The Chemistry Department at Portland State University includes several faculty who conduct research in the general area of Environmental Chemistry, including Professors Atkinson, Clare, Johansson, Pankow, and Wamser. These researchers also collaborate with faculty from across the whole PSU campus, including Physics, Geology, Environmental Science and Management, and Civil and Environmental Engineering. The interdisciplinary section spans the range from basic (thermodynamics of gas-to-particle conversion) to very applied (environmental monitoring campaigns and effects of pollution on artwork) and focuses on Renewable Energy, Air Quality, Climate Change, and Art Conservation. Ongoing projects include field studies of air quality and regional climate effects of air pollution in the Columbia River Gorge, etc. Facilities in the PSU Chemistry Department for environmental chemistry research include a state-of the-art mass spectrometry laboratory, exposure chamber, and various portable analytical instruments.
Aerosol effects on climate and aerosol loading in urban air
Daily measurements of aerosols in Houston.
Professor Atkinson's lab has developed a new type of aerosol measurement based on the recently popular Cavity Ring-down (CRD) approach. In this method, laser light is introduced into a stable optical cavity constructed from very highly reflective mirrors. The light bounces back and forth between the mirrors many times (the "ring" in ring-down) and slowly decays due to the small but finite losses at the mirrors (the "down"). This allows very small optical extinctions (of the order of 1 photon in one million) to be measured over about 1 meter of sample. The sample in this case is the ambient air, which is drawn through the instrument with a pump. The impact of aerosols (tiny particles in air) on visibility is evident - on low aerosol loading days, Mt. Hood is easily visible from downtown Portland, but on high aerosol loading days, you can't even see it. The fact that aerosols scatter light can be used to measure the amount of aerosols in the air, as shown in the data below from a field measurement campaign in Houston, Texas during the summer of 2006. The large daily excursions are due to changes in the mixing layer height (as the city heats up, the air above the surface gets more turbulent, which can dilute the effects of emissions) while the longer term changes are due to different synoptic scale weather patterns that brought African dust, continental sulfate, and wildfire-produced smoke aerosols to Houston at various times during the study. The green trace is the CRD extinction measurement and the other traces are other measures of the aerosol mass loading. Most measurements are selective for particular aspects of the aerosol (e.g., size or chemical composition) but the CRD is relatively non-specific, since all particle types interact with light.
Field studies like this one can answer questions about the emissions of aerosols in cities like Houston or Portland. One of the important sources of aerosols in cities is diesel engines, that produce a fairly toxic mixture of chemicals and particles. These measurements may be helpful in measuring the extent of the pollution and perhaps this can be related to public health effects. These measurements are also useful in predicting the effects of these particles on the climate, both on a regional scale and by inference of mixing and transport, on larger spatial scales. Particles can (and do) cool the Earth by scattering light back toward space, but the full extent of their impact on climate is still considered highly uncertain.
Materials and analyses for the science of art conservation
Dr. Lasseter Clare studying an object from the collection of the Portland Art Museum.
Dr. Tami Lasseter Clare is seeking to identify new polymeric clear coatings that better protect and have longer working lifetimes to conserve outdoor metalwork. Research in the Clare laboratory focuses on coatings that are environmentally friendlier, such as waterborne latex coatings, compared to conventional clear solvent-borne coatings. In addition, Dr. Lasseter Clare is interested in gaining a greater understanding of the effects of air quality and pollution on works of art. Collaborators and partners include art museums and art conservators. Her work on protective coatings for outdoor metalwork is in partnership with the Philadelphia Museum of Art.
Solar cells and artificial photosynthesis:
Schematic of natural (top) and artificial (bottom) photosynthesis.
The Wamser group studies solar energy conversion using organic materials and conductive polymers (sometimes called artificial photosynthesis). In one arrangement, nanofibers of porphyrin polymer (poly-TAPP) are used as a base structure for light absorption and hole conduction. The surfaces of the nanofibers are covered with a complementary dye (TCPP) and the pores of the nanofibers are filled with an appropriate electron conductor, such as TiO2.
New work will begin investigating using solar energy for photocatalytic formation of renewable resources, such as conversion of carbon dioxide to methanol.
Schematic of natural (left) and artificial (right) photosynthesis.