Antonio Febo

An atmospheric stability index based on radon progeny measurements for the evaluation of primary urban pollution

Abstract An atmospheric stability index for the evaluation of urban primary pollution, based on the elaboration of natural radioactivity data yielded by a stability monitor, has been developed. The instrument determines the atmospheric concentration of the short-lived decay products of radon, whose emanation rate can be assumed to be constant in the time and space scale of observation. The index gives information about the dilution properties of the lower boundary layer and allows to highlight the relevant role of the dilution factor in determining primary pollution events. The atmospheric stability indices have been calculated during a 1-yr study carried out in the urban area of Rome (October 1999–September 2000). On the basis of the index, every day of the period has been classified in terms of intensity of a potential primary pollution event. The comparison between this classification and the real concentration value of primary pollutants, measured in the background urban station of Rome, yielded very good results. This shows that the index constitutes a powerful and valuable tool for describing primary pollution events in urban areas and confirms that the role played by the mixing properties of the lower boundary layer is essential in determining primary pollution in urban areas.

Measurement of nitrous acid in milan, italy, by doas and diffusion denuders

Abstract Measurements of the atmospheric mixing ratio of nitrous acid have been carried out by means of the differential optical absorption system (DOAS) during a wintertime field study carried out in the urban area of Milan (Italy). Preliminary laboratory calibration of the DOAS was carried out by making use of a standard source of pure HONO which provided an interference-free UV absorption spectrum of HONG and recalculation of the absorption cross-section of this compound. Very high HONO mixing ratios, up to values exceeding 10 ppb, were measured during the campaign. DOAS results were compared with those obtained by using the annular denuder technique and good agreement was observed during the whole measurement period. On the basis of these measurements, a study on the relationship between the dynamic conditions of the lower boundary layer and the temporal trend of HONG mixing ratio can be carried out, in order to obtain indications about the sources of this species in urban atmospheres.

Evaluation of a High-Purity and High-Stability Continuous Generation System for Nitrous Acid

A flow-type system for the generation of nitrous acid in the mass flow rate range of 3.5-400 nmol/min is described. The system based on the reaction between gaseous hydrochloric acid, generated by means of a low-pressure permeation device, and solid sodium nitrite allows the continuous production of highly pure nitrous acid (purity >99.5%) and thus the generation of standard atmosphere in a very wide range of nitrous acid mixing ratio (5-20000 ppb). The system is of easy construction and exhibits a very high reproducibility and excellent long-term output stability. These features allow us to obtain any desired value of nitrous acid mass flow rate by simply tuning the temperature and flow rate values. As a consequence of the high purity of the generated compound, it was possible to obtain a clear absorption spectrum of nitrous acid without performing any correction for NO 2 interference.

Volatilization and oxidative artifacts of PM bound PAHs collected at low volume sampling (1): Laboratory and field evaluation

Laboratory and field studies were carried out to assess the effects of oxidative degradation and volatilization on PM10 bound polycyclic aromatic hydrocarbons (PAHs), collected at low volume condition according to the EU sampling reference method EN12341:2014 (flow rate 2.3 m3 h-1), on 47 mm quartz filters. For the laboratory experiments, pairs of twin samples were collected in field and, after treatments favoring decomposition or/and volatilization of PAHs on one sample, the PAH amount was compared with that of the corresponding untreated sample. Ozone exposure caused a general PAHs decay with more marked effects on benzo [a]pyrene, perylene and benz [a]anthracene; these compounds showed, similarly to benzo [ghi]perylene, correlations between ozone dose and losses. Treatments with zero air exhibited losses due to volatilization even for 5-ring PAHs up to benzo [a]pyrene, whereas a linear dependence was observed between filter PAH load and losses for benzo [a]anthracene, chrysene and benzofluoranthenes. Concentrations on samples collected simultaneously over 48, 24, 12 and 6 h were compared. Results confirmed a lack of temporal auto-consistency in the PAHs sampling methodology here adopted. In particular higher atmospheric PAH concentrations were ascertained on samples constituted by cumulative filters exposed over shorter sampling times. When 24-h and 2 × 12-h samples were compared, comparable losses were evaluated in the hot and cold seasons. This finding shows that, although in summer meteorology conditions favor sampling artifacts, the effectiveness of these phenomena continue in the winter, probably due to the larger amount of PAH available on the sampling filter (total PAHs ∼ 10 vs 0.5 ng m-3).

Emission of submicron aerosol particles in cement kilns: Total concentration and size distribution

Cement plants are responsible for particle and gaseous emissions into the atmosphere. With respect to particle emission, the greater part of is in the range from 0.05 to 5.0 µm in diameter. In the last years attention was paid to submicron particles, but there is a lack of available data on the emission from stationary sources. In this paper, concentration and size distribution of particles emitted from four cement kilns, in relationship to operational conditions (especially the use of alternative fuel to coal) of the clinker process are reported. Experimental campaigns were carried out by measuring particles concentration and size distribution at the stack of four cement plants through condensation particle counter (CPC) and scanning mobility particle sizer spectrometer (SMPS). Average total particle number concentrations were between 2000 and 4000 particles/cm3, about 8–10 times lower that those found in the corresponding surrounding areas. As for size distribution, for all the investigated plants it is stable with a unimodal distribution (120–150 nm), independent from the fuel used. Implications: The study provides information on submicron particles emitted from cement kilns in different driving conditions. In particular, the total particle number is modest and considerably lower than that measured in ambient air, whereas the particle size distribution could be influenced by the operational conditions.

Intercomparison between gas-chromatography and long-path UV DOAS techniques for the measurement of benzene and toluene in urban atmospheres

An intercomparison between DOAS and gas-chromatographic techniques for the measurement of the concentration of benzene and toluene in the air has been carried out in Milan, Italy during the winter of 1994. Measurements of the natural radioactivity due to Radon have been carried out for a direct description of the mixing properties of the atmosphere. The temporal trend of primary pollutants, including hydrocarbons, follow, as expected, that of radioactivity. The results show that large discrepancies between the two methods have to be associated with the stratification of the atmosphere caused by ground based inversions. Scatter plots of GC against DOAS data show acceptable agreements, while the nature of observed offsets in DOAS system need further investigation. The results also show that the measurements are self consistent as they fit the physio-chemical evolution of atmospheric pollution at the site of sampling. In addition, data obtained from DOAS may be used to describe the evaluation of vertical mixing through the ratio toluene/benzene. Data on this new and important aspect are also presented.

Intercomparison of DOAS and conventional analyzers in the measurement of atmospheric pollutants in an urban background monitoring site of Rome

An advanced monitoring station, equipped with a combination of DOAS system and classic monitoring devices, was set up in the urban background of Rome. An intercomparison between DOAS and gas-chromatographic technique for the measurement of the concentration level of benzene and toluene in the urban area has ben carried out. At the same time, an intercomparison between the DOAS and data provided by the chemiluminescent conventional analyzer has been developed to test the capability of DOAS system as a monitoring tool for secondary pollutants. The comparison between the data collected by the DOAS system and the conventional analyzer, provides quality assurance and reliability for the monitoring network and allows to understand the sources of the differences in instrumental responses. The results show that DOAS can be conveniently used for urban pollution monitoring.

New concept of enhanced monitoring station for urban air application

An advanced monitoring station was set up in the center of Milan, Italy. It is made up of several instruments for the measurement of atmospheric pollutants, including a DOAS system which is able to provide information of the time evolution of several primary and secondary atmospheric pollutants. A radioactivity monitor provides information about the time evolution of Radon daughters, thereby providing information about the evolution of the boundary layer. It is shown that pollution by primary pollutants can be described through a very simple model based on Radon observation. Secondary pollutants, like ozone and nitrogen dioxide can also be described by the same model. Observation in strong advective condition and during stability periods show that the presence of large concentration of nitrogen dioxide is due to radicalic processes which are also responsible for the formation of formaldehyde. The role of nitrous acid in the formation of radicals is also discussed.