Air quality modeling for policy development.

Atmospheric models constitute the best tools available for the setting of policy, and may, in some cases, be the only tools that are available. The best examples of their kind bring together all current knowledge of pollutant behavior in the atmosphere, making it possible to unravel the often complex interactions between pollutants and atmospheric dynamics. They also allow the possibility of evaluating hypothetical changes in emissions and other conditions to evaluate potential abatement strategies, or to assess the impact of proposed new emission sources. This paper provides an overview of mathematical atmospheric models and their application to the development of air quality policy. The paper discusses the types of atmospheric models currently in use, categorized by spatial scale, and the requirements for credible modeling. Issues associated with model validity and accuracy are described and case studies are reviewed to illustrate atmospheric model use in policy development and the need for careful analysis in interpreting model predictions.

Assessing the effects of transboundary ozone pollution between Ontario, Canada and New York, USA.

We investigated the effects of transboundary pollution between Ontario and New York using both observations and modeling results. Analysis of the spatial scales associated with ozone pollution revealed the regional and international character of this pollutant. A back-trajectory-clustering methodology was used to evaluate the potential for transboundary pollution trading and to identify potential pollution source regions for two sites: CN tower in Toronto and the World Trade Center in New York City. Transboundary pollution transport was evident at both locations. The major pollution source areas for the period examined were the Ohio River Valley and Midwest. Finally, we examined the transboundary impact of emission reductions through photochemical models. We found that emissions from both New York and Ontario were transported across the border and that reductions in predicted O3 levels can be substantial when emissions on both sides of the border are reduced.

Possible Sources for Some Trace Elements Found in Airborne Particles and Precipitation in Dorset, Ontario.

Two types of potential source contribution function analysis- Potential Source Contribution Function (PSCF) and Total Potential Source Contribution Function (TPSCF) analysiswere employed to study the source-receptor relationships for several trace elements (vanadium, selenium, arsenic, manganese, and indium) found in precipitation and airborne particles collected at Dorset, Ontario. This study identified areas in the United States and Canada as possible emission source areas that could contribute to the trace element concentrations observed at Dorset. The identified regions in the United States generally coincide well with the locations of known emission sources, whereas the possible source regions revealed in Canada could not be adequately explained because of the absence of emission source information. The likely emission sources for these trace elements include oiland coal-fired power plants, incinerators, motor vehicles, nonferrous metal smelters, iron and steel mills, ferrous-Mn alloy plants, and Mn chemicals production.