Katie Purvis-Roberts

Air Pollution Research

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The overall objective of my air pollution research program at Keck Science is to investigate pressing environmental issues from both a chemical and policy perspective. My research focus is on air pollution, using modern analytical chemistry techniques. This research program not only addresses critical environmental concerns, but also allows undergraduate students the opportunity to perform hands-on research in the laboratory and prepare them for future research opportunities.

My state-of-the art air pollution characterization laboratory consists of the following components: 1) A Particle Into Liquid Sampler (PILS) that allows for chemical speciation and mass concentration of ambient particulate matter pollution, 2) a Tapered Elemental Oscillating Microbalance (TEOM) for measurement of total particulate matter mass, 3) filter samplers for monitoring the chemical speciation of particles, and 4) analytical equipment such as ion chromatographs and gas chromatography-mass spectrometers. At the time I started this research, I had one of only five PILS samplers in the world, and I established an independent air pollution research program examining the water-soluble component of aerosols in Claremont.

Due to laboratory equipment cost and disciplinary diversity, atmospheric scientists often collaborate in larger field projects to obtain a more complete chemical and physical characterization of the aerosol they are studying. I therefore also work to develop deeper collaborations with atmospheric scientists on larger projects that ask more complex scientific questions. I have developed several collaborative research projects. One research collaboration was with scientists from the University of California, Los Angeles to study the evolution of Polycyclic Aromatic Hydrocarbons (PAHs) across the Los Angeles Basin. I also developed a NSF funded collaborative research program with scientists from the University of California, Riverside and the U.S. Department of Agriculture to study how alkyl amine gases incorporate into particulate matter air pollution, which has resulted in a very fruitful collaboration both for me and my students. We started collecting preliminary data and developing our ideas for our grant proposal during my sabbatical (2008-2009), but funding did not arrive to actually pursue the work until the end of July 2009. We recently finished experiments on this project, submitted another NSF grant proposal to further our work this past June, and are in the middle of writing four manuscripts.

Alkyl Amine Incorporation into Particulate Matter Air Pollution:
Environmental Chamber work at the Cocker Lab at University of California, Riverside

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The goal of the research that I do in collaboration with scientists from U.C. Riverside and from the USDA is to understand how aliphatic amine gases react to form particulate matter, both from environmental-chamber and field measurements. Particulate matter (PM) air pollution derives from a variety of anthropogenic and natural sources (industry, transportation, agriculture, sea salt) and can cause both health and environmental impacts. Aerosols are composed of a range of chemical components, including organics, inorganic salts, soot, and crustal material to name a few. Scientists are still trying to understand how the chemical composition of particulate matter changes with location, weather conditions, and nearby sources. Numerous studies have shown that significant concentrations of simple primary, secondary, and tertiary amines are present near animal feeding operations, such as dairies and feedlots, in high-parts per billion concentrations and that amines make up 10% of the total gas-phase nitrogen emitted. Amine gases can react with oxidants (OH and O3) in the atmosphere to form particulate matter, but it was unclear whether the reaction pathway was through oxidation to form a low-volatile oxidized amine or an acid-base reaction to form an amine salt. The goal of our project was to understand how amines observed in the environment [butylamine (BA), diethylamine (DEA), and trimethylamine (TMA)] react to form particulate matter with atmospheric oxidants.

Laboratory studies were done at the environmental chamber at CE-CERT. A 12,500 L Teflon chamber with humidity and temperature control was used for experiments. First the target amine was injected in to the chamber, followed by introduction of oxidants (either HOOH/UV irradiation, N2O5 or O3). Particle formation was monitored with a High Resolution Time-of-Flight Aerosol Mass Spectrometer (HR-ToF-AMS), Proton Transfer Reaction Mass Spectrometer (PT-RMS), Scanning Mobility Particle Sizer (SMPS), Aerosol Particle Mass Analyzer (APM), Volatility Tandem Differential Mobility Analyzer (VTDMA), and the PILS-IC. The PILS-IC data are critical to these studies because PILS-IC is the only instrument that provides quantitative, chemical data. The HR-ToF-AMS provides chemical speciation and aerosol size data, but not quantitatively. The PT-RMS was used to monitor gas phase amine concentrations before particle incorporation and data from the APM, VTDMA, and SMPS were used to calculate total particle mass and concentration.

Field work at dairy near Hanford, California

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Peer-Reviewed Publications


Katie Purvis-Roberts
Professor of Chemistry & Environmental Science
W.M. Keck Science Department of Claremont McKenna, Pitzer, and Scripps Colleges
925 N. Mills Ave.
Claremont, CA 91711
Phone: (909)607-9782
Fax: (909)621-8588