2.1 Current Monitoring Network

The irregular development and extension of large cities of the country together with continual increase of population needs more than tolerable capacity have resulted in all kinds of environmental irregularities and sever changes in the structure and the activities function.

Among these problems and difficulties, air pollution and its consequences have been considered one of the most complicated and important environmental problems so much so that in the recent years many experts and authorities, the responsible people and people have considered it noticeably.

With the development of the cities and population increase and the lack of control on air pollution the impacts of different regions air pollution accumulate together and in addition to local changes and regional occurrences cause universal changes. That is with the increase pollutants density, the air of different areas is polluted.

It is because of the importance of the subject and the necessity of air pollution control that in the past progressive communities and now most of the countries of the world think of finding the remedy and strategy to face the air pollution and the conquer against it has begun whether internally or externally levels.

Comprehensive measures and actions have also been taken or begun in local and regional levels.

The problem of air pollution has also been considered in our country so that the regulation of prevention from air pollution was approved by parliament’s commissions 13.7.1975 and recently the Islamic parliament has approved some cases about the prevention of air pollution and environmental safety of some polluted cities.

So one of the actions to face such problem is the measurement of pollutant parameters. In this area, problems such as locating and calculation of permanent station to estimate the amount of pollutants are important.

For this purpose, careful surveys and studies have been carried out (with the help and cooperation of Health Faculty). Locating was firstly done in Tehran and after receiving warrant from the municipalities, 5 stations were established and complete instruments were purchased to equip them.

These stations with the calculation of 5 kilometers radius from one to another stand in Tajrish square, Gholhak junction. Azadi square, Bahman Farhang Sara, villa avenue and lately one station has also been equipped in the new building of Department of Environment in Pardisan park which on the basis of calculations, 2o stations have been anticipated in Tehran and in the third five year plan a few of them will be established with equipments.

In the second and third five year project it was agreed that at least a monitoring station should be established in capital of provinces for measuring pollutants and gradually on the basis of estimates and calculations, first capital of provinces and then other cities will be under the coverage of establishing monitoring station.

The important parameters whose kit of measurement has been bought from manufacturing factory contain SO2, NO2, THC,HC TSA, CO and O3.

Measurement and calculation systems are computerized and their sensitive sensors are the kind of light chemistry.
 
 

1. Principles of air pollutants measurement in stationary station

 

Pollutant	Principles of measurement
SO2	Fluorescence caused by ultraviolet
NOx	Chemo-luminescence
CO	Concentrated infrared
O3	Ultraviolet rays – absorption
THC	Ionization caused by hydrogen
TSP	Ionization caused by beta (ß)

1. Principles of measurement of environment pollutants

by portable instruments

Chemo-luminescence Method

In these method the basis of the work is based on the measurement of photons caused by the reaction two or more special materials. The great resemblance between this method and basis of measurement in the way of photometric flame but the excitation of atoms and molecules of tested materials without the use of flame.

The property of luminescence of some compounds while reaction is the basis of planning of such instruments some of the chemical materials without the need to primitive activator energy (activation energy) arrive at reaction together and their atoms and molecules become excited which when returning to usual state give back their energy in the from of photons with certain wave length like the following reaction:

O₃ + No ® No₂ + O₂

No_{2 ®} No_{2 +} h

On the basis of such property (luminescence) the instruments are planned and made with their help we can be informed of the amount of gases like hydrogen oxide in the atmosphere.

Flame Ionization

Usually organic materials like Hydrocarbons are ionized in a certain temperature and particular conditions.

The considered temperature is analyzed and ionized by the flame in special case, which planned and installed for these purpose.

The resultant ions with the help of an instrument, which has opposite charge in relation to ions charge make an electrical current and complete a circuit.

The obtained electricity current after amplifying by electronic amplifiers transfer to hand or stable instrument.

No doubt the amount of obtained electricity is proportionate to the number of produced ions and the number of resulted ions in the case is proportionate to the amount of existed Hydrocarbons in the atmosphere.

Absorption of Radiation Methods

1. U.V light absorption
2. ß RD
3. NDIR

These properties have been used in planning and manufacturing a series of measurement instrument. Such measurement instruments have a case which testable sample enters into with a certain speed and volume. This case is regularly or alternatively is affected by a source of light (infra red or other bands) and at its other end there is an instrument that can change light energy into electricity.

When the considered material has not been entered the case, the amount of energy which reaches the detector is stable the maximum light energy changes into electricity. But when the testable material comes into the case, some of the radiated energy is absorbed by the measured material and thus less energy comes to the end of case where the detector is. In these systems the obtained electricity transfers to the hand or stable instrument after amplifying.

If the considered material stands more in the environment, the amount of energy, which has been radiated by light resource, is reduced (because of absorption in the way) and therefore, less electricity is produced by detector.

The table presented in this booklet contains measurement parameters such as CO, NO₂, SO₂, HC, TSM.

The centers or organizations, which are responsible for the monitoring of pollutants, are as follows:

1-Department of the Environment which has published the registered statistic of Tehran, from 1978.

2-Traffic control center

3-Air quality control company
 
 
 

Monitoring station	Parameters monitored	Monitoring technique	Organization responsible	Mode  of dissemination
Tehran	CO,HC,TSM, SO2,NO2,O3,dust	CO:Non Dispersive
Esfahan	//	Infrarad Spectroscopy NOx: Chemilumine scent
Shiraz	//	SO2: uv Floresence
Arak	//	O3: VS Light Absorb	Department of the Environment	Annual Publication of statistical booklets
Hamedan	//	HC: Flame Ionization Detector
Ahvaz	//	Dust: ß Radition
Tabriz	//	//

2.2-Sitting of Monitoring Stations.

The stationary stations in Tehran and other cities are intra city and with regard to their position, have been clearly obvious that as they are beside pollution source, are completely under the influence of source effect.

It is mentionable that in the way of selection the location of stations, some conditions such as considering pleasant distance from plant coverage, sensor height from the ground, considering pleasant distance from heavy traffic places are taken into consideration. More over, in choosing the distance of every station from each other an air radius about 4 kilometers has been considered.

2.3- Examples of Monitoring Results

This pollution statistics is about the central stations located on Ostad Nejatollahi Avenue, which is a commercial and residential area with too much traffic.

The specifications of air permanent protection station Ostad Nejatollahi Ave.:

• The height of sampling point from the surface of the ground is 3.5 meters.
• Its distance from the above avenue is 2.5 meters.
• Full automatic instruments which measures 24 hour.
• Measurement instrument of So₂ (in the way of colometry)
• Measurement instrument of No/No₂/No_x in the way of col.
• Ozone measurement instrument.
• Oxide carbon, hydrocarbon, methane, measurement instrument (in the way of gas chromatography)
• SPM measurement instrument (in the way of ß-radiation)

2.4- Data Availability

1. The statistics and information about the pollution of Tehran air are published yearly in the form of a booklet and all the statistics of air pollution with the percent of its pollutants are known. As for other cities of the country the information and statistics of air pollution are prepared and sent to the central organization in the form of a report to be surveyed.

2. The booklet containing the information about Tehran air pollution is available in the libraries of all university press and governmental organizations for the use of all. On request of more information, the experts of Department of the environment provide the applicants with all the exact data about air pollution.

Permanent measurement equipments of air pollution in our country are prepared by "Beisan pars Co." that is the agent of "Japanese Horiba co." and the equipments are calibrated by "Beisan pars Co." once a week, according to the directions of above mentioned company.

Since different equipments in all of stations have similar model, the way of their calibration is also the same.

2.6-Future development of monitoring networks

At present, the monitoring networks of the country need coordination with each other. For more developing the networks, suitable planning and financial facilities are necessary. All the current instruments should be designed with modern system and run. Seven stations are active in Tehran. In the future planning, the establishment of 2o instruments has been anticipated and large provinces of country have portable stations for measurement of air pollution. For the large states, the establishment of stationary station, is anticipated and planned. In Iran the private companies such as (Air Quality Control CO.) have the permanent control stations. These stations have been established in crowded centers of Tehran.

It is mentionable that we need approximately 100 stations in the whole country, 30 ones in Tehra And 70 ones in other states.