UCLA Department of Atmospheric & Oceanic Sciences

Aerosol Production of Hydrogen Peroxide

This study is investigating a highly oxidizing component of particulate matter, hydrogen peroxide, to determine its sources, prevalence, levels and behavior. Understanding the specific types of particulate matter toxicity is key to devising cost effective control strategies that improve human health.

Recent epidemiological studies have shown a strong relationship between particulate pollution and health outcomes, including mortality. Determining the ‘causative agent’ in particles responsible for damaging health is the subject of increasing study, but many questions remain. Reactive oxygen species, including hydrogen peroxide, are candidates for part of the adverse health effects caused by particle inhalation.

In this project, aerosol borne oxidants are being characterized, investigating the relationship between these toxic compounds and location, source type, aerosol type, and photochemical activity. Additionally, laboratory studies on model systems are underway to determine the source and behavior of peroxides in aerosols.

 

 

Projects

Optical Properties and Measurement Uncertainties of Black and Organic Carbon Aerosols

             Black carbon and organic carbon aerosols have substantial effects on the Earth’s climate, yet because of large uncertainties in both the optical properties, mass measurements and emissions of these materials, their impacts cannot be quantified with any accuracy.

             We are studying a series of model aerosols generated under realistic conditions using small engines and photochemical smog in a roof-top Teflon reaction chamber (shown at left). Aerosols are characterized with an extensive suite of techniques including in situ optical and off-line optical to off-line mass and composition analyzers. 

Polar Nephelometer

             A new, light, rugged instrument to measure angular scattering is being developed, verified, and applied. Refractive index data is being retrieved from the data using a genetic algorithms approach.      

 

 

 

Formation of Organic Acids

          Organic acids are ubiquitous, not only in the gas phase and in clouds and in rain, but also in aerosols. Field and experimental measurements of carboxylic acids produced by oxidation reactions with biogenic terpenes point to their key role in secondary aerosol formation. Several possible sources have been suggested for organic acids in the atmosphere. The largest of these sources include direct anthropogenic emissions, biogenic emissions biomass burning and homogeneous oxidation of hydrocarbons. The contribution of each source remains very uncertain and likely location-dependent.

          We are working to quantify production of large (four or more carbon atom) organic acids from gas-phase reactions, including HO₂ reactions with acylperoxy radicals, and ozone reactions with alkenes. Acid analysis is performed with gas chromatography/mass spectrometry.

              

 

Atmospheric Chemistry of Aerosols

Climate Impacts, Health Impacts

and Formation