CNR ISAC Rome Atmospheric Supersite Italy

Publications

  • Article
    Barnaba, Francesca; Bolignano, Andrea; Liberto, Luca Di; Morelli, Matteo; Lucarelli, Franco; Nava, Silvia; Perrino, Cinzia; Canepari, Silvia; Basart, Sara; Costabile, Francesca; Dionisi, Davide; Ciampichetti, Spartaco; Sozzi, Roberto; Gobbi, Gian Paolo
    Atmospheric Environment. 2017, Vol. 161, p. 288-305. DOI: 10.1016/j.atmosenv.2017.04.038
    • Publication URL http://www.sciencedirect.com/science/article/pii/S1352231017302820
    • Keywords Desert-dust, PM10, Air quality, Directive 2008/50/EC, Resuspension, Italy
    • Abstract In 2011 the European Commission (EC) released specific ‘Guidelines’ describing the methods to quantify and subtract the contribution of natural sources from the PM10 values regulated by the European Air Quality Directive (2008/50/EC). This work investigates the applicability to Italy of the EC-Methodology suggested for desert-dust, describes main limitations encountered and proposes specific modifications embedded within a ‘revised-Methodology’ to extend/improve its use. The revised-Methodology capabilities are evaluated using original, chemically-resolved mineral-dust mass concentration measurements, showing better performances in predicting timing and absolute values of the desert-dust contribution to the daily-PM10 with respect to the current EC-approach. The revised-Methodology is then translated into an automatic (user-independent) tool tailored to the expected final-users. This tool is applied over Central Italy across a 3-year long period (2012–2014), and over the whole Italian country for a calendar year (2012). The derived results confirm and extend to Italian regions never addressed before some previously observed features of the desert-dust impact over the country, such as a clear latitudinal dependence of the desert-dust impact on the yearly average PM10 (from more than 5 μg/m3 to less than 0.5 μg/m3, going from south to north Italy). The modifications introduced within the revised-Methodology also suggest a non-negligible role of desert-dust resuspension in areas characterized by both high traffic levels and soil sealing (urban areas and along the major Italian routes). In the Rome area, such an effect is found to add a contribution of about 2 μg/m3 (i.e., of 20) to the mean desert-dust load per dust day (about 10 μg/m3). At the national level, this effect contributes increasing the total number of desert-dust-driven exceedances of the PM10 daily limit value even in the northern regions, where the desert-dust impact on the PM10 yearly average is otherwise limited. These results also indicate the direction for possible mitigation strategies to be applied over impacted areas. The successful implementation of the revised-Methodology over Italy suggests it could represent a valid option for a nationwide standard procedure to quantify the desert-dust contribution to PM10, promoting the homogenisation of the relevant values annually reported to the EC.
  • Article
    Struckmeier, C.; Drewnick, F.; Fachinger, F.; Gobbi, G. P.; Borrmann, S.
    Atmospheric Chemistry and Physics. 2016, Vol. 16, Issue 23, p. 15277-15299. DOI: 10.5194/acp-16-15277-2016
    • Publication URL https://www.atmos-chem-phys.net/16/15277/2016/
    • Abstract Investigations on atmospheric aerosols and their sources were carried out in October/November 2013 and May/June 2014 consecutively in a suburban area of Rome (Tor Vergata) and in central Rome (near St Peter’s Basilica). During both years a Saharan dust advection event temporarily increased PM\(_{10}\) concentrations at ground level by about 12–17 µg m\(^{−3}\). Generally, in October/November the ambient aerosol was more strongly influenced by primary emissions, whereas higher relative contributions of secondary particles (sulfate, aged organic aerosol) were found in May/June. Absolute concentrations of anthropogenic emission tracers (e.g. NO\(_{x}\), CO\(_{2}\), particulate polycyclic aromatic hydrocarbons, traffic-related organic aerosol) were generally higher at the urban location. Positive matrix factorization was applied to the PM\(_{1}\) organic aerosol (OA) fraction of aerosol mass spectrometer (HR-ToF-AMS) data to identify different sources of primary OA (POA): traffic, cooking, biomass burning and (local) cigarette smoking. While biomass burning OA was only found at the suburban site, where it accounted for the major fraction of POA (18–24  of total OA), traffic and cooking were more dominant sources at the urban site. A particle type associated with cigarette smoke emissions, which is associated with a potential characteristic marker peak (\(m∕z 84\), C\(_{5}\)H\(_{10}\)N\(^{+}\), a nicotine fragment) in the mass spectrum, was only found in central Rome, where it was emitted in close vicinity to the measurement location. Regarding secondary OA, in October/November, only a very aged, regionally advected oxygenated OA was found, which contributed 42–53  to the total OA. In May/June total oxygenated OA accounted for 56–76  of the OA. Here a fraction (18–26  of total OA) of a fresher, less oxygenated OA of more local origin was also observed. New particle formation events were identified from measured particle number concentrations and size distributions in May/June 2014 at both sites. While they were observed every day at the urban location, at the suburban location they were only found under favourable meteorological conditions, but were independent of advection of the Rome emission plume. Particles from sources in the metropolitan area of Rome and particles advected from outside Rome contributed 42–70 and 30–58  to the total measured PM\(1\), respectively. Apart from the general aerosol characteristics, in this study the properties (e.g. emission strength) and dynamics (e.g. temporal behaviour) of each identified aerosol type is investigated in detail to provide a better understanding of the observed seasonal and spatial differences.
  • Article
    Leblanc, T.; Sica, R. J.; van Gijsel, J. A. E.; Haefele, A.; Payen, G.; Liberti, G.
    Atmospheric Measurement Techniques. 2016, Vol. 9, Issue 8, p. 4079-4101. DOI: 10.5194/amt-9-4079-2016
    • Publication URL https://www.atmos-meas-tech.net/9/4079/2016/
    • Abstract A standardized approach for the definition, propagation, and reporting of uncertainty in the temperature lidar data products contributing to the Network for the Detection for Atmospheric Composition Change (NDACC) database is proposed. One important aspect of the proposed approach is the ability to propagate all independent uncertainty components in parallel through the data processing chain. The individual uncertainty components are then combined together at the very last stage of processing to form the temperature combined standard uncertainty.

      The identified uncertainty sources comprise major components such as signal detection, saturation correction, background noise extraction, temperature tie-on at the top of the profile, and absorption by ozone if working in the visible spectrum, as well as other components such as molecular extinction, the acceleration of gravity, and the molecular mass of air, whose magnitudes depend on the instrument, data processing algorithm, and altitude range of interest.

      The expression of the individual uncertainty components and their step-by-step propagation through the temperature data processing chain are thoroughly estimated, taking into account the effect of vertical filtering and the merging of multiple channels. All sources of uncertainty except detection noise imply correlated terms in the vertical dimension, which means that covariance terms must be taken into account when vertical filtering is applied and when temperature is integrated from the top of the profile. Quantitatively, the uncertainty budget is presented in a generic form (i.e., as a function of instrument performance and wavelength), so that any NDACC temperature lidar investigator can easily estimate the expected impact of individual uncertainty components in the case of their own instrument.

      Using this standardized approach, an example of uncertainty budget is provided for the Jet Propulsion Laboratory (JPL) lidar at Mauna Loa Observatory, Hawai’i, which is typical of the NDACC temperature lidars transmitting at 355 nm. The combined temperature uncertainty ranges between 0.1 and 1 K below 60 km, with detection noise, saturation correction, and molecular extinction correction being the three dominant sources of uncertainty. Above 60 km and up to 10 km below the top of the profile, the total uncertainty increases exponentially from 1 to 10 K due to the combined effect of random noise and temperature tie-on. In the top 10 km of the profile, the accuracy of the profile mainly depends on that of the tie-on temperature. All other uncertainty components remain below 0.1 K throughout the entire profile (15–90 km), except the background noise correction uncertainty, which peaks around 0.3–0.5 K. It should be kept in mind that these quantitative estimates may be very different for other lidar instruments, depending on their altitude range and the wavelengths used.
  • Article
    Costabile, F.; Angelini, F.; Barnaba, F.; Gobbi, G.P.
    Atmospheric Environment. 2015, Vol. 102, p. 136-144. DOI: 10.1016/j.atmosenv.2014.11.064
    • Publication URL http://www.sciencedirect.com/science/article/pii/S1352231014009364
    • Keywords Black carbon, Single Scattering Albedo, Ultrafine BC, Mediterranean, Urban areas, Airport
    • Abstract In this work, we characterize the Black Carbon (BC) aerosol in an urban airport vs. urban background environment with the objective to evaluate when and how the ultrafine BC dominates the bulk aerosol. Aerosol optical and microphysical properties were measured in a Mediterranean urban area (Rome) at sites impacted by BC sources including fossil fuels (FF), and biomass burning (BB). Experimental BC data were interpreted through measurement-constrained simulations of BC microphysics and optical properties. A “scheme” to separate the ultrafine BC was experimented on the basis of the relation found between changes in the BC partitioning between Aitken and accumulation mode particles, and relevant changes in particle size distribution and optical properties of the bulk aerosol. This separation scheme, applied to experimental data, proved useful to reveal the impact of airport and road traffic emissions. Findings may have important atmospheric implications. The experimented scheme can help separating different BC sources (FF, BB, “aged” BC) when BC size distributions may be very difficult to obtain (satellite, columnar observations, routine monitoring). Indeed, separating the ultrafine BC from the fine BC may provide significant benefits in addressing BC impact on air quality and climate.
  • Article
    Gobbi, G. P.; Angelini, F.; Barnaba, F.; Costabile, F.; Baldasano, J. M.; Basart, S.; Sozzi, R.; Bolignano, A.
    Atmospheric Chemistry and Physics. 2013, Vol. 13, Issue 15, p. 7395-7404. DOI: 10.5194/acp-13-7395-2013
    • Publication URL https://www.atmos-chem-phys.net/13/7395/2013/
    • Abstract Particulate matter mass concentrations measured in the city of Rome (Italy) in the period 2001–2004 have been cross-analysed with concurrent Saharan dust advection events to infer the impact these natural episodes bear on the standard air quality parameter PM\(_{10}\) observed at two city stations and at one regional background station. Natural events such as Saharan dust advections are associated with a definite health risk. At the same time, the Directive 2008/50/EC allows subtraction of PM exceedances caused by natural contributions from statistics used to determine air quality of EU sites. In this respect, it is important to detect and characterise such advections by means of reliable, operational techniques. To assess the PM\(_{10}\) increase we used both the regional-background method suggested by EC Guidelines and a local background method, demonstrated to be most suited to this central Mediterranean region. In terms of exceedances, the two approaches provided results within ~20 of each other at background sites, and at ~50 of each other in traffic conditions.

      The sequence of Saharan advections over the city has been either detected by Polarization Lidar (laser radar) observations or forecast by the operational numerical regional mineral dust model BSC-DREAM8b of the Barcelona Supercomputing Centre. Lidar observations were also employed to retrieve the average physical properties of the dust clouds as a function of height. Over the four-year period, Lidar measurements (703 evenly distributed days) revealed Saharan plumes transits over Rome on 28.6 of the days, with minimum occurrence in wintertime. Dust was observed to reach the ground on 17.5 of the days totalling 88 episodes. Most (90) of these advections lasted up to 5 days, averaging to ~3 days. Median time lag between advections was 7 days. Typical altitude range of the dust plumes was 0–6 km, with the centre of mass at ~3 km a.g.l. BSC-DREAM8b model simulations (1461 days) predicted Lidar detectable (532 nm extinction coefficient > 0.005 km\(^{-1}\)) dust advections on 25.9 of the days, with ground contacts on 13 of the days. As in the Lidar case, the average dust centre of mass was forecast at ~3 km. Along the 703 day Lidar dataset, model forecast and Lidar detection of the presence of dust coincided on 80 of the cases, 92 coincidences are found within a ±1 day window.

      Combination of the BSC-DREAM8b and Lidar records leads to about 21 of the days being affected by presence of Saharan dust at the ground. This combined dataset has been used to compute the increase in PM with respect to dust-unaffected previous days. This analysis has shown Saharan dust events to exert a meaningful impact on the PM\(_{10}\) records, causing average increases of the order of 11.9 μg m\(^{-3}\). Conversely, PM\(_{10}\) increases computed relying only on the Lidar detections (i.e., presence of dust layers actually observed) were of the order of 15.6 μg m\(^{-3}\). Both analyses indicate the annual average contribution of dust advections to the city PM\(_{10}\) mass concentrations to be of the order of 2.35 μg m\(^{-3}\). The number of exceedances attributable to Saharan advections at the three station types addressed in this study (urban traffic, urban background and regional background) were found to be 25, 30 and 43, respectively. These results confirm Saharan advections in the central Mediterranean as important modulators of PM\(_{10}\) loads and exceedances.
  • Article
    Costabile, F.; Barnaba, F.; Angelini, F.; Gobbi, G. P.
    Atmospheric Chemistry and Physics. 2013, Vol. 13, Issue 5, p. 2455-2470. DOI: 10.5194/acp-13-2455-2013
    • Publication URL https://www.atmos-chem-phys.net/13/2455/2013/
    • Abstract Characterizing chemical and physical aerosol properties is important to understand their sources, effects, and feedback mechanisms in the atmosphere. This study proposes a scheme to classify aerosol populations based on their spectral optical properties (absorption and scattering). The scheme is obtained thanks to the outstanding set of information on particle size and composition these properties contain. The spectral variability of the aerosol single scattering albedo (dSSA), and the extinction, scattering and absorption Angstrom exponents (EAE, SAE and AAE, respectively) were observed on the basis of two-year measurements of aerosol optical properties (scattering and absorption coefficients at blue, green and red wavelengths) performed in the suburbs of Rome (Italy). Optical measurements of various aerosol types were coupled to measurements of particle number size distributions and relevant optical properties simulations (Mie theory). These latter allowed the investigation of the role of the particle size and composition in the bulk aerosol properties observed. The combination of simulations and measurements suggested a general paradigm built on dSSA, SAE and AAE to optically classify aerosols. The paradigm proved suitable to identify the presence of key aerosol populations, including soot, biomass burning, organics, dust and marine particles. The work highlights that (i) aerosol populations show distinctive combinations of SAE and dSSA times AAE, these variables being linked by a linear inverse relation varying with varying SSA; (ii) fine particles show EAE > 1.5, whilst EAE < 2 is found for both coarse particles and ultrafine soot-rich aerosols; (iii) fine and coarse particles both show SSA > 0.8, whilst ultrafine urban Aitken mode and soot particles show SSA < 0.8. The proposed paradigm agrees with aerosol observations performed during past major field campaigns, this indicating that relations concerning the paradigm have a general validity.