On a global scale, biogenic emissions of VOCs are estimated to exceed anthropogenic emissions by roughly a factor of ten. On a regional scale in and downwind of urban areas, the relative importance of anthropogenic and biogenic VOC emissions is dependent on the rates of anthropogenic emissions, the type and density of vegetation, and the light and temperature conditions that drive biogenic emissions. Accurate in-situ measurements of biogenic emissions of VOCs are crucial for our understanding of both the environmental parameters controlling emissions and their effects on tropospheric ozone and aerosol formation. Biogenic monoterpene emissions contribute to photochemical ozone formation and influence the atmosphere's oxidative capacity, while their oxidation products can be a significant factor in secondary aerosol formation, in particular in coniferous forest areas.
Under ARB funding, we have done research on biogenic VOC emissions in a ponderosa pine plantation at Blodgett Forest, a site that is typical of the mid elevation Sierra Nevada Mountains. We have collected the first canopy-scale, continuous, long-term flux measurements of a range of atmospherically active hydrocarbons including methylbutenol, ethanol, methanol, acetone, acetaldehyde, and a suite of monoterpenes. Using a Proton Transfer Reaction Mass Spectrometer (PTR-MS), we have also measured total terpene emissions. While using the scanning mobility particle sizing (SMPS) approach, we have observed particle formation a short while after terpene emissions. The field study data has been analyzed to understand the ecological and physical processes that control emission rates for use in improving and developing emission model algorithms and to improve our understanding of secondary organic aerosol formation.
Analysis of total and speciated concentrations of terpenes and their oxidation products have shown that earlier speciated monoterpene measurements may have missed a fraction of total terpene measurements. Analysis of the aerosol data has demonstrated many aerosol nucleation events. New patterns of terpene emissions at the mid elevations of the Sierra Nevada Mountains in the aftermath of precipitation events have also been observed.
Allen H. Goldstein has been an associate professor of biogeochemistry at the University of California at Berkeley and a core member of the Berkeley Atmospheric Sciences Center for the last seven years. Professor Goldstein's research addresses the interactions between atmospheric chemistry and terrestrial biogeochemistry, and how these interactions influence biosphere-atmosphere exchange and determine atmospheric composition. His recent focus has been on the interface between natural and anthropogenic influences on regional photochemistry, including formation of ozone and aerosols, as well as deposition and other loss processes.
He initiated a major new research program after arriving at UC Berkeley in 1996, studying biosphere-atmosphere exchange of hydrocarbons, ozone, carbon dioxide, water, and energy in a ponderosa pine plantation, focusing on the physiological controls on trace gas exchange, impacts of typical management practices, and interactions with atmospheric chemistry. For this work, he and his research group established a highly instrumented AmeriFlux site at Blodgett Forest that is now operational year-round. His uniquely continuous research program has benefited from a distinguished group of associate scientists and students who now direct biogeochemistry research programs in their own rights. Professor Goldstein and his research group have published approximately 50 papers since his arrival at Berkeley, with roughly half of them resulting from the research at Blodgett Forest.
10:30 a.m. - 11:30 a.m.
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Fine Particle Formation and Processing in a Sierra Nevada Forest
Atmospheric Science Department
Environmental Energy Technology Division
Lawrence Berkeley National Laboratory
Forested ecosystems emit significant amounts of volatile organic compounds (VOC), which impact atmospheric photochemistry through ozone and aerosol production. Upon oxidation, some of these VOC's produce semi-volatile reaction products that can partition into the aerosol phase to form Secondary Organic Aerosols (SOA). SOA can constitute a significant portion of rural aerosol mass. By scattering and absorbing incoming solar radiation, SOA can affect visibility, photochemistry, and climate. To study biosphere-atmosphere exchange of ozone and VOC and their effects on aerosol formation and processing, we have conducted a study at the Blodgett Forest Research Station in the Sierra Nevada Mountains of California. The research site includes automated instrumentation for the in-situ measurement of concentration and biosphere-atmosphere flux of VOC, ozone, aerosol integrated and size resolved instrumentation, and meteorological variables. Preliminary results have shown that particle concentrations are correlated with both biogenic and anthropogenic VOC concentrations. In addition, the formation of small nuclei model particles (<20 nm) has been observed just after noon on many days. This talk will focus on recent results from the Blodgett site focusing on the diurnal aerosol patterns at the site, the relative importance of anthropogenic and biogenic sources on aerosol concentrations, and correlations between VOC measurements, meteorology, and particle formation events. Melissa Lunden has been actively involved with regional and rural ambient air quality monitoring focusing on aerosol measurements. Her work on the South West Wyoming Air Resources Monitoring System (WARMS) concentrated on visibility and air quality in national parks and wilderness areas. She has worked as part of the Atmospheric Sciences Department at Lawrence Berkeley National Laboratory that has evaluated modeling programs to study the effects of new oil and gas exploration and production on air quality in the inter-mountain west. Dr. Lunden has also been engaged in research to characterize indoor concentrations of outdoor PM2.5 to aid in understanding the link between outdoor aerosol concentrations, exposure, and adverse health effects. She has participated in the Western Regional Air Partnership and her contribution to the Blodgett Forest Research Station is both unique and invaluable in observation of particle formation processes that is adding a new chapter to our understanding of aerosol formation.
1:00 p.m. - 2:00 p.m.
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Estimating Biogenic Emissions
Emission Factors, Leaf Areas, Leaf Masses, Vegetation Mapping, and Alternative Approaches for Biogenic Emission Estimation for California
John F. Karlik, D. Env.
University of California
Landcover characterization is necessary for modeling simulations for ozone, PM2.5, fire, and smoke. In California, a species-specific scaling-up approach has been used to develop biogenic emission inventories. Data for species-specific emission factors, leaf masses (or leaf areas), and species composition have been developed, acquired, validated, and incorporated into California's Biogenic Emissions Inventory through the Geographic Information Systems (BEIGIS) model. Because emissions factor and leaf mass data have been empirically obtained for only a small fraction of California's flora, a phylogenetic approach has been used to assign values to unmeasured species. Because of the diversity and complexity of California's vegetation (e.g. more than 6000 plant species), a more simplified methodology may be attractive. An alternative approach for biogenic emissions estimation could consider plants in terms of ecosystem assemblages or on a regional basis. Emissions inventory simulations would then be developed using generalized emission factors and leaf mass data for respective vegetation cover types, and may not require the detailed vegetation mapping necessary for BEIGIS simulations. Ecosystem or regional modeling approaches may, however, pose difficulties in climate change and land use change assessment applications, and may not be able to incorporate new emission modules as our understanding increases of the emission behaviors of plants. John F. Karlik is an environmental science/environmental horticulture advisor with the University of California Cooperative Extension. His work has included research in plant and atmospheric sciences. He has conducted a series of field-based biogenic research projects that have provided and validated databases for the BEIGIS simulation platform.
2:00 p.m. - 3:00 p.m.
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Measuring Trace Gas Fluxes from an Aircraft Platform
Paul V. Doskey, Ph.D.
Argonne National Laboratory
Nonmethane organic compounds (NMOC) are precursors to ozone and aerosol formation. Global-scale emissions of NMOCs from biogenic and anthropogenic sources are approximately 1200 and 130 Tg C a-1, respectively. Evaluations of NMOC emission inventories developed for rural and urban areas (which contain large uncertainties) necessitate direct measurement of landscape-scale fluxes. The main objectives of this research are (1) to develop aircraft-based methodologies for measuring the rate of exchange of NMOCs with environmental surfaces and (2) to make observations of the vertical flux and concentration profiles of NMOCs and their oxidation products above urban and rural landscapes in order to evaluate chemical-transport models and emission inventories. The measurement approach uses a variety of eddy sampling techniques in concert with fast- and slow-response chemical and turbulence sensors to determine air-surface exchange rates. A description of the eddy sampling techniques and sensors will be presented. In addition, a field experiment designed to measure the flux of isoprene from a forested site will be described. Paul V. Doskey has been an environmental chemist in Argonne National Laboratory's Environmental Research Division for the past 16 years. Dr. Doskey's research involves experimental and theoretical studies of the behavior of gas- and particle-phase organic substances in the atmosphere. His experimental studies include sampling and analytic technique development and also field measurements of ambient levels and air-surface exchange rates. Dr. Doskey has participated in multiagency field campaigns for the Department of Energy during the past ten years, studying the role of light hydrocarbons in the formation of ozone.
For more information on this Seminar please contact Ash Lashgari at (916) 323-1506 or send email to: email@example.com
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