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Industrial activity is a major source of sulphur compound emissions. The sulphuric acid and sulphur dioxide measurements in the vicinity of the industrial area and the oil refinery in Kilpilahti expressed great variation in concentration. The hourly mean values of concentration were categorized according to the area from where the air mass was travelling towards the measurement site. The statistical characteristics and diurnal behavior of emissions between these areas were significantly different.

We present a newly developed expansion chamber condensation particle counter-the versatile Size Analyzing Nuclei Counter (vSANC)-applicable for both laboratory as well as field measurements. The vSANC was optimized to achieve high flexibility in investigating aerosol particles from diameters of 1-2nm upwards at temperatures ranging from -20°C to +40°C and gas pressures ranging from 0.2 bar to 1.2 bar. The operation is based on heterogeneous nucleation of well-defined uniform supersaturated vapor on particles and subsequent droplet growth. Thereby particles, which are initially too small to be detected, grow to visible sizes. Starting from diameters of about 120nm they can be observed with an optical detection method-the multiple Constant Angle Mie Scattering method. This enables automated determination of droplet growth rates for precision verification of vapor supersaturation ranging from 5% up to the limit of homogeneous nucleation as well as absolute number concentrations ranging from 50/cc to 107/cc, ...

Aerosol particles may increase the amount of water vapor in the upper troposphere via microphysical changes in deep convective clouds. In this study aerosol optical depth data from the MODIS instrument onboard the Aqua satellite have been studied together with upper tropospheric humidity data from microwave humidity sounder onboard the MetOp-A satellite. An increase in upper tropospheric humidity connected to higher aerosol optical depth values is found. Caveats of the method are discussed.

We use the one-dimensional chemical-transport model SOSAA (model to Simulate the concentration of Organic vapors, Sulfuric Acid, and Aerosols) to study the complex processes of aerosols in the atmospheric boundary layer at a boreal forest site in southern Finland. With the detailed aerosol microphysics in SOSAA, we compared two theories for atmospheric nucleation. Results indicate that between the two theories, the organic nucleation mechanism works better than kinetic nucleation mechanism in Hyytiala, Finland. The model also suggests that a combination of different parameterizations may further improve the nucleation simulation. Compared to the measurements, the predicted particle number concentration by SOSAA is within a factor of 10 with a correlation coefficient of 0.68. The model captures 10 out of 11 observed event days in 2010.

A size-resolved condensation particle counter battery (SR-CPCb) was developed to infer the composition of freshly nucleated aerosol down to 1 nm in diameter. This was accomplished by exploiting the strong dependence of CPC counting efficiency on particle composition and CPC working fluid. The SR-CPCb consists of CPCs that are optimized for sub 2 nm particle detection using the following working fluids: diethylene glycol, water, and butanol. Laboratory characterizations of the SR-CPCb were performed for challenge aerosols of various compositions down to 1 nm in diameter.

In this study, we investigate the composition of nucleated nanoparticles formed from sulphuric acid, ammonia, amines, and oxidised organics in the CLOUD chamber experiments at CERN. The investigation is carried out via analysis of the particle hygroscopicity (size range of 15-63 nm), ethanol affinity (15-50nm), oxidation state (

Particle nucleation in Amazonia has been an enigma throughout decades of active scrutiny of natural nucleation processes; however, measurements have so far been thought to fail capturing an actual new particle formation (NPF) event. In this study we have analyzed latest measurements of ultra-fine particle size distributions alongside with air ion spectra and revealed a diurnal pattern of ultra-fine particle apparent growth. The revealed growth pattern is preceded by diurnal precipitation probability maxima, and simultaneous abundant ion production as detected by Neutral cluster and Air Ion Spectrometer (NAIS) data. Thus, we claim that by implementing statistical analysis of scanning mobility particle sizer (SMPS) data and combining with independent observations from Neutral cluster and Air Ion Spectrometer (NAIS) we can observe a consistent signal of NPF events in Amazonia.

We describe a 2D-VBS model of organic oxidation in the CERN CLOUD Experiment. Specifically, we model the steady-state supersaturations of organic compounds formed during the oxidation of pinanediol by OH. The steady state is controlled in the model almost entirely by production from OH oxidation and deposition to the chamber walls.

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.

Forest and peat bog fires occur almost every summer in several parts of Russian boreal forests due to long rainless and heat periods at summertime. Particulate matter and different gases (CO, CO2, NOx, O3, SO2) in air can be transported thousands of kilometers away from the fire areas. Increased concentrations of the different parameters, like carbon monoxide and aerosol particles were observed on certain days in Southern Finland and even Finnish Lapland during Russian wild fire episodes in summer 2010. During these days the wind direction was from East or Southeast to Finland.

Particle size distribution measurements from 7 nm to 850 nm are being conducted in Western Saudi Arabia utilizing a Differential Mobility Particle Sizer (DMPS). The early results show that the particle size distribution is highly variable, with signatures from the nucleation, Aitken, and accumulation mode. The accumulation mode dominates from midnight to early morning, after which an elevated Aitken mode appears, denoting to local morning activities. New particle formation begins regularly around 10 am, elevating first the nucleation mode concentrations and then the Aitken mode. During evening hours, the nucleation-and Aitken mode concentrations decrease, and the accumulation mode becomes dominant again. The average particle number concentration from December 2012 was 1640 ♯/cm3. The maximum particle concentration in the region is originated from new particle formation, with a maximum 1h-average of 11400 ♯/cm3.

The Particle Size Magnifier lowers the cut-off size of a Condensation Particle Counter even down to about 1 nm in mobility diameter. By scanning the supersaturation also size information of the particles can be gained. We demonstrated that the PSM can detect particles starting from molecular sizes. By combining the data with newly developed mass spectrometric methods particle formation and growth can be followed molecule by molecule.

An MALTE-BOX model is used to study the effects of oxidation of SO2 and BVOCs to new particle formation from Julich Plant Atmosphere Chamber and CERN CLOUD chamber measurements. Several days of continuously measurements were chosen for the simulation. Our preliminary results show that H2SO4 is one of the critical compounds in nucleation process. Nucleation involving the oxidation of BVOCs shows better agreements with measurements.

The mechanisms behind the nucleation of vapors forming new particles in the atmosphere had been proven difficult to establish. One main aim of the CLOUD experiment was to explore in detail these first steps of atmospheric new particle formation by performing extremely well controlled laboratory experiments. We examined nucleation and growth in the presence of different mixtures of vapors, including sulfuric acid, ammonia, dimethylamine, and oxidation products of pinanediol or α-pinene. Among the employed state-of-the-art instrumentation, a high-resolution mass spectrometer that directly sampled negatively charged ions and clusters proved particularly useful. We were able to resolve most of the chemical compositions found for charged sub-2nm clusters and to observe their growth in time. These compositions reflected the mixture of condensable vapors in the chamber and the role of each individual vapor in forming sub-2nm clusters could be explored. By inter-comparing between individual experiments and ambient observations, we try to establish which vapors participate in nucleation in the actual atmosphere, and how.

A global climate model is being run to study the consequences of Brazil transitioning from fossil to biofuels over the next few decades. Assuming all other factors constant, preliminary results suggest little to no climatic relevance.

Sulfur emissions from the Kola Peninsula smelter industry have been decreasing over the past two decades. We investigated the effect of this to new particle formation at SMEAR I station in Eastern Lapland, Finland, using long-term measurements of trace gases and aerosol size distributions. We show that the number of events per year has decreased and can be linked with the decreasing sulfur emissions from Kola.

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 distinguishable effect of atmospheric new particle formation (NPF) on Dc and κ was observed. Ambient aerosol was found to be internally mixed in the summer, and externally mixed during the rest of the year.

We studied the chemical composition of commonly used condensation particle counter calibration ions with a mass spectrometer and found that in our calibration setup the negatively charged ammonium sulphate, sodium chloride and tungsten oxide are the least contaminated whereas silver on both positive and negative and the three mentioned earlier in positive mode are contaminated with organics. We report cut-off diameters for Airmodus Particle Size Magnifier (PSM) 1.1, 1.3, 1.4, 1.6 and 1.6-1.8 nm for negative sodium chloride, ammonium sulphate, tungsten oxide, silver and positive organics, respectively. To study the effect of sample relative humidity on detection efficiency of the PSM we used different humidities in the differential mobility analyzer sheath flow and found that with increasing relative humidity also the detection efficiency of the PSM increases.

Long-term atmospheric dataset including aerosol field measurement and back trajectories was used to investigate the impact of temperature to the production of secondary organic aerosols from biogenic monoterpene emissions among boreal forest area. Temperature was equally divided into five bins ranging from 0 to 20 °C in this study, and all parameters were classified into the corresponding temperature bins. Own results suggest that increase in temperature causing an increase in MT emission will not necessarily result in the increase of secondary organic aerosol production. Therefore, to predict the aerosol production potential in the future with rising temperature, a simple extrapolation cannot be applied between the total aerosol production and temperature. In addition, the climatic feedback due to the increase in aerosol production to buffer the warming over boreal forest area may be less significant as previously expected.

In this work we present a study that aims to understand the new particle formation events and their underlying mechanism. Measurements were conducted during January-February 2013 at the Swiss high alpine research station Jungfraujoch which is predominantly located in the lower free troposphere. With the atmospheric pressure interface Time-of-Flight mass spectrometer (APi-TOF) the chemical composition of the ions (positive and negative) was measured during the nucleation process. It was observed that nucleation is correlated with a rise in the sulphuric acid concentration.

The role of ion-ion recombination in new particle formation is still unclear. In this work, we present a new method to estimate the size distribution of recombination products from atmospheric measurements. By applying our method to size distributions of charged and neutral clusters measured in Hyytiala, Finland, we show that only a minor fraction of all sub-2nm neutral clusters originate from ion-ion recombination in boreal forest conditions.

Freshly formed atmospheric nanoparticles have been observed to contain also such organic compounds which have too high saturation vapor pressure to condense on nanoparticles reversibly. The condensation of these compounds on the particles may be facilitated by particle phase processes that transform the compounds into less-volatile form. Here we use particle growth model MABNAG to study the effect of particle phase acid-base chemistry on the condensation of organic acids and bases.

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 resolution mass spectrometer was used in the setup as well.

Firstly, atmospheric ions play an important role in the fair weather electricity in Earth’s atmosphere. Small ions, or charged molecular clusters, carry electric currents in the atmosphere. These small ions are continuously present, and their lifetime in lower atmosphere is about one minute. It’s essential to find out a connection between the production rate of cluster ions, ion-ion recombination, and ion-aerosol attachment, and their ambient concentrations, in order to understand electrical properties of air. Secondly, atmospheric ions are important for Earth’s climate, due to their potential role in secondary aerosol formation, which can lead to increased number of cloud condensation nuclei (CCN), which in turn can change the cloud properties. Our aim is to quantify the connections between these two important roles of air ions based on field observations.

Atmospheric new particle formation is the dominant source of aerosol particles in the global atmosphere and an important player in aerosol climatic effects. The key steps of this process occur in the sub-2 nm size range. We have recently shown that at a lower-troposphere site (Hyytiala, Southern Finland) with abundant biogenic emissions and moderate anthropogenic influence, based on comprehensive observations of atmospheric clusters in the size range of 1-2 nm mobility diameter, there are significant differences between neutral and charged cluster properties. The differences are with respect to cluster size and chemical composition, and whether the observations were made in background conditions or during periods of active aerosol formation. According to our results, sub-2 nm clusters were always present and cluster concentrations were dominated by neutral ones in all sizes and almost all the time, indicating that cluster formation and their subsequent growth i.e. atmospheric aerosol formation were dominated by neutral pathways.

A comprehensive suite of chemical ionization mass spectrometers (CIMS) were deployed for chamber studies of monoterpene oxidation. The CIMS instruments were able to detect several different groups of compounds ranging from volatile to practically non-volatile. The compound groups showed very different behavior and correlations with aerosol number and mass. Results suggest that major gas phase contributors are not considered in current models.

The role of oxidized organic compounds in the process of new particle formation in the atmosphere is poorly known. Here we used the ultraclean and most sophisticated CLOUD chamber to investigate systematically particle formation in the presence of sulfuric acid and oxidized organics. We varied independently the concentrations of both of these components. In addition, nucleation was observed without and in the presence of ionic compounds. From the results a new parameterized description of nucleation was derived for global climate model simulations.

We have analyzed 184 formation events of new atmospheric aerosol particles, observed at a boreal forest site in Hyytiala, Southern Finland. Recognition, selection and classification of the formation events is based on continuous experimental size distribution data of submicron particles from a period of Jan 31st 1996–Sept 18th 1999 (1327 days). The apparent particle formation rates vary in the range of 0.001-1 particles/(cm3 s). The ultrafine particle growth rates vary in the range of 1–17 nm/h.

The effect of elevated nitric acid concentrations on mixed phase cirrus cloud (containing both supercooled liquid and frozen ice particles) cloud particle size and number concentration changes are studied using a detailed multicomponent condensation model. Our model calculations suggest that high nitric acid volume mixing ratios, which are measured in the upper troposphere, can decrease the geometric mean radius of activated cirrus cloud particle distributions and increase the activated cloud particle number concentrations. These changes can also have effects on cirrus cloud optical properties, such as cloud shortwave albedo.

Heterogeneous nucleation of binary n-propanol - water vapor mixtures on non-soluble or partially soluble 8nm Ag and NaCl particles has been investigated experimentally. At constant temperature the vapor activities have been stepwise increased and the number of particles activated to condensational growth shows a comparatively steep increase until all particles have been activated. Onset activities were obtained for various mixing ratios of the binary vapor mixtures. In contrast to homogeneous nucleation, for binary heterogeneous nucleation only a conucleation without significant mutual enhancement was observed. Heterogeneous nucleation calculations based on Fletcher theory using experimentally obtained contact angles have been performed. Satisfactory agreement of the slopes of the nucleation probability curves was observed. However, considerable deviations between experimental and theoretical onset activities indicate problems of the binary nucleation theory based on the capillarity approximation. For NaC...

The characteristic time scales of the condensation, coagulation and recombination during ion-induced nucleation have been investigated. The classical theory for ion-induced nucleation of water and sulfuric acid has been used in these calculations. The effect of the Coulomb potential on coagulation and condensation has also been taken into account. The results show that in certain conditions, with low preexisting particle concentrations and high atmospheric temperatures, the new particles can grow to the sizes they are stable even without electric charge. This system is however very sensitive to changes in preexisting aerosol particle concentration and temperature.

Formation and growth of aerosol particles during two international field campaigns have been analyzed. Aerosol particle size distributions measured using DMPS data are used together with five simple equations to obtain concentrations of condensable vapor, 3 nm and 1 nm size particles as well as to obtain source rate of condensable vapor. For this analysis the measured growth rates, condensational and coagulational sinks are needed.

An analytical formula, where the uptake coefficient is given as a function of mass accommodation coefficient, has been derived. The uptake coefficient is seen always to be smaller than or equal to the mass accommodation coefficient. The independence of the uptake coefficient on mass accommodation coefficient for small Knudsen number has been shown. If the boundary conditions, particularly the vapor pressure at the droplet surface are not well defined a significant error in the value of the mass accommodation coefficient can be found. The value obtained in not well defined conditions is typically smaller than the real value.

The importance of atmospheric aerosols to the global radiation balance, to cloud formation, and to alleged human health effects has motivated us to investigate the formation and growth of atmospheric aerosol particles. Formation of new atmospheric particles (diameter between 3 and 10 nm) has been observed in a wide variety of low and high altitude locations. These aerosol particles are a source of Aitken mode nuclei and, after growing, one of the major sources of atmospheric cloud condensation nuclei (CCN) thus affecting cloud formation and global radiation balance. While some studies show that the measured new particle formation rates could be explained by binary sulphuric acid - water nucleation, others, particularly those in the marine boundary layer, or over the continental sites, indicate that observed ambient nucleation rates exceed those predicted by the binary scheme. The observed ambient H2SO4 concentrations are much less than needed for binary nucleation but appropriate for ternary nucleation (w...

A classical theory of the ternary homogeneous nucleation of sulfuric acid—ammonia—water is presented. For NH3 mixing ratios exceeding 1 ppt, the presence of ammonia enhances the binary (sulfuric acid—water) nucleation rate by several orders of magnitude. However, the limiting component for ternary nucleation—as for binary nucleation—is sulfuric acid. The sulfuric acid concentration needed for significant ternary nucleation is several orders of magnitude below that required in binary case.

As a contribution to the Joint Experiment on Homogenous Nucleation, a version of a laminar flow diffusion chamber was developed for nucleation rate measurements. The design and operational characteristics of the chamber will be presented. Homogenous nucleation rates of n-pentanol were measured as a function of saturation ratio in the temperature range between 260 K and 290 K. The results were compared to the classical nucleation theory. The experimental results were three orders of magnitudes higher than the theoretical predictions. The difference was almost constant over the whole temperature range. The results were compared with results from other experimental devices, they were in good agreement at lower temperatures.