Tunisian Air Quality Monitoring Network Presentation

Abstract

It is among the basic missions of the National Agency for Environmental Protection (NAEP) to preserve and improve the quality of our nation's air. In order to accomplish this mission, the Agency must be able to evaluate the status of the atmosphere compared to clean air standards and historical informations. That's why the NAEP established since 1996 an Air Quality Monitoring Network (AQMN) composed by thirteen permanent monitoring stations, two mobiles laboratories and a data elaboration centre with the aim of characterizing human health exposure and public impacts of conventional pollutants. In Tunisia, that extends over 163900 km² and includes 24 metropolitans towns, there are several permanent monitoring stations located in many towns like Tunis, Sfax, Sousse, Gabès Tozeur, Kef. In this paper, some stations of Tunisia and its monitoring networks have been selected as representative sites of the investigated area. In Tunis, the selected monitoring stations were located in Traffic area (Bab Saadoun), in urban area (El Mourouj) and in a suburban area (Nahli). Each station is provided with automatic analyzers of O 3 , NOx, SO 2 , PM10, CO and with meteorological sensors such as temperature, barometric pressure, relative humidity, solar radiation, wind speed and direction. Nitrogen oxides, NO and NO 2 , were analysed using the chemiluminescence method. The measurement of ozone is based on the capacity of such gases to absorb ultraviolet rays with opportune wavelengths, generated by built-in lamp. Carbon monoxide CO is analyzed infrared rays absorption (IR). The measurement of PM10 is based on the beta ray attenuation method while SO 2 is analysed using a fluorescence method. For all parameters, the data are collected by the monitoring network every hour. The data were validated according to this protocol: first, a preliminary validation was carried out by the software, which invalidated all the data occurred in calibration hours and the data identified as artifacts then a manual calibration was carried out by the operators, considering the relations among the parameters. This way it is possible to verify that eventual critical data are related to real pollution situations. Moreover, meteorological data (wind speed and direction) were used to investigate about the influence of natural events on high or low concentration situations.

Full text

Tunisian Air Quality Monitoring Network Presentation
Hassen KCHIH
a*
,
Docteur Semia CHERIF
b
a)Agence Nationale de la Protection de l'Environnement, Centre Urbain Nord, Belvédère, Tunisie.
*auteur correspondant
b)
UR Chimie des Matériaux et de l’Environnement UR11ES25, ISSBAT, Université de Tunis El Manar, Tunisie.
Abstract
.
It is among the basic missions of the National Agency for Environmental Protection (NAEP) to preserve and improve
the quality of our nation's air. In order to accomplish this mission, the Agency must be able to evaluate the status of the
atmosphere compared to clean air standards and historical informations. That's why the NAEP established since 1996 an Air
Quality Monitoring Network (AQMN) composed by thirteen permanent monitoring stations, two mobiles laboratories and a data
elaboration centre with the aim of characterizing human health exposure and public impacts of conventional pollutants.
In Tunisia, that extends over 163900 km² and includes 24 metropolitans towns, there are several permanent monitoring stations
located in many towns like Tunis, Sfax, Sousse, Gabès Tozeur, Kef.
In this paper, some stations of Tunisia and its monitoring networks have been selected as representative sites of the investigated
area. In Tunis, the selected monitoring stations were located in Traffic area (Bab Saadoun), in urban area (El Mourouj) and in a
suburban area (Nahli).
Each station is provided with automatic analyzers of O
3
, NOx, SO
2
, PM10, CO and with meteorological sensors such as
temperature, barometric pressure, relative humidity, solar radiation, wind speed and direction .
Nitrogen oxides, NO and NO
2
, were analysed using the chemiluminescence method. The measurement of ozone is based on the
capacity of such gases to absorb ultraviolet rays with opportune wavelengths, generated by built-in lamp. Carbon monoxide CO is
analyzed infrared rays absorption (IR). The measurement of PM10 is based on the beta ray attenuation method while SO
2
is
analysed using a fluorescence method.
For all parameters, the data are collected by the monitoring network every hour . The data were validated according to this
protocol: first, a preliminary validation was carried out by the software, which invalidated all the data occurred in calibration
hours and the data identified as artifacts then a manual calibration was carried out by the operators, considering the relations
among the parameters. This way it is possible to verify that eventual critical data are related to real pollution situations.
Moreover, meteorological data (wind speed and direction) were used to investigate about the influence of natural events on high
or low concentration situations.
Key words: Air Monitoring, Tunisia, automatic analyzers, Permanent stations, air pollutants.