Abstract. A systematic study of black carbon (BC) vertical profiles measured at high-resolution over three Italian basin valleys (Terni Valley, Po Valley and Passiria Valley) is presented. BC vertical profiles are scarcely available in literature. The campaign lasted 45 days and resulted in 120 measured vertical profiles. Besides the BC mass concentration, measurements along the vertical profiles also included aerosol size distributions in the optical particle counter range, chemical analysis of filter samples and a full set of meteorological parameters. Using the collected experimental data, we performed calculations of aerosol optical properties along the vertical profiles. The results, validated with AERONET data, were used as inputs to a radiative transfer model (libRadtran). The latter allowed an estimation of vertical profiles of the aerosol direct radiative effect, the atmospheric absorption and the heating rate in the lower troposphere. The present measurements revealed some common behaviors over the studied basin valleys. Specifically, at the mixing height, marked concentration drops of both BC (range: from −48.4 ± 5.3 to −69.1 ± 5.5%) and aerosols (range: from −23.9 ± 4.3 to −46.5 ± 7.3%) were found. The measured percentage decrease of BC was higher than that of aerosols: therefore, the BC aerosol fraction decreased upwards. Correspondingly, both the absorption and scattering coefficients decreased strongly across the mixing layer (range: from −47.6 ± 2.5 to −71.3 ± 3.0% and from −23.5 ± 0.8 to −61.2 ± 3.1%, respectively) resulting in a single-scattering albedo increase along height (range: from +4.9 ± 2.2 to +7.4 ± 1.0%). This behavior influenced the vertical distribution of the aerosol direct radiative effect and of the heating rate. In this respect, the highest atmospheric absorption of radiation was predicted below the mixing height (~ 2–3 times larger than above it) resulting in a heating rate characterized by a vertical negative gradient (range: from −2.6 ± 0.2 to −8.3 ± 1.2 K day−1 km−1). In conclusion, the present results suggest that the BC below the mixing height has the potential to promote a negative feedback on the atmospheric stability over basin valleys, weakening the ground-based thermal inversions and increasing the dispersal conditions.

Abstract. Vertical aerosol profiles were directly measured over the city of Milan during three years (2005)(2006)(2007)(2008) of field campaigns. An optical particle counter, a portable meteorological station and a miniaturized cascade impactor were deployed on a tethered balloon. More than 300 vertical profiles were measured, both in winter and summer, mainly in conditions of clear, dry skies.The mixing height was determined from the observed vertical aerosol concentration gradient, and from potential temperature and relative humidity profiles. Results show that inter-consistent mixing heights can be retrieved highlighting good correlations between particle dispersion in the atmosphere and meteorological parameters. Mixing height growth speed was calculated for both winter and summer showing the low potential atmospheric dispersion in winter.Aerosol number size distribution and chemical composition profiles allowed us to investigate particle behaviour along height. Aerosol measurements showed changes in size distribution according to mixing height. Coarse particle profiles (d p >1.6 µm) were distributed differently than the fine ones (d p <1.6 µm) were, at different heights of the mixing layer. The sedimentation process influenced the coarse particle profiles, and led to a reduction in mean particle diameter for those particles observed by comparing data above the mixing height with ground data (−14.9±0.6% in winter and −10.7±1.0% in summer). Conversely, the mean particle diameter of fine particles increased above the mixing height under stable atmospheric conditions; the average inCorrespondence to: L. Ferrero (luca.ferrero@unimib.it) crease, observed by comparing data above the mixing height with ground data, was +2.1±0.1% in winter and +3.9±0.3% in summer. A hierarchical statistical model was created to describe the changes in the size distribution of fine particles along height. The proposed model can be used to estimate the typical vertical profile characterising launches within prespecified groups starting from: aerosol size and meteorological conditions measured at ground-level, and a mixing height estimation. The average increase of fine particle diameter, estimated on the basis of the model, was +1.9±0.5% in winter and +6.1±1.2% in summer, in keeping with experimental findings.

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To date, few studies have focused on PM air quality in offices, despite the fact that a lot of people spend\ud many working hours a day in such offices. The aim of the present study is to investigate PM1 and PM2.5\ud in offices in Milan (Northern Italy) and in the air outside those offices. The PM samples were analyzed to\ud determine the entity of certain compounds with possible direct or indirect adverse effects on human\ud health: PAHs, BpA, and water soluble inorganic ions.\ud A good correlation between outdoor and indoor PM mass concentrations emerged (R2 w0.87). The\ud maximum I/O concentration ratiowas 0.92, suggesting that the indoor PM levelwas always lower than the\ud outdoor level. The average infiltration factor, FINF,was 0.55, showing that about a half of the outdoor PMhad\ud come indoors. The indoor-generated particles, Cig, had values ranging from 0 to 4.4 mg m3 (<25% of the\ud indoor PM), showing that PM indoor sources had only made a limited contribution to total indoor PM.\ud The results of the indoor-to-outdoor comparisons for the aforementioned chemical compounds\ud demonstrate that the offices were characterized by the absence of effective indoor sources of particulatebound\ud PAHs and inorganic ions, whereas Cig was around 58% of the indoor concentration for BpA. Our\ud analysis of the FINF data pointed to the presence of a volatilization effect from PM for semi-volatile\ud compounds like ammonium nitrate and 4- or 5-ring PAHs, which affected the measurement of their\ud FINF. We propose the introduction of a new and simple parameter, called volatilization correction, to take\ud account of this effect

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The energy demands of data centers (DCs) worldwide are rapidly increasing, as are their environmental and economic costs. This paper presents a study conducted at Sannazzaro de' Burgondi (Po Valley), Italy, specifically aimed at optimizing the operating conditions of a DC designed for the Italian Oil and Gas Company (Eni) (5200 m(2) of Information Technology installed, 30 MW) and based on a direct free cooling (DFC) system. The aim of the study was to save the largest possible quantity of energy, while at the same time preventing aerosol corrosion. The aerosol properties (number size distribution, chemical composition, deliquescence relative humidity (DRH), acidity) and meteorological parameters were monitored and utilized to determine the potential levels of aerosol entering the DC (equivalent ISO class), together with its DRH. These data enabled us both to select the DC's filtering system (MERV13 filters) and to optimize the cooling cycle through calculation of the most reliable humidity cycle (60% of maximum allowed RH) applicable to the DFC. A potential energy saving of 81%, compared to a traditional air conditioning cooling system, was estimated: in one year, for 1 kW of installed information technology, the estimated energy saving is 7.4 MWh, resulting in 2.7 fewer tons of CO2 being emitted, and a financial saving of € 1100.

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Abstract. This study presents the first measured high resolution vertical profiles of black carbon and calculation of aerosol radiative forcing and atmospheric heating rates in the lower troposphere, over Italy and Europe. The calculation is based on vertical profiles of black carbon, aerosol number size distribution and chemical composition measured over three Italian basin valleys (Po Valley, Terni Valley and Passiria Valley) by means of a tethered balloon equipped with a micro-Aethalometer, an optical particle counter (OPC), a cascade impactor and a meteorological station. Experimental measurements allowed first the calculation of the aerosol optical properties. In this respect, the aerosol refractive index was calculated along height using the effective medium approximation applied to aerosol chemical composition; Mie calculations were performed on the base of the OPC number-size distribution which was corrected for the ambient aerosol refractive index. The obtained vertical profiles of aerosol optical properties were validated with AERONET data and were used as input to the radiative transfer model libRadtran. Vertical profiles of direct aerosol radiative forcing, atmospheric absorption and heating rate were calculated. Reported results evidenced common behaviours along height over the investigated basin valleys (an orographic feature present elsewhere in Europe): at the mixing height a marked a concentration drop of both BC (range: −48.4 ± 5.3% to −69.1 ± 5.5%) and particle number concentration (range: −23.9 ± 4.3% to −46.5 ± 7.3%) was evidenced. More in details, the percentage decrease of BC along height was higher than that measured for aerosol and thus, the BC content of the aerosol decreased along height; correspondingly the Single Scattering Albedo increased along height (range: +4.9 ± 2.2% to +7.4 ± 1.0%). Therefore, the highest atmospheric absorption was observed below the mixing height (range: +0.5 ± 0.1 W m−2 to +2.5 ± 0.2 W m−2) with the associated heating rate characterized by a vertical negative gradient (range: −0.5 K day−1 km−1 to −6.8 K day−1 km−1). As a result, the Black Carbon loaded below the mixing height potentially weakens the ground-based thermal inversions (common over basin valleys) thus promoting an increase of the atmospheric dispersal conditions.