A combined lidar-photometer method that permits the retrieval of vertical profiles of ash and non-ash (fine-mode) particle mass concentrations is presented. By using a polarization lidar, the contributions of non-ash and ash particles to total particle backscattering and extinction are separated. Sun photometer measurements of the ratio of particle volume concentration to particle optical thickness (AOT) for fine and coarse mode are then used to convert the non-ash and ash extinction coefficients into respective fine-mode and ash particle mass concentrations. The method is applied to European Aerosol Research Lidar Network (EARLINET) and Aerosol Robotic Network (AERONET) Sun photometer observations of volcanic aerosol layers at Cabauw, Netherlands, and Hamburg, Munich, and Leipzig, Germany, after the strong eruptions of the Icelandic Eyjafjallajokull volcano in April and May 2010. A consistent picture in terms of photometer-derived fine-and coarse-mode AOTs and lidar-derived non-ash and ash extinction profiles is found. The good agreement between the fine-to coarse-mode AOT ratio and non-ash to ash AOT ratio (<10% difference) in several cases corroborates the usefulness of the new retrieval technique. The main phases of the evolution of the volcanic aerosol layers over central Europe from 16 April to 17 May 2010 are characterized in terms of optical properties and mass concentrations of fine fraction and ash particles. Maximum coarse-mode 500 nm AOTs were of the order of 1.0-1.2. Ash concentrations and column mass loads reached maximum values around 1500 mu g/m(3) and 1750 mg/m(2), respectively, on 16-17 April 2010. In May 2010, the maximum ash loads were lower by at least 50%. A critical aspect of the entire retrieval scheme is the high uncertainty in the mass-to-extinction conversion for fresh volcanic plumes with an unknown concentration of particles with radii >15 mu m.

Chlorinated paraffins (CPs) are ubiquitous environmental contaminants. They fulfill all of the criteria (persistent, toxic, and subject to long-range transport) for persistent organic pollutants (POPs) according to the United Nations Economic Commission for Europe (UNECE). CPs are also under consideration for inclusion in the Stockholm Convention on POPs. Their presence has been shown in various environmental matrices in the industrialized parts of the world, as well as in remote regions such as the Arctic. The aim of this thesis was to increase the limited knowledge of the presence of CPs in the environment, their sources to the environment, and the resulting human exposure. An analytical procedure for the determination of CPs in environmental samples based on gas chromatography coupled to electron capture detection (GC-ECD) has been developed. GC-ECD is a relatively inexpensive instrument that is fast and easy to operate. These advantages open up the possibility for a comprehensive screening of the occurrence of CPs in the environment, including developing countries. Furthermore, the occurrence of CPs in ambient air and in indoor air and dust was studied. Elevated CP concentrations in indoor air (<5-210 ng/m3) were observed compared to ambient air (0.7-33 ng/m3), which is indicative of the presence of indoor emission sources. Indoor air and dust concentrations were used to estimate the human exposure to CPs via the indoor environment. Comparison of the estimates to available dietary intake estimates indicated that the indoor exposure pathways are not negligible. CP concentrations in ambient air from urban Stockholm were higher than in rural Aspvreten, Sweden. This indicates the presence of additional (emission) sources in urban areas compared to rural sites. Additionally, a seasonal variation of air concentrations was observed at both locations, suggesting temperature dependent emission sources for CPs. These observations were supported by a substance flow analysis of CPs performed for Stockholm. This study estimated the major emission sources of CPs to the Stockholm environment to be emissions from painted surfaces and in-place sealants.

This report is an outcome of a major research effort within the Swedish National Road Vehicle Emission Research Programme EMFO, carried out 2005-2008 in collaboration between IVL, Lund University, the City of Stockholm and VTI. The aims of the project were: − to determine the chemical and physical composition (i.e. the source profile) of road traffic generated airborne particles through both measurements in field and indoor measurements using a circular road simulator, − to clarify the role of different factors which influence the formation of airborne particles from vehicle tyres and road surface interactions by experimental studies in a road simulator and by measurements in urban environments, and determine the emission factors for various combinations of these factors, − to determine the traffic contribution to airborne particles in urban air and traffic environments and identify their origin (brake wear, tyre wear, road surface wear etc.), − to develop a scientific basis for proposals for cost-effective measures to reduce the occurrence of wear particles in urban air. Within the project extensive data have been collected by a variety of methods for measuring, sampling and analysing the chemical composition of primarily three different fractions of particulate matter - PM10, PM2.5, PM1. Emphasis has been on the PM10 fraction, in the case of which preferably the major Swedish cities experience significant problems with complying with the legally binding air quality standards. The collected data originate from indoor measurements in controlled runs with the VTI circular road simulator as well as ambient air measurements at both street and roof level in a variety of Swedish cities. Based on elemental (metals etc.) source profiles of various sources to the different particle fractions, derived from the literature or from measurements carried out within the project, several different receptor models (e.g. COPREM, PMF) were applied to the collected data to derive the contributions from exhaust, brake wear, tyre wear, road surface wear, long-range transport etc., to the measured concentrations of PM10 and other particle fractions in urban environments. Furthermore, from the measurements, emission factors (expressed in grams per vehkm) for the various particle fractions, as well as for a large number of contained metals (about 30 metals) were derived for a major city street in Stockholm. Total emission factors as well as emission factors for each of the different source types (exhaust, brake wear, tyre wear and road surface wear) have also been derived from the measurements. Corresponding emission factors for the two source types tyre wear and road surface wear have been derived from the measurements in the circular road simulator. From these measurements, emission factors have also been derived for different particle size (aerodynamic particle diameter) as well as for different speeds in the range 30-70 km/h and different types of tyres (studded tyres, friction tyres, summer tyres). The road pavement in the road simulator applied in these measurements was the same as the pavement of the city street in Stockholm where ambient air measurements of particulate matter were made. According to the road simulator experiments, studded tyres give rise to ten times higher emissions of PM10 than friction tyres, while PM10 emissions caused by summer tyres are almost negligible. The emission factor for PM10 derived from the road simulator experiments corresponds reasonably well with that derived from measurements in street canyons. The main sources of PM10 are road surface and tyre wear, while for PM2.5 the dominant contribution is often from long-range transport. The applied receptor models are complementary and partly yield different results. Regarding PM10, there is a large uncertainty especially as regards the contribution of tyre wear, due to a lack of knowledge regarding source profiles for different types of tyres.

Modelling nucleation and subsequent growth is a difficult task especially in global and regional models. Therefore it is important to know under which conditions the freshly nucleated particles are able to survive the coagulation barrier and grow to the Aitken mode sizes and further to cloud condensation nuclei thus affecting climate. By using a sectional aerosol dynamics model AEROFOR at various conditions, the regions of parameter space in which nucleation plays an important role are identified and the contour plots are presented. Sulphuric acid is assumed to participate in both nucleation and condensation processes, additionally there is present some other condensable vapour. Our simulations show that nucleation is almost always an important process in the atmosphere excluding the cases when condensable vapour concentration is not high enough so that the nucleated particles have time to coagulate away before reaching the Aitken mode sizes. Thus it is well established to include nucleation in regional/global models.

Aerosol formation and subsequent particle growth in ambient air have been frequently observed at a boreal forest site (SMEAR II station) in Southern Finland. The EU funded project BIOFOR (Biogenic aerosol formation in the boreal forest) has focused on: (a) determination of formation mechanisms of aerosol particles in the boreal forest site; (b) verification of emissions of secondary organic aerosols from the boreal forest site; and (c) quantification of the amount of condensable vapours produced in photochemical reactions of biogenic volatile organic compounds (BVOC) leading to aerosol formation. The approach of the project was to combine the continuous measurements with a number of intensive field studies. These field Studies were organised in three periods, two of which were during the most intense particle production season and one during a non-event season. Although the exact formation route for 3 nm particles remains unclear, the results can be summarised as follows: Nucleation was always connected to Arctic or Polar air advecting over the site, giving conditions for a stable nocturnal boundary layer followed by a rapid formation and growth of a turbulent convective mixed layer closely followed by formation of new particles. The nucleation seems to occur in the mixed layer or entrainment zone. However two more prerequisites seem to be necessary, A certain threshold of high enough sulphuric acid and ammonia concentrations is probably needed as the number of newly formed particles was correlated with the product of the sulphuric acid production and the ammonia concentrations. No such correlation was found with the oxidation products of terpenes. The condensation sink, i.e., effective particle area, is probably of importance as no nucleation was observed at high values of the condensation sink. From measurement of the hygroscopic properties of the nucleation particles it was found that inorganic compounds and hygroscopic organic compounds contributed both to the particle growth during daytime while at night time organic compounds dominated. Emissions rates for several gaseous compounds was determined. Using four independent ways to estimate the amount of the condensable vapour needed for observed growth of aerosol particles we get an estimate of 2-10 x 10(7) vapour molecules cm(-3). The estimations for source rate give 7.5-11 x 10(4) cm(-3) s(-1). These results lead to the following conclusions: The most probable formation mechanism is ternary nucleation (water-sulphuric acid-ammonia). After nucleation, growth into observable sizes (greater than or equal to3 nm) is required before new particles appear. The major part of this growth is probably due to condensation of organic vapours. However, there is lack of direct proof of this phenomenon because the composition of 1-5 nm size particles is extremely difficult to determine using the present state-of-art instrumentation.