AAAR 33rd Annual Conference
October 20 - October 24, 2014
Rosen Shingle Creek
Orlando, Florida, USA
Abstract View
The Role of Nucleation in Controlling Aerosol Size Distributions: Analysis of 10 Months of Recent Aerosol Size Distributions at a Non-Forested Agricultural Location
ROBERT BULLARD, Ashish Singh, Charles Stanier, University of Iowa
Abstract Number: 348 Working Group: Remote and Regional Atmospheric Aerosols
Abstract The formation and growth of new particles in the atmosphere are important phenomena that have an impact on global climate. Long-term records of aerosol size distributions are used to understand nucleation and its precursors. Urban environments and forested rural environments are well studied compared to rural agricultural environments. This study examines 10 months of aerosol size distribution measurements at the Bondville environmental and atmospheric research site (BEARS) in Bondville, IL. BEARS is located within a non-forested rural continental environment. Potential precursors to nucleation include locally emitted and regional sulfur dioxide, as well as ammonia emissions from agricultural operations.
Past work on long-term and seasonal analysis of particle number concentrations at BEARS revealed the highest average number concentrations in the spring and fall. Long-term decreases in SO$_2 concentration (1988 – 2012) in all seasons can account for decreases in particle number concentrations (1994 – 2012) in most seasons, but particle number concentrations are increasing or constant in the late spring, where particle concentrations are higher than all other seasons.
These past results are combined with aerosol size distribution data from July 2013 – May 2014 are used to a) identify relationships between elevated number concentrations and nucleation, b) identify nucleation event frequency and intensity for all seasons, and c) utilize available gas-phase precursor (sulfates, nitrates, and ammonium) data and solar intensity (UV-B) and cloud cover data at BEARS to determine factors contributing to nucleation and growth. This will provide information on nucleation in this agricultural setting, which may be typical of other agricultural locations in the Midwest.
Preliminary data shows frequency and intensity of nucleation events decreasing with colder temperatures. Peak diurnal patterns are well correlated with existing ground-based CPC, with peak number concentrations occurring in the mid morning and extending to the late afternoon.