Tuukka Petäjä

Bio: Tuukka Petäjä is an academic researcher from University of Helsinki. The author has contributed to research in topics: Aerosol & Particle. The author has an hindex of 82, co-authored 526 publications receiving 30572 citations. Previous affiliations of Tuukka Petäjä include Helsinki Institute of Physics & National Center for Atmospheric Research.

Atmospheric reactivity and oxidation capacity during summer at a suburban site between Beijing and Tianjin

Abstract: . Hydroxyl (OH) radicals, nitrate ( NO3 ) radicals and ozone ( O3 ) play central roles in the troposphere because they control the lifetimes of many trace gases that result from anthropogenic and biogenic origins. To estimate the air chemistry, the atmospheric reactivity and oxidation capacity were comprehensively analyzed based on a parameterization method at a suburban site in Xianghe in the North China Plain from 6 July 2018 to 6 August 2018. The total OH, NO3 and O3 reactivities at the site varied from 9.2 to 69.6, 0.7 to 27.5 and 3.3 × 10 - 4 to 1.8 × 10 - 2 s−1 with campaign-averaged values of 27.5±9.7 , 2.2±2.6 and 1.2 ± 1.7 × 10 - 3 s−1 ( ± standard deviation), respectively. NOx ( NO+NO2 ) was by far the main contributor to the reactivities of the three oxidants, with average values of 43 %–99 %. Alkenes dominated the OH, NO3 and O3 reactivities towards total nonmethane volatile organic compounds (NMVOCs), accounting for 42.9 %, 77.8 % and 94.0 %, respectively. The total OH, NO3 and O3 reactivities displayed similar diurnal variations with the lowest values during the afternoon but the highest values during rush hours, and the diurnal profile of NOx appears to be the major driver for the diurnal profiles of the reactivities of the three oxidants. A box model (a model to Simulate the concentrations of Organic vapors, Sulfuric Acid and Aerosols; SOSAA) derived from a column chemical transport model was used to simulate OH and NO3 concentrations during the observation period. The calculated atmospheric oxidation capacity (AOC) reached 4.5×108 molecules cm - 3 s - 1 , with a campaign-averaged value of 7.8×107 molecules cm - 3 s - 1 dominated by OH ( 7.7×107 molecules cm - 3 s - 1 , 98.2 %), O3 ( 1.2×106 molecules cm - 3 s - 1 , 1.5 %) and NO3 ( 1.8×105 molecules cm - 3 s - 1 , 0.3 %). Overall, the integration of OH, NO3 and O3 reactivities analysis could provide useful insights for NMVOC pollution control in the North China Plain. We suggest that further studies, especially direct observations of OH and NO3 radical concentrations and their reactivities, are required to better understand trace gas reactivity and AOC.

Measurements of humidified particle number size distributions in a Finnish boreal forest: derivation of hygroscopic particle growth factors

Abstract: Dry and humidified size distributions of atmospheric particles were characterised at the atmospheric research station SMEAR II, Finland between May and July 2004. Particles were classified in a size range between 3 and 800 nm at controlled relative humidities up to 90% by two instruments complementary in size range (HDMPS; Nano-HDMPS). Using the summation method, descriptive hygroscopic growth factors (DHGF) were derived for particle diameters between 70 and 300 nm by comparing dry and humidified size distributions. At 90% relative humidity, DHGF showed mean values between 1.25 and 1.45 in the accumulation mode, between 1.20 and 1.25 in the Aitken mode, and between 1.15 and 1.20 in the nucleation mode. Due to the high size resolution of the method, the transition in DHGF between the Aitken and accumulation modes, which reflects differences in the soluble fraction, could be pinpointed efficiently. For the accumulation mode, experimental DHGFs were compared to those calculated from a simplistic growth model initialised by in-situ chemical composition measurements, and yielded maximum deviations around 0.1. The variation in DHGF could only imperfectly be linked to meteorological factors. A pragmatic parameterisation of DHGF as a function of particle diameter and relative humiditity was derived, and subsequently used to study the sensitivity of the condensational sink parameter (CS) as a function of height in a well-mixed boundary layer.

The evolution of nucleation- and Aitken-mode particle compositions in a boreal forest environment during clean and pollution-affected new-particle formation events

Abstract: 1) Department of Physics, University of Kuopio, P.O. Box 1627, FI-70211 Kuopio, Finland (*corresponding author’s e-mail: petri.vaattovaara@uku.fi ) 2) Department of Physics, P.O. Box 64, FI-00014 University of Helsinki, Finland 3) Department of Environmental Sciences, University of Kuopio, P.O. Box 1627, 70211 Kuopio, Finland 4) Aerodyne Research Inc., 45 Manning Road, Billerica, MA 01821-3976, USA 5) Finnish Meteorological Institute, P.O. Box 503, FI-00101 Helsinki, Finland 6) current address: Department of Physics and Astronomy, FI-20014 University of Turku, Finland 7) current address: Maritime Research Centre, Mussalontie 428, FI-48310 Kotka, Finland

Intelligent and Scalable Air Quality Monitoring With 5G Edge

Abstract: Air pollution introduces a major challenge for societies, where it leads to the premature deaths of millions of people each year globally. Massive deployment of air quality sensing devices and data analysis for the resultant data will pave the way for the development of real-time intelligent applications and services, e.g., minimization of exposure to poor air quality either on an individual or city scale. 5G and edge computing supports dense deployments of sensors at high resolution with ubiquitous connectivity, high bandwidth, high-speed gigabit connections, and ultralow latency analysis. This article conceptualizes AI-powered scalable air quality monitoring and presents two systems of calibrating low-cost air quality sensors and the image processing of pictures captured by hyperspectral cameras to better detect air quality. We develop and deploy different AI algorithms in these two systems on a 5G edge testbed and perform a detailed analytics regarding to 1) the performance of AI algorithms and 2) the required communication and computation resources.

Characteristics of new-particle formation at three SMEAR stations

Abstract: We analyzed the size distributions of atmospheric aerosol particles measured during 2013– 2014 at Värriö (SMEAR I) in northern Finland, Hyytiälä (SMEAR II) in southern Finland and Järvselja (SMEAR-Estonia) in Estonia. The stations are located on a transect spanning from north to south over 1000 km and they represent different environments ranging from subarctic to the hemi-boreal. We calculated the characteristics of new-particle-formation events, such as the frequency of events, growth rate of nucleation mode particles, condensation and coagulation sinks, formation rate of 2 nm and 3 nm particles, and source rate of condensable vapors. We observed 59, 185 and 108 new-particle-formation events at Värriö, Hyytiälä and Järvselja, respectively. The frequency of the observed events showed an annual variation with a maximum in spring. The analysis revealed size dependence of growth rate at all locations. We found that the growth rate and source rate of a condensable vapor were the highest in Järvselja and the lowest in Värriö. The condensation sink and particle formation rate were of a similar magnitude at Hyytiälä and Järvselja, but several times smaller at Värriö. Tracking the origin of air masses revealed that the number concentration of nucleation mode particles (3–25 nm) varied from north to south, with the highest concentrations at Järvselja and lowest at Värriö. Trajectory analysis indicated that new-particle-formation events are large-scale phenomena that can take place concurrently at distant stations located even 1000 km apart. We found a total of 26 days with new-particle-formation events occurring simultaneously at all three stations.

Nanotoxicology: An Emerging Discipline Evolving from Studies of Ultrafine Particles

Abstract: Although humans have been exposed to airborne nanosized particles (NSPs; < 100 nm) throughout their evolutionary stages, such exposure has increased dramatically over the last century due to anthropogenic sources. The rapidly developing field of nanotechnology is likely to become yet another source through inhalation, ingestion, skin uptake, and injection of engineered nanomaterials. Information about safety and potential hazards is urgently needed. Results of older bio-kinetic studies with NSPs and newer epidemiologic and toxicologic studies with airborne ultrafine particles can be viewed as the basis for the expanding field of nanotoxicology, which can be defined as safety evaluation of engineered nanostructures and nanodevices. Collectively, some emerging concepts of nanotoxicology can be identified from the results of these studies. When inhaled, specific sizes of NSPs are efficiently deposited by diffusional mechanisms in all regions of the respiratory tract. The small size facilitates uptake into cells and transcytosis across epithelial and endothelial cells into the blood and lymph circulation to reach potentially sensitive target sites such as bone marrow, lymph nodes, spleen, and heart. Access to the central nervous system and ganglia via translocation along axons and dendrites of neurons has also been observed. NSPs penetrating the skin distribute via uptake into lymphatic channels. Endocytosis and biokinetics are largely dependent on NSP surface chemistry (coating) and in vivo surface modifications. The greater surface area per mass compared with larger-sized particles of the same chemistry renders NSPs more active biologically. This activity includes a potential for inflammatory and pro-oxidant, but also antioxidant, activity, which can explain early findings showing mixed results in terms of toxicity of NSPs to environmentally relevant species. Evidence of mitochondrial distribution and oxidative stress response after NSP endocytosis points to a need for basic research on their interactions with subcellular structures. Additional considerations for assessing safety of engineered NSPs include careful selections of appropriate and relevant doses/concentrations, the likelihood of increased effects in a compromised organism, and also the benefits of possible desirable effects. An interdisciplinary team approach (e.g., toxicology, materials science, medicine, molecular biology, and bioinformatics, to name a few) is mandatory for nanotoxicology research to arrive at an appropriate risk assessment.

Bounding the role of black carbon in the climate system: A scientific assessment

Abstract: Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

Anthropogenic and Natural Radiative Forcing

Abstract: This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

The formation, properties and impact of secondary organic aerosol: current and emerging issues

Abstract: Secondary organic aerosol (SOA) accounts for a significant fraction of ambient tropospheric aerosol and a detailed knowledge of the formation, properties and transformation of SOA is therefore required to evaluate its impact on atmospheric processes, climate and human health. The chemical and physical processes associated with SOA formation are complex and varied, and, despite considerable progress in recent years, a quantitative and predictive understanding of SOA formation does not exist and therefore represents a major research challenge in atmospheric science. This review begins with an update on the current state of knowledge on the global SOA budget and is followed by an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and the analytical techniques used to determine the chemical composition of SOA. A survey of recent laboratory, field and modeling studies is also presented. The following topical and emerging issues are highlighted and discussed in detail: molecular characterization of biogenic SOA constituents, condensed phase reactions and oligomerization, the interaction of atmospheric organic components with sulfuric acid, the chemical and photochemical processing of organics in the atmospheric aqueous phase, aerosol formation from real plant emissions, interaction of atmospheric organic components with water, thermodynamics and mixtures in atmospheric models. Finally, the major challenges ahead in laboratory, field and modeling studies of SOA are discussed and recommendations for future research directions are proposed.