Aerosol studies

Aerosol surface area is likely to be variable even within a remote marine air mass. Previous MBL aerosol studies describe changes in aerosol concentration and composition due to entrainment from the free troposphere (Bates et al., 1998, 2001 Covert et al., 1998). Raes et al. (1997) found an observable link between vertical transport patterns and aerosol variability in the MBL specifically in the Aitken mode (<0.2/u.m). Hence entrainment of aerosol from the free troposphere appears to occur frequently, even in remote MBL air masses. In addition, aerosols have the capacity to travel great distances in the free troposphere, before being entrained into the MBL. 

Abramson Aerosol Study of LSD TETRAHYDROCANNABINOLS ETHYL ALCOHOL BUTYROPHENONES VOLUNTEER STATISTICS FOLLOW-UP STUDIES THE NUREMBERG CODE... 

Chan, H-K., Use of single photon emission computed tomography in aerosol studies, J. Aerosol... 

Data on c clohexene and a pinene aerosols were reported by Schwartz after a preliminary report from the Battelle Institute group. The experimental conditions and analytic techniques were identical with those just described for the toluene aerosol study. Here again, only the methylene chloride-soluble, water-insoluble fractions were studied. They accounted for about 7% and 65% of the total aerosol mass generated from cyclohexene and a pinene, respectively. Grosjean (unpublished data) has investigated the chemical composition of cyclopentene, cyclohexene, and 1,7-octadiene aerosols. Experiments were conducted in an 80-m Teflon smog chamber filled with ambient air, with irradiation by... 

In another aerosol study with positive findings, only one concentration level was tested (Noa and ninait 1987a). 

Future development efforts in field study design and data management should 1) develop methodologies for choosing sampler location, sampling schedule, and sampling devices 2) measure the collection efficiency of available samplers as a function of particle size, windspeed and wind direction 3) create a series of "typical" design scenarios which can be specified for different aerosol study objectives 4) develop standardized data bases from which ambient and source information can be recovered. 

Data on urban soil from the Portland Aerosol Study (21) were used to obtain an order of magnitude comparison of source ratios to the coefficients of MN(C) in the models. If volatile carbon (21) is assumed to be approximately equal to extractable organic matter (this study) and using a 1 1 ratio for coarse to fine particle mass in New York City (based on our unpublished data), then a ratio of extractable organic matter to MN(C) of 118 can be estimated for urban soil. The coefficients for MN(C) in the models were 46 11 [equation (16)] and 70 26 [equation (19)] for CYC and ACE, respectively. This is quite reasonable agreement in view of the approximations made to obtain a ratio for the soil source. 

Bernstein, D. M. and K. A. Rahn. New York Summer Aerosol Study Trace Element Concentrations as a Function of Particle Size. Ann. N.Y. Acad. Sci. 322 87-97 (1980). 

Pitari, G., V. Rizi, L. Ricciardulli, and G. Visconti, High-Speed Civil Transport Impact Role of Sulfate, Nitric Acid Trihydrate, and Ice Aerosols Studied with a Two-Dimensional Model Including Aerosol Physics, J. Geophys. Res., 98, 23141-23164 (1993). 

Richards, L. W. Johnson, K. R. Shepard, L. S. Sulfate Aerosol Study Rockwell International Newbury Park, CA, 1978 Report AMC8000.13FR. 

The observational program included getting information about the content and properties of atmospheric aerosol and most substantial optically active MGCs (03, CO, NOx, S02, etc.), but concentrated on aerosol studies to retrieve data on direct and indirect aerosol RF (ARF). The most interesting (and in many respects unexpected) results were connected with detection of a thick aerosol layer in the troposphere (an important feature of aerosol chemical composition consisted in the presence of a considerable black carbon component) and distinct manifestations of the long-range transport of both aerosol and MGCs. 

Few, J.D., Short, M.D. Thomson, M.L. (1970) Preparation of 99mTc labelled particles for aerosol studies. Radiochemical Radioanalytical Letters, 5, 275-7. 

The factor t is an extremely important parameter in aerosol studies, as will be shown later. Properties of the particle (diameter and density) and of the medium (viscosity and density) are incorporated in this parameter, which has units of seconds. It represents a relaxation time for the aerosol particle. 

The process by which these particles migrate, either to a surface or to one another, is called diffusion, and their motion is described as brownian motion. Diffusion is important in aerosol studies because it represents the major dynamic effect acting on very small particles (d < 0.1 xm) and must be considered when the dynamics of these small particles are studied. 

Several electrical properties may be of interest in aerosol studies. These could include the distribution of charges carried by aerosol particles and the velocity of a charged particle in an electric field. This latter property, e.g., is important in determining such things as deposition rates or charge transfer rates. 

Acute inhalation toxicity can be conducted in an exposure chamber. It is recommended, but not required, that nose-only or head-only exposure be used for aerosol studies to minimize oral exposures due to animals licking compound off their fur. For nongaseous pesticides, introduction of the sample in the form of mist or dust becomes a necessity. The animals are exposed for 4 hr and then transferred to other containers for observations for at least 14 d. The median lethal concentration obtained is referred to as inhalation LC30 (Anonymous, 1998). 

However, as mentioned earlier, owing to the short half-life of positron emitters ( N—10min, O—2 min, "C—20 min, and F—110 min), ready access to a close by cyclotron and radiochemistry facility is required. This has restricted the wide spread use of the PET in aerosol studies. However, with the rapid growth of PET cyclotrons to meet the demand of the rapid expansion of clinical PET, access to this technology has improved considerably. 

Table III. Comparison of Linear-Regression Parameters for the Equation n = au + b from Various Sea-Salt Aerosol Studies...

With respect to safety and the use of phospholipids, no NDA-supporting chronic inhalation studies have been conducted except for those found in commercial pulmonary surfactants. These studies presumably will have involved intratracheal instillation and not aerosolization, since the primary indication is respiratory distress syndrome of the newborn. Nevertheless, the fact that these products are available suggests that synthetic versions of natural lipids such as dipalmitoyl phosphatidylcholine (DPPC) and dipalmitoyl phosphatidylglycerol (DPPG) are likely to be well tolerated. This assumption has been supported from subchronic aerosol studies in mice [60] and acute single-dose aerosol studies in man, the latter involving soy-derived phosphatidylcholines [61]. 

Figure 13.1 Atnuisphcrlc aerosol si/.c distributions measured at various locations in California by Whitby and Sverdrup (1980) a.s part of a Statewide aerosol. study (Aerosol Charaelerization Experiment). The hintodal distribuiion.s include a eoarsc mode idp > 2.3 Min) composed of wind-raised dust and other large particles, and they also include the accumulation mode (0.1 < dp < 2.3 Mm) resulting largely from gas-io-panicle conversion.

Combivent Inhalation Aerosol Study Group. In chronic obstructive pulmonary disease, a combination of ipratropium and albuterol is more effective than either agent alone. Chest 1994 105 1411-1419. 

Zetzsch et al, Hannover, now Bayreuth ca. 30001, Duran glass, thermostated -25 "C to ambient temperature aerosol studies... 

Schurath et al., Karlsruhe 84 m, thermostated -90 to +60 C, AIDA without light source, for aerosol studies... 

Numerous results from kinetic and mechanistic studies using photo-reactors have been obtained which have contributed significantly to an increase in our knowledge on atmospheric chemistry, in particularly in the gas phase. Some open questions still remain, e.g. the mechanisms of the photooxidation of aromatic hydrocarbons and the process of gas-to-particle conversion. More recently also aerosol studies are being carried out in chambers. Some very recent work has led now to a much better understanding of the photochemieal wall effects in chambers which produce OH radicals (Rohrer et al., 2005). 

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