Category Archives: VOC

Climate and air quality research onboard a zeppelin

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16052013608Since the beginning of May 2013, a zeppelin has been flying over southern Finland. The zeppelin was brought to Finland as part of a European project PEGASOS to measure aerosol particles and trace gases in the lowest layers of atmosphere up to about 1.5 km.

As part of PEGASOS (Pan-European Gas-AeroSOls-climate interactions Study), an international group of scientists studies the effect of human emissions to climate change. Last summer research flights with the zeppelin were carried out in polluted areas in Central and Southern Europe. This time, we measure in Finland where the air is cleaner, anthropogenic emissions smaller, and biogenic effects more important.

In Finland 30 scientists, 10 technicians and 2 pilots operate the zeppelin and the instruments it is carrying. While in Finland, the zeppelin is stationed at Jämijärvi airport and the flights are mostly directed between Jämijärvi and Hyytiälä or around Jämijärvi.

The “flying laboratory” build in the zeppelin is equipped with state-of-art scientific instruments specially designed to investigate aerosol particles and trace gases. The instruments are divided into three cabin layouts and only one can fly at a time. Each of the layouts has a specific scientific focus point: new particle formation, photochemistry, and secondary organic aerosol – together covering a wide range of atmospheric physics and chemistry.

The zeppelin complements the extensive ground-based measurements and airplane measurements carried out in the planetary boundary layer. This airship offers a unique combination of capabilities which is not available when employing other aircrafts. The airship can stay at nearly fixed position, making it possible to follow time development of various events, such as industrial emissions or particles from natural sources. On the other hand, the airship can change height quickly and operate also at low altitudes which allows for measurement of the vertical profiles of trace compounds with high time resolution, also at the lowest hundreds meter above ground.

The research flights will continue until mid-June 2013. So far, the measurements have given new information about atmospheric mixing and layering as well as transportation of particles and gases in the atmosphere and detailed information on spatial variation of fine particles and gases from natural and human made sources.

Hanna Manninen & Taina Yli-Juuti

Blog for the EU PEGASOS Project:
http://eu-pegasos.blogspot.fi/

PEGASOS Project home page:
http://pegasos.iceht.forth.gr/

 

Measuring smaller and smaller particles

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Katrianne Lehtipalo working with the Particle Magnifier in Hyytiälä.

Just a few years ago, there were no instruments which could detect recently formed atmospheric clusters, or the particle precursor vapours at atmospheric concentration levels. We needed to make those instruments ourselves. The largely unstudied size range at 1-3 nm is an area which calls for both scientific discoveries and technical innovations.

Airmodus is a spin-off company from the University of Helsinki, Division of Atmospheric Sciences. It was started in 2010 in order to commercialize some of the innovations that were needed for studying new particle formation.  Our flagship product is the Particle Size Magnifier, which is still the only commercially available particle counter detecting particles as small as 1 nm.

During the currently on-going PEGASOS campaign, there are Particle Size Magnifiers both at the ground station SMEAR II in Hyytiälä and up in the air carried by a Cessna airplane and the Pegasos zeppelin. This is the first time when airborne measurements start from 1 nm, so expectations from the results are high.

Katrianne Lehtipalo
Science Manager
Airmodus

A new book on Physical and Physiological Forest Ecology

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A new book, Physical and Physiological Forest Ecology, is now available from Springer. The editors are Prof. Pertti Hari, Prof. Kari Heliövaara, and Dr. Liisa Kulmala.

This important contribution is the result of decades of theoretical thinking and high-value data collection by the University of Helsinki examining forest ecosystems in great detail. The ecology is dominated by a qualitative approach, such as species and vegetation zones, but in contrast quantitative thinking is characteristic in the exact sciences of physics and physiology. The editors have bridged the gap between ecology and the exact sciences with an interdisciplinary and quantitative approach. This book recognises this discrepancy as a hindrance to fruitful knowledge flow between the disciplines, and that physical and physiological knowledge has been omitted from forest ecology to a great extent. Starting with the importance of mass and energy flows in the interactions between forest ecosystems and their environment, the editors and authors offer a strong contribution to the pioneer H. T. Odum and his work from over 50 years ago.

This book introduces a holistic synthesis of carbon and nitrogen fluxes in forest ecosystems from cell to stand level during the lifetime of trees. Establishing that metabolism and physical phenomena give rise to concentration, pressure and temperature differences that generate the material and energy fluxes between living organisms and their environment. The editors and authors utilize physiological, physical and anatomical background information to formulate theoretical ideas dealing with the effects of the environment and the state of enzymes, membrane pumps and pigments on metabolism. The emergent properties play an important role in the transitions from detailed to more aggregate levels in the ecosystem. Conservation of mass and energy allow the construction of dynamic models of carbon and nitrogen fluxes and pools at various levels in the hierarchy of forest ecosystems.

Testing the predictions of these theories dealing with different phenomena in forest ecosystems was completed using the versatile and extensive data measured at SMEAR I and II (Stations for Measuring Ecosystem Atmosphere Relations) and at six additional stands in Finland, and five stands in Estonia. The theories are able to predict fluxes at different levels in the forest ecosystem gaining strong corroboration in the numerous field tests. Finally, the combined results from different hierarchical levels in the forest ecosystem form the physical and physiological theory of forest ecology.

Book available here

Atmospheric Chemistry into the Future

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During the 10th – 13th of December 2012 (the week following AGU), the 4th Atmospheric Chemistry Mechanisms (ACM) Conference (100-150 participants) was held in Davis, California, USA. The conference was spiced with delicious food, high quality talks and state-of-the-art atmospheric chemistry science, and it is definitely recommendable. Every session was concluded with a general discussion concerning the topic of the session, which gives the impression that this is more like a workshop than an actual conference. The hottest topic seemed to be Criegee Intermediates and their potentially important atmospheric reactions with SO2 to form sulphuric acid. The meeting included a special session on amines, which both counted engineering talks on how to capture CO2 using amines (this is known as CCS: carbon capture and storage) and the following emission of amines to the atmosphere due to this process and potential effects, together with more traditional talks about atmospheric amine chemistry and amines role in atmospheric aerosol formation and growth.

There was a session on isoprene (which is the most biogenically emitted volatile organic compound (VOC) with 40% of the total global emission) and HOx (=OH + HO2) measurements and the interference in these. The chemistry of isoprene has been well debated in previous years and this session also included discussion on the sources, sinks and degradation (e.g. to alkylperoxy radicals and epoxides) of isoprene and its degradation products fate in the atmosphere. Five or so years ago, recycling of OH through isoprene reactions was a hot topic. However, it seems that this source of OH is not thought to be so significant any more.

The meeting also counted sessions on gas phase precursors to SOA (secondary organic aerosol) formation including a discussion on how important the explicity of the chemical mechanism has to be in order to get something reasonable. Modellers’ favourite tools, chemical mechanism generators, were also covered with presentations on the probably most used atmospheric chemical mechanism MCM (Master Chemical Mechanism) and what we can expect of its new version (MCM 4.0). This session also included presentations on the mechanism developments of SAPRC and BOREAM (which are near-explicit mechanisms like MCM) and GECKO-A (which is a explicit mechanism). New developments in theory and experiments, future legislative drivers, investigations in Titan’s atmosphere, geoengineering and bio-energy were also presented and discussed during the meeting.

Website: https://sites.google.com/site/atmoschemmech2012/home/about-the-conference

Participants from HY: Taina Yli-Juuti (atm division), Theo Kurtén (chemistry department) and Ditte Mogensen (atm division).

A new role for forests in atmospheric oxidation

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It is commonly known that forests emit volatile organic compounds (VOC) that participate in atmospheric chemistry and, when oxidised in the atmosphere, also form new aerosol particles. Ozone, the hydroxyl radical (OH) and the nitrate radical (NO3) are generally considered to be the dominant oxidants that initiate the removal of trace gases, including pollutants, from the atmosphere. But now a new finding by Lee Mauldin III, Mikko Sipilä, Pauli Paasonen, Tuukka Petäjä, Theo Kurtén, Veli-Matti Kerminen, Markku Kulmala and their collaborators suggests that forests also participate in the production of atmospherically relevant oxidants. In a recent Nature article, the group presented atmospheric observations from Hyytiälä supported by laboratory experiments and theoretical considerations that identified another compound, probably a stabilized Criegee intermediate (a carbonyl oxide with two freeradical sites) or its derivative, which has a significant capacity to oxidize sulphur dioxide and potentially other trace gases. This compound probably enhances the reactivity of the atmosphere, particularly with regard to the production of sulphuric acid, and consequently atmospheric aerosol formation. The oxidation chemistry of this compound seems to be tightly linked to the presence of alkenes of biogenic origin. Michael Boy and his group tested this idea for Hyytiälä and Hohenpeissenberg in Boy et al (2012). Photo of Hyytiälä by Juho Aalto.

Mauldin III et al (2012) A new atmospherically relevant oxidant of sulphur dioxide, Nature 488, 193–196

Online measurement of volatile organics in Hyytiälä

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Taina Ruuskanen has been working on measuring biosphere-atmosphere exchange of volatile organic compounds (VOC) for years. Originally, emissions were measured in little chambers with just one twig of a tree inside; but because VOCs participate in many chemical processes in the atmosphere and, especially, make tiny aerosol particles grow to climatically important sizes and into cloud droplets, it soon became evident that a more continuous and comprehensive observation technique is necessary. During her post-doc at the University of Innsbruck in Austria Taina worked with instrument manufacturers trying to get a new device, PTR-ToF (Proton Transfer Reaction  – Time of Flight mass spectrometer) function online with an eddy covariance system. This would allow the instantaneous and continuous observation of VOC fluxes between vegetation and the atmosphere. Taina and her group have spent the last year trying to
 make the measurement work in Hyytiälä, and this autumn they finally got good results. “Our preliminary results show that the flux method really works and I’m exited to dig out seasonal changes in the forest-atmosphere exchange of organic compounds from our one-year dataset!”, Taina says.

 

Ruuskanen et al., 2011, www.atmos-chem-phys.net/11/611/2011/ . Top: PTR-ToF in Hyytiälä for the first time; photo by Simon Schallhart. Bottom: Taina Ruuskanen in pensive mode.