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Filter-collected aerosol samples in the PM 1 and PM 10 fractions and particle number concentration were measured during experimental campaigns in a rural area near Bologna (Italy) in the periods 10–21 February 2014 and 19–30 May 2014. Ice nuclei particle (INP) concentrations measured off-line showed prevalently higher average values in the morning with respect to the afternoon, in the PM 1 fraction with respect to PM 1–10 (with the exception of the first campaign, at S w = 1.01), and at water saturation ratio S w = 1.01 with respect to S w = 0.96. The aerosol in the coarse size range (1–10 μm) contributed significantly to the total INP concentration. In the first campaign, the average INP concentration in the coarse fraction was 80% of the total in the morning and 74% in the afternoon, at S w = 1.01. In the second campaign, the contribution of the coarse size fraction to the INP number concentration was lower. On the whole, the results showed that the freezing activity of aerosol diameters larger than 1 μm needs to be measured to obtain the entire INP population. Sahara dust events (SDEs) took place during both campaigns, in the periods 17–20 February and 21–23 May 2014. Results show that the averaged particle number concentration was higher during SDE than during no-Saharan dust events. A low correlation between INP and total aerosol number concentration was generally measured, except for SDEs observed in February, in which the correlation coefficient between aerosol concentration in the coarse fraction and INP in the same range, at water supersaturation, was about 0.8. Precipitation events influenced the aerosol concentration. In the February campaign, lower values of INP and particle concentrations were measured in case of heavy rain events. During the May campaign, an average number concentration of the aerosol in the range 0.5–10 μm was slightly higher than on days when no precipitation was measured, the rainfall intensity being low. Only in a few cases did we note a sharp drop in INP in the PM 10 fraction at S w = 1.01 (26 May, 8 a.m. and 1 p.m.; 27 May, 1 p.m.). [ABSTRACT FROM AUTHOR]

For the first time, falling ice crystals were collected on glass slides covered with a thin layer of 2% formvar in chloroform at the Dome Concordia site (Dome C), Antarctica. Samplings were performed in the framework of the 27th Italian Antarctica expedition of the Italian National Program for Research in Antarctica in the period 21 February–6 August 2012. Events of clear-sky precipitations and precipitations from clouds were considered and the replicas obtained were examined under Scanning Electron Microscope (SEM). Several shapes of ice crystals were identified, including “diamond dust” (plates, pyramids, hollow and solid columns), and crystal aggregates varying in complexity. Single events often contained both small (10 μm to 50 μm) and large (hundreds of microns) crystals, suggesting that crystals can form simultaneously near the ground (height of a few hundred metres) and at higher layers (height of thousands of metres). Images of sampled crystal replicas showed that single bullets are not produced separately, but by the disintegration of combinations of bullets. Rimed ice crystals were absent in the Dome C samples, i.e. the only mode of crystal growth was water vapour diffusion. On considering the aerosol in the sampled crystals, we reached the conclusion that inertial impaction, interception and Brownian motion were insufficient to explain the scavenged aerosol. We therefore presume that phoretic forces play a role in scavenging during the crystal growth process. [ABSTRACT FROM AUTHOR]

The paper provides a review of past and a few new measurements of Ice-forming Nuclei (IN) in Antarctica. The few available published data were mostly obtained adopting different devices and methods and for a limited period of time. Consequently, data are scattered and give an incomplete picture of the Antarctic situation. It should be pointed out, however, that ice nucleation is an intricate process, depending on many parameters (supersaturation relative to ice and water, aerosol physical–chemical properties, possible conditioning and preactivation of particles, different modes of nucleation). Therefore, the uncertainty does not concern the Antarctic continent alone, but all measurements performed world-wide. A comparison of the published data can be made between Saxena and Weintraub (1988) at Palmer Station, and Ardon-Dryer et al. (2011) at the South Pole, as both studies measured IN in the immersion mode, even if at different temperature. Saxena and Weintraub (1988) obtained in three filters IN concentrations of about 104 m−3 at T=−6°C, −11°C and −13°C, and 103 m−3 at T=−17°C, in an additional filter (February–December 1983). At the South Pole Ardon-Dryer et al. (2011) obtained a concentration of about 5×102 m−3 at T=−19°C, and the IN concentration increased until about 40×103 m−3 at the activation temperature of −26°C. Such values are higher than those measured by Bigg (1973) near Antarctica, using a thermal diffusion chamber (deposition or deposition–condensation modes). IN concentrations measured at Terra Nova Bay are lower than those reported above, and are comparable to values reported for the Scott Base, Byrd Station and cruises at latitude 60°–70° S. [ABSTRACT FROM AUTHOR]

A commercial differential mobility particle sizer (DMPS), long and medium column DMA (Grimm Aerosol Technik L-DMA model 5.400; M-DMA model 5500), condensation particle counter (CPC, Grimm Aerosol Technik 5.403), and a fast mobility particle sizer (FMPS-TSI, model 3091), were deployed to determine the size distributions of ultrafine particles. Comparisons were performed using atmospheric aerosol, as well as laboratory aerosol generated by nebulizing Milli-Q water (Millipore Corporation) and a water suspension of Fe2O3in a Collison type atomizer. Results show that the DMPS generally measured higher particle number concentrations than the FMPS, above all for atmospheric aerosol compared to laboratory generated aerosol. With regard to size distribution, in both the atmospheric and laboratory-generated aerosols, the FMPS always showed a small peak around 10 nm, which was not shown by the M-DMPS. The agreement of the particle number concentration between the DMPS and FMPS was better in the 25–116 nm range for atmospheric aerosol, and in the 10–65 nm range for laboratory-generated aerosols. Since these instruments are scheduled to be run for air quality measurements and not only aerosol research purposes, there is an urgent need to establish working protocols in compliance with requirements with ISO 15900 requirements. [ABSTRACT FROM AUTHOR]

Abstract: During austral summer 2006, in the framework of the XXII Italian Antarctic expedition of PNRA (Italian National Program for Research in Antarctica), aerosol particle number size distribution measurements were performed in the 10–500 range nm over the Nansen Ice Sheet glacier (NIS, 74°30′ S, 163°27′ E; 85m a.s.l), a permanently iced branch of the Ross Sea. Observed total particle number concentrations varied between 169 and 1385cm−3. A monomodal number size distribution, peaking at about 70nm with no variation during the day, was observed for continental air mass, high wind speed and low relative humidity. Trimodal number size distributions were also observed, in agreement with measurements performed at Aboa station, which is located on the opposite side of the Antarctic continent to the NIS. In this case new particle formation, with subsequent particle growth up to about 30nm, was observed even if not associated with maritime air masses. [Copyright &y& Elsevier]

Abstract: The work presents a characterisation of aerosol sampled during three campaigns conducted in the Venice Lagoon from 30 June to 21 July 2004, from 15 February to 10 March 2005 and from 8 May to 25 May 2006. The results yield information about the physical–chemical characteristics of fine aerosol, the possible sources and its fate. Sulphate (SO4 2−), nitrate (NO3 −) and ammonium (NH4 +) are identified as the main water soluble components. The sum of these ions in the spring campaign 2006 varies from 51% to nearly 100% of PM2.5 fraction aerosol. NH4 + is found to be significantly correlated to non-sea-salt sulphate (nss-SO4 2−) and NO3 −, thus indicating the prevalent presence of ammonium nitrate and sulphate. The overall lack of a clear diurnal and seasonal cycle of sulphate suggests a transport from the Po Valley, while the diurnal and seasonal profile of nitrate concentrations suggests a prevalence of local generation. Sulphates from sea water through oxidation of dimethylsulfide (DMS) are not negligible (about 10% of the anthropogenic sulphate). The marine aerosol contribution to PM1 and PM2.5 fractions, calculated using Na+ as a tracer of sea-salts, is low (range 1–6%). In some cases chlorine depletion is observed. The content of chlorine in the aerosol particle is mostly higher than expected for marine environments (considered on the basis of Cl−/Na+ ratio). Therefore, specific sources for the element have been suggested. Oxalic acid anion, which accounts for 55% of the organic compounds examined, presents mean values 180 ng m−3 and 161 ng m−3 in the winter and spring campaigns, comparable with reported values in low polluted urban areas. In the winter campaign there is a high correlation between formate and acetate (R 2 =0.93), suggesting that a common source makes a high contribution to the measured concentrations. [Copyright &y& Elsevier]

Laboratory generated aerosols and aerosol sampled in a field campaign were studied to assess the repeatability of heterogeneous ice activation processes and verify if the ice nuclei particles maintained their nucleating capability. Experiments were performed using a filter technique, i.e. aerosol particles were sampled on black-gridded cellulose nitrate membrane filters and assessed for ice nucleating particles in a dynamic filter-processing chamber at our ISAC-CNR laboratory. The laboratory investigations used Arizona Test Dust (ATD) generated by nebulizing a suspension of ATD. After nebulization, the wet aerosol in the carrier gas was dried and then sampled on a filter. Aerosol field sampling (size range PM1 and PM10) was carried out in the Arctic (Ny-Ålesund, Svalbard) from 12 to 23 April 2019. The activation processes were repeated twice for each filter at temperatures of −22 °C and −18 °C. For aerosol, ATD runs were performed only in conditions of supersaturation (saturation ratio S w = 1.02), while for the Arctic aerosol, conditions below saturation were also considered (S w = 0.96). The experiments showed that approximately 40% of the ATD particles maintain their initial nucleating efficiency, both at T = −22 °C and − 18 °C, and at S w = 1.02, i.e. in the condensation freezing mode. The percentage of repeatability was higher for ATD with respect to the Artic-sampled aerosol processed in the condensation mode. This may depend on greater particle morphology variation of the mixed organic-inorganic aerosol due to the hydration and dehydration cycle. • Experiments showed that about 40% of ATD particles maintains the nucleating efficacy. • The repeatability was higher for ATD with respect to aerosol sampled in Arctic. • Variation of ice nucleating capability of the aerosol has atmospheric implication. • The ice nucleation shows both stochastic and deterministic behavior. [ABSTRACT FROM AUTHOR]

In this work, the ice nucleating effectiveness of Arizona Test Dust (ATD), bare and coated with NaCl, not examined in previous published papers, was investigated. The ATD, NaCl coated ATD, and NaCl aerosols were generated by nebulizing water suspensions of bare ATD, ATD-NaCl and NaCl solution. Dried aerosols were sampled on black-gridded cellulose nitrate membrane filters for ice nuclei assessment through a Dynamic Filter Processing Chamber device (DFPC). After water evaporation ATD-NaCl droplets gave rise to ATD particles coated with NaCl. Processing of filters was performed at −22 °C and − 18 °C, under sub- and super-saturated conditions (water saturation ratio S w < 1 and S w > 1, respectively). Additional experiments were performed by modifying the storage conditions of the filters to simulate variation of atmospheric conditions, i.e. air temperature and relative humidity. For this purpose, the filters were housed in Petri dishes, with silica gel, at +10 °C and −10 °C. As silica gel can desorb water from the aerosol capillary at low temperatures, storage conditions with and without silica gel can simulate the aerosol pre-activation atmospheric process. The highest activated fraction (AF) and ice-active surface site density (n s) values were obtained for ATD at −22 °C and S w = 1.02. Results showed a decrease in the AF and n s between bare and ATD coated with NaCl both at S w = 1.02 and S w = 0.96 and for filters stored in the presence of silica gel. The results obtained show the great influence exerted by NaCl coated insoluble aerosol on the ice nucleation. • Results show a decrease in ice nucleation efficiency in case of NaCl coated ATD. • These results extend toward higher temperatures previous laboratory studies. • Preactivation process was simulated by storing the filters in low RH conditions. • Activated fraction increases from sub to super-saturated water conditions. [ABSTRACT FROM AUTHOR]

Optical detectors for atmospheric aerosol concentration measurements are often used in air quality applications given their potentialities for online measurements of air quality parameters at high temporal resolution. In this work the performances of different optical aerosol detectors used in air quality applications have been tested and compared for urban background aerosol conditions. Simultaneous measurements of aerosol number concentrations, size distributions and mass concentrations were taken in two different periods: November 2013 – February 2014 and May–June 2014 at an urban background site in Lecce (Southeastern Italy). Measurements were carried out using an OPC Grimm (mod. 1.109), an OPC FAI (Multichannel Monitor) and an optical photometer Mie pDR-1200. Good correlation, with determination coefficients R 2 larger than 0.93 were found between particle number concentrations measured by the two OPCs both in accumulation (0.28–0.90 μm for FAI and 0.29–0.90 μm for Grimm) and coarse modes (1.10–10 μm for FAI and 1.15–11.25 μm for Grimm). Absolute counting for the accumulation fraction shows that Grimm OPC detects more particles (about 10%) than FAI OPC at concentration higher than 200,000 particles/L in condition of high RH. This could be due to the changes of the optical properties of particles in high RH conditions visible even if the inlets of the two instruments are conditioned for lowering RH in sampled air. The differences in the absolute counting of the coarse fraction does not seems to be related to RH effects. The performances in evaluating mass concentrations PM10, and PM2.5 were evaluated comparing OPCs and pDR-1200 outputs with reference gravimetric and β-ray methods (that appeared to be essentially equivalent). Good agreement between Grimm OPC and SWAM is found both in PM10 and PM2.5 fractions while FAI OPC revealed greater discrepancy and scatter with respect to reference measurements. The performances of the pDR-1200 photometer were lower with respect to the OPCs with a larger influence of RH and optical properties of particles. The analysis of diurnal average trends in number and mass concentrations as well as the high temporal resolution responses of the instruments showed that optical detectors could be very useful to investigate atmospheric aerosol for air quality applications and to individuate and investigate specific pollution events. However, especially if they are used for evaluating mass concentrations (PM1, PM2.5 or PM10), it is necessary to take into account RH effects (even if the inlet are conditioned) and, possibly, use optical detectors together with reference gravimetric or β-ray methods to check their response in the effective operative conditions. [ABSTRACT FROM AUTHOR]

The Arctic is warming at more than twice the rate of the global average. This warming is influenced by clouds, which modulate the solar and terrestrial radiative fluxes and, thus, determine the surface energy budget. However, the interactions among clouds, aerosols, and radiative fluxes in the Arctic are still poorly understood. To address these uncertainties, the Ny-Ålesund Aerosol Cloud Experiment (NASCENT) study was conducted from September 2019 to August 2020 in Ny-Ålesund, Svalbard. The campaign's primary goal was to elucidate the life cycle of aerosols in the Arctic and to determine how they modulate cloud properties throughout the year. In situ and remote sensing observations were taken on the ground at sea level, at a mountaintop station, and with a tethered balloon system. An overview of the meteorological and the main aerosol seasonality encountered during the NASCENT year is introduced, followed by a presentation of first scientific highlights. In particular, we present new findings on aerosol physicochemical and molecular properties. Further, the role of cloud droplet activation and ice crystal nucleation in the formation and persistence of mixed-phase clouds, and the occurrence of secondary ice processes, are discussed and compared to the representation of cloud processes within the regional Weather Research and Forecasting Model. The paper concludes with research questions that are to be addressed in upcoming NASCENT publications. [ABSTRACT FROM AUTHOR]

Abstract: The work presents the results of an experimental campaign performed at the Drop Tower Facility (Bremen) in microgravity conditions, concerning the scavenging process of an evaporating single droplet in stationary conditions. In the experimental conditions the thermo- and diffusiophoretic forces are the only ones that can determine the scavenging of the aerosol. The research is finalized to help solve the open question concerning the contribution of thermo- and diffusiophoretic forces in aerosol scavenging process due to cloud droplets. Although earlier theoretical and experimental papers have addressed this problem, the results are contradictory and inconclusive. As phoretic forces depend on aerosol diameter and water vapour pressure gradient, experiments were performed by changing the aerosol diameter (range 0.4μm–2μm) and the water vapour gradient. The experimental results show a prevalence of the diffusiophoretic over thermophoretic force, for the considered aerosol. The measured values of the particle velocities due to phoretic forces increase with increasing aerosol diameter and vapour pressure gradient. [Copyright &y& Elsevier]

The Venice Lagoon is subjected to long-range transport of contaminants via aerosol from the near Po Valley. Moreover, it is an area with significant local anthropogenic emissions due to the industrial area of Porto Marghera, the urban centres, and the glass factories and with emissions by ships traffic within the Lagoon. Furthermore, since 2005, the Lagoon has also been affected by the construction of the MOSE (Modulo Sperimentale Elettromeccanico--Electromechanical Experimental Module) mobile dams, as a barrier against the high tide. This work presents and discusses the results from chemical analyses of bulk depositions, carried out in different sites of the Venice Lagoon. Fluxes of pollutants were also statistically analysed on PCA with the aim of investigating the spatial variability of depositions and their correlation with precipitations. Fluxes of inorganic pollutants depend differently on precipitations, while organic compounds show a more seasonal trend. The statistical analysis showed that the site in the northern Lagoon has lower and almost homogeneous fluxes of pollutants, while the other sites registered more variable concentrations. The study also provided important information about the annual trend of pollutants and their evolution over a period of about five years, from 2005 to 2010. [ABSTRACT FROM AUTHOR]

The direct influence of ship traffic on atmospheric levels of coarse and fine particulate matter (PM2.5, PM10) and fifteen polycyclic aromatic hydrocarbons (PAHs) has been estimated in the urban area of Venice. Data analysis has been performed on results collected at three sites over the summer, when ship traffic is at a maximum. Results indicate that monitoring of the PM daily concentrations is not sufficiently detailed for the evaluation of this contribution, even though it could be useful for specific markers such as PAHs. Therefore a new methodology, based on high temporal resolution measurements coupled with wind direction information and the database of ship passages of the Harbour Authority of Venice has been developed. The sampling sites were monitored with optical detectors (DustTrack® and Mie pDR-1200) operating at a high temporal resolution (20s and 1s respectively) for PM2.5 and PM10. PAH in the particulate and gas phases were recovered from quartz fibre filters and polyurethane foam plugs using pressurised solvent extraction, the extracts were then analysed by gas chromatography- high-resolution mass spectrometry. Our results shows that the direct contribution of ships traffic to PAHs in the gas phase is 10% while the contribution to PM2.5 and to PM10 is from 1% up to 8%. [Copyright &y& Elsevier]

Ultrasonic anemometers are widely used to investigate turbulence in the surface layer. Some of their advantages are high-frequency sampling, the ability to work for long periods without a resident operator (even in adverse meteorological conditions), and their calibration related only to design parameters. In this paper an analysis of the random uncertainty associated with ultrasonic anemometer measurements is reported. The analysis is based on a statistical procedure that compares the simultaneous data taken with two identical anemometers operating in nominally identical conditions. Postprocessing of data has been carried out in different reference systems in order to evaluate how the random uncertainties change according to the postprocessing procedure used. Results show that uncertainty on wind velocity decreases with averaging time, and it can be as low as 1 cm s-1 for a typical averaging time of 30 min. The random uncertainty on average vertical wind velocity could also be as low as 1 cm s-1, and it is very sensitive to the effects of vertical misalignment. The analysis is based on six different measurement sets in which the anemometers have been deployed on a single mast or in two separate masts with and without additional detectors placed near the anemometers themselves. Results indicate that the uncertainty of all the measured parameters increases when the anemometer is used in configurations in which they are placed on separate masts. Several parameters also show an additional increase of uncertainty if other detectors are placed nearby. The relative random uncertainty on momentum and sensible heat fluxes, for typical averaging time, can be as low as 6%–7% and it could increase to a factor of 2–3 when they are placed on separate masts. Only small effects due to the influence of flow distortions caused by the presence of additional sensors have been found on fluxes and are mainly related to sensible heat flux. [ABSTRACT FROM AUTHOR]

Measurement campaigns at the high mountain Observatory Mt. Cimone (CMN; 2165 m a.s.l.) were performed during May 2014 and October 2015. The concentration of Ice Nucleating Particles (INPs) were measured offline with a dynamic filter processing chamber (DFPC), in the deposition and condensation mode, after collecting PM 1 and PM 10 aerosol samples. Presented INP data are the first ever published for a high mountain site in the Mediterranean basin. During the May campaign, parallel INP measurements were also carried out at San Pietro Capofiume (SPC), a low altitude rural background area within the Po Valley basin, by the same offline technique. The average INP PM10 concentration at CMN was 86 m −3 (saturation ratio S w = 1.01; T = −18 °C) during the May 2014 campaign, while it was 171 m −3 at SPC, in the same period. A lower average INP PM10 concentration was observed at CMN during October 2015 (43 m −3 ). A significantly higher activated fraction (AF) characterized the October 2015 campaign, suggesting that the seasonal changes in the aerosol sources have an impact on the INP efficiency of the aerosol at CMN. Super-micrometer INP contributed for ∼30% of total INP in the May 2014 campaign, at both sites, and for ∼70% in the October 2015 campaign, showing the importance of coarse particles in the INP population. The analysis of meteorological parameters, gaseous tracers concentrations and backwards trajectories suggests that the INP population at CMN is contributed by transport processes occurring at diverse spatial scales, from the local to the synoptic scale. During the Saharan Dust transport Event observed in May 2014, a reduction of the AF was observed, suggesting, for this case, a limited ice nucleating activity for Saharan dust particles. This may be due to physico-chemical aging of the Saharan dust particles during transport or to the relatively high activation temperature at which the experiments were performed in this study. [ABSTRACT FROM AUTHOR]

Indoor air samples from libraries and archives in Florence, Italy, were collected and analysed for a variety of volatile organic compounds. The aim was to perform a characterisation of the indoor air quality, and try to elucidate if there are VOCs that may cause or result from the determination of the cultural heritage institutions. All compounds of interest were regularly detected, with BTEXs (Benzene, Toluene, Ethylbenzene, Xylenes) being the most abundant and followed by cyclic volatile methylsiloxanes, aldehydes, terpenes and organic acids. The prevalence and qualitative characteristics, such as concentrations, profiles and indoor/outdoor ratios of BTEXs underline the important influence of the outdoor air infiltrations on the indoor air concentrations. Acetic acid that is a substance that can oxidise books and other exposed objects was detected at concentrations ranging between 1.04 and 18.9 μg m − 3 , while furfural, that is a known marker of paper degradation, was constantly present at concentrations that ranged between 5.26 and 32.6 μg m − 3 . This work shows the importance that indoor air quality monitoring campaigns can have in order to give early warning to cultural heritage institution managers about the impact that indoor air quality can have on exposed and/or preserved objects. [ABSTRACT FROM AUTHOR]

Cellulose acetate (CA) nanofibers were prepared via electrospinning to obtain a high quality factor (QF) fibrous mat for aerosol particle filtration. To this purpose, special attention was paid to the substrate material used to collect the nanofibers. Different materials (glassine paper, Lyocell, nylon grids) were investigated for use as substrates in the membrane spinning process. Membrane and membrane fiber morphologies were characterized by optical microscope and scanning electron microscope (SEM) analyses. Results show that the arrangement of the membrane fibers is directly correlated to the morphology of the collecting substrate material. Experiments shows that the electrospun nanofiber web tends to recreate the specific character of the supporting textile texture. A support with a pronounced bi-dimensional structure should be preferred. A regular grid, made of nylon, is selected for the composition with CA nanofibres. By maintaining the same support, various electrospinning parameters such as the spinning solution CA concentration (14 wt%, 18 wt%) and spinning volume (15–120 μL) of the membranes are tested in terms of air filtration performance. Filtration tests are performed by measuring the filter penetration against neutralized aerosol particles. Basis weight, solid volume fraction and thickness parameter were investigated to find the best arrangement. The filtration efficiency of stacked layers is analyzed at variable thickness of the building block element. An electrospun membrane of above 60 μm thickness, combined with the selected substrate, increases the QF and improve its reproducibility. The QF can be further increased with an optimized porosity of the nylon substrate. The best QF of 0.080±0.050 Pa −1 at 300 nm was obtained by spinning a 14 wt% CA solution in an acetone- DMSO-acetic acid solvent mixture on a nylon grid with 100 μm mesh size producing fleeces with a very low pressure drop (7 Pa). Thermogravimetric analyses (TGA) and SEM imaging demonstrated the stability of the composite filter morphology up to 200 °C. [ABSTRACT FROM AUTHOR]

Polylactide/polyhydroxybutyrate ( PLA / PHB ) nanofibers were prepared by electrospinning and functionalized with different amounts of ammonium-based ionic liquid ( IL ) belonging to quaternary ammonium compounds ( QACs ) to obtain a fibrous mat with antimicrobial properties for aerosol particle filtration. The filtration performance of these biopolymer nanofiber mats was evaluated by measuring the filter penetration of sodium chloride (NaCl) aerosol particles ranging from 20 to 600 nm. These filtration test results showed that the quality factors remain unvaried with the addition of IL and depend mostly on the electrospinning time. The “multi-layering” method was adopted to fabricate highly efficient nanofiber filters with a greatly reduced pressure drop. A quantitative analysis of the antimicrobial activity is also presented. The results show that renewable materials, such as PLA blended with PHB , can be considered for biodegradable filters, in line with the future trend to develop eco-sustainable products. Adding QAC salt to the biopolymer blend combines these qualities with an innovative bactericidal nanomaterial. [ABSTRACT FROM AUTHOR]

Abstract: The work presents the results of an experimental campaign performed at a rural site (S. Pietro Capofiume, near Bologna July 2007) concerning measurements of ice nuclei in different size classes of aerosol: PM1, PM2.5, PM10 and total suspended particles (TSP). Simultaneous measurements of particle number concentrations were also performed. Aerosol in the PM1 fraction contributes about 50% of the measured ice nuclei number concentration, and in the PM10 fraction contributes about 70–90%. Consequently, the dominant fraction of aerosol that can be activated as ice nuclei involves particles with aerodynamic diameter less than 10 μm. A positive correlation is observed between higher supersaturation with respect to ice and water (S ice and S w, respectively) values, and ice nuclei number concentration. The variations of S w from 2 to 10% and S ice from 20 to 32% (T air =−15 °C) determine an approximately threefold increase (from 110 to 337 m−3) in the ice nuclei average number concentration. There is no correlation between ice nuclei measured in the different size ranges, either with the particle number concentration measured with the counter spectrometer (d >0.3 μm) or with the condensation nuclei counter. [Copyright &y& Elsevier]

Abstract: Brownian diffusion of aerosol particles was studied in microgravity conditions using a digital holographic velocimeter. Based on digital image processing, the observed volume, recorded on a charge-coupled device (CCD) camera, is reconstructed slice by slice in order to achieve a full focused volume. Three dimensional coordinates of the particles are retrieved by such procedures and particle trajectories are reconstructed by analysing the sequence of the particle position. We deduced that the displacement of particles in microgravity, due to Brownian motion, follows a Gaussian distribution, like at 1 g. Particle sizes obtained from SEM measurements were in good agreement with those calculated from the three dimensional trajectories provided by the holographic microscope. [Copyright &y& Elsevier]

Although biogas production can have some benefits, there is a research gap on potential influence of biogas plant emissions on local air quality, thus an accurate and comprehensive evaluation of impacts of this technology is needed. This study deals with this issue by means of a characterisation of air pollution near an industrial area including a biogas production (from biomass) and combustion plant located in South Italy. The methodology consists in advanced statistical analysis on concentration of gaseous pollutants, particles concentration and size distribution in number and mass, and PM 2.5 chemical composition. High-temporal resolution measurements, supported by ancillary meteorological parameters, and source apportionment of PM 2.5 using Positive Matrix Factorization (PMF) receptor model, are performed. The integrated approach provides the emissive picture consisting in different anthropogenic sources (i.e. traffic, biomass burning, and industrial facilities) with particular focus on biogas plant emissions. Results showed that CO and nitrogen oxides were influenced by vehicular traffic and biomass combustion, however, a contribution of the plant to NO was observed. SO 2 was influenced mainly by transport from the industrial zone, but a second local contribution compatible with the emissions of the biogas plant was detected. Number particle concentrations were analysed in four size ranges: nanoparticles (D < 0.05 μm), ultrafine particles (D < 0.3 μm), accumulation (0.3 < D < 1 μm) and coarse particles (D > 1 μm). Nanoparticles and ultrafine particles were mainly influenced by vehicular traffic and biomass burning, instead, a contribution of the plant was individuated in the accumulation mode. PMF5 identified the contribution of six sources: crustal (14.7% ± 2.1% of measured PM 2.5); marine aerosol (aged) (12.9% ± 2.3%); biomass burning (32.8% ± 1.4%); secondary sulphate (19.7% ± 2.4%); primary industrial emissions (5.4% ± 2.3%); traffic and secondary nitrate (17.0% ± 3.9%). The plant is likely to contribute to both sources, the industrial and the traffic plus secondary nitrate. Unlabelled Image • Air quality was investigated near a biogas production and combustion plant. • Biomass burning was the main source for CO, NO X , nanoparticles, and PM 2.5. • Plant's contribution to NO, SO 2 , accumulation mode particles and nitrate were found. • PM 2.5 source apportionment showed relevant secondary contributions. • Biogas plant contributes to specific odorous compounds like DMA in PM 2.5. [ABSTRACT FROM AUTHOR]