Atmospheric particles properties

Atmospheric ions are important in controlling atmospheric electrical properties and conmumications and, in certain circumstances, aerosol fomiation [128. 130. 131. 138. 139, 140. 141. 142, 143, 144 and 145]. In addition, ion composition measurements can be used to derive trace neutral concentrations of the species involved in the chemistry. Figure A3.5.11 shows the total-charged-particle concentration as a frmction of... 

Gobbi et al., 1998). Although the relevant optical properties in the infrared have been investigated in laboratory studies (e.g., Toon et al., 1994 Richwine et al., 1995), they have not been probed for atmospheric particles. However, such studies clearly also have the potential to shed light on the composition of PSCs. 

The most detailed observations of extinction by the atmospheric particles responsible for the blue suns and moons widely observed in September 1950 were made by Wilson (1951). Subsequently, his and other data were thoroughly analyzed by Penndorf (1953). More recently, Porch et al. (1973) concluded on the basis of observations made at remote locations that bluing is a rather common property of the background (i.e., nonurban) aerosol. An elementary discussion of the blue moon, together with instructions on how to demonstrate one with cigarette smoke, was given by Bohren and Brown (1981). 

After release from fires, organic and some inorganic components undergo rapid or more delayed chemical transformation in the atmosphere. The physical properties as well as chemical composition of smoke particles may alter on the way from the source areas (biomass burning areas) to the measurement sites in Northern Europe. There are several reasons why particle properties change. Chemical components can, e.g., become oxidized or substituted in particles, but also the condensation of secondary material onto the LRT particles during the transport changes the particle properties. 

Tabazadeh, A. (2005). Organic aggregate formation in aerosols and its impact on the physicochemical properties of atmospheric particles. Atmos. Environ. 39,5472-5480. 

Atmospheric particles influence the Earth climate indirectly by affecting cloud properties and precipitation [1,2], The indirect effect of aerosols on climate is currently a major source of uncertainties in the assessment of climate changes. New particle formation is an important source of atmospheric aerosols [3]. While the contribution of secondary particles to total mass of the particulate matter is insignificant, they usually dominate the particle number concentration of atmospheric aerosols and cloud condensation nuclei (CCN) [4]. Another important detail is that high concentrations of ultrafine particles associated with traffic observed on and near roadways [5-7] lead, according to a number of recent medical studies [8-11] to adverse health effects. 

The sequence of phase transformations shown in Figure 2 is an approximationp largely because process variables such as time, atmosphere and properties of precursor hydroxides are not included. Thus, for example, bayerite and glbbslte may be converted to boehmite and thence to y-alumina during calcination if the particle size Is large and the precipitate Is moist [18]. 

Electrostatic charging is a complex phenomena and the degree to which it occurs is affected by a number of factors including contact surface properties of both materials coming into contact with each other, particle properties, the contact event (contact pressure, area, time, and frequency), and atmospheric conditions (21,22). Particle size, shape, surface nature, purity, roughness, and the properties of the powder and contact material... 

There are numerous hypotheses-but few definitive results-as to what physicochemical characteristics of atmospheric particles are responsible for adverse health effects (Samet 2000 Schlesinger 2000). Hypotheses include general properties such as mass, surface area, or size, as well as more specific chemical properties such as acidity or elevated concentrations of transition metals (Dreher et al. 1997 Samet 2000). For example, it has been suggested that particulate iron is toxic due to its ability to generate the strongly oxidizing hydroxyl radical through the Fenton reaction (Ohio et al. 1996 Smith and Aust 1997 Donaldson et al. 1998 van Maanen et al. 1999) ... 

First of all, volcanic activity must be mentioned it introduces both gases (see Section 2.3 and Subsection 3.6.2) and particles into the atmosphere. The particles play an important temporary role in the control of atmospheric optical properties and radiation balance. Thus, after the eruption of Krakatoa in 1883 unusual darkness was observed over Batavia and the height of the volcanic cloud reached the altitude of nearly 30 km (18 miles). After the violent eruption of the Agung volcano in 1963 the optical effect of ash particles was identified at several points of the Earth and a temperature increase of 2 C was measured in the stratosphere (see Cadle, 1973)due to the radiation absorption of particles. While an important part of volcanic particulate matter consists of dispersed lava, sulfuric acid also was detected in volcanic fume (Cadle, 1973). 

Several chemical compounds (water, ammonia, nitric acid, organics, etc.) can exist in both the gas and aerosol phases in the atmosphere. Understanding the partitioning of these species between the vapor and particulate phases requires an analysis of the thermodynamic properties of aerosols. Since the most important solvent for constituents of atmospheric particles and drops is water, we will pay particular attention to the thermodynamic properties of aqueous solutions. 

Diesel particulate emissions are a major source of fine and ultrafine atmospheric particles. These particles are of current interest due to their suspected adverse health effects and their impacts on the Earth s radiation balance, visibility impairment, and atmospheric chemistry. Diesel particles are typically aggregates of fine primary particles coated with condensed organic films. The most common technique to characterise the structure of the aggregates is TEM, which provides projected two-dimensional properties of aggregates. Thus, the actual structural properties of aggregates are inferred from the projected properties. However, few studies of the structural properties of aggregates produced from diesel engines have been reported. 

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