AAAR 31st Annual Conference
October 8-12, 2012
Hyatt Regency Minneapolis
Minneapolis, Minnesota, USA
Abstract View
Particulate Matter Chemistry in the San Joaquin Valley
SURESH RAJA, Srikar M. Reddy, Neelesh Sule, Whitney Rowe, Christopher Marlais, Scott Nester, Philip K. Hopke, Lin Lin, Xia Xiaoyan, Sriraam Ramanathan Chandrasekaran, Jon Klassen, James W. Sweet, Providence Engineering and Environmental Group
Abstract Number: 701 Working Group: Aerosol Chemistry
Abstract Particle pollution, especially fine particles with diameter less than 2.5 microns (PM2.5), is known to cause serious health problems as well as degrade visibility. In order to understand the changes in PM2.5 composition over time with an emphasis during the winter, a PM2.5 speciation sampling campaign was conducted at the San Joaquin Valley Air Pollution Control District’s Tranquillity monitoring site from November 7, 2011 to March 1, 2012. The PM2.5 speciation sampling campaign included 24-hour samples collected every third-day using three instruments: (1) a RAAS 2.5-400 speciation sampler and (2) a Tisch model, TE-1000, high volume sampler. In addition to this, a Magee Scientific Instruments, model AE-42, Aethalometer was continuously operated during this interval. Dominant ionic species in the Tranquillity samples were nitrate (NO3-) and ammonium (NH4+). Correlation plots of ammonium and nitrate suggested that a large excess of nitrate ions was present beyond that required to form ammonium nitrate. Analysis of excess sulfate concentrations revealed that when no excess sulfate was available, the PM2.5 mass concentrations were higher. This result was statistically significant at the 95% confidence level. The PM2.5 mass concentrations were higher when no excess sulfate was available because sufficient ammonia was available to react with nitric acid to form more ammonium nitrate particles. This, as a result, increased the PM2.5 mass concentration. In addition to this, speciation data collected from 2007 to 2011 by California Air Resources Board (CARB) in Fresno County was further analyzed to study the variations in PM2.5 chemistry. Analysis of data collected from this study, and from the CARB speciation network suggests that reductions in SO2 emissions may not be as effective as expected in mitigating high PM2.5 concentrations, and are unlikely to be effective without NOx control at the same time in this region.