Experimental studies on new particle formation and ions

Atmospheric aerosol particles have significant climatic effects. Secondary new particle formation is a globally important source of these particles. Currently, the mechanisms of particle formation and the vapours participating in this process are, however, not truly understood. The recently developed Neutral cluster and Air Ion Spectrometer (NAIS) was widely used in field studies of atmospheric particle formation. The NAIS was calibrated and found to be in adequate agreement with the reference instruments. It was concluded that NAIS can be reliably used to measure ions and particles near the sizes where the atmospheric particle formation begins. The main focus of this thesis was to study new particle formation and participation of ions in this process. To attain this objective, particle and ion formation and growth rates were studied in various environments - at several field sites in Europe, in previously rarely studied sites in Antarctica and Siberia and also in an indoor environment. New particle formation was observed at all sites were studied and the observations were used as indicatives of the particle formation mechanisms. Particle size-dependent growth rates and nucleation mode hygroscopic growth factors were examined to obtain information on the particle growth. It was found that the atmospheric ions participate in the initial steps of new particle formation, although their contribution was minor in the boundary layer. The highest atmospheric particle formation rates were observed at the most polluted sites where the role of ions was the least pronounced. Furthermore, the increase of particle growth rate with size suggested that enhancement of the growth by ions was negligible. Participation of organic vapours in the particle growth was supported by laboratory and field observations. It was addressed that secondary new particle formation can also be a significant source of indoor air particles. These results, extending over a wide variety of environments, give support to previous observations and increase understanding on new particle formation on a global scale.Hengittämämme ilma on esimerkki aerosolista. Ilmassa leijuvia pieniä, halkaisijaltaan nanometreistä mikrometreihin olevia hiukkasia kutsutaan aerosolihiukkasiksi. Hiukkasten pitoisuus, koostumus ja koko vaihtelevat ympäristöittäin. Aerosolihiukkaset vaikuttavat globaaliin ilmastoon viilentävästi; ne sirottavat auringon säteilyä takaisin avaruuteen ja toimivat pilvipisaroiden tiivistymisytiminä, vaikuttaen siten pilvien heijastavuuteen ja elinikään. Aerosolihiukkasten lähteitä ovat esimerkiksi aavikon pöly, merien pärskeet, kasvillisuus ja teollisuus. Hiukkasia syntyy myös sekundäärisesti ilmakehässä olevista kaasuista, kaasumolekyylien muodostaessa ryppäitä ja kasvaessa yhä useampien molekyylien tiivistyessä ryppäiden pinnalle. Aiemmat tutkimukset ovat osoittaneet, että tätä sekundääristä hiukkasmuodostusta tapahtuu laajalti ympäri maapalloa ja hyvinkin erilaisissa olosuhteissa. Koska sekundäärisesti muodostuneet hiukkaset ovat pieniä, vain muutaman molekyylin kokoisia, on niiden tutkiminen erityisen haastavaa. Hiukkasmuodostuksen täsmälliset mekanismit, sekä merkittävimmät hiukkasia muodostavat ja kasvattavat kaasut ovat yhä osin epäselviä. On esitetty, että ilmakehässä jatkuvasti läsnä olevat pienet varautuneet hiukkaset, ionit, voisivat olla merkittävä osatekijä hiukkasmuodostuksessa. Väitöskirjassani tutkin sekundääristen, kaasu-hiukkasmuuntuman kautta ilmakehään syntyvien, hiukkasten syntymekanismeja sekä varautuneiden hiukkasten, ionien, vaikutusta hiukkasten muodostumiseen. Mittauksia tehtiin Etelämantereella, Trans-Siperian junamatkalla Venäjällä, 12 paikassa Euroopassa sekä myös sisäilmassa. Kaikissa mittauspaikoissa havaittiin sekundääristä hiukkasmuodostusta. Mittausten perusteella laskettiin mm. hiukkasten muodostumis- ja kasvunopeuksia ja tuloksia hyödynnettiin hiukkasten syntymekanismien ja kasvun tutkimisessa. Johtopäätöksenä todettiin, että ionit voivat osallistua hiukkasmuodostuksen alkuvaiheisiin, joskin ionien merkitys prosessille on alailmakehässä pienehkö. Tulokset myös osaltaan tukevat aiempia tutkimuksia orgaanisten höyryjen osallistumisesta hiukkasten kasvuun. Uutta tietoa saatiin myös hiukkasten ja ionien ominaisuuksista ennestään vähemmän tutkituilla alueilla Etelämantereella ja Siperiassa. Väitöskirjatutkimuksen tulokset auttavat ymmärtämään hiukkasmuodostusta globaalina ilmiönä ja toimivat tärkeänä vertailutietona ilmastomalleille

On measurements of aerosol particles and greenhouse gases in Siberia and future research needs

The role of the world's boreal forest for our understanding of the climate system is indisputable. Due to the large area covered, the forest's biophysical (e.g. surface energy balance, albedo) and biogeochemical (e.g. bidirectional exchange of greenhouse gases or aerosol precursors) processes are known to affect today's climate, and will need to be accounted for in studies of climate feedbacks in response to anthropogenic warming. However, observations that are needed to develop and evaluate terrestrial and climate models are still relatively scarce, especially for the Siberian part of the boreal forest. Here, we present a short overview of aerosol and greenhouse gas measurements over Siberia, aiming to also survey a large fraction of the existing literature in Russian. We aim to highlight areas of least data coverage and argue that, due to the importance of Siberia in the global climate system, a coordinated research program is needed to address some of the open research questions: The Pan Siberian Experiment

The four-wavelength Photoacoustic Aerosol Absorption Spectrometer (PAAS-4 λ )

In this paper, the Photoacoustic Aerosol Absorption Spectrometer (PAAS-4λ) is introduced. PAAS-4λ was specifically developed for long-term monitoring tasks in (unattended) air quality stations. It uses four wavelengths coupled to a single acoustic resonator in a compact and robust set-up. The instrument has been thoroughly characterized and carefully calibrated in the laboratory using NO$_2$/air mixtures and Nigrosin aerosol. It has an ultimate 1σ detection limit below 0.1 Mm$^{−1}$, at a measurement precision and accuracy of 3 % and 10 %, respectively. In order to demonstrate the PAAS-4λ suitability for long-term monitoring tasks, the instrument is currently validated at the air quality monitoring station Pallas in Finland, about 140 km north of the Arctic circle. A total of 11 months of PAAS-4λ data from this deployment are presented and discussed in terms of instrument performance. Intercomparisons with the filter-based photometers of a continuous soot monitoring system (COSMOS), the Multi-Angle Absorption Photometer (MAAP), and Aethalometer (AE33) demonstrate the capabilities and value of PAAS-4λ, as well as for the validation of the widely used filter-based instruments

Direct radiative feedback due to biogenic secondary organic aerosol estimated from boreal forest site observations

We used more than five years of continuous aerosol measurements to estimate the direct radiative feedback parameter associated with the formation of biogenic secondary organic aerosol (BSOA) at a remote continental site at the edge of the boreal forest zone in Northern Finland. Our upper-limit estimate for this feedback parameter during the summer period (ambient temperatures above 10 degrees C) was -97 +/- 66 mWm(-2) K-1 (mean +/- STD) when using measurements of the aerosol optical depth (f(AOD)) and -63 +/- 40 mWm(-2) K-1 when using measurements of the 'dry' aerosol scattering coefficient at the ground level (f(sigma)). Here STD represents the variability in f caused by the observed variability in the quantities used to derive the value of f. Compared with our measurement site, the magnitude of the direct radiative feedback associated with BSOA is expected to be larger in warmer continental regions with more abundant biogenic emissions, and even larger in regions where biogenic emissions are mixed with anthropogenic pollution.Peer reviewe

Applicability of condensation particle counters to measure atmospheric clusters

This study presents an evaluation of a pulse height condensation particle counter (PH-CPC) and an expansion condensation particle counter (E-CPC) in terms of measuring ambient and laboratory-generated molecular and ion clusters. Ambient molecular cluster concentrations were measured with both instruments as they were deployed in conjunction with an ion spectrometer and other aerosol instruments in Hyytiälä, Finland at the SMEAR II station between 1 March and 30 June 2007. The observed cluster concentrations varied and ranged from some thousands to 100 000 cm -3. Both instruments showed similar (within a factor of ~5) concentrations. An average size of the detected clusters was approximately 1.8 nm. As the atmospheric measurement of sub 2-nm particles and molecular clusters is a challenging task, we conclude that most likely we were unable to detect the smallest clusters. Nevertheless, the reported concentrations are the best estimates to date for minimum cluster concentrations in a boreal forest environment

Cloud condensation nuclei production associated with atmospheric nucleation : a synthesis based on existing literature and new results

This paper synthesizes the available scientific information connecting atmospheric nucleation with subsequent cloud condensation nuclei (CCN) formation. We review both observations and model studies related to this topic, and discuss the potential climatic implications. We conclude that CCN production associated with atmospheric nucleation is both frequent and widespread phenomenon in many types of continental boundary layers, and probably also over a large fraction of the free troposphere. The contribution of nucleation to the global CCN budget spans a relatively large uncertainty range, which, together with our poor understanding of aerosol-cloud interactions, results in major uncertainties in the radiative forcing by atmospheric aerosols. In order to better quantify the role of atmospheric nucleation in CCN formation and Earth System behavior, more information is needed on (i) the factors controlling atmospheric CCN production and (ii) the properties of both primary and secondary CCN and their interconnections. In future investigations, more emphasis should be put on combining field measurements with regional and large-scale model studies.Peer reviewe

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

Observations from the NILU-UV Antarctic network since 2000

Póster elaborado para la SCAR Open Science Conference celebrada en Auckland, Nueva Zelanda los días 25-28 de agosto de 2014Total ozone and UV measurements have been performed with the NILU-UV radiometer at the station of Ushuaia (54◦S), Marambio (64◦S) and Belgrano II (77◦S) since 2000. The network was established in 1999/2000 by the Spanish Agencia Estatal de Meteorología (AEMET) in collaboration with the innishMeteorological Institute (FMI), the Argentinian Dirección Nacional del Antártico-Instituto Antártico (DNA-IAA) and Centro Austral de Investigaciones Cientificas (CADIC). The location of the network was chosen in order to monitor total ozone and UV radiation at different sides of the polar vortex: Belgrano II is mostly located inside the vortex, Marambio at various times inside, on the edge of, or outside the vortex, while Ushuaia is mostly outside the vortex.The MAR Project was financed by the National R+D Plan of the Spanish Ministry of Science and Technology (National Research Program in the Antarctic) under contract REN2000-0245-C02-01

Coupling an aerosol box model with one-dimensional flow : a tool for understanding observations of new particle formation events

Field observations of new particle formation and the subsequent particle growth are typically only possible at a fixed measurement location, and hence do not follow the temporal evolution of an air parcel in a Lagrangian sense. Standard analysis for determining formation and growth rates requires that the time-dependent formation rate and growth rate of the particles are spatially invariant; air parcel advection means that the observed temporal evolution of the particle size distribution at a fixed measurement location may not represent the true evolution if there are spatial variations in the formation and growth rates. Here we present a zero-dimensional aerosol box model coupled with one-dimensional atmospheric flow to describe the impact of advection on the evolution of simulated new particle formation events. Wind speed, particle formation rates and growth rates are input parameters that can vary as a function of time and location, using wind speed to connect location to time. The output simulates measurements at a fixed location; formation and growth rates of the particle mode can then be calculated from the simulated observations at a stationary point for different scenarios and be compared with the 'true' input parameters. Hence, we can investigate how spatial variations in the formation and growth rates of new particles would appear in observations of particle number size distributions at a fixed measurement site. We show that the particle size distribution and growth rate at a fixed location is dependent on the formation and growth parameters upwind, even if local conditions do not vary. We also show that different input parameters used may result in very similar simulated measurements. Erroneous interpretation of observations in terms of particle formation and growth rates, and the time span and areal extent of new particle formation, is possible if the spatial effects are not accounted for.Peer reviewe