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...

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 ...

Just over a year in the REAC-FORTE project, we have a system running to measure ozone reactivity and we brought it a few weeks ago to the SMEAR II field station for proof-of-concept measurements. We are testing in real conditions the system that we developed based on our experience in Boulder with the group of Prof. Detlev Helmig. While in the lab the temperature and the relative humidity are quite stable, this is not the case in the forest. As the temperatures are decreasing and the relative humidity increase as autumn approaches, it is a good period to get preliminary measurements and to check that our system can run undisturbed when environmental conditions are changing. As none of our other on-line instrument to measure the air composition (gas chromatograph coupled to a mass spectrometer) is available at this time for simultaneous measurements, we collect air samples on adsorption tubes with the help of an auto-sampler (sampling time: 4 hours). These samples are then ana...