluation of the impact of harbour activities on airquality in the urban area of Genoa (Italy)
No full textInfluence of relative humidity and aging on the optical properties of organic aerosols from burning African biomass fuels
No full textBiomass burning (BB) is a major source of atmospheric fine carbonaceous aerosols, which play a significant, yet uncertain, role in modulating the Earth’s radiation balance. However, accurately representing their optical properties in climate models remains challenging due to factors such as particle size, mixing state, combustion type, chemical composition, aging processes, and relative humidity (RH). In our study, we investigated BB organic-rich aerosols generated from smoldering sub-Saharan African biomass fuels. Fuel samples were collected in Africa and aerosols generated in the laboratory. We quantified key optical parameters, including mass cross-sections for extinction (2.04 ±0.32− 15.5 ±2.48 m2/g), absorption (0.04 ±0.01–0.3 ±0.1 m2/g), and scattering (1.9 ±0.68–15.3 ±5.5 m2/g). Wavelength-dependent properties were used to determine absorption and scattering Ångstro€m exponents. The single scattering albedo of these aerosols ranged from 0.8 ±0.03 to 1.0 ±0.04 and we observed a wavelength-dependent behavior. Extinction emission factors were determined at a wavelength of 550 nm, with values ranging from 42 ±5 to 293 ±32 m2 /kg. Notably, optical properties exhibited fuel-type dependence, with differences observed between hardwood samples and other fuels, such as grass and animal dung. Aging increased mass extinction and scattering cross-sections at 550 nm,while humidity had the opposite effect across all fuels. Nitrate radical oxidation, both in photo and dark aging conditions, also influenced these properties. The findings are expected to close the gap in our understanding of optical properties of BB aerosol emissions in one of the least studied regions of the world – Africa – providing information to climate and air quality models for the region
A synergic approach for PM2.5 source apportionment through receptor modelling and chemical transport model simulations
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Carbonate measurements in PM10 near the marble quarries of Carrara (Italy) by infrared spectroscopy (FT-IR) and source apportionment by Positive Matrix Factorization (PMF)
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