What's happening

May 2011

Visiting PhD student Eva Joˇ is completing a number of ozone reactivity measurements that will forward the Trees & VOCs project. The chemical engineer introduces compounds from trees or standards through a line to a reaction chamber, where the compounds react with known quantities of ozone. She is watching the signals from these reactions closely to see if they change after the reaction.

"What I like [about this project]: it's a mix of field work, lab work, and computer work," she explains. "It's not sitting in one place for 24 hours-especially when you can go out in the forest or on a research trip with Detlev."

December 2010

Congratulations and best wishes to graduate student Ryan Daly, whose research on sesquiterpenes was bound up with this project and who did much of the field work at CreekSide Nursery. He defended his master's thesis at the end of last month and has moved on to work with the EPA in North Carolina researching a very similar topic.

October 2010

Romain Baghi, our visiting student from the University of Toulouse, is back! He's here for two months to write a paper on the flowering trees experiment he performed last summer.

September 2010

As the last leaves fall from the trees, our work at Creekside Nursery is all wrapped up. All equipment has been brought back to the labs, and we can now start to process our data.

13 August 2010 

Next week the students working on our UROP project will be showing Sara Barber, from the Mile High Million Initiative, around their project site at CreekSide Nursery. They've made a lot of progress this summer and will be demonstrating their process, instruments, and some preliminary data.

July 2010 

We're in Michigan, performing our VOCs experiment in the woods not far from Michigan Tech. See a few photos from the field right here ---->

Our study was part of CABINEX--Community Atmosphere-Biosphere Interactions Experiments. The goal of CABINEX is to provide a collaborative environment in which a number of research institutions share resources to answer one common scientific topic: the effects of forest succession and biogenic volatile organic compounds (BVOCs) on microscale atmospheric chemistry within the canopy layer. Our study took place at the University of Michigan Biological Station.

June 2010 

We have just received funding to support three students this summer as part of an Undergraduate Research Opportunities Project (UROP). UROP projects create research partnerships between faculty and undergraduates. We are excited to engage Christopher Borke, Carly Baroch, and Erik Ware in the research process. They will be studying biogenic volatile organic compounds emitted from urban trees to assess the impact of planting of a high number of these trees through the City of Denver Mile High Million tree planting program. Trees species to be considered include Sugar Maple, Ohio Buckeye, Frontier Elm, Northern Hackberry, Turkish Hazelnut, Littleleaf Linden, London Planetree, American Basswood, and Japanese Zelkova. Trees will subjected to a branch enclosure experiment, in which volatile organic emissions released by their foliage will be captured on adsorbent tubes. Samples will subsequently be analyzed by a gas chromatography technique in INSTAAR’s Atmospheric Research Laboratory. Individual compounds and their emission rates will be identified using standard protocols that have been established. The emissions data and literature on compound reactivities and atmospheric production products will then be used to develop a comparison of these tree species and their impact on the urban atmosphere. This research will provide improved data and criteria to help urban foresters directing the planting of trees in the Colorado Front Range urban areas. In particular, this information will be beneficial for the tree selection and tree planting strategy for The Mile High Million program underway in the City of Denver.

26 May 2010 

Today the Institute for Environmental Solutions is hosting a workshop "Guidelines for Community Forestry Carbon Credit Projects" through its Tree Project. Shelly, our outreach person, is attending to gather ideas about how we can package our data to be of use to city and state foresters, city and regional planners, large landowners, and community organizers. She reports, "It's exciting to see people we've only been in touch with online before now."

April 2010  

We have collected a full year's worth of observations from our experiment at CreekSide Tree Nursery. With measurements taken every few minutes, that is a lot of data. Ryan is starting to crunch the numbers now. We are continuing to collect data as we move into full summer and the deciduous trees leaf out fully. It is interesting to see the trees' reactions to spring storms and winds.

October 2009 

Ava Jo, a graduate student from Ghent University, has been visiting for the past few weeks to learn about sesquiterpene analysis techniques with our team. She is here for a six-week research experience.

September 2009 

We've been measuring VOC emissions from one or two new tree species each week at CreekSide throughout the spring and summer. We've been focusing on deciduous trees in their different stages: leafing out, flowering, and fully leafed. Species include aspens, maples, oaks, and crabapples, all popular choices for Front Range yards and landscapes.

August 2009 

We are one of many groups looking at tree selection as a method for environmental management. As well as our partner, the City of Boulder Urban Forestry section, we recently connected with a Denver-based nonprofit called the Institute for Environmental Solutions. Their Tree Project seeks to identify how trees can be used to enhance energy and water conservation, carbon sequestration, and air quality.

July 2009 

We now have full leaf canopies to measure on trees at CreekSide Tree Nursery. Our rainy summer is letting us collect data in many different conditions.

June 2009 

There's now a poster on our trailer at CreekSide Tree Nursery, explaining what our experiment is about and how it works. Drop by the nursery to see it, or have a look online.

May 2009 

The trees are leafing out here in Boulder, and a new round of work is beginning at our field site in CreekSide Tree Nursery. Many urban shade tree species are in flower, such as crabapple and cherry trees. The team is interested to find out how springtime VOC emissions differ from emissions in full summer, after the flowers are gone and full leaf canopies take their places.

April 2009

For the second year in a row, Ryan showed several groups of 8th grade students the Trees and VOCs project during INSTAAR's annual Open House for Southern Hills Middle School. The students looked over a working setup of the equipment used to run the experiments, including a Teflon branch enclosure.

February 2009 

A new member of the team is here: Romain Baghi. A student intern, he will be in Boulder through July. Romain will be studying VOC emissions from trees, particularly emissions from urban trees during the spring flowering period. He will also work at the National Center for Atmospheric Research (NCAR) on a new database for the MEGAN atmospheric chemistry model. Romain is visiting from Paul Sabatier University in Toulouse, France.

December 2008 

The team is collecting lots of data at the Creekside Tree Nursery field site. Branch enclosures are set on several varieties of evergreen trees, including ponderosa pine, bristlecone pine, douglas fir, and Colorado black spruce, at a rate of one or two new species each week. (We'll get to deciduous trees in the spring through fall, when there are leaves on those branches.) The Nursery folks have been really helpful, moving several of the trees together by our trailer.

We have a new instrument that is really speeding up our experiment - a field version of a gas chromatograph. Ryan and Brooks put a lot of work into getting the instrument to work right. Now we can see data in the field, instead of having to take the record of observations back to the lab and analyze it there. It eliminates two steps from our process. Even better, it runs inlet and outlet samples at the same time, which gives us more accurate observations.

November 2008 

Brooks moved the trailer out to Creekside Tree Nursery today. They are starting field work and will be collecting data almost every day for the next two months, using branch enclosures set on some of the nursery's mature trees.

October 2008 - Detlev joins Denver advisory council

Because of his work on VOC emissions from trees, Detlev has been invited to join Denver's Tree by Tree - Mile High Million advisory council. Mayor Hickenlooper announced an ambitious tree-planting program for the City of Denver during his 2006 State of the City address; goals of the program include planting 1,000,000 new trees in the metropolitan Denver area by the year 2025.

By being on the advisory council, Detlev will be able to suggest tree species that will most effectively scrub ozone from the Denver urban area. Unfortunately he has to miss the first meeting Nov. 5 because he'll be on the ice in Greenland for another INSTAAR project--but he will help shape the initiative through the next several years.

September 2008 

We've all been busy writing up lab results this summer. Tan, Alex, and Detlev, working with Jana Milford and Christine Wiedinmeyer, have a paper in press on secondary organic aerosol from terpenes in the United States. Along with a few others, Alex and Detlev have just submitted a paper to the journal Atmospheric Measurement Techniques. Now we wait to find out if it is accepted for publication!

July 2008 

Numerous problems with equipment in the lab have been keeping us out of the field lately--we hope to get back out there soon. The issues mainly revolved around our cartridge analytical techniques. (We analyze SQT either using a gas chromatograph/mass spectrometer (GC/MS) in the field, or using adsorbent cartridges that are later run on a GC/MS in the lab.)  At the beginning of the summer we decided to change the adsorbent used in these cartridges to better able to capture certain monoterpenes and isoprenes. That wound up being pretty complicated and took awhile to sort out .

Additionally we have been calibrating and familiarizing ourselves with a new device called a LiCOR that measures carbon dioxide. We'll be able to use it to calculate respiration rates of the vegetation that we study.  This will give us a better understanding of the physical activity of the vegetation during our samples.  We've been doing some studies using this device just outside the INSTAAR building over the last week.

I'll send pictures of the cartridges that we have been analyzing as well as the enclosure studies measuring CO2 using the LiCOR tomorrow

May 2008 

The team is getting good results from its enclosure measurements. Biogenic VOCs react so quickly, and have such low vapor pressure, that they are difficult to measure using common techniques. So the team is working with branch enclosures, then multiplying the effect to see what might be happening over, say, an entire forest. These fluxes can then be used in models to determine how the VOCs influence atmospheric chemistry and aerosol processes. So far, the team has gathered new VOC emission data for highly reactive monoterpenes (MT) and sesquiterpenes (SQT) from a variety of plant species.

As well as measuring the amount and type of VOCs emitted from leaves in each enclosure, the data includes air temperature, relative humidity, and the amount of photosynthesis. The team has found that VOC emissions are dependent on both light and temperature. The data also shows that SQT emissions become increasingly important in warm weather conditions.

April 2008 

Ryan just finished giving a tour of the Mobile Biogenic VOC Monitoring Laboratory (a.k.a. The Trailer) to several small groups (about 75 total) of 8th grade students. The tours were part of INSTAAR's annual Open House for Southern Hills Middle School.

Ryan fielded lots of interesting questions during the Open House. Among his favorites were, "What trees are better for planting in Boulder to reduce ozone?"
(A: Low BVOC emitters (like oak and aspen) are preferred. Maple, pine, and eucalyptus are examples of moderate to high BVOC emitters. It is also important to consider the amount of biomass for each species (lots of leaves mean higher emissions.)
"Can you take measurements in bad weather?"
(A: Yes, as long as the instrumentation is safe. With the trailer we will be able to measure emissions throughout the year... rain/snow/hot/cold...)
"Is this the reason for the name of the 'Smoky Mountains'?"
(A: Yes, Biogenic emissions react with other compounds in the lower troposphere, resulting in aerosols that give the air its smoky or hazy appearance.)

March 2008 

If scientists aren't working in the lab, or in the field, where are they? Chances are they're writing an article, conference paper, or book chapter to share their work. INSTAAR grad student Tiffany Duhl, Detlev, and Alex have just published a literature review in Biogeosciences on sesquiterpene emissions from vegetation. Tan and former INSTAAR grad student John Ortega each have a couple papers in the works as well.

February 2008 

Why is Ryan spending so much time in the INSTAAR parking lot? Because that is where the instrument trailer is parked at the moment, and he is getting it ready for the summer field season. Summer seems like a long way off, but it won't be long before leaves start budding out on the tree branches and we'll want to start measuring.

January 2008 

Tanarit just completed his dissertation through the Department of Mechanical Engineering here at CU. Congratulations Dr. Sakulyanontvittaya! Tan studied sesquiterpene (SQT) emission rates and temperature and light dependencies using data he collected for this project. Some of the questions he addressed included:

  • What are the primary plants and ecosystems that emit SQT and contribute organic aerosols?
  • How much do biogenic SQTs contribute to aerosol mass in the atmosphere? Are SQTs a major source of organic aerosols in the United States?
  • How do SQT emissions and the resulting organic aerosols vary spatially? Which U.S. regions are most affected? How to they vary over time?
  • What weather conditions result in the highest and lowest SQT production and organic aerosol concentrations?

Fall 2007 

Tan, working with Alex, Christine Wiedinmeyer, and Jana Milford has incorporated the new emissions data from our experiments into the emission model MEGAN and the air chemistry and quality model CMAQ. Models like these help scientists predict how the natural world will act in different places and at different scales, so this was one of the most meaningful results of our project. Tan also presented a couple posters about this work at a conference in May in California; that helped get the word out to other scientists as well.

We have a new instrument trailer now that will house our instruments during field experiments. We hope to have it ready and kitted out in time for experiments at the CreekSide Nursery in May 2008.

Summer 2007 

Ryan is still in the lab, fine tuning the SQT calibration system (also called the capillary diffusion system or CDS).  This is an instrument that gives off one or many sesquiterpene compounds at a desired level (between 100 parts per billion volume and 100 parts per trillion volume--very small amounts!).  We use the CDS to calibrate our instruments and sampling techniques for field studies. That means that if we measure an amount of sesquiterpene emitted from some leaves, we want to know that we are measuring that amount accurately.

Over the next couple of months, the team wants to install the Field GC/MS in an enclosed trailer that we can take from place to place during field studies. We'd like to get out in the field, too, perhaps doing some sampling at Creekside Nursery using the Field GC/MS.

Spring 2007 

The team ran some preliminary studies using a mass spectrometer (Field GC/MS) and the results were not good. The instrument wasn't working right. Ryan spent a lot of time in the lab with the instrument pulled apart on a workbench. He was able to figure out that some of the parts in the mass spectrometer were just old and had reached the end of their lifespan. In a way it was like a car engine needing new spark plugs. Ryan replaced the parts and the Field GC/MS is back up and running.

After the instrument was improved, we participated in the first SQT measurement comparison experiment. This experiment was conducted in the NCAR greenhouse on three plant enclosures (loblolly pine, sunflower, eucalyptus). We took 13 different measurements of SQT. After four days of measurements in the greenhouse, the group moved into our laboratory where SQT standards (both individual compounds and SQT mixtures) from our capillary diffusion system were sampled. These data are now being analyzed by the participating groups and will be shared and compared for an evaluation of SQT sampling and calibration procedures.


In the summer and fall of 2006 we tinkered with the instrument we use to measure sesquiterpene and monoterpene emissions from tree leaves. After making it more efficient, we took the instrument over to our research sites at Creekside Nursery and in the National Center for Atmospheric Research (NCAR) greenhouse. We conducted about 30 separate enclosure experiments, collecting from 10 to 30 samples from each enclosure. In the fall and winter we analyzed that data for differences between tree species and differences caused by the trees responding to changes in air temperature.

We have found so far that sesquiterpenes are really dependent on the air temperature--more so than monoterpenes. We think that sesquiterpene emissions will be important on hot days and in places with warm climates. But from looking at data from loblolly pines, we know that there are many changes in sesquiterpene emission rates that don't seem to depend on temperature. We hope that this project will help us find out what those factors are, and how important they might be.

July 2010 - VOC experiment in Michigan.

This is Zeke the lift. Zeke hoisted us up to the tree canopy so that we could attach enclosures to the branches up high.

The ride up is the fun part.

Detlev carefully fixes a Teflon bag around a branch and attaches the hoses.

There's the enclosure, high in the canopy.

Then we set up our equipment in a van at the site, and built a scaffold to reach branches at in the lower canopy.

Ryan sets up our equipment in the van. Bring on the data!


June 2009 - An image of the poster on the side of our trailer at CreekSide Nursery. Want to read it? Download the PDF.


May 2009 - A branch enclosure. Photo by Romain Baghi.

May 2009 - Romain places a Teflon enclosure around a budding branch at CreekSide Tree Nursery, as spring draws deciduous trees into leafing out. Photo by Detlev Helmig.

April 2009 - Ryan shows middle school students a field experiment on VOC emissions from trees at INSTAAR's annual Open House. Photo by Romain Baghi.

April 2009 - Ryan at CreekSide Nursery, hooking up Teflon bags to the branches of a flowering crab apple tree. Photo by Romain Baghi.


December 2008 - Brooks and Ryan by a branch enclosure at Creekside Tree Nursery. You can see the inlet and outlet lines going to the enclosure behind Ryan.

December 2008 - The trailer that houses our experiment at Creekside Tree Nursery. Lines connect branch enclosures on the evergreen tree species to the ozone analyzer in the trailer.

December 2008 - The ozone analyzer. You can see the cartridges on the front of the device that we selected this summer.


July 2008 - Some of the cartridges the team has been working with in the lab, showing the different types of adsorbent materials that we are testing for our outdoor research. Each material has a different chemical makeup and porosity, making them stronger or weaker for adsorbing the emissions that are of interest. You can think of it like paper towels...some work better than others. The idea is to use the strongest adsorbent material possible that still allows us to remove the compounds in the lab; if the adsorbent is too strong then the compounds will not be released.

July 2008 - The enclosure work that we have been doing outside of INSTAAR testing our new LiCOR instrument that measures carbon dioxide - a way to monitor the vegetation's physical activity.


Ryan at the INSTAAR open house - April 2008

April 2008 - Ryan shows a group of students from Southern Hills Middle School how the team takes samples using the branch enclosure technique.

Inside the trailer, information taken from the samples runs through the team's equipment, like the mass spectrometer.


GC mass spectrometer.

This photo shows the mass spectrometer used to measure SQT emissions from tree leaves. Ryan has pulled it apart in the lab to replace some of its parts.



2009: "Measurement of atmospheric sesquiterpenes by proton transfer reaction-mass spectrometry (PTR-MS)," by S. Kim, T., Karl, D. Helmig, R. Daly, R. Rasmussen, and A. Guenther. Atmospheric Measurement Techniques, 2(1): 99-112.

2008. "Secondary organic aerosol from sesquiterpene and monoterpene emissions in the United States," by Tanarit Sakulyanontvittaya, Alex Guenther, Detlev Helmig, Jana Milford, and Christine Wiedinmeyer. Environmental Science & Technology 42(23): 8784-8790.

2008. "Approaches for quantifying reactive and low-volatility biogenic
organic compound emissions by vegetation enclosure techniques – Part A," by John Ortega and Detlev Helmig. Chemosphere 72(3): 343-364.

2008. "Approaches for quantifying reactive and low-volatility biogenic organic compound emissions by vegetation enclosure techniques – Part B: Applications," by John Ortega, Detlev Helmig, Ryan W. Daly, David M. Tanner, Alex B. Guenther, and Jeffrey D. Herrick. Chemosphere 72(3): 365–380.

2007. "Flux estimates and OH reaction potential of reactive biogenic volatile organic compounds (BVOCs) from a mixed northern hardwood forest," by John Ortega, Detlev Helmig, Alex Guenther, Peter Harley, Shelley Pressley, and Christoph Vogel. Atmospheric Environment 41(26): 5479-5495.

2007. "Sesquiterpene emissions from pine trees - Identifications, emission rates and flux estimates for the contiguous United States," by Detlev Helmig, John Ortega, Tiffany Duhl, David Tanner, Alex Guenther, et al. Environmental Science and Technology 41(5): 1545-1553.

2007. "Sesquiterpene emissions from vegetation: A review," by Tiffany Duhl, Detlev Helmig, and Alex Guenther. Biogeosciences Discussions, 4(6): 3987-4023.

2006. "Sesquiterpene emissions from loblolly pine and their contribution to biogenic aerosol formation in the Southeastern US," by Detlev Helmig, John Ortega, Alex Guenther, et al. Atmospheric Environment 40(22): 4150-4157.


This research is supported by the National Science Foundation grant no. ATM 0608582.


Any opinions, findings and conclusions or recomendations expressed in this material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.