Aerosol composition phase

Despite concerns over assumptions and approximations, size-resolved, multicomponent aerosol models are being employed at a variety of scales. An example at the scale of an urban air-shed is the study of Meng et al. (1998), which examined aerosol composition and size distribution for the South Coast Air Basin of California. Modeled aerosol substances included SO , NOf, NHJ, Na, CP, and secondary organics. Gas-phase... 

The campaigns at the 4 sites were conducted consecutively, not simultaneously. Therefore, seasonal changes in aerosol composition will have influenced the results. Although the consecutive sampling pattern is not very suitable for a direct comparison of the localities, our study provides a detailed information on distribution of compounds producing multiple biological effects in the inhalable fraction of atmospheric particulate matter and the gas-phase. 

The condensed phases also are important to the physical processes of the atmosphere however, their role in climate poses an almost entirely open set of scientific questions. The highest sensitivity of physical processes to atmospheric composition lies within the process of cloud nucleation. In turn, the albedo (or reflectivity for solar light) of clouds is sensitive to the number population and properties of CCN (Twomey, 1977). At this time, it appears impossible to predict how much the temperature of the Earth might be expected to increase (or decrease in some places) due to known changes in the concentrations of gases because aerosol and cloud effects cannot yet be predicted. In addition, since secular trends in the appropriate aerosol properties are not monitored very extensively there is no way to know... 

The predicted solids based on thermodynamic measurements and models derived from them depend strongly on chemical composition. However, small aqueous aerosols remain meta-stable with decreasing RH until reaching a crystallization relative humidity(CRH). In contrast, solid aerosols t e up water at the thermodynamically favored deliquescence relative humidity(DRH). This hysteresis causes a dependence of aerosol phase on RH history. 

The first scientists to investigate the coastal atmospheric presence of APs were Van Ry and Dachs, in a study conducted in the Hudson river estuary. GC-MS analyses showed that atmospheric NP isomer mixtures have a similar composition to technical mixtures, with relatively high total concentrations in the range of 0.0002—0.069 xg m-3 in the gas phase, and 0.0001-0.051 p,gm-3 in the aerosol phase. These concentrations are higher than those of polycyclic aromatic hydrocarbons and up to two orders of magnitude higher than polychlorinated biphenyl concentrations in impacted urban-industrial areas [32]. 

A promising detection principle utilizes similar nebulization procedure as applied in ELS, namely the corona-charged aerosol detectors, CAD. In CAD, the aerosol particles interact with an ionized gas (usually nitrogen). The particles become charged and electrically detected [294]. It has been shown that the response of CAD does not depend on the nature of analyte. On the other hand, the size of the aerosol depends on the mobile phase composition and it has to be calibrated. 

Actually measuring the composition and phase of PSCs and aerosols in the stratosphere is extremely difficult. Some direct measurements have been made by collecting aerosol samples and subsequently analyzing them using techniques such as X-ray energy-disper-... 

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