Markku Kulmala

Homogeneous nucleation of n-pentanol in a laminar flow diffusion chamber

Nucleation rate isotherms of n-pentanol were measured in laminar flow diffusion chamber. n-pentanol was chosen for nucleating vapor and helium for carrier gas as a part of a world wide joint experiment on homogeneous nucleation. Experimental temperature range was from 260 to 290 K. Experimental nucleation rate range was from 103 to 107 cm−3 s−1. The results were compared to the classical nucleation theory and experimental data found in literature. Experimental results were three orders of magnitude higher than predicted by the theory. The difference was constant over the whole experimental range. The saturation ratio dependency of nucleation rate was well predicted by the theory. The number of molecules in the critical clusters was quite consistent with the theory. The results were in reasonable agreement with data found in literature.

Homogeneous nucleation rates of higher n-alcohols measured in a laminar flow diffusion chamber

Nucleation rate isotherms of n-butanol, n-pentanol, n-hexanol, n-heptanol, and n-octanol were measured in a laminar flow diffusion chamber using helium as carrier gas. The measurements were made at 250-310 K, corresponding to reduced temperatures of 0.43-0.50, and at atmospheric pressure. Experimental nucleation rate range was from 10(3) to 10(7) cm(-3) s(-1). The expression and accuracy of thermodynamic parameters, in particular equilibrium vapor pressure, were found to have a significant effect on calculated nucleation rates. The results were compared to the classical nucleation theory (CNT), the self-consistency corrected classical theory (SCC) and the Hales scaled model of the CNT. The average ratio between the experimental and theoretical nucleation rates for all alcohols used was 1.5x10(3) when the CNT was used, and 0.2x10(-1) when the SCC was used and 0.7x10(-1) when the Hales scaled theory was used. The average values represent all the alcohols used at the same reduced temperatures. The average ratio was about the same throughout the temperature range, although J(exp)/J(the) calculated with the Hales scaled theory increased slightly with increasing temperature. The saturation ratio dependency was predicted closest to experiment with the classical nucleation theory. The nucleation rates were compared to those found in the literature. The measurements were in reasonable agreement with each other. The molecular content of critical alcohol clusters was between 35 and 80 molecules. At a fixed reduced temperature, the number of molecules in a critical cluster decreased as a function of alcohol carbon chain length. The number of molecules in critical clusters was compared to those predicted by the Kelvin equation. The theory predicted the critical cluster sizes well.

Identification and quantification of particle growth channels during new particle formation

Atmospheric new particle formation (NPF) is a key source of ambient ultrafine particles that may contribute substantially to the global production of cloud condensation nuclei (CCN). While NPF is driven by atmospheric nucle- ation, its impact on CCN concentration depends strongly on atmospheric growth mechanisms since the growth rate must exceed the loss rate due to scavenging in order for the parti- cles to reach the CCN size range. In this work, chemical com- position measurements of 20 nm diameter particles during NPF in Hyytiala, Finland, in March-April 2011 permit iden- tification and quantitative assessment of important growth channels. In this work we show the following: (A) sulfuric acid, a key species associated with atmospheric nucleation, accounts for less than half of particle mass growth during this time period; (B) the sulfate content of a growing parti- cle during NPF is quantitatively explained by condensation of gas-phase sulfuric acid molecules (i.e., sulfuric acid up- take is collision-limited); (C) sulfuric acid condensation sub- stantially impacts the chemical composition of preexisting nanoparticles before new particles have grown to a size suffi- cient to be measured; (D) ammonium and sulfate concentra- tions are highly correlated, indicating that ammonia uptake is driven by sulfuric acid uptake; (E) sulfate neutralization by ammonium does not reach the predicted thermodynamic end point, suggesting that a barrier exists for ammonia up- take; (F) carbonaceous matter accounts for more than half of the particle mass growth, and its oxygen-to-carbon ratio ( 0.5) is characteristic of freshly formed secondary organic aerosol; and (G) differences in the overall growth rate from one formation event to another are caused by variations in the growth rates of all major chemical species, not just one individual species.

Correction to “New parameterization of sulfuric acid‐ammonia‐water ternary nucleation rates at tropospheric conditions”

[1] In the paper ‘‘New parameterization of sulfuric acidammonia-water ternary nucleation rates at tropospheric conditions’’ by J. Merikanto et al. (J. Geophys. Res., 112, D15207, doi:10.1029/2006JD007977, 2007) the reported coefficients in the parameterized equation are numerically inaccurate for the calculation of ternary nucleation rates. The coefficients were given with six significant digits. However, this precision is not sufficient. Coefficients with 16 significant digits are given in Table 1. We also provide a Fortran code that calculates the reported parameterized nucleation rates and critical cluster sizes accurately (see auxiliary material). [2] Also, the term containing f15 in equation (8) in paragraph 18 should be multiplied by RH. The correct equation is

Cluster Measurements at CLOUD using a High Resolution Ion Mobility Spectrometer - Mass Spectrometer Combination

Mass spectrometry is powerful tool for environmental and atmospheric chemistry analysis. Modern mass spectrometers demonstrate low detection limits, high sensitivity, and high resolving power. However, such high performance is not always enough to identify ambient ion clusters due to the clusters braking at the atmospheric pressure-to-vacuum interface of mass spectrometer. This study presents a high resolution ion mobility spectrometer-time-of-flight mass spectrometer (IMS-TOF) in the CLOUD experiment. This combination of orthogonal analytical techniques allows obtaining structural information in addition to mass-to-charge separation.

Estimating the concentration of nucleation mode aerosol particles over South Africa using satellite remote sensing measurements

In this work satellite based observations were used to estimate the concentration of nucleation mode aerosols over South Africa. The nucleation mode aerosols can not be detected directly with satellite instruments since they are much smaller than the optically active aerosols, hence the concentrations were estimated using proxies introduced by Kulmala et al. (2011). Results showed enhanced values of both primary and regional scale nucleation proxies over the Mpumalanga Highveld industrial area, whereas over the Johannesburg-Pretoria megacity only the primary nucleation proxy showed elevated values. To estimate how well satellite based proxies work, the relation between satellite and in situ based quantities was studied in more detail. The correlation between aerosol optical depth (AOD) and condensation sink (CS) was 0.2-0.3 depending on the location. Boundary layer height affected the correlation somewhat, but there are other factors, such as the effect of dust on AOD, that are more likely to have a stron...

Comparison of formation conditions of secondary aerosol particles in boreal forests of Southern Finland and Siberia

Complex measurements of size distributions and chemical content of aerosols, trace gases SO2, NH3, ozone, and meteorological parameters were performed in boreal forests of Central Siberia during 03.2005–05.2006 at the rural station of Listvyanka. The data from Listvyanka are then analyzed from the point of view of their similarities and differences with respective data at Hyytiala background station (Southern Finland). The goal of this paper is to compare the conditions of formation of secondary aerosol particles in boreal forests in two different regions: in Southern Finland (Hyytiala station) and Siberia (Listvyanka station). Our main conclusion is that the particle formation–growth processes in Listvyanka occur in presence of high (compared to Hyytiala) concentrations of sulfur dioxide and ammonia. We show that their concentrations are enough for providing the particle growth up to 3.5 nm h−1 with much higher concentration of the nucleation mode particles in contrast to Hyytiala, where the sulfuric compounds are much less concentrated and the nucleation mode particles grow by consuming low volatile organic vapors that result from photochemical processing of highly volatile organic plant emissions. On the other hand, the nucleation bursts in Siberia occur more seldom than in Hyytiala. The difference in UVB irradiation regimes at Siberian stations and in Hyytiala can lead to different seasonal patterns of the particle formation–growth rates and the concentrations of nucleation mode in Siberia.

Characterization of diethylene glycol-condensation particle counters for detection of sub-3 nm particles

The counting efficiencies of 2 different types of diethylene-glycol (DEG) based Condensation Particle Counters (CPCs) is described and discussed. The development of two laminar flow CPCs, sensitive in the size range below 3 nm is described. The two types used are a modified TSI 3776 laminar diffusion-type CPC operating with DEG instead of butanol (DEG-CPC) and a turbulent mixing Particle Size Magnifier (PSM) A09 from Airmodus. For each of the two types two different systems with slightly different settings have been investigated, respectively. The two laminar flow CPCs were operated at different temperature settings, where one of the mixing type systems was running at a fixed saturation ratio and therefore had a fixed cut-off diameter and the other one was opaerated in scanning mode. Various different test aerosols have been generated to obtain cut-off curves for all four different CPCs. The main focus was on measuring the counting efficiencies under well controlled laboratory conditions. Therefore a high...

Long-term size-segregated cloud condensation nuclei counter (CCNc) measurements in a boreal environment and the implications for aerosol-cloud interactions

Ambient aerosol CCN and hygroscopic properties were measured with a size-segregated CCNc in a boreal environment of Southern Finland at the SMEAR II station since February 2009. The overall median critical diameter Dc for CCN activation is reported at 75 nm, exhibiting a clear maximum in February and a minimum in July. The overall median aerosol hygroscopicity parameter κ is reported at 0.22, indicating that ambient aerosol in Hyytiala is less hygroscopic than the global continental and European continental averages. It is, however, more hygroscopic than ambient aerosol in an Amazon rainforest, the European high alpine site or the mountainous forest. The low hygroscopicity in the boreal forest is attributed to a large organic fraction present in the aerosol mass comparative to other locations within Europe. Aerosol mass spectrometer (AMS) data were used to demonstrate a positive correlation between κ and sulphate and ammonia, and a negative correlation between κ and the organic mass fraction. No distingui...

Charged and neutral binary nucleation of sulfuric acid in free troposphere conditions

We present a data set of binary nucleation of sulfuric acid and water, measured in the CLOUD chamber at CERN during the CLOUD3 and CLOUD5 campaigns. Four parameters have been varied to cover neutral and ion-induced binary nucleation processes: Sulfuric acid concentration (1e5 to 1e8 molecules per cm^(−3)), relative humidity (10% to 80%), temperature (208-293K) and ion concentration (0-4000 ions per cm^(−3)). In addition, classical nucleation theory implemented with hydrates and ion induced nucleation is compared with the data set. Our model and data are also compared with nucleation rates measured at Puy de Dome in the tropopause.