Strengthening of the Air Quality Information System Working area 2: Application of a regional-scale model over the central part of Chile

When assessing air pollution problems, no single tool, in spite of accuracy and/or complexity, may give satisfactory answers regarding process understanding and efficient attainment measures. Hence, like any other environmental issue, dealing with air pollution requires of a systemic approach in which suites of tools ranging over a broad span of disciplines and considerations are applied. Dispersion modeling is one of the necessary tools to assess air pollution. Again, suites or batteries of dispersion models might be required. This work corresponds to the first attempt to assess the regional distribution of oxidized sulfur by means of a regional-scale modeling system. This is a cooperation project between the National Commission for the Environment (CONAMA) and the Swedish Meteorological and Hydrological Institute (SMHI) initiated in 1999. Several reasons justify the application of regional-scale modeling tool. Nearly one third of the population of Chile (i.e., about five million people) is found in the Metropolitan area of Santiago. This brings industries, private and public transportation, domestic and industrial energy consumption and other activities that result in large emissions of pollutants. From other cities and some large point sources in Central Chile emanate other pollutants and pollutant precursors. Of particular interest are the large copper smelters: Caletones, Ventanas and Chagres, which stand for ca. 95% of the total sulfur emissions in this part of Chile. The combination of meteorological conditions adverse to the ventilation and of large emissions of pollutants to the atmosphere promotes the occurrence of high concentrations of pollutants, which pose a risk for the population and the vegetation. Due to their physical and chemical characteristics many of the pollutants (inhalable particles, oxidized sulfur, oxidized nitrogen, hydrocarbons, ozone, etc.) are likely to be dispersed on a regional scale, i.e., over hundreds of kilometers downstream from the sources. Altogether, these considerations make it meaningful to apply a regional modeling tool with the purpose to determine the influences of different sources on the air quality of the central part of Chile. Particularly in view of the fact that urban areas and infrastructure in Central Chile, including interregional highways and trains, are expected to grow and develop further. To implement and evaluate such a tool has been the overall objective of this project. This project has provided a regional-scale dispersion model, a suite of validated meteorological data sets covering various typical meteorological conditions that affect Central Chile, including extreme conditions under El Niño and La Niña years. It has given valuable insights regarding the regional dispersion of oxidized sulfur in this part of the country, and an assessment of the contribution of the smelters to the air quality in the heavily populated Metropolitan area of Santiago. Furthermore it has produced relevant inputs for establishing a regional monitoring network. At last but not least, it has provided strongly needed Chilean knowhow in dispersion modeling. Altogether, this project has strengthen the air quality information system, improving our understanding of the intricate processes that govern the regional dispersion of pollutants and therefore of our environmental managing capabilities for facing and hopefully preventing those problems. Oxidized sulfur dispersion over Central Chile