Author
Tuukka Petäjä
Other affiliations: Helsinki Institute of Physics, National Center for Atmospheric Research, University of Tyumen ...read more
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.
Topics: Aerosol, Particle, Nucleation, Cloud condensation nuclei, Particle size
Papers published on a yearly basis
Papers
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TL;DR: In this paper, ground-based measurements using a tower were used to observe new particle formation in the Morgan Monroe State Forest (MMSF) in Southwestern Indiana in May 2008.
5 citations
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TL;DR: Zhang et al. as discussed by the authors found that ammonium nitrate-rich (NH4NO3-rich) fine particles acting as condensation sink are more effective in removing gaseous H2SO4 (effectiveness of the CS) driving NPF.
Abstract: Relatively high concentrations of preexisting particles, acting as a condensation sink (CS) of gaseous precursors, have been thought to suppress the occurrence of new particle formation (NPF) in urban environments, yet NPF still occurs frequently. Here, we aim to understand the factors promoting and inhibiting NPF events in urban Beijing by combining one-year-long measurements of particle number size distributions and PM2.5 chemical composition. Our results show that indeed the CS is an important factor controlling the occurrence of NPF events, with its chemical composition affecting the efficiency of the background particles in removing gaseous H2SO4 (effectiveness of the CS) driving NPF. During our observation period, the CS was found to be more effective for ammonium nitrate-rich (NH4NO3-rich) fine particles. On non-NPF event days, particles acting as CS contained a larger fraction of NH4NO3 compared to NPF event days under comparable CS levels. In particular, in the CS range from 0.02 to 0.03 s–1, the nitrate fraction was 17% on NPF event days and 26% on non-NPF event days. Overall, our results highlight the importance of considering the chemical composition of preexisting particles when estimating the CS and their role in inhibiting NPF events, especially in urban environments.
5 citations
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TL;DR: In this article, a comparison between three absorption photometers that measured the absorption coefficient ( σabs ) of ambient aerosol particles in 2012-2017 at SMEAR II, a measurement station located in a boreal forest in southern Finland is presented.
Abstract: . We present a comparison between three absorption photometers that measured
the absorption coefficient ( σabs ) of ambient aerosol particles in
2012–2017 at SMEAR II (Station for Measuring Ecosystem–Atmosphere Relations II), a measurement station located in a boreal forest
in southern Finland. The comparison included an Aethalometer (AE31), a multi-angle absorption photometer (MAAP), and a particle soot absorption
photometer (PSAP). These optical instruments measured particles collected on
a filter, which is a source of systematic errors, since in addition to the
particles, the filter fibers also interact with light. To overcome this
problem, several algorithms have been suggested to correct the AE31 and PSAP
measurements. The aim of this study was to research how the different
correction algorithms affected the derived optical properties. We applied
the different correction algorithms to the AE31 and PSAP data and compared
the results against the reference measurements conducted by the MAAP. The
comparison between the MAAP and AE31 resulted in a multiple-scattering correction factor ( Cref ) that is used in AE31 correction algorithms to
compensate for the light scattering by filter fibers. Cref varies
between different environments, and our results are applicable to a boreal
environment. We observed a clear seasonal cycle in Cref , which was
probably due to variations in aerosol optical properties, such as the
backscatter fraction and single-scattering albedo, and also due to
variations in the relative humidity (RH). The results showed that the
filter-based absorption photometers seemed to be rather sensitive to the
RH even if the RH was kept below the recommended value of 40 %. The
instruments correlated well ( R≈0.98 ), but the slopes of the
regression lines varied between the instruments and correction algorithms:
compared to the MAAP, the AE31 underestimated σabs only
slightly (the slopes varied between 0.96–1.00) and the PSAP overestimated
σabs only a little (the slopes varied between 1.01–1.04 for a
recommended filter transmittance >0.7 ). The instruments and
correction algorithms had a notable influence on the absorption
Angstrom exponent: the median absorption Angstrom exponent
varied between 0.93–1.54 for the different algorithms and instruments.
5 citations
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TL;DR: In this paper, an inverse method based upon process control theory was developed to scale aerosol nucleation, emissions, and growth so that the model-measurement bias in three measured aerosol properties exponentially decays.
Abstract: . Atmospheric aerosol microphysical processes are a
significant source of uncertainty in predicting climate change.
Specifically, aerosol nucleation, emissions, and growth rates, which are
simulated in chemical transport models to predict the particle size
distribution, are not understood well. However, long-term size distribution
measurements made at several ground-based sites across Europe implicitly
contain information about the processes that created those size
distributions. This work aims to extract that information by developing and
applying an inverse technique to constrain aerosol emissions as well as
nucleation and growth rates based on hourly size distribution measurements.
We developed an inverse method based upon process control theory into an
online estimation technique to scale aerosol nucleation, emissions, and
growth so that the model–measurement bias in three measured aerosol
properties exponentially decays. The properties, which are calculated from
the measured and predicted size distributions, used to constrain aerosol
nucleation, emission, and growth rates are the number of particles with
a diameter between 3 and 6 nm, the number with a diameter greater than 10 nm,
and the total dry volume of aerosol ( N3–6 , N10 , Vdry ),
respectively. In this paper, we focus on developing and applying the
estimation methodology in a zero-dimensional “box” model as a
proof of concept before applying it to a three-dimensional simulation in
subsequent work. The methodology is first tested on a dataset of synthetic
and perfect measurements that span diverse environments in which the true
particle emissions, growth, and nucleation rates are known. The inverse
technique accurately estimates the aerosol microphysical process rates with
an average and maximum error of 2 % and 13 %, respectively. Next, we
investigate the effect that measurement noise has on the estimated rates.
The method is robust to typical instrument noise in the aerosol properties
as there is a negligible increase in the bias of the estimated process rates.
Finally, the methodology is applied to long-term datasets of in situ size
distribution measurements in western Europe from May 2006 through June 2007.
At Melpitz, Germany, and Hyytiala, Finland, the average diurnal
profiles of estimated 3 nm particle formation rates are reasonable, having
peaks near noon local time with average peak values of 1 and 0.15 cm −3 s −1 , respectively. The
normalized absolute error in estimated N3–6 , N10 , and Vdry at
three European measurement sites is less than 15 %, showing that the
estimation framework developed here has potential to decrease
model–measurement bias while constraining uncertain aerosol microphysical
processes.
4 citations
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TL;DR: In this paper, the optical particle detector used in AQT530 (Vaisala Ltd.) air quality sensor in the laboratory is characterized and a measurement campaign with a network of 25 sensors in Helsinki, Finland in 2020-2021 is performed.
Abstract: Poor air quality influences the quality of life in the urban environment. The regulatory observation stations provide the backbone for the city administration to monitor urban air quality. Recently a suite of cost-effective air quality sensors has emerged to provide novel insights into the spatio-temporal variability of aerosol particles and trace gases. Particularly in low concentrations these sensors might suffer from issues related e.g., to high detection limits, concentration drifts and interdependency between the observed trace gases and environmental parameters. In this study we characterize the optical particle detector used in AQT530 (Vaisala Ltd.) air quality sensor in the laboratory. We perform a measurement campaign with a network of AQT530 sensors in Helsinki, Finland in 2020-2021 and present a long-term performance evaluation of five sensors for particulate (PM10, PM2.5) and gaseous (NO2, NO, CO, O3) components during a half-year co-location study with reference instruments at an urban traffic site. Furthermore, short-term (3-5 weeks) co-location tests were performed for 25 sensors to provide sensor-specific correction equations for the fine-tuning of selected pollutants in the sensor network. We showcase the added value of the verified network of 25 sensor units to address the spatial variability of trace gases and aerosol mass concentrations in an urban environment. The analysis assesses road and harbor traffic monitoring, local construction dust monitoring, aerosol concentrations from fireworks, impact of sub-urban small scale wood combustion and detection of long-range transport episodes on a city scale. Our analysis illustrates that the calibrated network of Vaisala AQT530 air quality sensors provide new insights into the spatio-temporal variability of air pollution within the city. This information is beneficial to, for example, optimization of road dust and construction dust emission control as well as provides data to tackle air quality problems arising from traffic exhaust and localized wood combustion emissions in the residential areas.
4 citations
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TL;DR: 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.
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.
7,092 citations
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University of Illinois at Urbana–Champaign1, Joint Institute for the Study of the Atmosphere and Ocean2, Cooperative Institute for Research in Environmental Sciences3, University of Leeds4, University of Oslo5, United States Environmental Protection Agency6, University of Michigan7, Pacific Northwest National Laboratory8, German Aerospace Center9, United States Department of Energy10, Max Planck Society11, University of Tokyo12, National Oceanic and Atmospheric Administration13, Forschungszentrum Jülich14, Norwegian Meteorological Institute15, Indian Institute of Technology Bombay16, China Meteorological Administration17, Peking University18, Met Office19, Desert Research Institute20, Clarkson University21, Stanford University22, European Centre for Medium-Range Weather Forecasts23, International Institute of Minnesota24, Goddard Institute for Space Studies25, Yale University26, University of Washington27, University of California, Irvine28
TL;DR: In this paper, the authors provided an assessment 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.
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.
4,591 citations
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01 Jan 2014
TL;DR: Myhre et al. as discussed by the authors presented the contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC) 2013: 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)
3,684 citations
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University of Gothenburg1, University College Cork2, Paul Scherrer Institute3, Weizmann Institute of Science4, Chalmers University of Technology5, Norwegian Meteorological Institute6, University of Antwerp7, Carnegie Mellon University8, University of Lyon9, Centre national de la recherche scientifique10, University of California, Berkeley11, University of York12, Leibniz Institute for Neurobiology13, University of Mainz14, University of Florida15, University of Colorado Boulder16, Forschungszentrum Jülich17, Ghent University18, University of Manchester19, Aix-Marseille University20, California Institute of Technology21
TL;DR: In this article, an overview of the atmospheric degradation mechanisms for SOA precursors, gas-particle partitioning theory and analytical techniques used to determine the chemical composition of SOA is presented.
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.
3,324 citations