In this paper, a new way to apportion the absorption coefficient (babs) of carbonaceous atmospheric aerosols starting from a multi-wavelength optical analysis is shown. This methodology can ...disentangle and quantify the contribution to total absorption of equivalent black carbon (EBC) emitted by wood burning (EBCWB) and fossil fuel (EBCFF) as well as brown carbon (BrC) due to incomplete combustion. The method uses the information gathered at five different wavelengths in a renewed and upgraded version of the approach usually referred to as Aethalometer model. Moreover, we present the results of an apportionment study of carbonaceous aerosol sources performed in a rural area and in a coastal city, both located in the North-West of Italy. Results obtained by the proposed approach are validated against independent measurements of levoglucosan and radiocarbon. At the rural site the EBCWB and EBCFF relative contributions are about 40% and 60% in winter and 15% and 85% in summer, respectively. At the coastal urban site, EBCWB and EBCFF are about 15% and 85% during fall. The OC contribution to the wood burning source at the rural site results approximately 50% in winter and 10% in summer and about 15% at the coastal urban site in fall. The new methodology also provides a direct measurement of the absorption Ångström exponent of BrC (αBrC) which resulted αBrC = 3.95 ± 0.20.
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•Aerosol light absorption at several λs due to Black and Brown Carbon is measured.•The value of Ångström exponent of Brown Carbon is directly extracted by raw data.•The new apportionment procedure disentangles fossil and wood burning contributions.•Equivalent Black Carbon and Organic Carbon are separately apportioned.•The procedure is validated against independent Levoglucosan and 14C determination.
The LABEC laboratory, the INFN ion beam laboratory of nuclear techniques for environment and cultural heritage, located in the Scientific and Technological Campus of the University of Florence in ...Sesto Fiorentino, started its operational activities in 2004, after INFN decided in 2001 to provide our applied nuclear physics group with a large laboratory dedicated to applications of accelerator-related analytical techniques, based on a new 3 MV Tandetron accelerator. The new accelerator greatly improved the performance of existing Ion Beam Analysis (IBA) applications (for which we were using since the 1980s an old single-ended Van de Graaff accelerator) and in addition allowed to start a novel activity of Accelerator Mass Spectrometry (AMS), in particular for
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C dating. Switching between IBA and AMS operation became very easy and fast, which allowed us high flexibility in programming the activities, mainly focused on studies of cultural heritage and atmospheric aerosol composition, but including also applications to biology, geology, material science and forensics, ion implantation, tests of radiation damage to components, detector performance tests and low-energy nuclear physics. This paper describes the facilities presently available in the LABEC laboratory, their technical features and some success stories of recent applications.
This work will present preliminary results concerning the use of time-resolved ion beam induced luminescence applied to provenance studies of lapis lazuli. Measurements were performed at the pulsed ...beam facility at LABEC laboratory in Florence. Lapis lazuli is a semi-precious gemstone, used as ornament since the early civilizations that can be found in few places on Earth. The importance of this work lies in understanding the origin of various samples of lapis lazuli, from which it may be possible to gain insight into trade routes from ancient times. The samples studied in this work originated from Chile, Afghanistan, Tajikistan, Myanmar, and Siberia. The stones were irradiated with 3MeV protons and the resulting luminescence was detected by a photomultiplier tube, whose output was acquired using a sampling digitizer VME module (CAEN/V1720). Wavelength discrimination was performed at 430nm utilizing a range of beam currents. The results showed that, by changing the beam current intensity, one can study different features of lapis lazuli, and this may aid in distinguishing lapis lazuli from different provenances.
We report the design and preliminary test results of a 14C beam monitor developed for the online monitoring for radiocarbon dating. The challenge of the INFN CHNet-Lilliput experiment is to measure ...the amount of carbon in very small samples (down to a few micro-grams) with a very low concentration of radiocarbon. For this purpose, a new dedicated beam monitor for 14C ions (Energy ≃ 10 MeV) uses a silicon solid state detector made of 4 independent sectors, active area 50 × 50 mm2 and 300 μm thickness. The detector was preliminary tested in the INFN Laboratory of Bari and then installed on the final part of the Accelerator Mass Spectrometry (AMS) beam line at the INFN-LABEC Laboratory of Firenze (Italy) where sample measurements for radiocarbon dating are performed since 2004.
•Preliminary test results of a 14C beam monitor for the online monitoring for radiocarbon dating.•The challenge of the INFN CHNet-Lilliput experiment is to measure the amount of carbon in very small samples.•A new dedicated beam monitor for 14C ions (Energy ∼10 MeV) uses a silicon solid state detector made of 4 independent sectors (300μm thickness).•The detector was tested in the INFN Laboratory of Bari and then installed at the INFN-LABEC (Firenze).
Many versatile applications in the life/earth science are based on the measurement of the radiocarbon. These applications are often limited by the minimum amount of carbon that can be measured in the ...sample: minimum size radiocarbon samples can be affected by contamination introduced during the sample preparation. Comprehensive systematic investigations to reduce the sample size limit down to a few micrograms carbon are currently in progress in the INFN CHNet−Lilliput experiment. For such goal, a new original graphite preparation facility has been installed at the INFN Laboratory of Bari (Italy). The CO2 from the combusted sample is purified using a simple vacuum line set-up. The produced graphite targets will be measured using the Accelerator Mass Spectrometry (AMS) at the INFN-LABEC Laboratory of Florence (Italy) where, since 2004, sample measurements for radiocarbon dating are performed.
•A new original graphite preparation facility has been installed at the INFN Laboratory of Bari (Italy).•The procedure to convert a raw sample into suitable graphite involves three stages: the pre-treatment process, the combustion of the sample and the graphitization process.•The produced graphite targets is measured using the Accelerator Mass Spectrometry (AMS) at the INFN-LABEC Laboratory of Florence (Italy).•Preliminary performance results have been obtained and several tests are planned with several materials.
A high resolution time of flight (TOF) system has been developed at LABEC, the 3MV Tandem accelerator laboratory in Florence, in order to improve the sensitivity of AMS measurements on carbon samples ...with ultra-low concentration and also to measure other isotopes, such as 129I. The system can be employed to detect and identify residual interfering particles originated from the break-up of molecular isobars. The set-up has been specifically designed for low energy heavy ions: it consists of two identical time pick-off stations, each made up of a thin conductive foil and a Micro-Channel Plate (MCP) multiplier. The beamline is also equipped with a silicon detector, installed downstream the stop TOF station.
In this paper the design of the new system and the implemented readout electronics are presented. The tests performed on the single time pick-off station are reported: they show that the maximum contribution to the timing resolution given by both the intrinsic MCP resolution and the electronics is ⩽500ps (FWHM). For these tests, single particle pulsed beams of 2–5MeV protons and 10MeV 12C3+ ions, to simulate typical AMS conditions, were used.
The preliminary TOF and TOF-E (TOF-energy) measurements performed with carbon beams after the installation of the new system on the AMS beam line are also discussed. These measurements were performed using the foil–MCP as the start stage and a silicon detector as the stop stage. The spectra acquired with carbon ions suggest the presence of a small residual background from neighboring masses reaching the end of the beamline with the same energy as the rare isotope.
Bones are potentially the best age indicators in a stratigraphic study, because they are closely related to the layer in which they are found. Collagen is the most suitable fraction and is the ...material normally used in radiocarbon dating. Bone contaminants can strongly alter the carbon isotopic fraction values of the samples, so chemical pretreatment for
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C dating by accelerator mass spectrometry (AMS) is essential. The most widespread method for collagen extraction is based on the Longin procedure, which consists in HCl demineralization to dissolve the inorganic phase of the samples, followed by dissolution of collagen in a weak acid solution. In this work the possible side effects of this procedure on a modern bone are presented; the extracted collagen was analyzed by ATR-IR spectroscopy. An alternative procedure, based on use of HF instead of HCl, to minimize unwanted degradation of the organic fraction, is also given. A study by ATR-IR spectroscopic analysis of collagen collected after different demineralization times and with different acid volumes, and a study of an archaeological sample, are also presented.
Recently, developments have been made to the external scanning microbeam of INFN-LABEC laboratory in Florence. A new system for mechanical sample scanning was implemented. This system allows us to ...acquire large maps (up to 2020cm2), of great interest in the Cultural Heritage field. In parallel, the possibility of using carbon microbeams for experiments, such as, for example, ion beam modification of materials and MeV Secondary Ion Mass Spectrometry, has been investigated. As a test application, Particle Induced X-ray Emission with carbon microbeams has been performed on a lapis lazuli stone. First results for both wide area imaging and external carbon microbeams are briefly reported.
In the last few years some new implementations and upgrades have been made to the external scanning microbeam of INFN-LABEC laboratory in Florence, enriching the existing PIXE, PIGE, BS, IBIL set-up ...with complementary techniques, when possible allowing for simultaneous multi-technique analyses. We developed a system, compatible with the existing set-up, for the out-of-vacuum detection of the forward scattered particles. This system makes feasible the external-STIM (Scanning Transmission Ion Microscopy) and external-FS (Forward Scattering), now both available at our beamline. Test measurements are shortly presented.
In the combustion and graphitization line for 14C-AMS samples used at INFN-LABEC for archaeological and geological applications, samples are burnt using an elemental analyser (EA). Advantages and ...drawbacks of EAs are known, a drawback being the possibility to introduce some contaminations or memory effects. Different parts inside an EA, e.g. the autosampler and the gas-chromatography column, might in principle be responsible of such problems.
During a measurement run some time ago, we measured, indeed, radiocarbon concentration values somewhat higher than usual in nominally blank samples. These “bad” data could be explained by memory effects. By assuming a constant contribution from the sample of the prior combustion, this effect might be corrected: indeed, by repeating cycles of sequential combustions of standards and blanks, we observed a good reproducibility of the amount of contamination from the previous sample needed to explain the results. However, we were obviously unhappy with the fact itself of such corrections being needed, and several tests were performed to identify the source of contamination and eliminate it. Eventually, we succeeded in finding the cause of this failure and in recovering the full performance of the system.
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