BACCI

Work Packages

WP1 WP2 WP3 WP4 WP5 WP6 WP7 WP8 WP9 WP10

Work Packages

WP 1. Fluxes of biogenic precursor compounds

Professors and senior researchers involved: Hari, Kulmala, Larsen, Janson, Barthelmie and Pryor

Organic compounds make up a significant or sometimes dominating fraction of atmospheric aerosols. They have both primary and secondary sources. The secondary organic aerosol (SOA) is formed when low volatility products are formed by the atmospheric oxidation of volatile organic compounds (VOC). VOCs are emitted into the troposphere from anthropogenic and biogenic sources. We have studied Nordic emissions of biogenic organic compounds for many years using both chamber and micrometeorological techniques (Janson 1993; Janson and de Serves, 2001; Janson et al., 2001; Hakola et al., 1998; Rinne et al., 2000a;b). We have shown that most of the VOCs in Finland and Sweden are emitted from vegetation (Simpson et al., 1999; Lindfors et al., 2000) and that the biogenic sources are very important. A multinational study on the Biogenic VOC Emissions and Photochemistry in the Boreal Regions of Europe (BIPHOREP) was coordinated by the FMI research group in 1995-1997 (Laurila et al., 1999) and another international study on the relation between BVOC and new particle formation in the boreal forest (BIOFOR) was coordinated by the University of Helsinki in 1998-2000 (Kulmala et al., 2001). Results of previous work (see references above) have shown that the most likely biogenic precursor hydrocarbons for secondary organic aerosol (SOA) in the Nordic countries are the monoterpenes (C10H16), emitted by both pine and spruce as well as by some deciduous species. Air temperature is the best known and most studied driving force for emissions and temperature dependent emission potentials have been derived for the main Nordic species. We will study the source strengths of VOC from a physico-biological point of view, their atmospheric chemistry and the influence on aerosol formation. Leaf level cuvette measurements will yield information on the differences in emission patterns from pine, spruce, and birch canopies within the source area of the micrometeorological measurements. These very local scale variations are expected to have an effect on the photochemical processes and aerosol formation in the forest environment. An interesting link and potentially important feedback between the forest ecosystem, greenhouse gases, and climate is through increased forest growth due to increasing temperatures and CO2 fertilization. An increase in Nordic forest biomass would increase BVOC emissions and thereby even SOA production. This couples the climate effect of CO2 with that of aerosols in a novel way. Besides VOCs, emission/deposition rates of NOx and O3 will be measured because of their importance to atmospheric chemistry.

Hence there is also a need for numerical schemes to describe the chemistry and production of condensable matter from organic compounds. Detailed numerical mechanisms of the chemistry and partitioning of monoterpenes have been presented by (Barthelmie and Pryor, 1999, 2002), based on experimental results (mainly from smog chambers) and known alkene chemistry. Since the models provide specific product information, the results can be compared with field studies and used to identify candidate tracer compounds of monoterpene oxidation to assist the design of experimental studies. Research is underway to develop similar mechanisms for a range of other organics focusing on anthropogenic emissions from the transport sector.

Tasks during 2002-2005

Continuous chamber measurements at SMEAR stations and Riso to obtain NOx and O3 exchange.
Measurements of local scale variations of biogenic VOCs (including condensable oxygenated compounds) in deciduous and coniferous canopies
Campaign-wise gas phase and aerosol phase VOC measurements
Modelling of plant gas exchange and plant physiological processes
The connection between plant physiology and biogenic VOC emissions
Reporting the results in scientific Journals and scientific Conferences

WP 2. Aerosol source emission and deposition fluxes

Professors and senior researchers involved: Larsen, Barthelmie, DeLeeuw, Hansson, Hari, Kulmala, Nielsen, Nilsson, Noone, O�Dowd, Pryor, Rannik, Ström, Swietlicki, Viisanen,

The usage of the eddy covariance (EC) technique for sub micrometer aerosol particles has become a very useful technique in recent years (e.g. Buzorius et al, 1998; Nilsson and Rannik, 2001; Nilsson et al., 2001; Nemitz et al., 2000a,b). When used to study deposition fluxes, the EC technique can reveal the deposition velocity and turnover time of aerosol particles, for example over the Boreal forest (Buzorius et al., 1998), Arctic Ocean (Nilsson and Rannik, 2001), Antarctica (Grönlund et al., 2002), and moorland vegetation (Nemitz et al., 2002). Rates of particle removal from the atmosphere are a key determinant of particle burden, transport and effects (Asman et al, 1996). However, there is a significant discrepancy between the numerical models of particle dry deposition and observed particle fluxes, especially for extremely rough and porous surfaces such as forests and cities, where there is a factor of ten discrepancy (Pryor, 2002).
The EC technique will reveal the actual source emission strength e.g. the primary source of aerosol particles from the ocean. Small droplets are ejected into the atmosphere when bubbles burst at the sea surface in white caps. This source plays an important role for the sea-air exchange of water, sea salt, organic compounds, and pollutants being potentially important for the climate. The sea salt aerosol has a large influence on the atmospheric sulfur cycle and influences the climate effects of the anthropogenic sulfate aerosol (O'Dowd et al, 1999c). In addition, sea salt is an important tracer in the climate record of Arctic and Antarctic snow and ice cores. The primary marine aerosol also has an organic component. A recent hypothesis even suggests that life originated in primary marine aerosol particles rich on organic compounds rather than in the ocean itself (Dobson et al., 2000). However, the existing estimates and parameterizations of the primary marine aerosol source span a range of 6-10 orders of magnitude (Andreas, 1998). The sub-micrometer part of this aerosol source has almost been entirely neglected, and very little is known about the relative contribution, size and composition of the organic component. The uncertainties of the effect on gas exchange are on the order of 3-7 (Larsen et al., 1995, 2000, Pryor and Barthelmie, 2000).
In 1996 we managed to make the first successful direct measurements of the primary marine aerosol source flux from the Ocean while operating an EC system over the Norwegian Sea, Barents Sea and Arctic Ocean (Nilsson et al, 2001). These experiments have resulted in a size resolved parameterization of the aerosol number flux (Mårtensson et al., 2002). We will also reanalyse data applying improved analysis techniques and models for the motion of particles in the small-scale turbulence flow (DeLeeuw et al, 2000). The spray production will also influence the many types trace gases and particles in the marine air both through heterogeneous chemistry or simple dissolution or skin layer disruption, and thus will also influence the surface exchange rates for these substances (DeLeeuw et al, 2002, Jacobs et al, 2002). However, these effects are so far not included in neither air-pollution nor climate models.
Three relaxed eddy accumulation (REA) systems (e.g. Baker, 2000; Pryor et al., 2002) will be developed by different partners. One is for the SMEAR II station to study aerosol fluxes over the Boreal forest. CO2, momentum, heat and aerosol fluxes are measured simultaneously by the EC system in SMEAR II (e.g. Rannik, 1998; Markkanen et al., 2001) in conjunction with the REA data to gain understanding on the emissions and the chemical and physical processes at the landscape level. The measurements of CO2 and VOC emissions at SMEAR II and in Pallas link this part of WP2 tightly to WP1. A second REA system will be developed at RISOE aimed at determining particle fluxes over a spectral and composition range in order to validate the models developed for gas and particle deposition, for both marine and extremely rough conditions for use in numerical models (Pryor et al., 1999; Pryor and Sørensen, 2000). The third REA system will be developed at MISU to be deployed over the sea with the goal to separate the sea salt and organic fractions, and to characterize the organic compounds found in different size ranges. This REA system will also be used to study aerosol emissions in the urban environment, see WP 7.

Tasks during 2002-2005

Continuous EC measurements of aerosol fluxes and other fluxes at SMEAR II.
Development of three REA systems for aerosol flux measurements over the Boreal forest and Ocean, for gas and particle deposition, and for primary aerosol emissions
Collection and analysis of data for a database of in situ aerosol flux measurements at sea (Barents sea, Norwegian sea, Arctic Ocean, Pacific Ocean, North Atlantic Ocean)
Laboratory experiments on aerosol formation from simulated bubble bursting, the size resolved number and mass flux with chemical composition, the effects of organic films etc.
Improve the size resolved source parameterization so that it separates sea salt and organic compounds. Improved parameterisation on the role of marine spray production for deposition and gas fluxes. Application of the new and improved parameterizations in process models as well as regional and global models.
Reporting the results in scientific Journals and scientific Conferences

WP 3. Atmospheric aerosol precursor chemistry

Professors and senior researchers involved: Janson, Viisanen, Kulmala, Paatero, Hakola, Pryor, Barthelmie

The formation and growth of atmospheric aerosols are closely related to atmospheric chemistry. Emissions of organic and inorganic gases and their gas phase reactions with hydroxyl and nitrate radicals as well as with ozone result in part in the formation of condensable vapours. For example, inorganic sulphur dioxide is oxidised in the atmosphere to form sulphuric acid and sulphate aerosols. Highly reactive monoterpenes (WP1), which are emitted by boreal vegetation, are the source of biogenic organic aerosols. The hydroxyl radical (OH) is the most important daytime atmospheric oxidant, and its concentration is dependent on the photolysis of tropospheric ozone and on water vapour concentration. Locally, the budget of tropospheric ozone is determined by long-range transport and reactions involving nitrogen oxides (NOx=NO+NO2) and volatile organic compounds (VOC) under sunlight. Nighttime chemistry is dependent on ozone and the nitrate radical, which in turn is created by the reaction between ozone and NO2. Atmospheric precursor chemistry and SOA formation is thus driven by precursor emissions and concentrations as well as concentrations of other key photochemical species (CO, VOC, NOx, O3) and photolytically active sunlight/photolysis frequencies. Measurements of all the key photochemical species are a prerequisite for evaluation of SOA from volatile organic compounds. According to measurements, UV irradiance and the actinic flux are very sensitive to local factors, such as cloudiness, aerosol and pollutant (e.g. ozone) concentrations, and albedo (e.g. Seckmeyer et al., 1997; Los et al., 1997). Recently, Dickerson et al. (1997) have reported that UV-scattering aerosols such as sulphate particles reduce the available UV radiation near the surface, but increase it substantially a few hundred meters above. Thus, in the boundary layer, they enhance the photolysis frequency of e.g. NO2. Air mass classification, using e.g. natural radio nuclides (Paatero and Hatakka, 2000), is therefore important, and it will be applied also for the aerosol formation studies.

Heterogeneous chemistry is increasingly acknowledged as a key determinant of particle and gas concentrations (Pryor et al., 2001). However, although phase change has been demonstrated to be of critical importance to particle behavior and removal of trace chemicals from the atmosphere, heterogeneous chemical processes are largely excluded from current atmosphere-chemical transport models. Parameterization of heterogeneous chemistry in a process level Lagrangian model has been commenced resulting in the CHEM-COAST model (Pryor et al., 2001) and will be extended to include non-salt reactions.

Tasks during 2002-2005

Continuous UV and concentration profile measurements of SO2, O3, NOx
Campaign-wise VOC measurements
Development of atmospheric chemistry models
The parameterisations into a Lagrangian transport-chemistry model (CHEM- COAST).
Air mass classification according to radio nuclides
Reporting the results in scientific Journals and scientific Conferences

WP 4. Chemistry and Thermodynamics of organic aerosols

Professors and senior researchers involved: Hov, Kahnert, Riekkola, Martinsson, Swietlicki, Laaksonen, Kulmala, Viisanen, Bilde, Hillamo, Kerminen, Hansson, Kiss

Aerosol formation, transformation and fate in the lower troposphere include several physical and chemical processes. Our knowledge of aerosol chemistry has still many gaps because of limitations in the analytical techniques and of numerous chemical compounds involved. The most developed is the sampling and analytical techniques of the inorganic fraction in the major aerosol mass modes (Aitken, accumulation and coarse modes) (Teinilä et al., 2000; Hillamo et al., 2001; Kerminen et al., 2001). There has also been progress in developing analytical methods for quantifying the amount and composition of carbonaceous material in atmospheric aerosol particles (Faccini et al., 1999, Kiss et al., 2001, Kriv�csy et al., 2000, Kerminen et al., 1999; Viidanoja et al., 2000a,b). The nucleation mode can currently be detected using physical methods, but its chemical composition is not well-known (Mäkelä et al., 2001). Although there are some studies on nucleation mode composition, for better understanding of atmospheric aerosol processes there is an urgent need for methods that can reveal the chemical compounds that this mode consists of. The data on organic fraction of the major modes is still scarce as the speciation or solubility is concerned. The chemical characterisation of the aerosol can also be obtained by particle-induced X-ray emission (PIXE) (Martinsson et al., 2001a; Papaspiropoulos et al. 2002). Acidic particulate matter has been a major focus of the EMEP program since it was started to study the long-range transport of pollutants within Europe. Perhaps the largest challenges within the field of chemical characterization of atmospheric aerosols now concern carbonaceous compounds (Molnar et al., 1999, Jacobson et al., 2000). Within the NCoE we will thus develop and optimise analytical methods for the quantitative determination of organic tracers and relevant particulate matter in atmospheric samples.
The carbonaceous aerosols can be grouped according to their solubility in water and solvents, to provide a broad characteristic of their physical behaviour. Based on solubility, particulate matter can be defined as water-soluble organic carbon fraction (WSOC) and water insoluble organic carbon fraction (WINSOC) (Zappoli et al., 1999). The WINSOC fraction can be further separated into SEPOC = Solvent extractable polar organic compounds; SENOC = Solvent extractable non-polar organic compounds and NEC = non extractable organic compounds. The SENOC fraction contains mainly non-polar substances like PAH and alkenes. The SEPOC fraction contains polar chemicals like carbonylic acids and carboxylic compounds as well as alcohols.

The organic analytical analysis of the different groups as described above will be pursued using a set of very advanced analytical techniques as combination of supercritical fluid extraction and on-line coupled liquid chromatography- gas chromatography (SFE-LC-GC) with mass spectrometry (Shimmo et al., 2001 and 2002), Comprehensive two-dimensional GC (GCxGC) is a new multidimensional technique, which allows extremely high separation power. [Hyötyläinen et al., 2002 and Lewis et al., 2000] and LC-MS-MS (Kiss et al., 2001).

The most challenging task is to measure organic compounds in air and aerosol particles in real time (in-situ). A new portable gas-aerosol time of flight mass spectrometer will be constructed in the laboratory to meet this task. [Jayne et al., 2000 and Tobias et al., 2001] Organic composition will be measured as a function of particle size. The aim is to be able to measure particles smaller than 100 nm or even smaller than 30 nm.

In order to be able to understand the formation and growth processes of atmospheric aerosols and cloud droplets their thermodynamic properties should be known. In the atmosphere where there are multicomponent, multiphase mixtures, their thermodynamic state and phase diagrams are typically very complex. Crucially important thermodynamic measurements and modelling, to obtain thermodynamically consistent vapour pressures, chemical activities, surface tensions and densities for organic compounds and their water solutions (for the importance see e.g. Korhonen et al., 1999) as a function of temperature and composition, will be performed. The organic compounds will be selected based on 1) measurements of gas-phase organic compounds and 2) measurements of larger particle chemical compositions during observed nucleation events. The estimation of vapour pressures of pure organic compounds and their water solutions can be carried out using existing methods (Reid et al., 1987; Viisanen, 1991). The results will be compared with experimental thermodynamic data when available. Due to the lack of data for organic solutions, surface tension measurements with the ring method (Kr�ss KS10, Tension meter) will be performed. Another line of analysis is the focused on analysis of the hygroscopic growth depending on above measured properties using the TDMA technique.

Tasks during 2002-2005

Laboratory measurements of the hygroscopic and cloud-nucleating aerosol properties of selected WSOC that will be used as model compounds, representing different functional groups (neutral compounds, mono- and dicarboxylic acids, and polycarboxylic acids including humic-like substances)
Development of reliable collection methods of particulate matter, sampling of aerosol in several European background areas
SEM-EDX and TEM micro-chemical analysis of selected aerosol particles separated according to their hygroscopic and cloud-nucleating properties
OC/EC, WSOC/WISOC ratios
Chemical analysis of organic aerosols, Separation of organic fractions
Surface tension and density measurements of atmospherically relevant compounds
Vapour pressure and chemical activity measurements of atmospherically relevant compounds
Development of thermodynamic model for inorganic/organic solutions as a function of temperature and composition
Development of aerosol mass spectrometer
Reporting the results in scientific Journals and scientific Conferences

WP 5. Nucleation, Theories and Experiments

Professors and senior researchers involved: Laaksonen, Vehkamäki, Kulmala, Lushnikov, Viisanen, Zapadinsky, Lihavainen, Strey, Wagner

Development of nucleation theories, modelling, and nucleation rate parameterizations will be performed. So far, conclusions on whether or not certain substances cause nucleation in the atmosphere conditions are usually based on predictions given by the classical nucleation theory (CNT). CNT treats the nucleating molecular clusters as macroscopic droplets which is a questionable approach since the nucleating clusters often contain less than fifty molecules. Our aim is to investigate the nucleation of various vapors using molecular dynamics (MD) and Monte Carlo (MC) simulation techniques. We will start with sulfuric acid and water, and at the second stage add ammonia and various organic vapors to the nucleating system. We will also use the density functional theory of nucleation (DFT) to gain insight to the molecular level details of nucleation phenomena. So far, we have carried out ab initio calculations on small sulfuric acid-water clusters (Arstila et al 1998), classical MD (Laasonen et al, 2000) and MC (Vehkamäki and Ford, 1999) simulations of argon nucleation, as well as DFT calculations of nucleation in binary systems imitating water and different organic molecules (Laaksonen et al., 1995, Napari and Laaksonen 2000). The results will be compared with experimental data and with CNT predictions, and we aim toward an assessment of the importance of different nucleation mechanisms in the atmosphere. Also, a new nucleation mechanism based on stable dimers (Lushnikov and Kulmala, 1998) will be applied to atmospheric conditions. Based on the simulation results we will develop parametrisized analytic formulas describing the rate of nucleation in atmospheric conditions which can be applied in large-scale atmospheric models.

We have recently carried out experimental laboratory studies on homogeneous nucleation. Starting from pure water nucleation (Viisanen et al., 2000) through binary nucleation of water-sulphuric acid (Viisanen et al., 1997) to ternary nucleation of water - n-nonane - n-butanol (Viisanen and Strey, 1996). For Binary nucleation studies we developed a turbulent gas mixing chamber (TGMC) with new working principle (Viisanen et al., 1997). Experimental laboratory studies to obtain homogeneous nucleation rates for ternary nucleation of water-sulphuric acid-ammonia vapours in atmospheric conditions will be performed. We will start with relevant atmospheric concentrations like sulphuric acid concentration around 107 - 108 molecules per cc and ammonia concentration below 100 ppt. The measurements will be performed to obtain ternary nucleation rates as a function of temperature, relative acidity, relative humidity and relative basicity. For that purpose we will regulate the temperature of our mixing chamber (using Lauda thermostats) using same principle as in earlier water studies (Viisanen et al., 1993). These experiments are important for atmospheric simulations and for validation of basic nucleation theories.

Tasks during 2002-2005

MD simulations of sulphuric acid hydrates
MC simulations of ideal ternary clusters, of ternary clusters of water - sulphuric acid - ammonia, and MC simulations with multicomponent clusters
Development of DFT to different molecular level phenomena
Dimer/multimer channels for homogeneous nucleation
Ternary nucleation experiments of sulphuric acid - water - ammonia system
Nucleation experiments with organic vapours
Comparison with theories, Validity of nucleation theories
Experiments on heterogeneous nucleation
Parameterisation of homogeneous ternary nucleation of water - sulphuric acid -ammonia and ion induced nucleation
Reporting the results in scientific Journals and scientific Conferences

WP 6. Formation and growth of atmospheric aerosols

Professors and senior researchers involved: Kulmala, Laaksonen, Nilsson, O�Dowd, Joutsensaari, Lehtinen, Hansson, Ström, Swietlicki, Martinsson, Bilde

Experimental laboratory studies to obtain growth rates of organic vapours in atmospheric conditions will be performed. The measurements will be performed to obtain growth rates as a function of temperature, relative humidity and vapour concentration using laminar flow diffusion chamber (LFDC) (Hämeri et al., 1996, Lihavainen, 2000). Different systems will be investigated: A) homomolecular systems of organic acids. B) binary acid mixtures: such mixtures have been proposed as formation precursors in the literature and are therefore interesting to study. C) acid / water mixtures: these mixtures are the most likely to be present in the atmosphere and therefore particularly important to study. D) other mixtures: organic acids/ H2SO4 and/or NH3: these different species can be present simultaneously in the atmosphere and enhance condensation processes, as it is the case for the H2SO4 / H2O / NH3 systems.
Each studied system will be characterized on as wide a range as possible of the relevant parameters in order to have detailed information on the mechanisms (the growth rate, the hygroscopic properties and solubility to organic liquids). This direct approach should bring more accuracy to the measurements and will be based on direct characterizations of the dynamical properties in the chamber and on the monitoring of the precursors' gas-phase concentrations. The development of a reliable and accurate method to connect the LFDC and the monitoring technique will be part of the project. The growth of different systems will be investigated in order to obtain information both from a fundamental point of view and also on the occurrence of such mechanisms in the atmosphere.

In contrast to laboratory conditions, the formation of aerosol in the atmosphere can be kinetically limited by some of the intermediate steps of its formation processes. The equilibrium state is thus not necessarily the aerosol itself but can be, for example, thermodynamically stable clusters (TSC), as we have recently shown (Kulmala et al., 2000). Although there is strong indication that the water-sulphuric acid-ammonia nucleation mechanism (Korhonen et al., 1999) explains the formation of new atmospheric aerosols (diameter < 3 nm) in many circumstances, the condensation of these vapours does not explain the observed growth rates of the particles (Kulmala et al., 2000), and in atmospheric conditions nucleation and growth are decoupled (Kulmala et al., 2000). Detailed theoretical modelling to obtain the growth from 1 nm to 20 nm will be performed. The possible steps in the growth process include a1) heterogeneous nucleation of organic insoluble vapours on a ternary (water-sulphuric acid ammonia) nucleus or a2) activation of the nucleus for condensation of soluble organic vapours (a process analogous to activation of cloud droplets, see Köhler theory; e.g. Kulmala et al., 1997); and b) the multicomponent condensation of organic and inorganic vapours. The activity coefficients and surface tensions obtained in phase one will be used. The growth rates will be calculated in atmospheric conditions.

Aerosol dynamic modelling (nucleation, condensation, coagulation, deposition) with gas phase chemistry to obtain the atmospheric significance of condensation of organic vapours will be performed. The growth rates obtained in previous phase will be used. The aerosol dynamics and atmospheric chemistry model used in the present research is based on the model recently developed by our research group (Pirjola and Kulmala, 1998; Pirjola 1999). In these models aerosol formation and growth including aerosol dynamics to evaluate sink terms for condensable molecules and gas phase chemistry to include source terms for these molecules will be used. Process models will be coupled with dispersion models. In the chemistry part of the model the chemistry of O3, NOx, VOC and other relevant species will be related to aerosol formation. The effects of meteorological dynamics on aerosol processes will be studied by applying the aerosol dynamic models in a Lagrangian approach including wave motions and atmospheric mixing.

Formation and growth of aerosol particles have been observed and will be observed at atmospheric conditions. Our research group is participating or has participated in several field campaigns. These include continuous measurements performed at our field stations and several international intensive campaigns. In future field campaigns we will focus on aerosol formation and growth and also on the composition and hygroscopic properties of nucleation and Aitken mode particles. One of most important factors to determine is organic compounds. Specifically, the growth of freshly formed atmospheric aerosols may often take place due to condensation of organic compounds (Marti et al, 1997). Unfortunately, the measurement of the organic content of aerosol particles smaller than around 50 nm in diameter is difficult and in many cases impossible. We are currently developing a new technique (organic tandem differential mobility analyser, OTDMA) for measurement of the organic content of aerosols. After 2002 we will develop a new version of the instrument, aimed at measuring the organic content with diameters as low as 5 - 8 nm. The new OTDMA`s will be used in field campaigns world wide to obtain information on the composition of atmospheric particles and on their interactions with organic gases.

Tasks during 2002-2005

Heterogeneous nucleation as a starting point of aerosol growth
TSC:s and their activation
Multicomponent condensation of organic and inorganic vapours
Further development of aerosol dynamic model
Growth experiments using above mentioned mixtures with monodisperse aerosols
Formation and growth experiments using different concentrations of pre-existing aerosols
Experiments at different atmospheric conditions
Continuous measurements of aerosol formation and growth at 10 background and in 2 urban sites
Campaign wise experiments on particle hygroscopicity and their composition in our own stations
Interpretations of experimental results and comparison with model results
Field campaigns within QUEST in Ireland (2002), Finland (2003), Italy (2004), including vertical profiles throughout the boundary layer, which was missing on the BIOFOR project, and participation in several (around 10) other field campaigns
Reporting the results in scientific Journals and scientific Conferences

WP 7. Emissions of particles in Europe

Professors and senior researchers involved: Pacyna, Hansson, Nilsson, Johansson, Viisanen, Larssen

Particles can be generated from natural and anthropogenic sources. In general, it is estimated that the annual total amount of particles from these sources is about 3000 million tonnes and 400 million tonnes, respectively. Particles from natural sources are in terms of mass overwhelmingly coarse particles. Their origin is from wind erosion, sea-spray formation and similar processes. Anthropogenic emissions on the other hand, contribute about 60 % to the total fine particle mass in the atmosphere. Behind these estimates lie large uncertainties in terms of source assessment, speciation, and characterisation of the atmospheric particles, not to mention the different life times of particles. Anthropogenic primary particle emissions are distributed over many different sectors and activities. There are marked differences between countries, both in terms of implementation of control technologies and in the relative importance of sectors (Pacyna and Pacyna, 2001). The chemical composition of the particulate emissions is less well known than the chemical composition of the particles in ambient air. As mentioned above, inorganic minerals are mainly emitted from processes, particularly from cement and iron and steel industry, and as fly ash from coal combustion. Organic compounds and soot are mainly emitted from small combustion sources, mobile sources and from processes associated with petroleum extraction and refining. The ratio of organic to elementary carbon in these emissions is rather variable, from less than 1 in the case of emissions from diesel engines, up to 5-10 for low-calorific fuels such as lignite, peat and firewood.

For dispersion model calculations, an updated emission inventory is needed as input to the calculations. Work is currently undertaken by the TNO, in co-operation with the European Environment Agency, the Task Force on Emission Inventories and Projections, EMEP Centers, and the European Union to establish a European database for current emissions. In this upgrading, attempts are also made to include chemical speciation, which will be of use both in the modeling and in the interpretation of measurement results. Several improvements of the TNO inventory are expected, including the use of more complete and accurate emission factors, information on spatial distribution within the 50 km by 50 km grid, and information on chemical speciation. NILU being responsible for EMEP CCC actively takes part in this effort and will make the results as well as their competencies on emissions available for the modeling within the NCoE (Lukewille et al., 2001; Lazaridis et al., 2000).
Recently, Dorsey et al. (2002) measured the particle emissions from traffic and other human activities in Edinburgh by eddy covariance (EC) and to relate these to traffic intensity and meteorological conditions (Dorsey et al, 2002). A large part of the emissions was sub micrometer particles. Since fine aerosol particles have been pointed out as especially hazardous for the health (Areskoug et al., 2000), it is well motivated to study this aerosol source further. Since March 2002 we have an aerosol EC system running in a tower in central Stockholm, see WP 2. The footprint of the EC system contains some industry, living areas, as well as large roads and several smaller streets. The first measurements indicates weak deposition fluxes in nighttime and a sharp increase in the morning to a day time source flux on the order of 108-109 particles m-2s-1 following the rush hours, which indicates a traffic related source. We intend to add a relaxed eddy accumulation (REA) system to the project to be able to measure the mass flux of e.g. particulate metals from the traffic. Intense campaigns are planned in a street canyon and nearby a highway, and with additional instrumentation, including an optical particle counter (OPC), in order to study the size resolved aerosol flux. Our objectives are to learn more about the aerosol emission processes in the urban environment, to try to establish the composition and strength of this source, and its contribution to the urban aerosol, ultimately aiming at a source flux parameterization. The project includes an emission inventory based on traffic intensity and emission factors in order to compare the direct flux measurements with traditional emission inventories.

Tasks during 2002-2005

Emission inventories
Collection of aerosol emission flux data for different urban and traffic intense environments.
Formulate a size resolved source parameterization for the aerosol number emission fluxes in the urban environment.
Compare the urban aerosol source measurements and parameterization with emission inventories.
Reporting the results in scientific Journals and scientific Conferences

WP 8. Parameterisation of aerosol formation for large scale models

Professors and senior researchers involved: Nilsson, Ekman, Ström, Kulmala, Rannik, O�Dowd, Laaksonen, Vehkamäki

The aerosol nucleation process is extremely sensitive to atmospheric spatial and temporal variability in temperature and vapor pressures (Easter and Peters, 1995), e.g. due to turbulent mixing (Nilsson and Kulmala, 1998) and atmospheric waves (Nilsson et al., 2000). Such dynamic meteorological processes are all on the sub-grid scale of regional or global climate models. Furthermore, they mostly act on a time scale shorter than the time step of these large models. Therefore, when an aerosol nucleation parameterization code is applied in a large atmospheric model, the aerosol formation can only be based on the time and space averaged temperatures and vapor concentrations at the spatially sparse grid points and at the time steps of the model. This can cause a large underestimation of the actual aerosol formation rate, unless the effects of these sub-grid scale processes on the nucleation are parameterized and connected e.g. to the turbulence closure or convective scheme of the large model. With detailed aerosol models we can derive parameterizations of the enhancement in aerosol nucleation when forced by such atmospheric processes and thereby make it possible to include these effects in a realistic manner in global or regional climate models.

Several investigators have observed aerosol nucleation in the vicinity of deep convective clouds. It has been hypothesized that this is because Cumulus clouds lift precursor gases from the boundary layer up to the free troposphere and scavenge preexisting aerosol, which cause favorable conditions for nucleation in the outflow of the clouds. However, observations and model simulations indicate that the process is more complex than this. In any case, the most reasonable approach to be able to include this potentially aerosol source in large models is to develop a parameterization, which estimates the final aerosol production by each convective cloud, but this cannot be done without further analysis of existing data with help of detailed aerosol and cloud resolving models.
The focus of the EC project BIOFOR was the frequent (50-60 days/year) observations of nucleation events in the European continental boundary layer, followed by growth from a few nm to the size of CCN in 1-2 days. This type of formation of nanometer sized aerosol particles and potential CCN, has been observed frequently in the European continental boundary layer from the sub-arctic Lapland, over the remote boreal forest in southern Finland (Mäkelä et al., 1997), central Europe (Birmilli and Wiedensohler, 2000) to rural United Kingdom (Coe et al., 2000). This is the clearest observational evidence so far of a connection between aerosol nucleation and CCN formation. During BIOFOR, we found a correlation between the onset of nucleation and turbulence during the formation of a convective and turbulent mixed layer (Nilsson et al., 2001). This indicates a connection between convection and entrainment, and nucleation. By triggering binary nucleation, or the growth of thermodynamically stable clusters formed by ternary nucleation (H2O+H2SO4+NH3) (Kulmala et al., 2000) to detectable size, the boundary layer dynamics are able to explain the observed diurnal sequence of nucleation. Important parts of the new EC project QUEST have been designed to challenge this problem.
Another task of the work program is to develop a parameterization scheme suitable for use in regional and global climate models of the growth of the particles to form cloud condensation nuclei and the effect of increased aerosol concentrations on cloud and precipitation formation. Existing and new field data will be analyzed in close connection to all model simulations. The European Commission QUEST and PARTS projects (both running from 2002-2004) are important parts in this matter.

Tasks during 2002-2005

Test the hypothesis that aerosol nucleation occurs in the entrainment zone of the convective and turbulent continental boundary layer against the new field data and in process models.
Test the hypothesis that aerosol nucleation occurs in or near deep convective clouds with field data and in aerosol process models, in a boundary layer model, and in a cloud resolving mesoscale model.
Develop parameterisations of the enhancement of aerosol nucleation by sub grid scale processes to be delivered to work package 9.
Develop parameterisations of the growth of nucleation particles to form cloud condensation nuclei to work package 9.
Reporting the results in scientific Journals and scientific Conferences

WP 9. Modeling of regional and global distribution of aerosols and their contribution to radiative forcing and regional pollution

Senior researchers: Isaksen, Myhre, Hov, Stordal, Nilsson, Rodhe, Ekman, Kulmala, Laaksonen

This WP is focused on the large-scale transport and transformation of natural and man-made particles and their impact on the radiation balance. This will include natural components like sea salt and soil dust and particles where the distribution is strongly influenced by man-made emissions (sulphate, organic particles, black carbon). The emphasis will be on processes that describe the interactions that occur on regional to global scale and their impact on the regional pollution level, weather and climate. Model studies of the current distribution and future changes of gases and particles will be performed.

A number of Chemistry Transport Models (CTMs) will be used, including the global scale Oslo CTM2, the hemispheric scale NILU CTM and the regional scale HIRLAM. The Oslo and NILU models have extensive chemical schemes, which calculate interactively the ozone/OH distribution and the sulphur (SO2, DMS, sulphate) chemistry (Myhre et al., 1998). They are also used to study sea salt, mineral dust (Myhre and Stordal, 2001), and organic particle distribution (the latter currently only in the global model). Work is underway to extend the particle scheme (particle formation, number of compounds) used in the interactive chemical calculations in the global as well as the regional. The radiative forcing will be calculated using radiative transfer models including clouds. With the above-mentioned models it is possible to simulate explicitly daily variations of important dynamical parameters for aerosol chemistry and physics such as temperature, precipitation, cloudiness and relative humidity (Tilmes et al., 2000; Grini et al., 2002; Karlsdottir et al., 2000).

In this WP, a major emphasis is put on the parameterisation of nucleation and aerosol growth processes in large-scale models, making use of results from WP2, 5, 7 and 8. The aerosol nucleation process is extremely sensitive to atmospheric spatial and temporal variability in temperature and vapor pressures (Easter and Peters, 1995), e.g. turbulent mixing (Nilsson and Kulmala, 1998) and atmospheric waves (Nilsson et al., 2000). Aerosol nucleation has also been observed in or near deep convective clouds (Ström et al., 1999) and the growth of these particles and their role in cloud formation is not yet clearly understood. The dynamic meteorological processes listed above are all on the sub-grid scale of regional or global climate models. Furthermore, they mostly act on a time scale shorter than the time step of these large models. Therefore, when an aerosol code is applied in a large atmospheric model, the aerosol formation can only be based on the time and space averaged temperatures and vapor concentrations at the spatially sparse grid points and at the time steps of the model. This can cause a large underestimation of the actual aerosol formation rate, unless the effects of these sub grid scale processes on the nucleation are parameterized and connected e.g. to the turbulence closure or convective scheme of the large model. With detailed aerosol models we can derive parameterizations of the enhancement in aerosol nucleation when forced by such atmospheric processes and thereby make it possible to include these effects in global or regional climate models.

The CTM models need to be validated against available observations, both in situ data sampled at the surface or in aircraft campaigns, e.g. SAFARI-2000, SHADE, TARFOX and INDOEX, as well as satellite data, e.g. CALIPSO. Efforts will be made to focus the inter-comparisons between models and observations such that data from different observation platforms can be used simultaneously. This will enhance the possibility to extrapolate results from in-situ measurements to regional and global scales using a combination of satellite data and model simulations.

Tasks during 2002-2005

Develop improved descriptions of physical and chemical processes affecting the model simulations of the regional and global scale concentration of aerosol particles
Develop parameterizations of the enhancement of aerosol nucleation by sub-grid scale processes.
Simulate synoptic scale nucleation in regional models and to what degree these nucleation processes contribute to CCN production on the synoptic time scale.
Estimate the climate forcing on European and global scales that results from the CCN production.
Development of model validation using satellite and in-situ observations
Reporting the results in scientific journals and conferences

WP 10. Atmospheric gas-aerosol-cloud interactions

Clouds are an integral part of the radiation budget for the earth, and at present represent the largest uncertainty in our understanding of anthropogenic climate forcing. Cloud processes also determine where and when precipitation will occur, which is a key part of the Earth�s hydrological cycle. Despite their fundamental importance, many of the processes that control the formation and life cycle of clouds remain poorly understood. Each cloud droplet begins its life as an aerosol particle, and a large fraction of the atmospheric aerosol originally formed from gas-phase compounds. So to understand the processes influencing e.g. cloud formation, precipitation development, and phase changes, we must first understand which particles do and do not form cloud droplets. We must understand how other gaseous species in the atmosphere influence droplet nucleation. We need to understand how the material scavenged into cloud droplets influences the phase transition from liquid water to ice. Developing a deeper understanding of these processes and of the gas-aerosol-cloud interactions that drive them requires a combination of observational process studies and theoretical and laboratory investigations that are coupled to each other in a logical fashion.

The fundamental theory (called Köhler theory) about cloud droplet formation has undergone an important development in recent years. Recent extensions of this theory have shown that water-soluble gases, substances of slight solubility, surfactants, and condensation kinetics can, in combination, significantly alter droplet populations and sizes (Kulmala et al., 1997, Charlson et al., 2001). Droplets of virtually the same size as would be predicted with the traditional theory occur at somewhat higher populations, producing clouds that are identical in appearance but are thermodynamically different, leading to (usually) higher albedos and lower saturation ratios of water vapour, ratios even below unity in some cases. More broadly, inclusion of these new factors erases a conceptual boundary between what we call "cloud" and "aerosol" or "haze," and an "aerosol-cloud continuum" results in which subtle changes in thermodynamic state lead to substantial changes in cloud albedo.

Exploration and use of this modified Köhler theory is limited by the need to develop new thermodynamic data for compounds (particularly organics) of atmospheric interest. This data would most efficiently be produced by a combination of laboratory and field experiments. We have shown in the recent years (Kulmala et al. 1993, Laaksonen et al. 1997, Laaksonen et al. 1998) that certain semi volatile gases, capable of condensing on aerosols at relative humidities just below 100%, can affect the formation processes of clouds and fogs substantially. We will expand this line of studies to incorporate the effect of liquid phase chemistry. For example, we will study how the hygroscopic mass (sulphate) of aerosols is increased at RH < 100% by the chemical transformation of sulphur dioxide absorbed by the particles, and what effects this additional mass has on the formation and subsequent properties of clouds. (The sulphate formation inside existing clouds has been studied extensively for years, but not much attention has been paid to sulphate chemistry just prior to cloud formation.) We will also provide parameterisations of the effects of various gases on cloud properties that can be incorporated into large-scale (e.g. climate) models.

Clouds seldom use up all of the available aerosol particles when they form. Determining the partitioning of aerosol between those particles that are scavenged into cloud droplets and those that are not is key to understanding how anthropogenic emissions of aerosols can affect cloud properties. In situ process experiments have documented how man-made aerosol emissions influence the albedo of warm clouds (Noone, et al. 2000) and precipitation (Ferek, et al. 2000). Anthropogenic aerosols also influence the properties of cold cirrus clouds (Ström & Ohlsson, 1998). Understanding how pollution aerosols are incorporated into clouds and affect their properties and development is necessary before we can correctly assess anthropogenic influences on clouds and climate.

The processes causing droplets to freeze - the transition between super cooled water and ice - is still very poorly understood. The optical and microphysical properties of clouds change drastically as a result of this transition. Recent aircraft investigations have shed new light on some of these processes (Field, et al., 2001). Clearly, more work is needed on all fronts - laboratory and field experiments and improvements in models of heterogeneous freezing - in order to make progress on understanding ice formation in the atmosphere.

Tasks during 2002-2005

Development of cloud and fog models
Parameterisations of cloud droplet activation
Measurements of aerosol scavenging in clouds, both from aircraft and ground-based experiments
Investigating the chemical influences on cloud droplet formation
Reporting the results in peer-reviewed journals and scientific conferences

up
Suomen Akatemia
Pohjoismainen Huippuyksikköhaku
PL 99, 00501 Helsinki

Research Unit on

Biosphere - Aerosol - Cloud - Climate Interactions

Research Unit leader:

Prof. Markku Kulmala (University of Helsinki, Department of Physical Sciences)

The Research Unit (Senior Scientists):

Finland: Prof. Markku Kulmala, Prof. Pertti Hari, Prof. Ari Laaksonen, Prof. Yrjö Viisanen, Prof. Marja-Liisa Riekkola, Doc. Kari Lehtinen, Doc. Hanna Vehkamäki, Doc. Yllar Rannik, Doc. Kari Hartonen, Doc. Tuulia Hyötyläinen, Doc. Heli Siren, Doc. Veli-Matti Kerminen, Dr. Risto Hillamo, Dr. Tuomo Pakkanen, Dr. Jorma Joutsensaari
Norway: Prof. Oystein Hov, Prof. Frode Stordal, Prof. Ivar Isaksen, Dr. Gunnar Myhre, Dr Michael Kahnert, Dr. Josef Pacyna
Sweden: Prof. Hans-Christen Hansson, Doc. Johan Ström, Doc. Robert Jansson, Doc. Christer Johansson, Prof. Henning Rodhe, Doc. Douglas Nilsson, Prof. Kevin Noone, Prof. Bengt Martinsson, Doc. Erik Swietlicki
Denmark: Prof. Sören Larsen, Prof. Sara Pryor, Doc. Merete Bilde, Dr. Rebecka Barthelmie, Dr. Jakob Man, Dr. Niels Morten Nielsen

Sites of the research:

University of Helsinki (UHEL), Department of Physical Sciences
University of Helsinki (UHEL), Department of Forest Ecology
University of Helsinki (UHEL), Department of Chemistry
University of Kuopio (UKU), Department of Applied Physics
Finnish Meteorological Institute (FMI)
Norwegian Institute of Air Research (NILU)
University of Oslo, Department of Geophysics
University of Stockholm, Institute of Applied Environmental Research (ITMI)
University of Stockholm, Department of Meteorology
University of Lund, Department of Nuclear Physics
Risö National Laboratory
University of Copenhagen. Department of Chemistry

Research Programme and Research Plans 2002 - 2007

1. SUMMARY:

Our main objective is to study the importance of aerosol particles on climate change and on human health. Particularly, we will focus on a) the effect of biogenic aerosols on global aerosol load, b) aerosol-cloud-climate interaction and c) the relationships between the atmosphere and different ecosystems (ocean and boreal forest). During the recent years it has become obvious that homogeneous nucleation events of fresh aerosol particles take frequently place in the atmosphere, and that homogeneous nucleation and subsequent growth have a significant role in determining atmospheric aerosol load. In order to be able to understand this we need to perform studies on formation and growth of biogenic aerosols including a) formation of their precursors by biological activities, b) related micrometeorology, c) atmospheric chemistry, and d) atmospheric phase transitions. Our approach covers both experimental (laboratory and field experiments including development of novel instrumental techniques) and theoretical (basic theories, simulations, model development) approaches.

The work is divided into 10 work packages all operated in a well-defined manner to meet the primary objectives.

CONNECTIONS TO PILOT PROGRAMME:

The work performed by the Research Unit will focus on several aspects mentioned in the Pilot programme. Namely, we cover several fields of basic natural science (physics, chemistry, meteorology, geophysics, oceanography (partly), and biology). We are investigating the basic atmospheric processes (formation and growth of aerosol particles and cloud droplets, atmospheric chemistry of organic compounds) and ecosystem processes (side products of photosynthesis as source of organic vapours), the aerosol-cloud-climate interactions as well as different feedbacks between climate and ecosystems.

General Background

The study of atmospheric physics and chemistry as a scientific discipline goes back to the 18th century when the principal issue was identifying the major chemical components of the atmosphere. In the late 19th and 20th century attention turned to the so-called trace gases and aerosol particles. Recently, the importance of atmospheric aerosols to global radiation, cloud formation, and alleged human health effects has motivated several investigations. Trace gases and atmospheric aerosols are tightly connected with each other via physical, chemical, meteorological and biological processes occurring in the atmosphere and at the atmosphere-biosphere interface (see e.g. Seinfeld and Pandis, 1998).

The Intergovernmental Panel on Climate Change (IPCC) gave, in their 2001 report, an estimation of the global and annually averaged radiative forcing for direct and indirect contributions from both greenhouse gases and aerosols, along with natural changes associated with the solar energy output. The complexity of the combined direct and indirect forcing from both aerosols and gases was highlighted, as was the importance to underpin our understanding of each of these individual components to radiative forcing in an integrated system, thereby reducing the error in current estimates of radiative forcing and developing a truly predictive capability for anthropogenic effects on climate change.

IPPC (2001) has revised their older prediction of the global average temperature increase during the next century from 1.0-3.5 to 1.4-5.8 K. The increase in the upper limit of the prediction is largely due to the role of aerosols in the climate of the Earth: it is believed that reduction of pollution will result in reduced direct and indirect (via clouds) scattering of sunlight back to the space. However, as can be seen from the large uncertainty of the estimated temperature increase, not enough is known about the role of natural and anthropogenic aerosols in climate processes. Atmospheric aerosol particles influence the Earth's radiation balance directly by scattering and absorbing solar radiation, and indirectly by acting as cloud condensation nuclei (CCN) (e.g. Charlson et al., 1992). Recently some progress has been made in evaluating the radiative effects of various aerosol components such as sulphate, organics, black carbon, sea-salt, and crustal species (Chuang et al., 1997; Haywood and Ramaswamy, 1998; Kaufman and Fraser, 1997; Winter and Chylek, 1997; Sokolik and Toon, 1996).

Despite these efforts, substantial uncertainties still remain in quantifying the contribution from each source, particularly, for biogenic and natural emissions, including organic vapours. Without understanding the contribution of natural emissions of aerosols and particles to radiative forcing, we can never hope to accurately predict or understand the true effect of anthropogenic emissions.

Among the key questions in reducing error bars are how aerosol particles are formed, how they will grow from clusters of a few molecules to CCN sizes (>100 nm) and how they will form cloud droplets. Once formed, clouds have a very extensive influence on the Earth's radiation budget through their albedo and greenhouse effects. With global warming, future cloud properties are likely to change due to the warmer and moister conditions, and possibly due to increased aerosol particle emissions from both primary (e.g. wind generated sea-spray) and secondary aerosols (from biogenically and anthropogenically influenced gas-to-particle conversion processes). Clouds are, however, rather crudely presented in global and regional climate models (GCM, RCM). Processes, such as nucleation, droplet activation during condensation, diffusive growth, droplet evaporation, droplet coalescence and conversion to raindrops, are very crudely taken into account in present-day atmospheric large-scale models. For example, we have recently shown the importance of aerosol formation and growth processes to CCN concentrations (Kulmala et al., 2000) as well as the effect of nitric acid and other semi volatile gases in influencing cloud formation processes. In particular, they enhance the cloud droplet population, thereby increasing cloud reflectance (Kulmala et al., 1993; Laaksonen et al., 1997). The importance of including multi-component aerosol populations, and the dynamic feedback in the cloud forming processes, along with the importance of coupling chemical and physical processes in predicting cloud droplet populations have been illustrated by O`Dowd et al., (1999a; 1999b).

However, it is extremely difficult to estimate the magnitude of these effects on the radiation budget without climate model simulations. For this purpose, parameterisations of the nucleation and growth processes as well as the nitric acid effect suited for climate models are required, since explicit treatment of relevant processes are not possible in computationally intensive general circulation models.

Organic compounds represent a significant fraction of atmospheric aerosols resulting from the oxidation process of volatile organic compounds (VOC). VOCs are emitted into the troposphere from anthropogenic and biogenic sources. The forests exchange gases with the atmosphere; they transpire water, photosynthesise carbon dioxide and emit VOCs and act as sources/sinks to nitrogen oxides (NOx) and ozone (O3). All these fluxes have strong annual cycles reflecting the annual patterns of the activity of trees and the environment. Photosynthesis has a key role in the gas exchange between trees and the atmosphere, it is coupled with transpiration and it evidently provides material for VOC emissions. During the dormant period in winter photosynthesis is inhibited and it recovers slowly in the spring (Pelkonen and Hari 1980). The dependence of photosynthesis on the environment and the stomatal regulation is strong and present models are able to describe it well (Hari et. al., 1999). The connection between VOC emissions and photosynthesis is weakly known, highlighting the need for more intensive investigations into links between VOC emissions and photosynthesis.

Atmospheric aerosol particles in urban areas, on the other hand, cause loss of visibility (e.g. Finlayson-Pitts and Pitts, 2000) and health effects (Dockery and Pope, 1994). Heavily industrialized areas suffer from pollution fogs (smogs) that are often related to coal burning and nowadays also to traffic. The most well known example of such smogs is the London "pea-souper" smog, which occurred every once in a while until the 50�s, when coal burning was forbidden. Besides visibility degradation, the London smog episodes caused serious health effects and "excess deaths". A significant part of health problems related to atmospheric aerosols and fog droplets, since particles having diameters less than 10 mm can penetrate deep into the respiratory system (Dockery and Pope, 1994). Recently, the effect of ultra-fine particles has been discussed and their local variations have been investigated (e.g. Buzorius et al., 1999).

Research Plan and priorities

Objectives

Objectives and research methods:

Our main objective is to study the importance of aerosol particles on climate change and on human health. Particularly, we will focus on a) the effect of biogenic aerosols on global aerosol load; b) aerosol-cloud-climate interaction and c) relationships between atmosphere and different ecosystems (ocean and boreal forest). During the recent years it has become obvious that homogeneous nucleation events of fresh aerosol particles take frequently place in the atmosphere, and that homogeneous nucleation and subsequent growth have significant role in determining atmospheric aerosol load. In order to be able to understand this we need to perform studies on formation and growth of biogenic aerosols including a) formation of their precursors by biological activities, b) related micrometeorology, c) atmospheric chemistry, and d) atmospheric phase transitions. Our approach covers both experimental (laboratory and field experiments including development of novel instrumental techniques) and theoretical (basic theories, simulations, model development) approaches.

Research methods

The work is divided into 10 work packages all operated in a well-defined manner to meet the primary objectives.