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Marko Kaasik and Veljo Kimmel

The modeling of air pollution in Estonia during Soviet Union period was complicated both due to ignorance of decision-makers and deficiency of good tools affecting also current situation.

Current practice is divided roughly into two parts: 1) official side relying on obsolete and not validated Russian models from the eighties not enabling to model most important polluter in cities - the traffic and 2) researcher side dealing with development and use of advanced computers and new modeling tools.

Estonian legislation requires that companies and other institutions having stationary air pollution sources should perform or order air pollution dispersion calculations to get (or renew) the permission to emit air pollution. The former USSR standard for air pollution dispersion calculations OND-86 (based on the research results by M.Y. Berlyand) was established by the Ministry of Environment in 1992 as the official method. Therefore, two computer codes based on OND-86 developed in Main Geophysical Observatory, St. Petersburg, Russia were widely used. Users are institutions related to the Ministry of Environment, some research institutes (e.g. Institute of Ecology) and environmental consulting companies. Professor Berlyand's method has strong limitations (fair performance only for elevated point sources, no deposition fluxes, very simplified meteorology etc.) and therefore does not allow to model traffic pollution. Since 2000 Gaussian and Lagrangian models are officially accepted as well.

The list of models used for research and environmental impact assessment (EIA) purposes consist from 4 applications:

• AEROPOL developed at Tartu Observatory and most extensively used by Hendrikson & Ko Environmental Consults. The model relies on stationary Gaussian dispersion and enables to use point, line and area sources and calculates also dry and wet deposition. AEROPOL is described by Kaasik (1997, 2000) and validated in internationally accepted way (the author defended in 2000 his PhD);
• AirViro developed by Indic AB (Sweden) and used by Tallinn City Government for urban air pollution calculations (Gaussian and numerical dispersion schemes);
• CAP88-PC developed by US EPA and Oak Ridge National Laboratory, used by the Institute of Physics (Tartu) for studies of dispersion and further migration of radio-nuclei from industrial emissions;
• In Estonian Institute of Meteorology and Hydrology a backward tracing method for air pollution trajectories (references only in Russian).

Since the most important application of air pollution models concerns urban-side regulatory purposes, hereby also such practical results are given. The urban air quality modeling is performed for Tallinn (AirViro and AEROPOL) - the capital of Estonia, and other larger towns: Tartu, Narva, and Kuressaare (AEROPOL). Due to the fact that official statistics embraces only emissions from relatively large stationary pollution sources (industrial enterprises, power plants and boiler houses) for correct modeling the traffic and domestic heating emissions were investigated. Traffic density counting was performed by Stratum, Hendrikson & Ko, Tartu Observatory and NGO GAIAA (Kaasik, Kaasik, Kimmel 2000).

Scientists made earlier some sporadic attempts to develop air pollution models for local and regional scales - like Laigna and Potashnik (1990) and Klimova (1993), but the developed models were not validated and used in practice.

Thus, the description shows that Estonian air pollution modeling requires much effort both for establishing a system to follow EU air pollution Directives, requirements and international modeling practice, and for encouraging researchers-modelers to follow up these requirements and to grow new knowledge in the area at present and in future.

First steps towards establishing better modeling system were already made: 1) the Ministry of Environment has made the principal decision to launch in the frame of EU accession process the project for air pollution modeling system development for whole country with estimated cost of 1.5 million EEK ( equivalent to 96 000 EUR, http//www.envir.ee/, only in Estonian) to meet the requirements of EU directives , and 2) A proposal for two-year research project for developing numerical meso-scale air pollution modeling supporting the development of regulatory modeling system was made by Marko Kaasik to the Estonian Science Foundation.

References

Kaasik, M., 2000. Parameterisation of Atmospheric Boundary layer in the Numerical Model of Air Pollution Transport. Ph.D.Thesis. Tartu University Press.
Kaasik, M., 2000. Validation of models AEROFOUR and AEROPOL using the model validation kit at Mol. International Journal of Environment and Pollution, in print
M.Kaasik, V.Liblik, H.Kaasik 1999. Long-term deposition patterns of airborne wastes in the North-East of Estonia. Oil Shale, 16, p. 315-329.
Kaasik, M., Kimmel, V., Kaasik, H. 2000. Air quality modeling system for a medium-sized town: a case study in Estonia. to be published in International Journal of Environment and Pollution
Laigna, K.J., Potashnik, E.L., 1990: Mathematical Model for Predicting the Atmospheric Pollution State in the Areas of Local and Regional Scale, Estonian Scientific Research Institute of Scientific-Technical Information and Technical-Economic Research, Tallinn, 342p.
Klimova, E., 1993: Modelling of transfer and impact on ecosystems of emissions from oil-shale power plants in Estonia. Oil Shale, 10, p. 67 - 78.