Browsing by Subject "ION-INDUCED NUCLEATION"

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  • Ehrhart, Sebastian; Ickes, Luisa; Almeida, Joao; Amorim, Antonio; Barmet, Peter; Bianchi, Federico; Dommen, Josef; Dunne, Eimear M.; Duplissy, Jonathan; Franchin, Alessandro; Kangasluoma, Juha; Kirkby, Jasper; Kuerten, Andreas; Kupc, Agnieszka; Lehtipalo, Katrianne; Nieminen, Tuomo; Riccobono, Francesco; Rondo, Linda; Schobesberger, Siegfried; Steiner, Gerhard; Tome, Antonio; Wimmer, Daniela; Baltensperger, Urs; Wagner, Paul E.; Curtius, Joachim (2016)
    Binary nucleation of sulphuric acid-water particles is expected to be an important process in the free troposphere at low temperatures. SAWNUC (Sulphuric Acid Water Nucleation) is a model of binary nucleation that is based on laboratory measurements of the binding energies of sulphuric acid and water in charged and neutral clusters. Predictions of SAWNUC are compared for the first time comprehensively with experimental binary nucleation data from the CLOUD chamber at European Organization for Nuclear Research. The experimental measurements span a temperature range of 208-292K, sulphuric acid concentrations from 110(6) to 110(9)cm(-3), and distinguish between ion-induced and neutral nucleation. Good agreement, within a factor of 5, is found between the experimental and modeled formation rates for ion-induced nucleation at 278K and below and for neutral nucleation at 208 and 223K. Differences at warm temperatures are attributed to ammonia contamination which was indicated by the presence of ammonia-sulphuric acid clusters, detected by an Atmospheric Pressure Interface Time of Flight (APi-TOF) mass spectrometer. APi-TOF measurements of the sulphuric acid ion cluster distributions (H2SO4)HSO4 with i = 0, 1, ..., 10) show qualitative agreement with the SAWNUC ion cluster distributions. Remaining differences between the measured and modeled distributions are most likely due to fragmentation in the APi-TOF. The CLOUD results are in good agreement with previously measured cluster binding energies and show the SAWNUC model to be a good representation of ion-induced and neutral binary nucleation of sulphuric acid-water clusters in the middle and upper troposphere.
  • Myllys, Nanna; Ponkkonen, Tuomo; Passananti, Monica; Elm, Jonas; Vehkamäki, Hanna; Olenius, Tinja (2018)
    The role of a strong organobase, guanidine, in sulfuric acid-driven new-particle formation is studied using state-of-the-art quantum chemical methods and molecular cluster formation simulations. Cluster formation mechanisms at the molecular level are resolved, and theoretical results on cluster stability are confirmed with mass spectrometer measurements. New-particle formation from guanidine and sulfuric acid molecules occurs without thermodynamic barriers under studied conditions, and clusters are growing close to a 1:1 composition of acid and base. Evaporation rates of the most stable clusters are extremely low, which can be explained by the proton transfers and symmetrical cluster structures. We compare the ability of guanidine and dimethylamine to enhance sulfuric acid-driven particle formation and show that more than 2000-fold concentration of dimethylamine is needed to yield as efficient particle formation as in the case of guanidine. At similar conditions, guanidine yields 8 orders of magnitude higher particle formation rates compared to dimethylamine. Highly basic compounds such as guanidine may explain experimentally observed particle formation events at low precursor vapor concentrations, whereas less basic and more abundant bases such as ammonia and amines are likely to explain measurements at high concentrations.
  • Lee, Shan-Hu; Gordon, Hamish; Yu, Huan; Lehtipalo, Katrianne; Haley, Ryan; Li, Yixin; Zhang, Renyi (2019)
    New particle formation (NPF) represents the first step in the complex processes leading to formation of cloud condensation nuclei. Newly formed nanoparticles affect human health, air quality, weather, and climate. This review provides a brief history, synthesizes recent significant progresses, and outlines the challenges and future directions for research relevant to NPF. New developments include the emergence of state-of-the-art instruments that measure prenucleation clusters and newly nucleated nanoparticles down to about 1 nm; systematic laboratory studies of multicomponent nucleation systems, including collaborative experiments conducted in the Cosmics Leaving Outdoor Droplets chamber at CERN; observations of NPF in different types of forests, extremely polluted urban locations, coastal sites, polar regions, and high-elevation sites; and improved nucleation theories and parameterizations to account for NPF in atmospheric models. The challenges include the lack of understanding of the fundamental chemical mechanisms responsible for aerosol nucleation and growth under diverse environments, the effects of SO2 and NOx on NPF, and the contribution of anthropogenic organic compounds to NPF. It is also critical to develop instruments that can detect chemical composition of particles from 3 to 20 nm and improve parameterizations to represent NPF over a wide range of atmospheric conditions of chemical precursor, temperature, and humidity. Plain Language Summary In the atmosphere, invisible to the human eye, there are many microscopic particles, or nanoparticles, that affect human health, air quality, and climate. We do not fully understand the chemical processes that allow these fine particles to form and be suspended in the air nor how they influence heat flow in Earth's atmosphere. Laboratory experiments, field observations, and modeling simulations have all shown different results for how these particles behave. These inconsistencies make it difficult to accurately represent the processes of new particle formation in regional and global atmospheric models. Scientists still need to develop instruments that can measure the smallest range of nanoparticles and to find ways to describe particle formation that allow for differences in temperature, humidity, and level of pollution.
  • Kürten, A.; Li, C.; Bianchi, F.; Curtius, J.; Dias, A.; Donahue, N. M.; Duplissy, J.; Flagan, R. C.; Hakala, J.; Jokinen, T.; Kirkby, J.; Kulmala, M.; Laaksonen, Ari; Lehtipalo, K.; Makhmutov, V.; Onnela, A.; Rissanen, M. P.; Simon, M.; Sipilä, M.; Stozhkov, Y.; Tröstl, J.; Ye, P.; McMurry, P. H. (2018)
    A recent CLOUD (Cosmics Leaving OUtdoor Droplets) chamber study showed that sulfuric acid and dimethylamine produce new aerosols very efficiently and yield particle formation rates that are compatible with boundary layer observations. These previously published new particle formation (NPF) rates are reanalyzed in the present study with an advanced method. The results show that the NPF rates at 1.7 nm are more than a factor of 10 faster than previously published due to earlier approximations in correcting particle measurements made at a larger detection threshold. The revised NPF rates agree almost perfectly with calculated rates from a kinetic aerosol model at different sizes (1.7 and 4.3 nm mobility diameter). In addition, modeled and measured size distributions show good agreement over a wide range of sizes (up to ca. 30 nm). Furthermore, the aerosol model is modified such that evaporation rates for some clusters can be taken into account; these evaporation rates were previously published from a flow tube study. Using this model, the findings from the present study and the flow tube experiment can be brought into good agreement for the high base-to-acid ratios (similar to 100) relevant for this study. This confirms that nucleation proceeds at rates that are compatible with collision-controlled (a.k.a. kinetically controlled) NPF for the conditions during the CLOUD7 experiment (278 K, 38% relative humidity, sulfuric acid concentration between 1 x 10(6) and 3 x 10(7) cm(-3), and dimethylamine mixing ratio of similar to 40 pptv, i.e., 1 x 10(9) cm(-3)).
  • Kangasluoma, Juha; Attoui, Michael (2019)
    This review discusses the developments in aerosol instrumentation that have led to the current vapor condensation based instruments capable of detecting sub-3 nm particles. We begin from selected reports prior to the year 1991, which have advanced the technology or understanding in condensation particle counting toward sub-3 nm sizes, and continue to more in depth review of the past efforts after 1991. We discuss how the developments in the calibration methods have progressed the development of particle counting techniques, and review briefly the sub-3 nm calibration experiments and cluster production methods used in calibration experiments. Based on these reviews, we identify several technological and scientific advances for the future to improve the accuracy, understanding, and technology of sub-3 nm particle counting. Copyright (c) 2019 American Association for Aerosol Research
  • Neitola, K.; Brus, D.; Makkonen, U.; Sipilä, Mikko; Mauldin III, Roy; Sarnela, N.; Jokinen, T.; Lihavainen, H.; Kulmala, Markku (2015)
    Sulfuric acid is known to be a key component for atmospheric nucleation. Precise determination of sulfuric-acid concentration is a crucial factor for prediction of nucleation rates and subsequent growth. In our study, we have noticed a substantial discrepancy between sulfuric-acid monomer concentrations and total-sulfate concentrations measured from the same source of sulfuric-acid vapor. The discrepancy of about 1-2 orders of magnitude was found with similar particle-formation rates. To investigate this discrepancy, and its effect on nucleation, a method of thermally controlled saturator filled with pure sulfuric acid (97% wt.) for production of sulfuric-acid vapor is applied and rigorously tested. The saturator provided an independent vapor-production method, compared to our previous method of the furnace (Brus et al., 2010, 2011), to find out if the discrepancy is caused by the production method itself. The saturator was used in a H2SO4-H2O nucleation experiment, using a laminar flow tube to check reproducibility of the nucleation results with the saturator method, compared to the furnace. Two independent methods of mass spectrometry and online ion chromatography were used for detecting sulfuric-acid or sulfate concentrations. Measured sulfuric-acid or total-sulfate concentrations are compared to theoretical predictions calculated using vapor pressure and a mixing law. The calculated prediction of sulfuric-acid concentrations agrees very well with the measured values when total sulfate is considered. Sulfuric-acid monomer concentration was found to be about 2 orders of magnitude lower than theoretical predictions, but with a temperature dependency similar to the predictions and the results obtained with the ion-chromatograph method. Formation rates are reproducible when compared to our previous results with both sulfuric-acid or total-sulfate detection and sulfuric-acid production methods separately, removing any doubts that the vapor-production method would cause the discrepancy. Possible reasons for the discrepancy are discussed and some suggestions include that the missing sulfuric acid is in clusters, formed with contaminants found in most laboratory experiments. One-to-two-order-of-magnitude higher sulfuric-acid concentrations (measured as total sulfate in this study) would contribute to a higher fraction of particle growth rate than assumed from the measurements by mass spectrometers (i.e. sulfuric-acid monomer). However, the observed growth rates by sulfate-containing vapor in this study does not directly imply a similar situation in the field, where sources of sulfate are much more diverse.