• María Rosario Méndez Gil and José Carlos Fernández Balseiro. Chemical Engineering Department. Universidade de Santiago de Compostela.
  
• Emilio Abad, CESGA.

Scientific efforts to understand the phenomena of acid deposition involve a combination of laboratory experiments, field experiments and modeling analysis. Laboratory experiments provide the basic data on the individual chemical and physical processes; field experiments are usually designed to study a limited number of atmospheric processes under conditions in which a few processes are dominant; so that comprehensive models that allow multiple processes to occur simultaneouslly are required for data analysis. The STEM-II model was developed to provide a theoretical basis to investigate the relationships between the emssions, atmospheric transport, chemical transformation, removal processes, and the resultant distribution of air pollutants and deposition patterns.

During this year the porting of the STEM-II model to the VPP300 and the AP3000 was done. The photochemical model was adapted to work with the domain information, emissions from As Pontes Power Plant, and meteorological data. The model was run during June, 21th, 1997, firstly considering only the transport of pollutants and secondly with transport and gas phase chemistry, so the influence of the reactions in gas phase on the conversion of SO2 to SO4-2 in a domain around As Pontes Power Plant could be determined and the results of the simulation for another species (NOx, O3, ...) could be verified. The domain under study is located in Galicia. This is a region charaterized for its high precipitation. Because of that, it was considered very important to run the model including both gas and aquous phase chemistry in order to compare the conversion of SO2 to SO42- and NOx to NO3- with and without aquous phase and to know the wet and dry deposition of the pollutants in the whole domain.