(270b) Evaluation of Long-Range Transport of Atmospheric Particulate Matter Using a Regional Chemical Transport Model

An important aspect of designing effective control strategies for fine particulate matter (PM) concentrations is the quantification of the contributions of different source types and source regions to PM levels in a given area. Our goal is to quantify how much of the particulate matter in different locations is the result of local sources, short-range transport and long-range transport. We will discuss and compare two approaches to reaching this goal and results found using both approaches. The first approach is focused on source regions and the second is focused on receptor regions.

We have used PMCAMx, a regional three-dimensional chemical transport model, to study these impacts of pollutant sources and transport on particulate matter concentrations in the Eastern United States using PSAT (Particulate Matter Source Apportionment Technology). PSAT is a computationally efficient particulate matter apportionment algorithm that is able to track source contributions to both primary and secondary particulate matter in regional chemical transport models such as PMCAMx.

For the source focused approach, transport of pollutants is studied by tracking the emissions from source regions in order to study how far and in what direction these emissions are being transported. For the receptor region focused approach, transport of pollutants is studied by tracking the pollutants emitted from a series of rings around a receptor region of interest. This approach allows for the fullest understanding of the distance pollutants have been transported before they reach the receptor region we are studying but is slower than the source region focused approach since only one receptor region can be studied at a time. We will compare the results from both of these approaches looking at the impacts to primary organic aerosol, SO₂, particulate sulfate and particulate nitrate. These species are representative of most species of interest in the atmosphere since they include a primary non-reactive species (primary organic aerosol), a primary reactive species (SO₂), a non-volatile secondary PM species (particulate sulfate), a semi-volatile secondary species (particulate nitrate) and a precursor ? product pair (SO₂ and particulate sulfate).

The source region focused approach is applied to study the contributions of 11 different source regions in the Eastern United States, ranging in size (both in terms of land area and emissions) from the Ohio River Valley to Little Rock, AR. These impacts are quantified using a variety of measures to account for both the distance that the pollutants are transported and the overall impact the emissions have on pollutant concentrations in the region. The receptor region focused approach is used to evaluate the distance of transport for six receptor regions, ranging from remote regions (such as Great Smoky Mountains National Park) to urban regions (such as Pittsburgh, PA). Influences of several hundred miles have been found for secondary aerosol components from emissions originating in the larger source regions while primary aerosols show impacts predominately on the local scale. Of the source regions studied, the impact to surrounding areas is largest for the Ohio River Valley, the Mid-Atlantic region and Southwestern Pennsylvania and smallest for Little Rock, AR and St. Louis, MO.