Reactivit'Air

In our latest publication, we investigated with total hydroxyl radical (OH) reactivity measurements our understanding of emissions from three tree species found in the boreal forest. The unexplained fraction of the reactivity remain high in some circumstances. We recently published in Biogeosciences the results of our study from 2017, where we analysed the emissions from three different trees with gas chromatographic methods and total OH reactivity instrumentation. We analysed emissions at the branch level with enclosure for birch, spruce, and pine. Our findings are that emissions do vary in amount and composition throughout the growing season and we could show, based on reactivity measurements, that the emissions are not fully characterized chemically. In particular when trees were subject to stress (that was clearly visible with, for instance, browning leaves or needles) the reactivity of the emissions increased a lot and we observed simultaneously an increase of emissions of Green L...

For many, 2020 will be remembered as quite a unique year, as many around the world are affected by the coronavirus pandemic and stay home for work, schools are closed, and everyone adapt to the unusual situation. In particular, for scientists, 2020 will be the year of the cancellations of not only international conferences, but also measurement campaigns. Last year, I was trying to organise a measurement campaign in Switzerland in 2020 for my projec t, but for various reasons, this was not possible. As an alternative, we decided to bring reactivity instruments (for both OH and ozone reactivity, the very first time this combination has been ever used to our knowledge) to Pallas in the Finnish Lapland in late March. As Anssi and I were preparing for the trip, COVID-19 slowly took on the news' cycle and Switzerland got hit quite badly by the pandemic. Did we just dodged a bullet? I guess we took a lucky decision without knowing. Still the first cases of COVID-19 were reported als...

After a long journey to get them published, the results of our hydroxyl radical (OH) reactivity measurements in the boreal forest in 2016 are now available in Atmospheric Chemistry and Physics . The final manuscript has been substantially modified from its discussion version, mostly to improve its readability and remove unnecessary parts. The most consequential changes did not severely impact our conclusions, though. Here I give a summary of the findings from our study that includes measurements at the SMEAR II boreal forest station in Hyytiälä, Finland, from April to July 2016, as well as modelling results from our colleagues at the University of Helsinki. We found large total OH reactivity values occurred when the soil was thawing after snow melted (late April). These reactivity peaks were even higher than the high total OH reactivity values in summer (July). Comparing the total OH reactivity measured with the OH reactivity calculated from the known chemical composition at ...

This year was my first time at the General Assembly of the European Geosciences Union (EGU). Even though it felt overwhelming at times, it is also a very stimulating conference including sessions related to important topics beyond scientific topics, such as short courses about various subjects (e.g. peer-review, grants) and more general sessions about scientists' well-being and diversity and equality for instance. The EGU General Assembly (GA) is a week-long conference taking place yearly in Vienna since 2005 (the first GA was in Nice, France, in 2004). It is huge (really!) and brings together over 16'000 scientists (new record this year) from 113 countries representing all fields related to space and Earth Science, such as atmospheric sciences, climate science, oceanography, biogeosciences, cryosphere research, hydrology, seismology, volcanology, planetary science, among many others. As the Atmospheric Sciences division is on of the largest of EGU and as I have be...

It is a yearly routine: the temperature slowly increase and there is more light. It is then time to transport our instrumentation to the field! After our measurement campaign in Lapland last year (I wrote about it previously here and here ), this year we are back at the SMEAR II station in Hyytiälä in southern Finland. The SMEAR II station has become a hotspot for atmospheric sciences starting from the mid-1990s. The Finnish Meteorological Institute performs routine measurements there and research is also conducted at the site on Biogenic Volatile Organic Compounds (BVOCs) and other topics related to air quality. We performed an OH reactivity study at this site in 2016 (which is currently under review for Atmospheric Chemistry and Physics, see the open discussion ), which was building on previous studies by Sinha et al. (2010) and Nölscher et al. (2012) . Then, we extended the study period to include the spring and not only summer as the mentioned earlier studies. One result of ...

Following the installation of our instrumentation at Lompolojänkkä in the Finnish Lapland, the intensive measurement campaign was set for July. I spent two weeks there with my colleague and friend Dr. Simon Schallhart and decided to share with my readers some extracts of my campaign journal. Figure 1. From top to bottom: posing in front of the FMI car; unloading the car from the train in Rovaniemi; the measurement site at Lompolojänkä; wetland chamber; reindeer out of the apartment's window; hiking on Pallastunturit; stormy clouds over Lompolojänkä; oil leak; the FMI car being towed away; birthday champagne at the sauna; evening view over Pallasjärvi lake; branch enclosure for emissions measurements. (Photo credits: Arnaud Praplan and Simon Schallhart, CC-BY-4.0 ) 1 July 2018: The departure. 03:12PM. Today is warm and sunny. I came to FMI around 1PM to meet Simon and load the car. It took less time than expected and everything fitted! Yay! There was time to go to the sh...

From 10 to 15 June I visited with a few of my colleagues the Gordon Research Conference 2018 on Biogenic Hydrocarbons and the Atmosphere . The conference was held in Les Diablerets, close to my native city in the Swiss Alps. Gordon Research Conferences are known to be at the cutting-edge of research with their policy of presenting latest results and strict rules about not disclosing anything that has been discussed at the conference to non-participants. It encourages discussing cutting edge research in an informal setting with lots of horizontal learning. Young and established researchers mix very well during meals, poster sessions, and free time activities. This was my second Gordon Research Conference after the one on Atmospheric Chemistry last year in Maine, U.S.A. It was a great opportunity to catch up with colleagues from various institutions, in particular with other researchers using the Comparative Reactivity Method (CRM) for total OH reactivity measurements. We could disc...

The Arctic is predicted to warm up at a quicker pace than other parts of the globe due to climate change. Therefore dramatic changes are expected to happen in that region in the future and scientists express an increasing interest for this region.  As one of our main research interest is focused about substances released into the atmosphere by vegetation (biogenic volatile organic compounds, BVOCs) spring always marks the time when our instruments get to travel again to places after spending the winter in the laboratory for testing and optimization purposes. This year our group is setting up measurements of BVOCs (and other VOCs) and of hydroxyl radical (OH) reactivity in the Arctic. The Finnish Meteorological Institute has been active at Pallas in the Finnish Arctic as early as 1935. Since 1994 Pallas-Sodankylä is established as one of the global observation station of the Global Atmospheric Watch (GAW) programme . The station has one node in Sodankylä at FMI's Arctic Resear...

As part of my postdoctoral work at the Finnish Meteorological Institute, I developed a new implementation of the Comparative Reactivity Method to measure total hydroxyl (OH) reactivity from ambient air and emissions. The description of the instrument and results from our first study in Helsinki to test the instrument's performances have been published in Atmospheric Environment (open access). The total OH reactivity (also called total OH loss rate) is a measure of how much reactive compounds are present in the air. A higher amount of compounds reduces the lifetime of OH. It appears that the total OH reactivity in forested environments is higher than expected from known measured compounds, mostly volatile organic compounds (VOCs) emitted from the vegetation. In order to study this missing OH sink also observed in the summer in the boreal forest (Sinha et al., 2010; Nölscher et al., 2012) during various seasons, Dr. Heidi Hellén proposed to develop an instrument based on the ...