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Influence of Relative Humidity and Temperature on Secondary Organic Aerosol Formation

EPA Grant Number: F5B10208
Title: Influence of Relative Humidity and Temperature on Secondary Organic Aerosol Formation
Investigators: Warren, Bethany
Institution: University of California - Riverside
EPA Project Officer: Willett, Stephanie H.
Project Period: September 1, 2004 through June 1, 2008
Project Amount: $105,809
RFA: STAR Graduate Fellowships (2005)
Research Category: Academic Fellowships

Description:

Objective:

Particulate matter (PM) suspended in ambient air increases human morbidity and mortality, impairs visibility, damages property, and impacts global climate change. Secondary organic aerosol (SOA) contributes a significant portion of the PM2.5 concentration in urban airsheds. Understanding SOA formation mechanisms for anthropogenic hydrocarbons in the presence of water and at various temperatures will provide necessary information to improve SOA predictions. These improvements will aid in determining effective reduction strategies to reduce PM2.5.

Approach:

Utilizing UC Riverside’s state-of-the-art environmental chamber, SOA formation mechanisms will be determined for photochemical and ozonolysis experiments at atmospherically relevant concentrations. The chamber’s temperature control features and the argon arc light allow for a thorough investigation into SOA temperature dependence. The argon arc lamp is an ideal source of light due to its replication of ground-level sun radiation and because the light intensity does not vary with temperature changes. Humidity effects will be studied using a newly designed humidification system that fills the chamber with purified air at a constant humidity. A differential mobility analyzer (DMA) will be used to determine the concentration and number of particles formed during these experiments, along with a gas chromatograph to monitor the decay of the parent hydrocarbon. A tandem differential mobility analyzer (TDMA) will be used to measure the water uptake of the particles formed during experiments. This information will improve our understanding of SOA formation mechanisms at atmospheric conditions.

Expected Results:

SOA formation is expected to decrease with the increase of temperature, due to the vapor pressures of the formed compounds. The influence of water on SOA formation will vary depending on the parent hydrocarbon and other substrates present. Any results from these experiments will help in the determination of SOA formation mechanisms.

Supplemental Keywords:

chamber, secondary organic aerosols (SOA), humidity, water, temperature, particulate matter (PM), particles, air pollution, haze, formation, tandem differential mobility analyzer (TDMA), photochemical, ozonolysis, , Air, Scientific Discipline, RFA, particulate matter, Environmental Chemistry, Environmental Monitoring, ambient measurement methods, hydrocarbons, airborne aerosols, secondary organic aerosols, air sampling, aerosol formation, monitoring of organic particulate matter, atmospheric chemistry, atmospheric particulate matter, climate and chemistry, atmospheric aerosol particles, airborne particulate matter

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The perspectives, information and conclusions conveyed in research project abstracts, progress reports, final reports, journal abstracts and journal publications convey the viewpoints of the principal investigator and may not represent the views and policies of ORD and EPA. Conclusions drawn by the principal investigators have not been reviewed by the Agency.

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