A New PM Sampler with a Built-In Black Carbon Continuous Monitor

open6We introduce a new instrument for sampling the airborne particulate matter (PM) while monitoring the black carbon (BC) atmospheric concentration. The concentration of PM and BC are usually measured by separate instruments with possible systematics differences even in the collecting inlets. The new equipment is based on a low-volume sequential PM sampler, fully compliant with the EU-CEN and US-EPA regulatory standards, with a built-in optical BC monitor. The BC concentration is continuously measured during the sampling in the PM accumulated on the filter while the PM concentration can be obtained off-line by a standard gravimetric analysis. The optical set-up, upstream the collecting filter, is composed by a single wavelength light source (λ = 635 nm) and a photodiode, placed in way to receive the light backscattered by the filter surface at a fixed angle. The mechanical arrangement does not introduce any perturbation to the PM sampling. Thanks to an original calibration curve, the sample absorbance is deduced from the output signal of the photodiode. Finally, the BC concentration is obtained through the Mass Absorption Coefficient (MAC). After the sampling and the PM gravimetric determination, the same filter can be sent to other compositional analyses. Thermo-optical quantification of the Elemental and Organic Carbon (EC and OC) in the filter sample can thus be exploited to tune the MAC value to the PM composition of a particular site. The main features of the new instrument and the set of validation tests against other PM samplers and BC monitors of widespread use (i.e.,: Multi Angle Absorption Photometer and aethalometer) are detailed and discussedopenLorenzo Caponi,Gianluca Cazzuli,Giulio Gargioni,Dario Massabò,Paolo Brotto, Paolo PratiCaponi, Lorenzo; Cazzuli, Gianluca; Gargioni, Giulio; Massabo', Dario; Brotto, Paolo; Prati, Paol

ChAMBRe \u2013 the development of an atmosferic simulation chamber for bioaerosol studies and aerosol optical properties investigation

Environmental simulation chambers are small to largescale facilities where atmospheric conditions can be monitored in real-time under control to reproduce realistic environments and to study interactions among their constituents. Up to now, they have been used mainly to study chemical and photochemical processes that occur in the atmosphere, but the high versatility of these facilities allows for a wider application covering all fields of atmospheric aerosol science. ChAMBRe (Chamber for Aerosol Modelling and Bioaerosol Research) is the stainless steel atmospheric simulation chamber (volume approximately 3 m3, see Figure 1) recently installed at the National Institute of Nuclear Physics in Genoa (INFN-Genova) in collaboration with the Environmental Physics Laboratory at the Physics Department of Genoa University (www.labfisa.ge.infn.it). The scientific activities at ChAMBRe focus on the following topics: 1) Bioaerosol properties A strong improvement in the understanding of bioaerosol behaviour can be provided by atmospheric chamber experiments, that allow for a scientific intermediate approach between \u201cin vitro\u201d and \u201cin vivo\u201d analysis. Aerosol with realistic composition, including living micro-organisms, can be injected in artificial environments with controlled physical and chemical parameters and then accurately analyzed. In particular, a systematic approach can be used for a better description of micro-organisms viability, of colonies growing modulation and other issues relevant to their spread and their pathogenicity. Very promising results in this direction were obtained by the authors at the CESAM facility at CNRS-LISA (Brotto et al. 2015), while similar results were obtained nearly at the same time at AIDA chamber at KIT (Amato et al. 2015). ChAMBRe experiments are carrying on this path to contribute in getting a deeper understanding of the still unclear mechanisms that control the evolution of bioaerosols in atmosphere and in particular of their bacterial components. 2) Aerosol optical properties \u2013 methodologies and instruments testing The instrumental development efforts at the Environmental Physics Laboratory of the University of Genoa, recently resulted in a new Multi Wavelength Absorbance Analyser (Massab\uf2 et al. 2015) which measure the light absorption on aerosol loaded filters at five wavelengths from UV (absorption bands of organic compounds, mineral dust) to near infrared (carbon soot,\u2026). Furthermore, a new data reduction methodology has been introduced to disentangle the concentration of Black and Brown carbon in atmospheric aerosol, demonstrating the need to mitigate not only exhaust but also non-exhaust emissions, as a potentially important source of PM10. The atmospheric chamber is an effective tool to produce known aerosol mixtures and to test the performance of the optical technology. Actually, there is an on-going collaboration with the CNRS-LISA team working at CESAM following that procedure that will be soon replicated at ChAMBRe facility. ChAMBRe has recently joined the Eurochamp consortium, the European atmospheric chamber facilities network. The network activities have been included in an infrastructure-oriented research project proposal that is going to be submitted within March 2016 to the H2020-INFRAIA call within EU Horizon 2020 Programme. We would like to acknowledge prof. J.F. Doussin and LISA laboratories (http://www.lisa.univ-paris12.fr/en) for providing us part of the chamber structure and for the very useful and fruitful technical discussions

The effect of Brown Carbon on thermal-optical analysis: a correction based on optical multi-wavelength analysis

Carbonaceous aerosol (CA) plays an important role in environmental issues like air quality, human health and 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 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 differentthermal protocols can be currently used. The main hypothesis at the basis of the technique is that on their different optical properties: while EC is strongly light absorbing, OC is generally transparent in the visible range. However, another fraction of light-absorbing carbon exists which is not black and it is generally called brown carbon (BrC) (Andreae and Gelencs\ue9r, 2006). We introduced a new way to apportion the absorption coefficient (babs) of carbonaceous atmospheric aerosols starting from a multi-wavelength optical analysis (Massab\uf2 et al., 2015). This analysis was performed thanks to the MWAA, an instrument developed at the Physics Department of University of Genoa (Massab\uf2 et al., 2013). 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 (Sandradewi et al., 2008). Moreover, with some assumptions, also the quantification of OC coming from fossil fuels and wood burning can be obtained. Thermal-optical methods 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. Furthermore, the presence in the sample of BrC can shift the split point since it is light absorbing also @ 635nm, the typical laser wavelength used in this technique (Chen et al., 2015). We have recently introduced a new possibility, based on the apportionment of the absorption coefficient of particleloaded filters, for correcting the thermo-optical analysis of PM samples (Massab\uf2 et al, 2016). We present here the results of an apportionment study of carbonaceous aerosol sources performed in an Alpine area, validated against independent measurements of levoglucosan. We also present developments of the thermo-optical analysis correction (Massab\uf2 et al., 2016) which lead to a better homogeneity between the results obtained with different thermal protocols

Results of the first European Source Apportionment intercomparison for Receptor and Chemical Transport Models

In this study, the performance of the source apportionment model applications were evaluated by comparing the model results provided by 44 participants adopting a methodology based on performance indicators: z-scores and RMSEu, with pre-established acceptability criteria. Involving models based on completely different and independent input data, such as receptor models (RMs) and chemical transport models (CTMs), provided a unique opportunity to cross-validate them. In addition, comparing the modelled source chemical profiles, with those measured directly at the source contributed to corroborate the chemical profile of the tested model results. The most used RM was EPA- PMF5. RMs showed very good performance for the overall dataset (91% of z-scores accepted) and more difficulties are observed with SCE time series (72% of RMSEu accepted). Industry resulted the most problematic source for RMs due to the high variability among participants. Also the results obtained with CTMs were quite comparable to their ensemble reference using all models for the overall average (>92% of successful z-scores) while the comparability of the time series is more problematic (between 58% and 77% of the candidates’ RMSEu are accepted). In the CTM models a gap was observed between the sum of source contributions and the gravimetric PM10 mass likely due to PM underestimation in the base case. Interestingly, when only the tagged species CTM results were used in the reference, the differences between the two CTM approaches (brute force and tagged species) were evident. In this case the percentage of candidates passing the z-score and RMSEu tests were only 50% and 86%, respectively. CTMs showed good comparability with RMs for the overall dataset (83% of the z-scores accepted), more differences were observed when dealing with the time series of the single source categories. In this case the share of successful RMSEu was in the range 25% - 34%.JRC.C.5-Air and Climat

Interband and intraband effects in the upper critical field of disordered MgB2

In this work the superconducting properties of disordered MgB2 in applied magnetic field are studied within the lambda(theta theta) model, by taking into account the presence of both interband and intraband scattering with impurities. This approach allows to extract the suppression of the critical temperature T-c and the enhancement of the upper critical field H-c2, as a consequence of the introduction of impurities in the samples. We analyze the dependence of H-c2 on temperature, anisotropy of the electronic structure, and intraband sigma and pi band scattering rates. Comparing our numerical calculations with experimental data on irradiated samples, we find that irradiation defects mainly affect the mobility of sigma carriers. These results rationalize why the H-c2 anisotropy of irradiated samples is quickly reduced with increasing doses and full suppression of superconductivity occurs at rather low-resistivity values. Moreover, our calculations point out that disorder in the pi bands affects only weakly the coupling constants and thus it could yield a significant enhancement of H-c2 without severe suppression of T-c

An integrated PM2.5 source apportionment study: Positive Matrix Factorisation vs. the Chemical Transport Model CAMx

none8Receptor and Chemical Transport Models are commonly used tools in source apportionment studies, even if different expertise is required. We describe an experiment using both approaches to apportion the PM2.5 (i.e., particulate matter with aerodynamic diameters below 2.5 m) sources in the city of Genoa (Italy). A sampling campaign was carried out to collect PM2.5 samples daily for approximately six month during 2011 in three sites. The subsequent compositional analyses included the speciation of elements, major ions and both organic and elemental carbon; these data produced a large database for receptor modelling through Positive Matrix Factorisation (PMF). In the same period, a meteorological and air quality modelling system was implemented based on the mesoscale numerical weather prediction model WRF and the chemical transport model CAMx to obtain meteorological and pollutant concentrations up to a resolution of 1.1 km. The source apportionment was evaluated by CAMx over the same period that was used for the monitoring campaign using the Particulate Source Apportionment Technology tool. Even if the source categorisations were changed (i.e., groups of time-correlated compounds in PMF vs. activity categories in CAMx), the PM2.5 source apportionment by PMF and CAMx produced comparable results. The different information provided by the two approaches (e.g., real-world factor profile by PMF and apportionment of a secondary aerosol by CAMx) was used jointly to elucidate the composition and origin of PM2.5 and to develop a more general methodology. When studying the primary and secondary components of PM, the main anthropogenic sources in the area were road transportation, energy production/industry and maritime emissions, accounting for 40% - 50%, 20% - 30% and 10% - 15%, of PM2.5, respectively.M. C. Bove; P. Brotto; F. Cassola; E. Cuccia; D. Massabò; A. Mazzino; A. Piazzalunga; P. PratiBove, MARIA CHIARA; Brotto, Paolo; Cassola, Federico; Cuccia, ELEONORA SIMONA; Massabo', Dario; Mazzino, Andrea; A., Piazzalunga; Prati, Paol

Impact of Model Resolution and Initial/Boundary Conditions in Forecasting Flood-Causing Precipitations

In late summer and autumn Mediterranean coastal regions are quite regularly affected by small-scale, flood-producing convective systems. The complexity of mesoscale triggering mechanisms, related to low-level temperature gradients, moisture convergence, and topographic effects contributes to limit the predictability of such phenomena. In the present work, a severe convection episode associated to a flash flood occurred in Cannes (southern France) in October 2015, is investigated by means of numerical simulations with a state-of-the-art nonhydrostatic mesoscale model. In the modelling configuration operational at the University of Genoa precipitation maxima were underestimated and misplaced. The impact of model resolution as well as initial and boundary conditions on the quantitative precipitation forecasts is analyzed and discussed. In particular, the effect of ingesting a high-resolution satellite-derived sea surface temperature field is proven to be beneficial in terms of precipitation intensity and localization, especially when also associated with the most accurate lateral boundary conditions