ISSN 1239-6095 (print),   ISSN 1797-2469 (online)
© Boreal Environment Research 2014

Contents of Volume 19 supplement B

Preface. Boreal Env. Res. 19 (suppl. B): 1.
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Kulmala, M., Lappalainen, H. K., Bäck, J., Laaksonen, A., Nikinmaa, E., Riekkola, M.-L., Vesala, T., Viisanen, Y., Aalto, T., Boy, M., Dal Maso, M., Ehn, M., Hakola, H., Hari, P., Hartonen, K., Hämeri, K., Hölttä, T., Junninen, H., Järvi, L., Kurten, T., Lauri, A., Laurila, T., Lehtipalo, K., Lihavainen, H., Lintunen, A., Mammarella, I., Manninen, H. E., Petäjä, T., Pihlatie, M., Pumpanen, J., Rinne, J., Romakkaniemi, S., Ruuskanen, T., Sipilä, M., Sorvari, S., Vehkamäki, H., Virtanen, A., Worsnop, D. R. & Kerminen, V.-M. 2014: Finnish Centre of Excellence in Physics, Chemistry, Biology and Meteorology of Atmospheric Composition and Climate Change: summary and outlook. Boreal Env. Res. 19 (suppl. B): 2–19.
Abstract
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Raivonen, M., Joensuu, J., Keronen, P., Altimir, N. & Kolari, P. 2014: Assessment of field monitoring of plant fluxes of oxidized nitrogen with two types of detectors. Boreal Env. Res. 19 (suppl. B): 20–34.
Abstract
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Keronen, P., Reissell, A., Chevallier, F., Siivola, E., Pohja, T., Hiltunen, V., Hatakka, J., Aalto, T., Rivier, L., Ciais, P., Jordan, A., Hari, P., Viisanen, Y. & Vesala, T. 2014: Accurate measurements of CO2 mole fraction in the atmospheric surface layer by an affordable instrumentation. Boreal Env. Res. 19 (suppl. B): 35–54.
Abstract
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Taipale, R., Sarnela, N., Rissanen, M., Junninen, H., Rantala, P., Korhonen, F., Siivola, E., Berndt, T., Kulmala, M., Mauldin, R. L. III, Petäjä, T. & Sipilä, M. 2014: New instrument for measuring atmospheric concentrations of non-OH oxidants of SO2. Boreal Env. Res. 19 (suppl. B): 55–70.
Abstract
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Timonen, H., Aurela, M., Carbone, S., Saarnio, K., Frey, A., Saarikoski, S., Teinilä, K., Kulmala, M. & Hillamo, R. 2014: Seasonal and diurnal changes in inorganic ions, carbonaceous matter and mass in ambient aerosol particles in an urban, background area. Boreal Env. Res. 19 (suppl. B): 71–86.
Abstract
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Rantala, P., Taipale, R., Aalto, J., Kajos, M. K., Patokoski, J., Ruuskanen, T. M. & Rinne, J. 2014: Continuous flux measurements of VOCs using PTR-MS — reliability and feasibility of disjunct-eddy-covariance, surface-layer-gradient, and surface-layer-profile methods. Boreal Env. Res. 19 (suppl. B): 87–107.
Abstract
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Järvi, L., Nordbo, A., Rannik, Ü., Haapanala, S., Riikonen, A., Mammarella, I., Pihlatie, M. & Vesala, T. 2014: Urban nitrous-oxide fluxes measured using the eddy-covariance technique in Helsinki, Finland. Boreal Env. Res. 19 (suppl. B): 108–121.
Abstract
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Kulmala, M., Nieminen, T., Nikandrova, A., Lehtipalo, K., Manninen, H. E., Kajos, M. K., Kolari, P., Lauri, A., Petäjä, T., Krejci, R., Hansson, H.-C., Swietlicki, E., Lindroth, A., Christensen, T. R., Arneth, A., Hari, P., Bäck, J., Vesala, T. & Kerminen, V.-M. 2014: CO2-induced terrestrial climate feedback mechanism: From carbon sink to aerosol source and back. Boreal Env. Res. 19 (suppl. B): 122–131.
Abstract
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Olascoaga, B., Juurola, E., Pinho, P., Lukeš, P., Halonen, L., Nikinmaa, E., Bäck, J. & Porcar-Castell, A. 2014: Seasonal variation in the reflectance of photosynthetically active radiation from epicuticular waxes of Scots pine (Pinus sylvestris) needles. Boreal Env. Res. 19 (suppl. B): 132–141.
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Hari, P., Bäck, J., Heliövaara, K., Kerminen, V.-M., Kulmala, L., Mäkelä, A., Nikinmaa, E., Petäjä, T. & Kulmala, M. 2014: Towards quantitative ecology: Newton’s principia revisited. Boreal Env. Res. 19 (suppl. B): 142–152.
Abstract
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Virkkula, A., Pohja, T., Aalto, P. P., Keronen, P., Schobesberger, S., Clements, C. B., Petäjä, T., Nikmo, J. & Kulmala, M. 2014: Airborne measurements of aerosols and carbon dioxide during a prescribed fire experiment at a boreal forest site. Boreal Env. Res. 19 (suppl. B): 153–181.
Abstract
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Keskinen, H., Kortelainen, A.-M., Jaatinen, A., Yli-Pirilä, P., Joutsensaari, J., Romakkaniemi, S., Hao, L. Q., Torvela, T., Miettinen, P., Virtanen, A., Worsnop, D. R., Laaksonen, A. & Smith, J. N. 2014: Increased hygroscopicity of Arizona Test Dust seeds by secondary organic aerosol coating from α-pinene ozonolysis. Boreal Env. Res. 19 (suppl. B): 182–190.
Abstract
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Nieminen, T., Asmi, A., Dal Maso, M., P. Aalto, P., Keronen, P., Petäjä, T., Kulmala, M. & Kerminen, V.-M. 2014: Trends in atmospheric new-particle formation: 16 years of observations in a boreal-forest environment. Boreal Env. Res. 19 (suppl. B): 191–214.
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Lehtipalo, K., Leppä, J., Kontkanen, J., Kangasluoma, J., Franchin, A., Wimmer, D., Schobesberger, S., Junninen, H., Petäjä, T., Sipilä, M., Mikkilä, J., Vanhanen, J., Worsnop, D. R. & Kulmala, M. 2014: Methods for determining particle size distribution and growth rates between 1 and 3 nm using the Particle Size Magnifier. Boreal Env. Res. 19 (suppl. B): 215–236.
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Zhou, L., Nieminen, T., Mogensen, D., Smolander, S., Rusanen, A., Kulmala, M. & Boy, M. 2014: SOSAA — a new model to simulate the concentrations of organic vapours, sulphuric acid and aerosols inside the ABL — Part 2: Aerosol dynamics and one case study at a boreal forest site. Boreal Env. Res. 19 (suppl. B): 237–256.
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Neitola, K., Brus, D., Makkonen, U., Sipilä, M., Lihavainen, H. & Kulmala, M. 2014: Effect of addition of four base compounds on sulphuric-acid–water new-particle formation: a laboratory study. Boreal Env. Res. 19 (suppl. B): 257–274.
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Leino, K., Riuttanen, L., Nieminen, T., Dal Maso, M., Väänänen, R., Pohja, T., Keronen, P., Järvi, L., Aalto, P. P., Virkkula, A., Kerminen, V.-M., Petäjä, T. & Kulmala, M. 2014: Biomass-burning smoke episodes in Finland from eastern European wildfires. Boreal Env. Res. 19 (suppl. B): 275–292.
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Peräkylä, O., Vogt, M., Tikkanen, O.-P., Laurila, T., Kajos, M. K., Rantala, P. A., Patokoski, J., Aalto, J., Yli-Juuti, T., Ehn, M., Sipilä, M., Paasonen, P., Rissanen, M., Nieminen, T., Taipale, R., Keronen, P., Lappalainen, H. K., Ruuskanen, T. M., Rinne, J., Kerminen, V.-M., Kulmala, M., Bäck, J. & Petäjä, T. 2014: Monoterpenes’ oxidation capacity and rate over a boreal forest: temporal variation and connection to growth of newly formed particles. Boreal Env. Res. 19 (suppl. B): 293–310.
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Makkonen, U., Virkkula, A., Hellén, H., Hemmilä, M., Sund, J., Äijälä, M., Ehn, M., Junninen, H., Keronen, P., Petäjä, T., Worsnop, D. R., Kulmala, M. & Hakola, H. 2014: Semi-continuous gas and inorganic aerosol measurements at a boreal forest site: seasonal and diurnal cycles of NH3, HONO and HNO3. Boreal Env. Res. 19 (suppl. B): 311–328.
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Kristensson, A., Johansson, M., Swietlicki, E., Kivekäs, N., Hussein, T., Nieminen, T., Kulmala, M. & Dal Maso, M. 2014: NanoMap: Geographical mapping of atmospheric new-particle formation through analysis of particle number size distribution and trajectory data. Boreal Env. Res. 19 (suppl. B): 329–342.
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Baranizadeh E., Arola, A., Hamed, A., Nieminen, T., Mikkonen, S., Virtanen, A., Kulmala, M., Lehtinen, K. & Laaksonen, A. 2014: The effect of cloudiness on new-particle formation: investigation of radiation levels. Boreal Env. Res. 19 (suppl. B): 343–354.
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Kyllönen, K., Paatero, J., Aalto, T. & Hakola, H. 2014: Nationwide survey of airborne mercury in Finland. Boreal Env. Res. 19 (suppl. B): 355–367.
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Jaatinen, A., Romakkaniemi, S., Anttila, T, Hyvärinen, A.-P., Hao, L. Q., Kortelainen, A., Miettinen, P., Mikkonen, S., Smith, J. N., Virtanen, A. & Laaksonen, A. 2014: The third Pallas Cloud Experiment: Consistency between the aerosol hygroscopic growth and CCN activity. Boreal Env. Res. 19 (suppl. B): 368–382.
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Manninen, H. E., Bäck, J., Sihto-Nissilä, S.-L., Huffman, J. A., Pessi, A.-M., Hiltunen, V., Aalto, P. P., Hidalgo, P. J., Hari, P., Saarto, A., Kulmala, M. & Petäjä, T. 2014: Patterns in airborne pollen and other primary biological aerosol particles (PBAP), and their contribution to aerosol mass and number in a boreal forest. Boreal Env. Res. 19 (suppl. B): 383–405.
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Juurola, E., Korhonen, J. F. J., Kulmala, L., Kolari, P., Taipale, U., Rasinmäki, J., Ruuskanen, T., Haapoja, T., Bäck, J., Levula, J., Riuttanen, L., Kyrö, E.-M., Dzhedzhev, I., Nikinmaa, E., Vesala, T. & Kulmala, M. 2014: Knowledge transfer of climate-ecosystem-interactions between science and society — Introducing the Climate Whirl concept. Boreal Env. Res. 19 (suppl. B): 406–411.
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Kulmala, M., Lappalainen, H. K., Bäck, J., Laaksonen, A., Nikinmaa, E., Riekkola, M.-L., Vesala, T., Viisanen, Y., Aalto, T., Boy, M., Dal Maso, M., Ehn, M., Hakola, H., Hari, P., Hartonen, K., Hämeri, K., Hölttä, T., Junninen, H., Järvi, L., Kurten, T., Lauri, A., Laurila, T., Lehtipalo, K., Lihavainen, H., Lintunen, A., Mammarella, I., Manninen, H. E., Petäjä, T., Pihlatie, M., Pumpanen, J., Rinne, J., Romakkaniemi, S., Ruuskanen, T., Sipilä, M., Sorvari, S., Vehkamäki, H., Virtanen, A., Worsnop, D. R. & Kerminen, V.-M. 2014: Finnish Centre of Excellence in Physics, Chemistry, Biology and Meteorology of Atmospheric Composition and Climate Change: summary and outlook. Boreal Env. Res. 19 (suppl. B): 2–19.

The Finnish Centre of Excellence (FCoE) in "Physics, Chemistry, Biology and Meteorology of Atmospheric Composition and Climate Change" (2008–2013) completed its research activity at the end of 2013. The FCoE research was originally focused on enhanced process-level understanding of various couplings between atmospheric CO2 concentrations, photosynthesis, biogenic volatile organic compounds (BVOC), aerosol particles and clouds. During the FCoE period, the scientific scope moved gradually towards the so-called all-scale concept. In this paper we summarize its main scientific achievements, and give an outlook for future scientific activities and focus.
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Raivonen, M., Joensuu, J., Keronen, P., Altimir, N. & Kolari, P. 2014: Assessment of field monitoring of plant fluxes of oxidized nitrogen with two types of detectors. Boreal Env. Res. 19 (suppl. B): 20–34.

Chemiluminescence-based measurements of oxidized nitrogen can be specific to NOx or can also detect other NOy compounds, depending on the equipment. We monitored chamber fluxes of oxidized nitrogen in Scots pine shoots under field conditions, and changed from a NOy measurement to the more NOx-specific measurement. The aims of this study were to evaluate how the NOx measurement system performs in comparison with the NOy measurement system in dynamic field measurements, and whether the new measurements provide information on the composition of the NOy emissions reported in earlier studies. We found that absolute NOx concentrations were slightly more inaccurate than the earlier NOy concentrations but that the new analyzer led to an improvement in the measurement of NOx fluxes. Simultaneous NOy and NOx flux measurements from chambers indicated that the measured NOy fluxes often include compounds other than NOx. We found no clear plant-related NOx emissions.
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Keronen, P., Reissell, A., Chevallier, F., Siivola, E., Pohja, T., Hiltunen, V., Hatakka, J., Aalto, T., Rivier, L., Ciais, P., Jordan, A., Hari, P., Viisanen, Y. & Vesala, T. 2014: Accurate measurements of CO2 mole fraction in the atmospheric surface layer by an affordable instrumentation. Boreal Env. Res. 19 (suppl. B): 35–54.

We aimed to assess the feasibility of an affordable instrumentation, based on a non-dispersive infrared analyser, to obtain atmospheric CO2 mole fraction data for background CO2 measurements from a flux tower site in southern Finland. The measurement period was November 2006–December 2011. We describe the instrumentation, calibration, measurements and data processing and a comparison between two analysers, inter-comparisons with a flask sampling system and with reference gas cylinders and a comparison with an independent inversion model. The obtained accuracy was better than 0.5 ppm. The inter-comparisons showed discrepancies ranging from –0.3 ppm to 0.06 ppm between the measured and reference data. The comparison between the analyzers showed a 0.1 ± 0.4 ppm difference. The trend and phase of the measured and simulated data agreed generally well and the bias of the simulation was 0.2 ± 3.3 ppm. The study highlighted the importance of quantifying all sources of measurement uncertainty.
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Taipale, R., Sarnela, N., Rissanen, M., Junninen, H., Rantala, P., Korhonen, F., Siivola, E., Berndt, T., Kulmala, M., Mauldin, R. L. III, Petäjä, T. & Sipilä, M. 2014: New instrument for measuring atmospheric concentrations of non-OH oxidants of SO2. Boreal Env. Res. 19 (suppl. B): 55–70.

In addition to the hydroxyl radical (OH), also other oxidants of sulphur dioxide (SO2) can play a substantial role in the production of atmospheric sulphuric acid (H2SO4). Some of these non-OH oxidants are stabilized Criegee intermediates (sCIs) formed in the ozonolysis of alkenes. This paper introduces an FR-CI-APi-TOF instrument which measures the total concentration of all non-OH oxidants (X) reacting with SO2 at a reasonable rate. The instrument consists of a flow reactor (FR) and a chemical ionisation (CI) atmospheric pressure interface (APi) time of flight (TOF) mass spectrometer. The first field measurements at a boreal forest site indicated that the summer concentration, production rate and apparent lifetime of X were (0.5–8.0) x 105 cm–3, (0.3–1.6) x 106 cm–3 s–1 and 0.1–1.8 s, respectively. The estimated concentration and production rate of sCIs formed in the ozonolysis of monoterpenes were substantially lower, possibly indicating the presence of sCIs from other alkenes. Further instrument development is needed to reduce the uncertainties in FR-CI-APi-TOF measurements.
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Timonen, H., Aurela, M., Carbone, S., Saarnio, K., Frey, A., Saarikoski, S., Teinilä, K., Kulmala, M. & Hillamo, R. 2014: Seasonal and diurnal changes in inorganic ions, carbonaceous matter and mass in ambient aerosol particles in an urban, background area. Boreal Env. Res. 19 (suppl. B): 71–86.

Concentration and composition of the fine particulate matter (PM) was measured using various online methods for 13 months in an urban, background area in Helsinki, Finland. Seasonal differences were found for ions and carbonaceous compounds. Biomass burning was found to increase inorganic ion and elemental carbon (EC) concentrations in winter, whereas organic carbon (OC) contribution was highest during summer due to secondary aerosol formation. Diurnal cycles, with maxima between 06:00 and 09:00, were recorded for EC and nitrate due to traffic emissions. In addition, the concentrations measured with the online and offline PM sampling devices were compared using regression analysis. In general, a good agreement (r2 = 0.60–0.95) was found. During the year-long measurements, on average 65% of PM2.5 was identified by submicron chemical analyses (ions, OC, EC). As compared with filter measurements, the high resolution measurements provided important data on short pollution plumes and diurnal changes.
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Rantala, P., Taipale, R., Aalto, J., Kajos, M. K., Patokoski, J., Ruuskanen, T. M. & Rinne, J. 2014: Continuous flux measurements of VOCs using PTR-MS — reliability and feasibility of disjunct-eddy-covariance, surface-layer-gradient, and surface-layer-profile methods. Boreal Env. Res. 19 (suppl. B): 87–107.

We measured VOC fluxes using disjunct-eddy-covariance (DEC), surface-layer-gradient (SLG), and surface-layer-profile (SLP) methods with proton transfer reaction mass spectrometry (PTR-MS) above a boreal forest in Hyytiälä, Finland. Our aim was to examine the reliability and feasibility of these methods for long-term measurements at low-flux conditions typical for boreal forests. The compounds targeted were formaldehyde, methanol, acetaldehyde, acetone, isoprene/methylbutenol fragment, methylbutenol, hexanal, hexenal and monoterpenes. We carried out a 10-day comparison between the techniques and used longer continuous data sets for the feasibility study. Out of these surface layer methods, the SLP method performed the best. We found out that with the SLP method we were able to detect fluxes for all the targeted compounds except formaldehyde. The method had also smaller detection limits and better data coverage than the DEC method. The systematic error of both SLP and SLG techniques was estimated to be around 10% for these measurements and it was caused by the high frequency attenuation for the DEC and by the turbulence parametrization for the SLP. As a conclusion the SLP method can be recommend for long-term flux measurements in low-flux conditions.
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Järvi, L., Nordbo, A., Rannik, Ü., Haapanala, S., Riikonen, A., Mammarella, I., Pihlatie, M. & Vesala, T. 2014: Urban nitrous-oxide fluxes measured using the eddy-covariance technique in Helsinki, Finland. Boreal Env. Res. 19 (suppl. B): 108–121.

Using the eddy covariance technique, nitrous oxide (N2O) fluxes were measured at the semi-urban SMEAR III station in Helsinki, Finland, between 21 June and 27 November 2012. The measurement period covered a seasonal change from summer to autumn allowing us to examine variations in the N2O fluxes by season. Also, varying land cover around the measurement site enabled us to study the effects of different urban land covers on the N2O exchange. Overall, the measurement surroundings acted as a source of N2O with a median and quartile deviation for the campaign of 1.7 ± 2.0 µmol m–2 h–1. The net emissions were slightly higher from the direction of green areas than from the direction of roads under heavy traffic indicating that vegetation cannot be neglected in the urban N2O exchange studies. No seasonal change in the N2O flux during the measurement campaign was found.
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Kulmala, M., Nieminen, T., Nikandrova, A., Lehtipalo, K., Manninen, H. E., Kajos, M. K., Kolari, P., Lauri, A., Petäjä, T., Krejci, R., Hansson, H.-C., Swietlicki, E., Lindroth, A., Christensen, T. R., Arneth, A., Hari, P., Bäck, J., Vesala, T. & Kerminen, V.-M. 2014: CO2-induced terrestrial climate feedback mechanism: From carbon sink to aerosol source and back. Boreal Env. Res. 19 (suppl. B): 122–131.

Feedbacks mechanisms are essential components of our climate system, as they either increase or decrease changes in climate-related quantities in the presence of external forcings. In this work, we provide the first quantitative estimate regarding the terrestrial climate feedback loop connecting the increasing atmospheric carbon dioxide concentration, changes in gross primary production (GPP) associated with the carbon uptake, organic aerosol formation in the atmosphere, and transfer of both diffuse and global radiation. Our approach was to combine process-level understanding with comprehensive, long-term field measurement data set collected from a boreal forest site in southern Finland. Our best estimate of the gain in GPP resulting from the feedback is 1.3 (range 1.02–1.5), which is larger than the gains of the few atmospheric chemistry-climate feedbacks estimated using large-scale models. Our analysis demonstrates the power of using comprehensive field measurements in investigating the complicated couplings between the biosphere and atmosphere on one hand, and the need for complementary approaches relying on the combination of field data, satellite observations model simulations on the other hand.
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Olascoaga, B., Juurola, E., Pinho, P., Lukeš, P., Halonen, L., Nikinmaa, E., Bäck, J. & Porcar-Castell, A. 2014: Seasonal variation in the reflectance of photosynthetically active radiation from epicuticular waxes of Scots pine (Pinus sylvestris) needles. Boreal Env. Res. 19 (suppl. B): 132–141.

Epicuticular waxes influence leaf reflectance, but the spatiotemporal dynamics in their reflectance properties have not been properly characterized, and its consequences remain unknown. In this study, we analysed the seasonal changes in wax reflectance of Scots pine needles. It tended to decrease with needle age and towards lower positions within the canopy. In addition, we also identified a clear seasonal pattern of variation superimposed on the of above-mentioned wax weathering effect. We conclude that spatiotemporal dynamics in wax optical properties need to be considered in studies that implicitly assume constant light absorption, particularly when different leaf age classes, canopy positions or seasons are compared, and especially in species with substantial amount of waxes. We suggest that the observed dynamics in wax reflectance could represent a new photoprotective mechanism operating at the seasonal scale as they modulate the absorption of the photosynthetically active radiation (PAR) over time.
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Hari, P., Bäck, J., Heliövaara, K., Kerminen, V.-M., Kulmala, L., Mäkelä, A., Nikinmaa, E., Petäjä, T. & Kulmala, M. 2014: Towards quantitative ecology: Newton’s principia revisited. Boreal Env. Res. 19 (suppl. B): 142–152.

Qualitative argumentation dominates the research in ecology, whereas quantitative approaches characterize the physical and chemical studies. Further development of powerful quantitative methods is needed in ecology to improve the utilization of ecological knowledge in the research of present changes on the globe and to enhance the utilization of physical knowledge in ecology. Here, we (1) define new concepts that enable the quantitative formulation of the most essential features of photosynthesis, and (2) derive exact predictions of the relationship between photosynthesis and light together with the action of stomata. We predicted 300 daily patterns of photosynthesis of a pine shoot from 50000 measurements of light, temperature and water-vapor concentration in the field. Our theory predicted 95%–97% of the variance of measured photosynthesis. Our example indicates that the theory-formation approach can successfully be applied in ecology to describe photosynthesis, a phenomenon fundamental to life on Earth.
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Virkkula, A., Pohja, T., Aalto, P. P., Keronen, P., Schobesberger, S., Clements, C. B., Petäjä, T., Nikmo, J. & Kulmala, M. 2014: Airborne measurements of aerosols and carbon dioxide during a prescribed fire experiment at a boreal forest site. Boreal Env. Res. 19 (suppl. B): 153–181.

During a prescribed fire experiment, CO2 and particle number concentrations, light scattering and absorption coefficients were measured from a Cessna 172 airplane. Peak number concentrations were (3 ± 1) x 106 cm–3 and they decreased faster than what can be explained by coagulation alone. The single-scattering albedo of particles grew from the values of 0.4 ± 0.1 closest to the emissions to the values of 0.8 ± 0.1 at the distance of 400 m from the emissions. The mean Ângström exponent of absorption, 1.70 ± 0.24, is in line with the published spectral absorption values of wood-smoke aerosol. The estimated emission factors were 1600 ± 1020, 5.9 ± 6.3 and 1.4 ± 1.0 g kg–1 (dry biomass), for CO2, particulate organic matter and black carbon (BC), respectively, and (4.8 ± 2.9) x 1015 particles per kg (dry biomass) for the particle number. The BC emission factor may be overestimated by a factor of about 1.6 ± 0.2 due to condensation of organics on the filter of the absorption photometer. During the smoldering phase, there were clear indications of new particle formation.
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Keskinen, H., Kortelainen, A.-M., Jaatinen, A., Yli-Pirilä, P., Joutsensaari, J., Romakkaniemi, S., Hao, L. Q., Torvela, T., Miettinen, P., Virtanen, A., Worsnop, D. R., Laaksonen, A. & Smith, J. N. 2014: Increased hygroscopicity of Arizona Test Dust seeds by secondary organic aerosol coating from α-pinene ozonolysis. Boreal Env. Res. 19 (suppl. B): 182–190.

Organic compounds can enhance the hygroscopic properties of insoluble dust particles and thereby affect their cloud condensation nuclei activity in the atmosphere. In this study, Arizona Test Dust (ATD) particles were exposed to oxidized organic vapors from the ozonolysis of α-pinene in a laboratory chamber. The particle size-dependent morphology, inorganic and organic composition and hygroscopic properties were studied. The dust consisted of particles with a range of morphologies from spherical to geometrical, with a size range from 50 nm to 1 µm. Exposure to oxidized organics resulted in a separate mode of secondary organic aerosol (SOA) particles with size ranging below 100 nm and a well-mixed ATD + SOA mode at larger sizes. The O:C mole ratio for the organics produced from α-pinene ozonolysis was stable at 0.4 ± 0.05 in all experiments. The results showed that the hygroscopicities of the ATD particles with a diameter of 100–150 nm were enhanced by a factor of four with the addition of SOA, corresponding to a particulate organic volume fraction of ~0.6 and an average k of 0.09.
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Nieminen, T., Asmi, A., Dal Maso, M., P. Aalto, P., Keronen, P., Petäjä, T., Kulmala, M. & Kerminen, V.-M. 2014: Trends in atmospheric new-particle formation: 16 years of observations in a boreal-forest environment. Boreal Env. Res. 19 (suppl. B): 191–214.

New-particle formation (NPF) is globally an important source of climatically-relevant atmospheric aerosols. Here we explore the inter-annual variability and trends in sources and sinks of atmospheric nanoparticles in a boreal forest environment. We look into the precursor vapors leading to the aerosol formation, NPF frequency, as well as the formation and growth rates of the freshly-formed particles. The analysis is based on 16 years of data acquired from the Station for Measuring Ecosystem–Atmosphere Relations (SMEAR II) in Hyytiälä, Finland. The results indicate that the probability of NPF is connected to both air mass origin, explaining a large part of the year-to-year variability in the number of NPF events, and concentrations of low-volatile vapours. The probability of NPF increases with increasing gaseous sulphuric acid concentrations, but even better association is found between the NPF probability and product of sulphuric acid and low-volatile organic vapour (proxy) concentrations. While the concentrations of both sulphuric acid (evaluated by proxy) and sulphuric-acid precursor sulphur dioxide decreased over the 16-year measurement period, the new-particle formation and growth rates slightly increased. On the other hand, the proxy concentrations of oxidized organics increased in all seasons except in winter. The contribution of sulphuric acid to the particle growth was minor, and the growth rate had a clear connection with the ambient temperature due to higher emissions of biogenic volatile organic compounds at higher temperatures. For a given sulphuric acid concentration evaluated by proxy, particle formation rates tended to be higher at higher temperatures.
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Lehtipalo, K., Leppä, J., Kontkanen, J., Kangasluoma, J., Franchin, A., Wimmer, D., Schobesberger, S., Junninen, H., Petäjä, T., Sipilä, M., Mikkilä, J., Vanhanen, J., Worsnop, D. R. & Kulmala, M. 2014: Methods for determining particle size distribution and growth rates between 1 and 3 nm using the Particle Size Magnifier. Boreal Env. Res. 19 (suppl. B): 215–236.

The most important parameters describing the atmospheric new particle formation process are the particle formation and growth rates. These together determine the amount of cloud condensation nuclei attributed to secondary particle formation. Due to difficulties in detecting small neutral particles, it has previously not been possible to derive these directly from measurements in the size range below about 3 nm. The Airmodus Particle Size Magnifier has been used at the SMEAR II station in Hyytiälä, southern Finland, and during nucleation experiments in the CLOUD chamber at CERN for measuring particles as small as about 1 nm in mobility diameter. We developed several methods to determine the particle size distribution and growth rates in the size range of 1–3 nm from these data sets. Here we introduce the appearance-time method for calculating initial growth rates. The validity of the method was tested by simulations with the Ion-UHMA aerosol dynamic model.
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Zhou, L., Nieminen, T., Mogensen, D., Smolander, S., Rusanen, A., Kulmala, M. & Boy, M. 2014: SOSAA — a new model to simulate the concentrations of organic vapours, sulphuric acid and aerosols inside the ABL — Part 2: Aerosol dynamics and one case study at a boreal forest site. Boreal Env. Res. 19 (suppl. B): 237–256.

Natural and anthropogenic aerosols may have a great impact on climate as they directly interact with solar radiation and indirectly affect the Earth’s radiation balance and precipitation by modifying clouds. In order to quantify the direct and indirect effects, it is essential to understand the complex processes that connect aerosol particles to cloud droplets. Modern measurement techniques are able to detect particle sizes down to 1 nm in diameter, from ground to the stratosphere. However, the data are not sufficient in order to fully understand the processes. Here we demonstrate how the newly developed one-dimensional column model SOSAA was used to investigate the complex processes of aerosols at a boreal forest site for a six-month period during the spring and summer of 2010. Two nucleation mechanisms (kinetic and organic) were tested in this study, and both mechanisms produced a good prediction of the particle number concentrations in spring. However, overestimation of the particle number concentration in summer by the organic mechanism suggests that the OH oxidation products from monoterpenes may not be the essential compounds in atmospheric nucleation. In general, SOSAA was correct in predicting new particle formation events for 35% of the time and partly correct for 45% of the time.
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Neitola, K., Brus, D., Makkonen, U., Sipilä, M., Lihavainen, H. & Kulmala, M. 2014: Effect of addition of four base compounds on sulphuric-acid–water new-particle formation: a laboratory study. Boreal Env. Res. 19 (suppl. B): 257–274.

Effect of four different base compounds [ammonia (NH3), monomethyl- (MMA), dimethyl- (DMA) and trimethylamine (TMA)] on sulphuric-acid–water nucleation was studied using a laminar flow tube. The concentration and size distribution of freshly-formed particles were monitored with an Ultrafine Condensation Particle Counters (UCPC) and a Differential Mobility Particle Sizer (DMPS) system. Two separate experiments were conducted. In the first experiment, the sulphuric acid concentration was measured using a mass spectrometer and the amount of base compound input was determined. In the second experiment, the concentration of base compounds in the flow tube was directly measured with an online ion chromatograph. All experiments were conducted at the constant temperature of 298 K and relative humidity of 30%, as well as constant sulphuric acid concentration. The concentration of the added base compounds was increased stepwise from 27 up to 25000 pptv. An enhancement of the particle nucleation rate was observed only with TMA, and the maximum enhancement factor (EF) was approximately 5.5 at the TMA concentration of 2500 pptv. The possible nucleation enhancement by the other base substances was most probably saturated due to background contaminant levels of DMA, MMA and NH3. Detection of the base compounds was discussed, and the results obtained in this study were compared with those from other similar laboratory experiments found in literature.
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Leino, K., Riuttanen, L., Nieminen, T., Dal Maso, M., Väänänen, R., Pohja, T., Keronen, P., Järvi, L., Aalto, P. P., Virkkula, A., Kerminen, V.-M., Petäjä, T. & Kulmala, M. 2014: Biomass-burning smoke episodes in Finland from eastern European wildfires. Boreal Env. Res. 19 (suppl. B): 275–292.

Biomass burning emissions from intensive wildfires in eastern Europe were observed in Finland in the spring of 2006 and in the late of summers 2006 and 2010. The smoke plumes were detected at three ground-measurement stations around Finland and in the lower troposphere after long-range transport from fire areas. The vertical extent of the smoke was estimated by flight measurements over southern Finland and the measurements were compared with CALIPSO satellite data from 29 July 2010. The history of the arriving air masses was analysed by using backward trajectories and MODIS fire detections. The smoke plumes had elevated concentrations of aerosol particle number, black carbon, CO, CO2, SO2, O3 and NOx, and the differences as compared with the background air were clear. The smoke was observed to be highly scattering, with a single-scattering albedo of 0.96 ± 0.01. The median particle size was 60%–250% larger during the plume days than during July–August on average, and the growth of smoke particles was observed even after long-range transport of several hundreds of kilometres.
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Peräkylä, O., Vogt, M., Tikkanen, O.-P., Laurila, T., Kajos, M. K., Rantala, P. A., Patokoski, J., Aalto, J., Yli-Juuti, T., Ehn, M., Sipilä, M., Paasonen, P., Rissanen, M., Nieminen, T., Taipale, R., Keronen, P., Lappalainen, H. K., Ruuskanen, T. M., Rinne, J., Kerminen, V.-M., Kulmala, M., Bäck, J. & Petäjä, T. 2014: Monoterpenes’ oxidation capacity and rate over a boreal forest: temporal variation and connection to growth of newly formed particles. Boreal Env. Res. 19 (suppl. B): 293–310.

The subject of the study was the effect of monoterpene oxidation on the growth of particles during new-particle formation (NPF) events at the SMEAR II measurement station in Hyytiälä, southern Finland, during 2006–2011. The nighttime oxidation capacity, i.e. how readily the atmosphere can oxidize monoterpenes, was found to be dominated by the nitrate radical, whereas the daytime oxidation capacity was mainly dominated by ozone. The mean lifetimes of monoterpenes ranged from about one hour to several hours, depending on the time of year and day. A strong link was found between the growth rate of particles of 7–20 nm in diameter during the NPF events and monoterpene oxidation by ozone during the preceding night. Our findings suggest that during nighttime a build-up of primarily oxidized monoterpenes in the atmosphere occurs, and that these compounds can be oxidized by the hydroxyl radical after sunrise, promoting the particle growth.
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Makkonen, U., Virkkula, A., Hellén, H., Hemmilä, M., Sund, J., Äijälä, M., Ehn, M., Junninen, H., Keronen, P., Petäjä, T., Worsnop, D. R., Kulmala, M. & Hakola, H. 2014: Semi-continuous gas and inorganic aerosol measurements at a boreal forest site: seasonal and diurnal cycles of NH3, HONO and HNO3. Boreal Env. Res. 19 (suppl. B): 311–328.

In a boreal forest environment at Hyytiälä (SMEAR II station), Finland, from 21 June 2010 to 31 April 2011, concentrations of gases (HCl, HNO3, HONO, NH3, SO2) and inorganic ions (Cl, NO3, SO42–, NH4+, Na+, K+, Mg2+, Ca2+) in PM10 and PM2.5 particles were measured with an on-line ion chromatograph MARGA 2S. The MARGA data were compared with those of the filter samples and the Aerosol Mass Spectrometer. The linear-regression slopes derived from MARGA against the filter data were 0.98, 1.08, 0.50 and 1.31 for SO2, SO42–, HNO3 and NO3, respectively. The respective coefficients of determination (r2) were 0.89, 0.90, 0.70 and 0.93. After installing a concentration column, improved values of cation slopes of 1.00, 1.19, 0.88, 1.00, 0.73 and 0.89 for NH3, NH4+, Na+, K+, Mg2+, and Ca2+, respectively, were obtained. The corresponding coefficients of determination (r2) were: 0.79, 0.83, 0.95, 0.90, 0.85 and 0.62. According to these results, traditional filter collection can be replaced with the MARGA instrument at background sites, if a concentration column is used at least for the cations. This would improve the temporal resolution of the observations. The average concentrations of nitrogen-containing gases were highest in the summer (NH3: 0.47 ppb, HNO3: 0.10 ppb and HONO: 0.11 ppb), which can be explained by the higher temperatures and increased amounts of sunlight followed by stronger agricultural and soil-related sources. In the summer, clear diurnal cycles were found in all N-containing gases, but in the winter the concentrations remained low most of the time and no diurnal cycles were observed. The concentration of ammonia was found to depend exponentially on the prevailing temperature, the increase with temperature being strongest in dry conditions.
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Kristensson, A., Johansson, M., Swietlicki, E., Kivekäs, N., Hussein, T., Nieminen, T., Kulmala, M. & Dal Maso, M. 2014: NanoMap: Geographical mapping of atmospheric new-particle formation through analysis of particle number size distribution and trajectory data. Boreal Env. Res. 19 (suppl. B): 329–342.

Particle number size distributions at various field sites are used to identify atmospheric new-particle formation (NPF) event days. However, the spatial distribution of regionally extensive events is unknown. To remedy this situation, the NanoMap method has been developed to enable the estimation of where NPF occurs within 500 km from any field station using as input size distribution and meteorological trajectories only. Also, the horizontal extension of NPF can be determined. An open-source program to run NanoMap is available on the internet. NanoMap has been developed using as an example the Finnish field site at Hyytiälä. It shows that there are frequent NPF events over the Baltic Sea, but not as frequent as over Finland for certain wind directions; hence NanoMap is able to pinpoint areas with a low or high occurrence of NPF events. The method should be applicable to almost any field site.
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Baranizadeh E., Arola, A., Hamed, A., Nieminen, T., Mikkonen, S., Virtanen, A., Kulmala, M., Lehtinen, K. & Laaksonen, A. 2014: The effect of cloudiness on new-particle formation: investigation of radiation levels. Boreal Env. Res. 19 (suppl. B): 343–354.

The effect of cloudiness on the occurrence of atmospheric new-particle formation events at two measurement stations, SMEAR II in Hyytiälä, Finland and San Pietro Capofiume (SPC) in Italy, was investigated. As an indicator of cloudiness, we use the relative radiation intensity (I/Imax) defined as the ratio of measured global radiation and the modeled clear-sky global radiation. We studied the relationship between the occurrence of new-particle formation (NPF) events and I/Imax using multi-year data sets. The results showed that, at both sites, the radiation intensity (I) should be at least about 50% of its maximum possible value (Imax) for a clear NPF event to occur. In SPC, clearly higher relative radiation intensity was typically required for the occurrence of an NPF event than in Hyytiälä. Also, the features of anomalous days, i.e either NPF events that occurred in cloudy conditions or non-events that occurred in clear-sky conditions, were explained using the environmental variables sulfur dioxide and condensation sink.
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Kyllönen, K., Paatero, J., Aalto, T. & Hakola, H. 2014: Nationwide survey of airborne mercury in Finland. Boreal Env. Res. 19 (suppl. B): 355–367.

Continuous measurements of total gaseous mercury (TGM) at an urban background station in Helsinki, Finland, were performed in 2006–2007. Additionally, a one-month campaign to measure TGM continuously from a moving car was organized in 2007, when several cities and industrial areas around Finland were surveyed. In Helsinki, a one-year average of 1.54 ± 0.20 ng m–3 was measured, which is about the global average for this persistent pollutant. The highest concentrations, up to 2500 ng m–3, were measured during firing practice that took place next to the station. Seasonal and diurnal variation was studied, and trajectory maps were constructed to analyze mercury source regions. In the mobile measurement campaign, concentrations varying between 1.0 and 13.8 ng m–3 were measured. The highest concentrations (above 10 ng m–3) were recorded close to former chlor-alkali plants that used mercury in their electrolytic production process.
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Jaatinen, A., Romakkaniemi, S., Anttila, T, Hyvärinen, A.-P., Hao, L. Q., Kortelainen, A., Miettinen, P., Mikkonen, S., Smith, J. N., Virtanen, A. & Laaksonen, A. 2014: The third Pallas Cloud Experiment: Consistency between the aerosol hygroscopic growth and CCN activity. Boreal Env. Res. 19 (suppl. B): 368–382.

Measurements of aerosol chemical and hygroscopic properties and cloud condensation nuclei were carried out as a part of the third Pallas Cloud Experiment. In this study, the aerosol hygroscopicity parameter, k, was determined using data from instruments operating in the sub-saturated and supersaturated water vapour regimes, as well as from measurements of aerosol chemical composition. During the campaign, k varied from ~0.01 to ~0.37 as derived by Cloud Condensation Nuclei counter and Hygroscopic Tandem Differential Mobility analyser data, and from ~0.13 to ~0.60 as derived from Aerosol Mass Spectrometer data, the average values being 0.11 and 0.29, respectively. CCN closure calculations showed that the sub-saturated growth factor retrieved CCN concentration is lower than the measured one. Overall, at the Pallas site, aerosol hygroscopicity was size dependent with hygroscopicity increasing with size. Hence, size dependent information on composition is needed to predict CCN concentrations relevant to cloud droplet formation.
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Manninen, H. E., Bäck, J., Sihto-Nissilä, S.-L., Huffman, J. A., Pessi, A.-M., Hiltunen, V., Aalto, P. P., Hidalgo, P. J., Hari, P., Saarto, A., Kulmala, M. & Petäjä, T. 2014: Patterns in airborne pollen and other primary biological aerosol particles (PBAP), and their contribution to aerosol mass and number in a boreal forest. Boreal Env. Res. 19 (suppl. B): 383–405.

We studied variation in concentrations of airborne pollen and other particles of biological origin in a boreal forest in Finland during 2003–2004. The highest concentrations of pollen were observed in late spring and early summer, whereas the peak concentrations of other particles of biological origin (including e.g. fungal spores) occurred in August–September. Although the patterns in concentrations in 2003 and 2004 were similar, the concentration levels were significantly different between the years. The contribution of pollen and other particles of biological origin led to an increase in the measured particulate matter (PM) mass during the pollen season (mass of pollen and other particles of biological origin 5.9 and 0.4 µg m–3, respectively, in respect to PMtotal mass of 9.9 µg m–3) but the effect on total particle number was negligible. The other particles of biological origin constituted the largest fraction of measured primary biological aerosol particle (PBAP) numbers (~99%), whereas pollen showed a higher relative mass fraction (~97%) of PBAP. These results underline the important contribution of PBAP to coarse atmospheric particle mass providing up to 65% of the total mass during the peak pollen season.
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Juurola, E., Korhonen, J. F. J., Kulmala, L., Kolari, P., Taipale, U., Rasinmäki, J., Ruuskanen, T., Haapoja, T., Bäck, J., Levula, J., Riuttanen, L., Kyrö, E.-M., Dzhedzhev, I., Nikinmaa, E., Vesala, T. & Kulmala, M. 2014: Knowledge transfer of climate-ecosystem-interactions between science and society — Introducing the Climate Whirl concept. Boreal Env. Res. 19 (suppl. B): 406–411.

Making scientific principles behind the forest–atmosphere interactions more understandable for the general public would help them to follow and evaluate the political or personal decisions related to climate and climate change. Climate Whirl is a concept developed by a trans-disciplinary group of researchers in the area of science, art, education and software design. It aims at introducing a holistic view on climate and ecosystem research, using not only the traditional scientific communication channels, but also artistic manifestations in the form of workshops, exhibitions, seminars and interactive websites. Our aim is to increase public awareness of the interactions between climate and forests, as well as of the role of boreal forests in climate change. An already existing website Carbon Tree is a starting point that provides tools utilised in the further development of the concept. We present the first activities of the concept: Carbon Tree website, Interactive Carbon Tree installation, Hyytiälä Art Residency and interdisciplinary workshops.
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