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John Ortega

Page history last edited by Nicholas Clements 10 years, 9 months ago

John Ortega is a research associate working at both the National Center for Atmospheric Research and the Mechanical Engineering Department at CU Boulder.


John's work is multi-faceted and involves measurements of volatile organic compounds, instrument development, particle size distribution measurements and analysis.  He has been involved with a number of ground- and aircraft-based field campaigns, most recently in the 2012 DC3 campaign (Deep Convective Clouds and Chemistry) flying a custom-built and programmed scanning mobility particle sizer measuring particle size distributions from 10-120 nm at altitudes up to 45,000 ft.  Other recent activities include monitoring methane and hydrogen sulfide gasses from oil and gas development and developing an inexpensive low-power sensor array to quantitatively distinguish between natural gas and gasoline signatures.



The Missouri study was focused on aerosol and gas-phase measurements in the northern Ozarks, which is an ecosystem dominated by high isoprene emitting tree species.  Our group has a history of making particle and gas-phase measurements in Colorado, and other mixed forests, but this ecosystem is relatively new to us.  So one of the science questions that we addressed was:  "Is new particle formation suppressed in environments where the biogenic VOC mixure is dominated by isoprene (vs. conifer-dominated forests monoterpenes by monoterpenes and 2-methyl-3-buten-2-ol or “MBO”)?



We measured particle size distributions from 10 nm to 3 um and gas-phase biogenic volatile organic compound fluxes (using a proton-transfer mass spectrometer = PTR-MS) from May 1 until October 22, 2012.  There was also an intensive campaign during July and August focused on trace gasses (ozone, CO, NO-NO2, SO2) leaf-level measurements, speciated monoterpene fluxes, and particle cluster measurements (down to 1nm mobility diameter).  Ongoing or continuous measurements by the University of Missouri included CO2, water and energy fluxes and pre-dawn water potential measurements.  This year was unprecedented in terms of high temperatures and drought in the Midwest and our data indicates that biogenic emissions and carbon sequestration were highly suppressed relative to previous years, until a significant rain event happened in August.  This brought the forest “back to life”.  Data analysis is still ongoing to determine if new particle formation events were suppressed due to a high isoprene:MT ratio.  The figure shows the healthy forest from the top of the flux tower (during late spring before the drought fully set in).


Another recent project was the Deep Convection Clouds and Chemistry experiment based in Salina, KS.  This campaign was designed to understand how ground-level emissions are transported and reacted as they are involved in thunderstorms.  Part of the chemistry in thunderstorms is initiated by NOx from lightning.  So the experiment had extensive network of lightning mapping from ground sites.  The first figure shows the GV aircraft equipped with inlets above and below the body of the plane as well as wing-tip probes.  The 2nd figure shows the flight track and particle size distributions that occurred downwind of a convective system over Missouri, Illinois and Indiana on June 21, 2012.  This is interesting in that we can see the appearance of the smallest particles, and that they grow over time.

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