Category Archives: Aerosols

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

Are diesel engines the answer in mitigating traffic emissions?

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Photo: Antti Mannermaa in Tekniikka & Talous

Diesel engines are amongst the largest emission sources in urban air. The emissions consist of soot particles of about 40-80 nm in diameter. The engines emit also nanoparticles at less than 20 nm or so in diameter, consisting of various hydrocarbons and possibly also sulphur (in case of sulphur-containing fuel).

Why is it so attractive to switch to diesel instead of a less emitting gasoline engine? The answer is in fuel economy. In Finland, the national policy towards the diesel fleet has changed over the last couple of years. Today the price per liter is almost equal for both diesel and E10 gasoline. The owner of the diesel car needs to pay a monthly tax, and the savings must come from the more economical engine.

The emissions of diesel engines are rather well know and there is a continuous effort to limit the emissions even more. In 2013, the new EURO VI limits for heavy-duty vehicles will be 0.01 g/kWh for PM (particulate matter) and 0.4 g/kWh for NOx. If you compare these to the EURO I values just 20 years ago the change is dramatic: EURO I for PM was 0.36 g/kWh and for NOx 8 g/kWh. Unfortunately, the diesel engines tend to be strong and last forever, so we have to wait for a while until the fleet has majority of EURO VI level engines.

In order to cut down the emissions to EURO VI level, changes in engine technology alone will not be sufficient. This emphasises the importance of the after-treatment of the exhaust gases. Several different types of catalysts and filters exist. How well do these work? What is their efficiency? Answering these questions requires intensive research.

What makes the development towards lower emissions even more challenging is the need to consider also the effects of new type of fuels. It is possible to produce diesel fuel from biomass-based renewable energy sources, and research towards this goal is already going on. These new-generation fuels aim for a lower CO2 footprint.

I am acting as an opponent for a recent PhD thesis from Tampere Technical University that has focused on all of these aspects in a wide set of experiments. The overall message of the thesis is clear: with new technology, one can fight against particle and gaseous emissions successfully together with lower greenhouse gas emissions.

By Prof Kaarle Hämeri (aerosol physics, Division of Atmospheric Sciences)

See original blog post at http://hameri.blogspot.fi. The link for the press release of the thesis work can be found here in Finnish.

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