Lina Vitali

On the complexity of the boundary layer structure and aerosol vertical distribution in the coastal Mediterranean regions: a case study

The planetary boundary layer structure in the coastal areas, and particularly in complex orography regions such as the Mediterranean, is extremely intricate. In this study, we show the evolution of the planetary boundary layer based on in situ airborne measurements and ground-based remote sensing observations carried out during the MORE (Marine Ozone and Radiation Experiment) campaign in June 2010. The campaign was held in a rural coastal Mediterranean region in Southern Italy. The study focuses on the observations made on 17 June. Vertical profiles of meteorological parameters and aerosol size distribution were measured during two flights: in the morning and in the afternoon. Airborne observations were combined with ground-based LIDAR, SODAR, microwave and visible radiometer measurements, allowing a detailed description of the atmospheric vertical structure. The analysis was complemented with data from a regional atmospheric model run with horizontal resolutions of 12, 4 and 1 km, respectively; back-trajectories were calculated at these spatial resolutions. The observations show the simultaneous occurrence of dust transport, descent of mid-tropospheric air and sea breeze circulation on 17 June. Local pollution effects on the aerosol distribution, and a possible event of new particles formation were also observed. A large variability in the thermodynamical structure and aerosol distribution in the flight region, extending by approximately 30 km along the coast, was found. Within this complex, environment-relevant differences in the back-trajectories calculated at different spatial resolutions are found, suggesting that the description of several dynamical processes, and in particular the sea breeze circulation, requires high-resolution meteorological analyses. The study also shows that the integration of different observational techniques is needed to describe these complex conditions; in particular, the availability of flights and their timing with respect to the occurring phenomena are crucial.

Modeling Air Quality over Italy with MINNI Atmospheric Modeling System: From Regional to Local Scale

This study shows part of the results obtained during the operational evaluation of MINNI atmospheric modeling system over Italy. MINNI is the Italian Integrated Assessment Modelling System for supporting the International Negotiation Process on Air Pollution and assessing Air Quality Policies at national/local level sponsored by the Italian Ministry of the Environment. The evaluation was carried out for both meteorology and air quality for the years 1999 and 2005. Changes of meteorological variables and of ozone concentrations in relation to the change of horizontal grid resolution were also investigated. The results show the capability of the modelling system to reconstruct the meteorological and ozone fields over Italy.

Study of the Impact of Low vs. High Resolution Meteorology on Air Quality Simulations Using the MINNI Model Over Italy

Modelling air quality requires the description of a large number of processes interacting each other. In order to properly model concentrations of atmospheric pollutants it is crucial to have a realistic reproduction of meteorological parameters, which can be critical in areas presenting a complex orography like the Italian peninsula. This work shows an analysis of the results obtained with the national model MINNI at two different horizontal resolutions (20 and 4 km), for a whole year over Italy. Comparisons between modelled and observed temperature and pollutants concentrations are carried out. The prediction of temperature is improved with the increase of model spatial resolution, as it is for pollutants like NO2 and CO, while the improvement is not always evident for O3 concentrations. Results are discussed providing an interpretation of the observed features.

Ozone Modeling over Italy: A Sensitivity Analysis to Precursors Using BOLCHEM Air Quality Model

The sensitivity of ozone to the reduction of NOx and VOC over Italy has been investigated with the air quality model BOLCHEM, which includes two photochemical mechanisms: SAPRC-90 and CB-IV. The study has been carried out for some case studies during the years 1999 and 2003. The results show the relative importance of precursors in reducing the ozone levels and allow identifying regions of Italy where local emissions reduction strategies are less effective. This study also shows the effect of the errors in isoprene inventories on ozone concentrations.

BOLCHEM Air Quality Model: Performance Evaluation over Italy

The modeling system BOLCHEM for air quality simulations has been run to study the evolution of tropospheric ozone over the Italian peninsula during 1999. The comparison of measured and modeled ozone time series shows that BOLCHEM predicts well the ozone concentrations. The summer cases are better simulated than the winter ones. The model configuration using SAPRC90 meets always the US-EPA criteria for the statistical indexes UPA, MNBE and MANGE. The Italian peninsula has a very complex topography, therefore the separation of meteorology and chemistry in offline simulations can lead to a loss of potentially important information about atmospheric processes, which often have a much smaller time scale than the meteorological output frequency. Here, we show the ability of a new developed air quality model, BOLCHEM, to reproduce the observed ozone concentrations for four clear sky periods (one from winter, the others from summer season) selected based on Meteosat images of Europe. The calculated O3 concentrations were compared with measurements made at rural or semi-rural stations. The statistical measures recommended by the U.S. Environmental Protection Agency (US-EPA, 2005) for air quality model validations were also computed for hourly values of ozone concentration. BOLCHEM couples the meteorological model BOLAM (Buzzi et al., 2003) to SAPRC90 (Carter, 1990), and CB-IV (Gery et al., 1989) as alternative photochemi- cal mechanisms. The mechanisms were chosen since they adopt different criteria for grouping the organic gases: CB-IV groups the organics according to bond type, while SAPRC90 groups them according to molecule type. Figure 1 shows that the agreement between simulated and measured ozone concentrations is good for both summer and winter. Generally, the model has diffi- culties in reproducing low ozone concentrations observed during the winter and during the night. A more extensive discussion of the results can be found in Mircea et al. (2007). Table 1 shows the statistical indexes recommended by US-EPA (US- EPA, 2005). It can be seen that generally, UPA is lower than 35%, MNBE is lower than 15%, MANGE is lower than 30-35%.

Application of a Land Cover Indicator to Characterize Spatial Representativeness of Air Quality Monitoring Stations Over Italy

In order to achieve a cost-effective control of air quality in one region and to evaluate effects on population of long term exposure to air pollution, the assessment of spatial representativeness of air quality monitoring stations is of fundamental relevance. In this work, the area of representativeness has been assessed by means of a synthetic indicator describing the dependency of concentration on land cover distribution. The rationale is that, the more variable is the indicator in the surroundings of the station, the less representative are the concentrations measured at the air quality station in the surroundings. Pollutants under investigation were PM2.5 and O3 and the CORINE land cover map of 2006 was used with ad hoc modifications. The variability of the indicator was explored within circular buffers around the sites, with increasing radii resulting below the established threshold of 20 % for almost all cases. Results showed that the methodology allows an useful and quick assessment of spatial representativeness of a monitoring site, without the need of dedicated measurement campaigns.

Air quality modeling and inhalation health risk assessment for a new generation coal-fired power plant in Central Italy

An assessment of potential carcinogenic and toxic health outcomes related to atmospheric emissions from the new-generation coal fired power plant of Torrevaldaliga Nord, in Central Italy, has been conducted. A chemical-transport model was applied on the reference year 2010 in the area of the plant, in order to calculate airborne concentrations of a set of 17 emitted pollutants of health concern. Inhalation cancer risks and hazard quotients, for each pollutant and for each target organ impacted via the inhalation pathway, were calculated and mapped on the study domain for the overall ambient concentrations and for the sole contribution of the plant to airborne concentrations, allowing to assess the relative contribution of the power plant to the risk from all sources. Cancer risks, cumulated on all pollutants, resulted around 5 × 10-5 for the concentrations from all sources and below 3 × 10-7 for the plant contribution, mainly targeting the respiratory system. On each part of the study domain, the plant contributed for less than 6% to the overall cancer risk. Hazard quotients from all sources, cumulated on all pollutants, reached values of 2.5 for the respiratory and 1.5 for the cardiovascular systems. Hazard quotients of non-carcinogenic risks from the plant, cumulated on all pollutants, resulted below 0.03 for the respiratory system and 0.02 for the cardiovascular system. On each part of the study domain, the plant contributed for less than 5% to the respiratory and cardiovascular risks. Both cancer risks and hazard quotients related to the plant are far below international thresholds for human health protection, while the values from all sources require consideration. The proposed method provides an instrument for prospective health risk assessment of large industrial sources, with some limitations presented and discussed.

M-TraCE: a new tool for high-resolution computation and statistical elaboration of backward trajectories on the Italian domain

Air backward trajectory calculations are commonly used in a variety of atmospheric analyses, in particular for source attribution evaluation. The accuracy of backward trajectory analysis is mainly determined by the quality and the spatial and temporal resolution of the underlying meteorological data set, especially in the cases of complex terrain. This work describes a new tool for the calculation and the statistical elaboration of backward trajectories. To take advantage of the high-resolution meteorological database of the Italian national air quality model MINNI, a dedicated set of procedures was implemented under the name of M-TraCE (MINNI module for Trajectories Calculation and statistical Elaboration) to calculate and process the backward trajectories of air masses reaching a site of interest. Some outcomes from the application of the developed methodology to the Italian Network of Special Purpose Monitoring Stations are shown to assess its strengths for the meteorological characterization of air quality monitoring stations. M-TraCE has demonstrated its capabilities to provide a detailed statistical assessment of transport patterns and region of influence of the site under investigation, which is fundamental for correctly interpreting pollutants measurements and ascertaining the official classification of the monitoring site based on meta-data information. Moreover, M-TraCE has shown its usefulness in supporting other assessments, i.e., spatial representativeness of a monitoring site, focussing specifically on the analysis of the effects due to meteorological variables.