47 research outputs found
Fine Particle Emissions from Solid Biofuel Combustion Studied With Single Particle Mass Spectrometry
Fine Particle Emissions from Solid Biofuel Combustion Studied With Single Particle Mass Spectrometry - Identification of markers for Organics, Soot and Ash Components
Characteristics of Welding Fume Aerosol Investigated in Three Swedish Workshops
Potentially high human exposures to nanometer sized airborne particles occur due to welding and other thermal processes in industrial environments. Detailed field measurements of physical and chemical particle characteristics were performed in three work-shops in Sweden. Measurements were performed both in the plume 5-20 cm above the welding point and in the background air (more than 5 m away from the nearest known particle source). Particle number and mass concentrations were measured on-line. A low pressure impactor was used for size-resolved chemical particle composition. The in-plume measurements generated the chemical signatures for different welding processes. These signatures were then used to identify contributions from various processes to the particle concentrations in different size classes. The background number and mass concentrations increased by more than an order of magnitude during intense activities in the work-shops compared to low activities during breaks
External trade monthly statistics 1/1988/Commerce exterieur statistiques mensuelles 1988.1
In
urban environments, airborne particles are continuously emitted,
followed by atmospheric aging. Also, particles emitted elsewhere,
transported by winds, contribute to the urban aerosol. We studied
the effective density (mass-mobility relationship) and mixing state
with respect to the density of particles in central Copenhagen, in
wintertime. The results are related to particle origin, morphology,
and aging. Using a differential mobility analyzer-aerosol particle
mass analyzer (DMA-APM), we determined that particles in the diameter
range of 50–400 nm were of two groups: porous soot aggregates
and more dense particles. Both groups were present at each size in
varying proportions. Two types of temporal variability in the relative
number fraction of the two groups were found: soot correlated with
intense traffic in a diel pattern and dense particles increased during
episodes with long-range transport from polluted continental areas.
The effective density of each group was relatively stable over time,
especially of the soot aggregates, which had effective densities similar
to those observed in laboratory studies of fresh diesel exhaust emissions.
When heated to 300 °C, the soot aggregate volatile mass fraction
was ∼10%. For the dense particles, the volatile mass fraction
varied from ∼80% to nearly 100%
In-situ characterization of metal nanoparticles and their organic coatings using laser-vaporization aerosol mass spectrometry
Saturation Vapor Pressures and Transition Enthalpies of Low-Volatility Organic Molecules of Atmospheric Relevance: From Dicarboxylic Acids to Complex Mixtures
Processing of Soot by Controlled Sulphuric Acid and Water Condensation - Mass and Mobility Relationship
The effects of atmospheric processing on soot particle morphology were studied in the laboratory using the Differential Mobility Analyzer-Aerosol Particle Mass Analyzer (DMA-APM) and the DMA-DMA (Tandem DMA) techniques. To simulate atmospheric processing, combustion soot agglomerates were altered by sulphuric acid vapor condensation, relative humidity (RH) cycling, and evaporation of the sulphuric acid and water by heating. Primary investigated properties were particle mobility size and mass. Secondary properties, derived from these, include effective density, fractal dimension, dynamic shape factor, and the mass fraction of condensed material. A transformation of the soot particles to more compact forms occurs as sulphuric acid and water condense onto fresh soot. The particle mass increases and initially the mobility diameter decreases, indicating restructuring of the soot core, likely due to surface tension forces. For a given soot source and condensing liquid, the degree of compaction depends strongly on the mass (or volume) fraction of condensed material. For water and sulphuric acid condensing on combustion soot, a mass increase of 2-3 times is needed for a transformation to spherical particles. In the limit of spherical particles without voids, the effective density then approaches the inherent material density, the fractal dimension approaches 3 and the dynamic shape factor approaches 1. Our results indicate that under typical atmospheric conditions, soot particles will be fully transformed to spherical droplets on a time scale of several hours. It is expected that the morphology changes and addition of soluble material to soot strongly affect the optical and hygroscopic properties of soot