Category Archives: Chemistry

Climate and air quality research onboard a zeppelin

Posted on by

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

Posted on by

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

Sulphur deposition causes a large‐scale growth decline in boreal forests in Eurasia

Posted on by
Reply

Map of sulphur depositions for the study sites in 1980. Adopted from Savva & Berninger (2010).

Human activity has altered climate, atmospheric carbon dioxide concentrations, and the concentrations of several pollutants over the last few decades. At the same time, short‐term reactions of tree growth to climatic variations have changed during the last few decades, for reasons that are poorly understood. However, the effects of the pollutants on growth of boreal forests in these remote areas have not been quantified, but even small changes in the productivity of boreal forest should have a large effect on the carbon balance.

The growth of Scots pine, the most important forest species in boreal Eurasia, has declined by about 17% or 0.0025 mm per year from the 1930s to the 1980s in northern Eurasia. We determined this by analysing 40 tree ring chronologies north of 60°N latitude and and factoring out the age and climate effects. Although the study sites were previously considered low‐pollution pristine environments, the growth decrease was significantly related to sulphur depositions. Additionally, we observed that the sulphur depositions rendered the Scots pine forests more sensitive to drought. Although the negative effects of local pollution on plant growth have been widely observed in the past, the long-term effects of sulphur emissions and its spread to ecosystems distant from the sources of pollution have never been previously documented at such a large scale.

These results are of fundamental importance for attempts to preserve the functioning of these forest ecosystems: sulphur deposition rates are still increasing in several regions of the world including the forested boreal areas of north-eastern China and eastern Russia. On the other hand, according to the European Monitoring and Evaluation Programme (EMEP) model, sulphur deposition at 35 sites in boreal Eurasia has been decreasing with a rate ranging from 0.25 to 2.92 kg S ha-1 per every 5 years over the period 1980 to 2000. This decrease in sulphur deposition should slow down the growth decline in boreal Eurasia, but the rate of growth decline will depend upon the ability of trees to recover from sulphur deposition effects, and combination of other environmental factors, such as the frequency of droughts.

Yulia Savva* and Frank Berninger*°

*Departement des Sciences Biologiques, Université du Québec à Montréal, Montreal, Quebec, Canada
°Department of Forest Ecology, University of Helsinki

Savva, Y., and F. Berninger (2010), Sulphur deposition causes a large‐scale growth decline in boreal forests in Eurasia, Global Biogeochemical Cycles 24, GB3002, doi:10.1029/2009GB003749.

 

 

 

Land-atmosphere interactions in urban environment

Posted on by
Reply

Today, more than half of world’s population resides in urban areas, and this fraction is

View off the roof top of Dynamicum showing the SMEAR III measuring tower. Photo: Antti-Jussi Kieloaho.

further expected to increase rapidly in the next decades. Thus, a growing number of people will be affected by urban climate. The ability to understand the processes leading to this specific micro-climate is crucial for sustainable urban planning and our quality of life.

In our Centre of Excellence, the Micrometeorology group has been observing the interactions between urban surface and the above atmosphere at the urban measurement station SMEAR III (Station for Measuring Ecosystem Atmosphere Relations) since 2005. We measure the vertical exchange of energy, water, carbon dioxide and aerosol particles with the state-of-the-art methodology, the eddy covariance technique, at two locations:  on a measurement mast in semi-urban Kumpula and in downtown Helsinki on top of Hotel Torni.  In addition to these continuous measurements, our group also conducts short-term campaigns to observe the land-atmosphere exchange of N2O and volatile organic compounds (VOC) in this urban micro-climate.

The aim of these measurements is to collect long time series of simultaneously measured exchange processes to develop parameterizations for various atmospheric models, and to understand the processes and their changes in time. We are interested how the different urban land use types, particularly green areas, affect the vertical exchange of different variables. For example, as a rough estimate for carbon dioxide, Annika Nordbo, Leena Järvi, Sami Haapanala, Curtis Wood and Timo Vesala recently found that if natural areas cover over 80% of the urban surface, the uptake of vegetation exceeds the carbon dioxide emissions in the source area (Nordbo et al. 2012). Thus, our measurements provide information for urban planners as well as evaluation data for air quality, numerical weather forecast and climate models.

The measurements are also part of the new Urban Boundary-layer Atmosphere Network (UrBAN) which combines a variety of different instrumentation providing data of the interaction between an urban surface and the atmosphere at different spatial scales. The network is a joint effort by the Finnish Meteorological Institute and the Division of Atmospheric Sciences. We also collaborate with groups around the world working with urban flux measurements. The near future plan is to compare the turbulent energy balance fluxes from Beijing and Helsinki using both measurements and modelling approaches.

Webpages:
http://www.atm.helsinki.fi/SMEAR/index.php/smear-iii
http://urban.fmi.fi

Reference
A. Nordbo, L. Järvi, S. Haapanala, C.R. Wood and T. Vesala (2012b). Fraction of natural area as main predictor of net CO2 emissions from cities. Geophys. Res. Lett., 39, L20802, doi: 10.1029/2012GL053087

Are diesel engines the answer in mitigating traffic emissions?

Posted on by
Reply

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.

Mind-mapping nitrogen cycling in boreal forests

Posted on by
Reply

Mind-map of nitrogen cycling in boreal forests by the N group and collaborators: Dynamic nitrogen (N) pools processes in a boreal forest. Arrows stand for processes between the pools, red dots mark unknowns in the N cycle, and green dashed lines name ongoing or coming projects to solve some of the questions.

Reactive nitrogen (N) has a key role in the atmospheric chemistry and functioning of boreal forests. After years of studying the complex interactions of N cycling in boreal forests, Janne Korhonen et al. (2012) have calculated the N balance of the Hyytiälä SMEAR II Scots pine forest. The study shows that the forest ecosystem is a very efficient N recycler. Based on the new results, the atmospheric N deposition is much higher than previously estimated, and dry and wet organic deposition are important components of the total N input. However, although the pools, annual inputs, outputs and overall N cycling in the boreal forest have been resolved, new questions arise of the short-term dynamic N processes (such as amine formation via decomposition of soil organic nitrogen). These processes are important for the atmospheric chemistry and connect N even to climate effects of aerosols.

The N group at the Division of Atmospheric Sciences (Janne Korhonen, Antti-Jussi Kieloaho, and supervisors Mari Pihlatie and Jukka Pumpanen) are applying and developing new methods together with chemists, physicists and microbiologists. Current projects linking N and the atmosphere include studies on amine concentrations and fluxes, and the effect of fresh carbon input on soil organic nitrogen turnover (NITRGOFUNGI). In the future, our main focus in the nitrogen research will be to estimate reactive N emissions from soil and canopy, N transformations, and the fate of N deposited on to the forest canopy.

Contributors to the mind-map (working in the Division’s nitrogen group):

  • Jussi Heinonsalo (microbiology)
  • Maarit Raivonen (forest ecology)
  • Johanna Joensuu (forest ecology)
  • Timo Vesala (professor, micrometeorology)
  • Jukka Pumpanen (soil ecology)

Atmospheric Chemistry into the Future

Posted on by
Reply

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

Posted on by
Reply

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