The ENVIBASE-Project

Documentation / Online Handbook

Air Quality

Description of the Problem

Rome is located about 30 km from the Tirrenian Sea. The sea has a very positive influence in moderating the high and low peaks of meteorological phenomena, particularly the air temperature. This fact has a generally positive influence on the air quality, because it limits the conditions of the thermal inversion phenomenon, which produces air stagnation thereby allowing pollution to increase. Moreover, the sea causes sea breeze phenomena, which have the effect of keeping an active air circulation and contributing to the limitation of air stagnation and pollution.

The industrial sector in Rome is small compared to other capital cities in Europe. The pollution levels are mainly due to household energy consumption and to transport. According to rough estimates, the contribution of car traffic to air pollution is about 85 % of the total pollution (about 80 % of transportation consists in private vehicles, cars and motorbikes, while only 7 % consists in electric power transportation), the contribution of household heating is 10 % and is diminishing because of the growing use of methane, and the contribution of industrial plants is about 5 %.

In order to control the pollution level, a monitoring network has been operating for several years to support decision-making on emergency and structural provisions.

In order to avoid, in the very short run, high concentration levels of pollution, not only structural but particularly emergency provisions have been established. Since the emergency provisions consist of "attention warnings" and the restriction of car traffic, the structural improvement of air quality is particularly important because it avoids emergency provisions and car traffic restrictions.

At the moment, structural provisions, together with favourable climatic conditions and the development of catalytic converters, have led to a stable air quality improvement. "Attention warnings" dropped from ninety-one in 1993 to twenty-six in 1996, while car traffic restrictions dropped from nine in 1993 to three in 1996. Structural provisions consist of regulations dealing with the periodic compulsory control of the emissions of each single car (the so-called "bollino blu," blue stamp); the implementation of a plan of parking areas restricted by parking meters aimed at producing disincentive for private car use in the central area and coincided with the corresponding implementation of a public transportation programme which increased the number of busses and frequency of trips and incentives given to households for the substitution of fuel boilers with methane boilers.

A progressive decrease of carbon oxide (CO), nitrogen oxide, and dioxide emissions were surveyed from 1993 to 1996 due to the above provisions in the car traffic sector. Provisions in the household heating sector mainly led to a decrease of about 50% of sulphur dioxide (SO₂) concentrations. From the point of view of this pollution compound, Rome has very low values, not only compared to the values showed by other European capital cities, but even compared to the much stricter values required for the conservation of the archaeological and architectural heritage. On the other hand, total suspended particles concentration, still due to car traffic, does not show substantial improvements, while ozone concentration shows a slight increase. The programmes for the future consist in further development of public transportation, particularly railway, tramway, and subway.

Data Sources

A monitoring network which consists of twelve monitoring stations of four different types was established in the past years. The different types are due both to the location in the city territory and to the kind of monitored parameters.

One station is located in a large historic park, Villa Ada, that is far from the polluting source and inside the city; it surveys all the parameters. Four stations are located in urban high density residential areas with medium or low traffic concentration; they survey the nitrogen oxide. Five stations are located in urban areas with high traffic concentration; they survey the carbon and nitrogen oxides and the dusts. Two stations are located in suburban areas for the evaluation of components of smog of photochemical origin, and particularly ozone and PAN (Perossiacetilnitrate).

The stations are managed by the Latium Region, according to the standards fixed by laws and regulations. The stations are part of a network established at the level of the Province of Rome ("Centro Provinciale di Roma," "Central Office of the Province of Rome"); such a network consists of twenty stations, which as a whole make use of sixty-nine analysers and thirty-four meteorological sensors. Every hour the network makes available to the database about 177 parameters, of which 130 are chemical parameters and forty-seven are meteorological data.

Methods

Air quality data are elaborated at different levels. A basic level consists in the computation of simple statistics. Hourly values surveyed every day are averaged in order to obtain the hourly distribution in the 24 hours and the monthly distribution in the year for specific years. For some pollutants, the calculations are made not only for the mean but for the percentile (i.e. 98^th percentile). Computations are also made about the number of events in which thresholds were overcome (i.e. attention warning and alarm warning thresholds) and the number of hours of parametric values beyond the threshold. Synthetic indices are calculated from statistical parameters (i.e. Photochemical Activity Index, which is the summation of hourly values of O₃ and NO_x; or the air quality index, the so-called INQUARIA, which is made from the combination of scores given to each pollutant concentration, according to the maximum hourly values).

Results

Every year the central office of the Province of Rome publishes an annual report which synthesises the monitoring activity. The report makes an evaluation of the pollution levels for each type of pollutant surveyed by the monitoring network. The evaluation is accompanied by tables and graphics illustrating the main statistical parameters and indices.

The daily mean value or hourly maximum value, for the pollutants used as parameters, are diffused via teletext, both in the quantitative version of pollutant concentration (unit measure: µg/m³) and in the qualitative one (scores ranging from "good" to "unacceptable"). Moreover, information for tourists via monitors located in touristic areas is going to be developed.

Uses

The elaborated data constitute the basis for structural and emergency provisions. A direct link exists between daily results of the monitoring campaign and emergency provisions. According to the values surveyed in the monitoring stations, the attention and alarm warnings are released in real time.