AAAR 36th Annual Conference October 16 - October 20, 2017 Raleigh Convention Center Raleigh, North Carolina, USA
Abstract View
Investigating Chemical and Physical Atmospheric Properties of Wintertime Persistent Cold Air Pool Events in Salt Lake City for Air Quality Assessments
CESUNICA IVEY, Xia Sun, Sivaraman Balachandran, Yongtao Hu, Armistead G. Russell, Heather Holmes, University of Nevada Reno
Abstract Number: 176 Working Group: Source Apportionment
Abstract More than one million people live in Salt Lake Valley, Utah, where wintertime pollution reaches unhealthy levels due to the unique meteorology and orography of the region. Persistent cold air pool (PCAP) events occur when high pressure ridges create stagnant conditions over a valley, which hampers large-scale advection and reduces surface wind speeds. During PCAP periods the fraction of incoming solar radiation that reaches the valley floor is also reduced, leading to temperature inversions that allow pollution to build. Pollution levels continue to climb until a washout event removes the pollutants from the valley. Washout events include high winds or precipitation events with advection or wet deposition related removal processes, respectively. In this work, novel source apportionment techniques are applied for January 2007 to analyze source composition and source impacts for the Salt Lake Valley during PCAP events. First, a hybrid source-oriented apportionment model is applied over continental U.S. to determine observation and model-based impacts from 20 sources, including agricultural activities, fossil fuel combustion, dust, and metals processing. Then, a secondary bias correction method is applied to better quantify the source impacts on secondary PM2.5, which constitutes the majority of the PM2.5 mass. Further, PM2.5 source profiles for the Salt Lake Valley were developed using a nonlinear optimization and data assimilation approach, which takes into account observed PM2.5 data and model uncertainties. The optimized profiles are unique in that they are developed using both modeled and observed data, creating local profiles for the area of interest. The chemical mass balance model was applied for the years 2003-2015 using the optimized source profiles, highlighting the major sources of pollution during PCAP periods in the Salt Lake Valley.