The present Air Quality Management System in Riga was started in 1992 as a result of co-operation between two cities - Riga and Norköping (Sweden) supported by BITS (The Swedish Agency for International Technical and Economic Co-operation).

AIRVIRO air quality management system in Riga City Council (RCC) is running by a HP 9000 series workstation in real time regime. A digital map of Riga with scale 1:10000 as a part of software covers an area of 20x 20 km and is used both for accurate wind field calculations and the visualisation of results. Special meteorological equipment is on-lined via modem in order to evaluate the atmospheric stability and to measure different parameters necessary for dispersion models.

• One part of system is supposed to run a local measurement network . The number of stations and their type is not limited (our system is collecting data from 5 DOAS stations in Riga and meteorological station (Riga Airport).
• The second part of the system is intended for data analyses. Special statistical software package gives a possibility to analyse all measured data in many different ways and to understand the air pollution as consequences of social behaviour and meteorological conditions at the same time.
• The third part - emission databases (EDB)- contains data about pollution sources. All sources are divided in three groups - point, line and area sources. Line sources - streets - are mainly specified by traffic intensity in one-hour level and variation during a day, week and season. In our system there are more than 300 point and square sources and about 150 line sources (streets) counted for all Riga.
• Main part of system - dispersion calculations. This part is used for two purposes - city planning and forecast of pollution levels when weather is changed. For both of it is possible to take into account all polluting sources.

The main idea of using the system is to monitor the present air quality and pollution levels in the city. Another aim would be to support city authorities with information needed to produce cost effective decisions in order to sustain healthy urban living standards and quality. The main groups of questions and problems are following:

• Where are the most polluted areas within the city? What kind of sources causes the largest impact on those areas?

• How to change the traffic flows in different streets to decrease their impact on parts of the city with cultural and historical importance?

• How pollution levels will be changed when new residential areas are built or changes in development of existing areas will occur?

• What is the optimal number and location of gasoline stations and many-floor car parking places?

• What will the consequences be when traffic intensity and vehicle speed will be changed between different streets?

All air polluting objects (except boilers (combustion chambers) with power smaller than 0.2 MW - following from legislation of Latvia's Government) institutions, heating enterprises plants, factories etc. which operation are connected with emissions in air, must manage maximal permissible emission amount calculations. This document goes through the examination of experts in Greeter Riga Regional Environmental Board and often the expertise gives permit. Accordingly the latest legislation of the Cabinet of Ministers of Latvia it is necessary to receive an agreement from Environmental Department of RCC as well. Nowadays in Riga city there is only one data base - AIRVIRO - which enumerate most of all enterprises and has facility to calculate dispersion curves for all registered emissions (background). LHMA secured newest version of this software - ENVIMAN, and is preparing similar data base, not only about air polluters in Riga, but in all the Latvia, including largest towns and border with Lithuania ( to measure transboundary pollution transfer).