Set-up of a multi wavelength polar photometer for off-line absorption coefficient measurements on 1-h resolved aerosol samples

In this paper, a polar photometer (PP_UniMI) was set up to measure the aerosol absorption coefficient (\u3c3ap) at four wavelengths (\u3bb) on 1-h resolved aerosol samples collected using a streaker sampler. Due to the characteristics of such samples (small deposit area, low aerosol load, and limited substrate thickness 12 10 \u3bcm), the main technical developments aimed at reaching suitable limits of detection (LODs). To this aim, multiple scattering between the sample and a suitable substrate were exploited to amplify the system sensitivity to absorbing particle load. In the paper, the development and test of this innovative approach is presented. LODs for \u3c3ap in the range 5.0\u201311.6 Mm 121 were reached, depending on the wavelength. Such values were suitable for the analysis of 1-hour resolved samples collected at an urban background site in Milan (Italy) during a test campaign of 1-week carried out in winter 2015. The methodology was validated comparing \u3c3ap measurements performed by PP_UniMI at \u3bb=635 nm on the streaker sample to the data obtained by a Multi-Angle Absorption Photometer (MAAP) operated in parallel. Agreement within 10% was found. To check the results obtained at other wavelengths, \uc5ngstr\uf6m Absorption Exponent (AAE) was calculated from \u3c3ap measurements at 4-\u3bb. The AAE values resulted in the range of expectations for aerosol emitted by fossil fuel combustion (0.8\u20131.2) and wood burning (0.9\u20133.5), which are the main sources contributing to absorbing aerosol in urban areas in winter. The analytical methodology can be extended to samples collected with high time resolution using other high-time resolution samplers (e.g. drum rotating impactors). This is \u2013 as far as we know \u2013 the first time that \u3c3ap measurements are performed on streaker samples collected with 1-h resolution. Our results thus set PP_UniMI as an important tool for the community performing high time resolved sampling to widen the characterisation of such samples and to further develop source apportionment studies

Open History Map

OpenHistoryMap aspires to become the open source geographical system for archaeological information, both from an academic and an educational point of view. There are many fragmented online web-GIS experiences targeted at very specific projects, but no tool enables a broader overview of both research and studies. For these reasons, in order to create an Open Access platform, one of the most important aspects is the creation of tools that can facilitate both the sharing of archaeological spatial and temporal information as well as the easy reuse of the generated data. OpenHistoryMap is supposed to create a tool that is both a map of the archaeological world as well as a repository for the connected data within structured research papers. The project finds its roots first of all within the collective experience of ‘archaeology’ that refers to non-expert users, and in the second place within the academic scientific experience of research centres and universities. While the first approach gives an integrated and reliable picture of the cultural item, the second provides consistent and solid datasets with a perspective on the mixture of specific types of information

B-physics with Nf=2N_f=2 Wilson fermions

We report the final results of the ALPHA collaboration for some B-physics observables: $f_B$, $f_{B_s}$ and $m_b$. We employ CLS configurations with 2 flavors of $O(a)$ improved Wilson fermions in the sea and pion masses ranging down to 190 MeV. The b-quark is treated in HQET to order $1/m_b$. The renormalization, the matching and the improvement were performed non-perturbatively, and three lattice spacings reaching $a=0.048$ fm are used in the continuum extrapolation

Development of a dual-wavelength thermo-optical transmittance analyser: characterization and first results

Carbonaceous aerosol (CA) plays an important role in many different issues ranging from human health to global climate change. It mainly consists of organic carbon (OC) and elemental carbon (EC) although a minor fraction of carbonate carbon could be also present. Thermal-optical methods (TOT/TOR) are presently the most widespread approach to OC/EC speciation. Despite their popularity, there is still a disagreement among the results, especially for what concerns EC as different thermal protocols can be used. In fact, the pyrolysis occurring during the analysis can heavily affect OC/EC separation, depending on PM composition in addition to the used protocol. The main hypothesis at the basis of the technique relies on the optical properties of EC and OC: while EC is strongly light absorbing, OC is generally transparent in the visible range. However, a fraction of light-absorbing OC exists: the Brown Carbon (BrC) (Andreae and Gelencs\ue9r, 2006). The presence in the sample of BrC can shift the split point since it is slightly absorbing also @ 635nm, the typical laser wavelength used in this technique (Chen et al., 2015). At the Physics Department of the University of Genoa, a Sunset EC/OC analyser unit has been modified in order to monitor the optical transmittance during the thermo-optical analysis at two different wavelengths: 635 nm (the original wavelength of the instrument) and 405 nm (Fig.1). The additional use of the 405 nm transmittance measurement provides valuable information about the composition of the sample as well as on the pyrolytic carbon formation, both able to affect the instrumental \u201csplit point\u201d (i.e. the moment of the analysis in which the laser transmittance is back to its starting value, thus defining EC/OC separation). We present here the new instrument set-up, providing its full characterization with \u201csynthetic\u201d samples (i.e. mixtures of sucrose, graphitic carbon, and pure scattering particles). Moreover, we show also the results obtained analysing at 2-\uf06c - with both NIOSH and EUSAAR_2 protocols - real PM samples collected in very different conditions (i.e. summer-winter) and sites (ranging from urban to rural/mountain). Furthermore, we have recently introduced a new possibility, based on the apportionment of the absorption coefficient (babs) of particle-loaded filters, for correcting the thermo-optical analysis of PM samples (Massab\uf2 et al, 2016), an example in Fig.2. The apportionment is based on the optical analysis performed by the Multi-Wavelength Absorbance Analyser (MWAA), an instrument developed at the Physics Department of the University of Genoa (Massab\uf2 et al., 2015). The apportionment method uses the information gathered at five different wavelengths in a renewed and upgraded version of the approach usually referred to as Aethalometer model (Sandradewi et al., 2008). We present here also the results of the thermo-optical analysis correction (Massab\uf2 et al., 2016) applied to the dual-\uf06c analysis, which lead to a better homogeneity between the results obtained with different thermal protocols

Light extinction estimates using the IMPROVE algorithm: The relevance of site-specific coefficients

Atmospheric aerosol and gases affect visibility by scattering and absorbing the incoming radiation (Watson, 2002; Pitchford et al, 2007). While the role of gases is relatively well understood, the effect of particulate matter (PM) is more complicated to be assessed since it depends on several factors such as particles size distribution and chemical composition as well as meteorological parameters (e.g. relative humidity \u2013 RH). The U.S. Interagency Monitoring of Protected Visual Environments (IMPROVE) network proposed a method to retrieve atmospheric light extinction coefficient (bext, Mm-1) in national parks from compositional and meteorological data (Malm et al, 1994; Watson, 2002). The result of this approach (often called chemical light extinction) allows the evaluation of visibility indicators such as visual range (VR) via the Koschmieder equation VR=3.912/bext. In this study we tailored the IMPROVE equation using site-specific dry mass extinction efficiencies and hygroscopic growth functions in order to obtain bext estimates which better reflect the typical atmospheric characteristics of the sampling site and period. The revised formulation was tested for the first time in the urban area of Milan, for two weeks during the winter season in 2015. Moreover, it was applied to a large and fully characterized dataset referred to PM1 samples collected in winter 2012. Following the IMPROVE algorithm (Malm et al, 1994; Watson, 2002; Pitchford et al, 2007) the chemical light extinction equation used in this work was: bext = k1 x f1(RH) x [AMSUL] + k2 x f2(RH) x [AMNIT] + k3 x f3(RH) [OM] + k4 x [fine soil] + bap + 0.60 x [coarse mass] + 0.33 x [NO2] (ppb) + Rayleigh scattering, where inputs are the concentrations of the five major PM components (ammonium sulphate - AMSUL, ammonium nitrate AMNIT, organic matter - OM, fine soil, coarse mass) in \u3bcg m-3, NO2 concentration (in ppb), Rayleigh scattering by gases (Mm-1) and aerosol light absorption coefficient (bap, Mm-1) measured with a home-made polar photometer on PTFE filters. Dry mass extinction efficiencies (k1-k4, m2 g-1) for every chemical component of interest were calculated considering size distributions measured in Milan (Vecchi et al, 2012), particles densities and complex refractive indices (Watson, 2002). Furthermore, hygroscopic growth functions fi(RH), defined as the ratios between ambient and dry aerosol scattering coefficients bsp), were also calculated (using hygroscopic growth factors taken from the literature) and were applied to those PM components (AMSUL, AMNIT and OM), whose bsp are enhanced by their water uptake at medium-high RH values. It is worthy to note that in the original IMPROVE algorithm (Malm et al, 1994; Watson, 2002) the hygroscopic growth function f(RH) is calculated referring only to AMSUL ygroscopic properties and it is applied also to AMNIT, whereas OM is considered as non-hygroscopic. Non-negligible discrepancies were found between tailored dry mass extinction efficiencies and the original IMPROVE ones. Furthermore, differences between calculated fi(RH) and IMPROVE hygroscopic growth function were found. The methodology here described was applied to a PM1 dataset thus retrieving the extinction contribution given by the different PM1 components as well as by the major aerosol sources. Both methodological and experimental results will be shown in the presentation. This work shows that \u2013 due to the large variability in size distributions and aerosol composition at sites with different characteristics (e.g. urban, industrial, rural) \u2013 it is advisable to calculate site-specific k1-k4 and fi(RH) coefficients instead of using the original IMPROVE ones, which refer to aerosol properties measured at U.S. national parks

Decay constants of B-mesons from non-perturbative HQET with two light dynamical quarks

We present a computation of B-meson decay constants from lattice QCD simulations within the framework of Heavy Quark Effective Theory for the b-quark. The next-to-leading order corrections in the HQET expansion are included non-perturbatively. Based on Nf=2 gauge field ensembles, covering three lattice spacings a (0.08-0.05)fm and pion masses down to 190MeV, a variational method for extracting hadronic matrix elements is used to keep systematic errors under control. In addition we perform a careful autocorrelation analysis in the extrapolation to the continuum and to the physical pion mass limits. Our final results read fB=186(13)MeV, fBs=224(14)MeV and fBs/fB=1.203(65). A comparison with other results in the literature does not reveal a dependence on the number of dynamical quarks, and effects from truncating HQET appear to be negligible.Comment: 16 pages including figures and table

The b-quark mass from non-perturbative Nf=2N_f=2 Heavy Quark Effective Theory at O(1/mh)O(1/m_h)

We report our final estimate of the b-quark mass from $N_f=2$ lattice QCD simulations using Heavy Quark Effective Theory non-perturbatively matched to QCD at $O(1/m_h)$. Treating systematic and statistical errors in a conservative manner, we obtain $\overline{m}_{\rm b}^{\overline{\rm MS}}(2 {\rm GeV})=4.88(15)$ GeV after an extrapolation to the physical point.Comment: 15 pages including figures and tables; as published in Phys.Lett.B / typo in table 4 corrected / footnote 1 expande

High time-resolved multi-wavelength measurements of light absorption properties of atmospheric aerosol using a polar photometer

Black Carbon (BC) is the main absorber of solar radiation among the aerosol components, it influences cloud processes, and alters the melting of snow and ice cover. On global scale, it is currently identified as the second most important individual climate-warming component after CO2, but uncertainties on the radiative forcing related to BC-radiation interaction still cover more than one order of magnitude. Moreover, weakly absorbing organic material (brown carbon, BrC) in the form of particle coating or as particle as-is can be considered a further important contributor to aerosol absorption. The peculiarity of BrC is that it is very effective in the absorption of short-\u3bb radiation whereas its contribution to aerosol absorption is negligible in the red or near-IR bands. It is noteworthy that BC and BrC can also be used for source apportionment purposes (e.g. they can be helpful for the discrimination between fossil fuels combustion vs. biomass burning). Thus, work is currently ongoing to develop instrumentation able to give more and more detailed information on the absorption properties of atmospheric aerosol, possibly related to mixing and/or size information, and BC content. Moving in this frame, a multi-\u3bb polar photometer (PP_UniMI) has been developed at the Department of Physics of the University of Milan in the last years. The instrument is based on the measurement on the scattering plane of the light transmitted and scattered in the forward and back hemispheres by unloaded and loaded samples using a rotating photodiode. Data reduction aiming at the determination of the sample absorbance follows Petzold et al. (2004) and therein cited literature. In its original version (see details in Vecchi et al., 2013) the PP_UniMI allowed measuring aerosol deposited on 47 mm diameter filters at a single wavelength (\u3bb), then further upgraded to 4-\u3bb (870, 633, 532, 405 nm). In this work, we improved PP_UniMI to provide the absorption properties of the aerosol collected with high-time resolution using a streaker sampler. Such sampler collects aerosol segregated in two size-classes (fine and coarse) on a rotating frame with hourly resolution. The deposit corresponding to 1-hour sampling is collected on 1x8 mm2 streaks. To analyse such deposits, suitable pairs of lenses were used to reduce the spot-size down to about 1 mm diameter (see Figure 1). A 1-mm diameter pinhole was added to the set-up in order to ensure that the spot was small enough to allow the single-streak measurement. It is noteworthy that some laser sources are placed at 90\ub0 respect to the incident direction on the filter, thus mirrors are present in the set-up. The new set-up or the instrument was validated against independent measurements carried out using a Multi-Angle Absorption Photometer for what concerns the red-light results. The results presented here will include the validation of the instrumentation and the results of one-week winter campaign. Data reduction will aim at evidencing high time-resolved trends of multi-wavelength aerosol absorption. This is important both for gaining insight into aerosol absorption properties (still poorly known) and for source identification purposes

4-hours resolution data to study PM10 in a “hot spot” area in Europe

Nowadays, high-time resolved aerosol studies are mandatory to better understand atmospheric processes, such as formation, removal, transport, deposition or chemical reactions. This work focuses on PM10 physical and chemical characterisation with high-time resolution: elements (from Na to Pb), ions and OC/EC fractions concentration were determined during two weeks in summer and two in winter 2006 with 4-hours resolution. Further measurements aimed at hourly elemental characterisation of fine and coarse fractions and at the determination of particles number concentration in the 0.25\u201332 \u3bcm size range in 31 bins. The chemical mass closure was carried out in both seasons, enhancing intra-day differences in PM10 composition. In Milan, the highest contribution came from organic matter (34% and 33% in summer and winter, respectively); other important contributors were secondary inorganic compounds (16% and 24% in summer and winter, respectively) and, in summer, crustal matter (14%). Temporal trends showed strong variations in PM10 composition during contiguous time-slots and diurnal variations in different components contribution were identified. Moreover, peculiar phenomena, which would have hardly been detected with 24-hours samplings, were evidenced. Particles removal due to precipitations, aerosol local production and long range transport were studied in detail