Contribution of long range transport to local fine particulate matter concerns

We have utilized the Particulate Matter Source Apportionment Technology (PSAT) in PMCAMx (a regional chemical transport model) to quantify the contributions from local emissions and short range (under 100 km), mid range (100-550 km) and long range (over 550 km) pollutant transport to both primary and secondary particulate matter concentrations using the Eastern United States as a test case. We have studied these contributions for two urban (Pittsburgh, Pennsylvania and Atlanta. Georgia) and one rural area (Great Smoky Mountains National Park) during all seasons. The local emissions impacts to elemental carbon (EC) in major urban areas were found to be substantial with approximately 50% of the EC coming from local sources and 80% emitted within 200 km of the receptor. The local sources are even more important during the night contributing around 60% of the EC and then dropping to around 40% during the early afternoon. The EC in the rural Great Smoky Mountains was mainly the result of sources 100-550 km away. The seasonal variation of the EC source area contributions is small. There was also little difference between high and low EC concentration days. The contributions to secondary aerosol species were found to be more regional with more than 50% of the sulfate and secondary organic aerosol (SOA) originating from SO2 and VOC sources that were more than 200 km away from the receptor. The importance of sources further away increased during the winter because of the lower photochemical activity. While mid range transport dominated in the summer the sulfate and SOA levels in all areas, long range transport became the most important sulfate and SOA source during the winter in the colder Northeastern US and of sulfate in the warmer South. (C) 2011 Elsevier Ltd. All rights reserved.