Browsing by Subject "FORMATION RATES"

Sort by: Order: Results:

Now showing items 1-7 of 7
  • Kontkanen, Jenni; Olenius, Tinja; Kulmala, Markku; Riipinen, Ilona (2018)
    Atmospheric new particle formation (NPF) occurs by the formation of nanometer-sized molecular clusters and their subsequent growth to larger particles. NPF involving sulfuric acid, bases and oxidized organic compounds is an important source of atmospheric aerosol particles. One of the mechanisms suggested to depict this process is nano-Kohler theory, which describes the activation of inorganic molecular clusters to growth by a soluble organic vapor. In this work, we studied the capability of nano-Kohler theory to describe the initial growth of atmospheric molecular clusters by simulating the dynamics of a cluster population in the presence of a sulfuric acid-base mixture and an organic compound. We observed nano-Kohler-type activation in our simulations when the saturation ratio of the organic vapor and the ratio between organic and inorganic vapor concentrations were in a suitable range. However, nano-Kohler theory was unable to predict the exact size at which the activation occurred in the simulations. In some conditions, apparent cluster growth rate (GR) started to increase close to the activation size determined from the simulations. Nevertheless, because the behavior of GR is also affected by other dynamic processes, GR alone cannot be used to deduce the cluster growth mechanism.
  • Bianconi, M.; Smith, G. P.; Haines, C. P.; McGee, S. L.; Finoguenov, A.; Egami, E. (2018)
    We report direct evidence of pre-processing of the galaxies residing in galaxy groups falling into galaxy clusters drawn from the Local Cluster Substructure Survey (LoCuSS). 34 groups have been identified via theirX-ray emission in the infall regions of 23 massive (<M-200 > = 10(15) M-circle dot) clusters at 0.15 <z <0.3. Highly complete spectroscopic coverage combined with 24 mu m imaging from Spitzer allows us to make a consistent and robust selection of cluster and group members including star-forming galaxies down to a stellar mass limit of M* = 2 x 10(10) M-circle dot. The fraction f(SF) of star-forming galaxies in infalling groups is lower and with a flatter trend with respect to clustercentric radius when compared to the rest of the cluster galaxy population. At R approximate to 1.3 r(200), the fraction of star-forming galaxies in infalling groups is half that in the cluster galaxy population. This is direct evidence that star-formation quenching is effective in galaxies already prior to them settling in the cluster potential, and that groups are favourable locations for this process.
  • Määttänen, Anni; Merikanto, Joonas; Henschel, Henning; Duplissy, Jonathan; Makkonen, Risto; Ortega, Ismael K.; Vehkamäki, Hanna (2018)
    We have developed new parameterizations of electrically neutral homogeneous and ion-induced sulfuric acid-water particle formation for large ranges of environmental conditions, based on an improved model that has been validated against a particle formation rate data set produced by Cosmics Leaving OUtdoor Droplets (CLOUD) experiments at European Organization for Nuclear Research (CERN). The model uses a thermodynamically consistent version of the Classical Nucleation Theory normalized using quantum chemical data. Unlike the earlier parameterizations for H2SO4-H2O nucleation, the model is applicable to extreme dry conditions where the one-component sulfuric acid limit is approached. Parameterizations are presented for the critical cluster sulfuric acid mole fraction, the critical cluster radius, the total number of molecules in the critical cluster, and the particle formation rate. If the critical cluster contains only one sulfuric acid molecule, a simple formula for kinetic particle formation can be used: this threshold has also been parameterized. The parameterization for electrically neutral particle formation is valid for the following ranges: temperatures 165-400K, sulfuric acid concentrations 10(4)-10(13)cm(-3), and relative humidities 0.001-100%. The ion-induced particle formation parameterization is valid for temperatures 195-400K, sulfuric acid concentrations 10(4)-10(16)cm(-3), and relative humidities 10(-5)-100%. The new parameterizations are thus applicable for the full range of conditions in the Earth's atmosphere relevant for binary sulfuric acid-water particle formation, including both tropospheric and stratospheric conditions. They are also suitable for describing particle formation in the atmosphere of Venus.
  • 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)).
  • Kulmala, Markku; Petaja, Tuukka; Kerminen, Veli-Matti; Kujansuu, Joni; Ruuskanen, Taina; Ding, Aijun; Nie, Wei; Hu, Min; Wang, Zhibin; Wu, Zhijun; Wang, Lin; Worsnop, Douglas R. (2016)
    Formation of new atmospheric aerosol particles is a global phenomenon that has been observed to take place in even heavily-polluted environments. However, in all environments there appears to be a threshold value of the condensation sink (due to pre-existing aerosol particles) after which the formation rate of 3 nm particles is no longer detected. In China, new particle production has been observed at very high pollution levels (condensation sink about 0.1 s(-1)) in several megacities, including Beijing, Shanghai and Nanjing as well as in Pearl River Delta (PRD). Here we summarize the recent findings obtained from these studies and discuss the various implications these findings will have on future research and policy. (C) Higher Education Press and Springer-Verlag Berlin Heidelberg 2016
  • Liu, Tie; Kim, Kee-Tae; Yoo, Hyunju; Liu, Sheng-Yuan; Tatematsu, Ken'ichi; Qin, Sheng-Li; Zhang, Qizhou; Wu, Yuefang; Wang, Ke; Goldsmith, Paul F.; Juvela, Mika; Lee, Jeong-Eun; Toth, L. Viktor; Mardones, Diego; Garay, Guido; Bronfman, Leonardo; Cunningham, Maria R.; Li, Di; Lo, Nadia; Ristorcelli, Isabelle; Schnee, Scott (2016)
    We observed 146 Galactic clumps in HCN (4-3) and CS (7-6) with the Atacama Submillimeter Telescope Experiment 10 m telescope. A tight linear relationship between star formation rate and gas mass traced by dust continuum emission was found for both Galactic clumps and the high redshift (z > 1) star forming galaxies (SFGs), indicating a constant gas depletion time of similar to 100 Myr for molecular gas in both Galactic clumps and high z SFGs. However, low z galaxies do not follow this relation and seem to have a longer global gas depletion time. The correlations between total infrared luminosities (L-TIR) and molecular line luminosities (L-mol') of HCN (4-3) and CS (7-6) are tight and sublinear extending down to clumps with L-TIR similar to 10(3) L-circle dot. These correlations become linear when extended to external galaxies. A bimodal behavior in the L-TIR-L-mol' correlations was found for clumps with different dust temperature, luminosity-to-mass ratio, and sigma(line)/sigma(vir). Such bimodal behavior may be due to evolutionary effects. The slopes of L-TIR-L-mol' correlations become more shallow as clumps evolve. We compared our results with lower J transition lines in Wu et al. (2010). The correlations between clump masses and line luminosities are close to linear for low effective excitation density tracers but become sublinear for high effective excitation density tracers for clumps with L-TIR larger than L-TIR similar to 10(4.5) L-circle dot. High effective excitation density tracers cannot linearly trace the total clump masses, leading to a sublinear correlations for both M-clump-L-mol' and L-TIR-L-mol' relations.
  • Reeves, Andrew M. M.; Balogh, Michael L.; van der Burg, Remco F. J.; Finoguenov, Alexis; Kukstas, Egidijus; McCarthy, Ian G.; Webb, Kristi; Muzzin, Adam; McGee, Sean; Rudnick, Gregory; Biviano, Andrea; Cerulo, Pierluigi; Chan, Jeffrey C. C.; Cooper, M. C.; Demarco, Ricardo; Jablonka, Pascale; De Lucia, Gabriella; Vulcani, Benedetta; Wilson, Gillian; Yee, Howard K. C.; Zaritsky, Dennis (2021)
    We use photometric redshifts and statistical background subtraction to measure stellar mass functions in galaxy group-mass (4.5-8 x 10(13) M-circle dot) haloes at 1 < z < 1.5. Groups are selected from COSMOS and SXDF, based on X-ray imaging and sparse spectroscopy. Stellar mass (M-stell(ar)) functions are computed for quiescent and star-forming galaxies separately, based on their rest-frame UVJ colours. From these we compute the quiescent fraction and quiescent fraction excess (QFE) relative to the field as a function of M-stel(lar). QFE increases with M-st(ellar), similar to more massive clusters at 1 < z < 1.5. This contrasts with the apparent separability of M-stellar, and environmental factors on galaxy quiescent fractions at z similar to 0. We then compare our results with higher mass clusters at 1 < z < 1.5 and lower redshifts. We find a strong QFE dependence on halo mass at fixed M-ste(ll)ar; well fit by a logarithmic slope of d(QFE)/dlog (M-halo) similar to 0.24 +/- 0.04 for all M-stellar and redshift bins. This dependence is in remarkably good qualitative agreement with the hydrodynamic simulation BAHAMAS, but contradicts the observed dependence of QFE on M-stellar. We interpret the results using two toy models: one where a time delay until rapid (instantaneous) quenching begins upon accretion to the main progenitor ( 'no pre-processing') and one where it starts upon first becoming a satellite ('pre-processing'). Delay times appear to be halo mass-dependent, with a significantly stronger dependence required without pre-processing. We conclude that our results support models in which environmental quenching begins in low-mass ( 1.