Acidic particles

Acid Deposition. Acid deposition, the deposition of acids from the atmosphere to the surface of the earth, can be dry or wet. Dry deposition involves acid gases or their precursors or acid particles coming in contact with the earth s surface and thence being retained. The principal species associated with dry acid deposition are S02(g), acid sulfate particles, ie, H2SO4 and NH HSO, and HN02(g). Measurements of dry deposition are quite sparse, however, and usually only speciated as total and total NO3. In general, dry acid deposition is estimated to be a small fraction of the total... 

Airstream neutralization of acid aerosols by NH3 present in the airway-lumen reduces the health risk associated with acid particles by reducing the acid concentration prior to particle deposition.- In addition, the liquid lining of the respiratory tract probably acts as a chemical buffer," further reducing the health hazard posed by inspired acid particles. Principal factors controlling airstream neutralization of acid aerosols, which is considered to be a diffusion-limited process, are particle surface area, and particle... 

The column consists of a glass tube of 13-14 mm. internal diameter, 24 cm. long from lower end to the side arm, which has an internal diameter of 7 mm. It is important that these dimensions be observed in order to avoid polymerization of the product. It has been found in checking that better results are obtained by making indentations in the tube at frequent intervals and at different angles these tend to reduce the number of cinnamic acid particles which are carried over with the vapor. A column of the Vigreux type would no doubt also be suitable. 

Eudragit RS microspheres containing chitosan hydrochloride were prepared by the solvent evaporation method using an acetone/liquid paraffin solvent system, and their properties were compared with Eudragit RS microspheres without chitosan. The content of pipemidic acid, an antibacterial, increased in larger microspheres as a consequence of cumulation of undissolved pipemidic acid particles in larger droplets. Pipemidic acid release was faster from microspheres with chitosan [212]. 

Boyle (1661) attempted to provide a more definite concept and attributed the sour taste of acids to sharp-edged acid particles. Lemery, another supporter of the corpuscular theory of chemistry, had similar views and considered that acid-base reactions were the result of the penetration of sharp acid particles into porous bases (Walden, 1929 Finston Rychtman, 1982). However, the first widely accepted theory was that of Lavoisier who in 1 111 pronounced that oxygen was the universal acidifying principle (Crosland, 1973 Walden, 1929 Day Selbin, 1969 Finston Rychtman, 1982). An acid was defined as a compound of oxygen with a non-metal. 

Lovejoy, E. R., and D. R. Hanson, Measurement of the Kinetics of Reactive Uptake by Submicron Sulfuric Acid Particles, J. Phys. Chem., 99, 2080-2087 (1995). 

Sulfate shows two peaks, one in the coarse particle mode associated with sea salt, and one in the fine particle mode. The smaller peak is expected since the nss-S04 is formed from the oxidation of S02 and other sulfur-containing compounds such as dimethyl sulfide. The small size of particles containing ammonium reflects the uptake of the gaseous base NH3 into the smaller acidic particles. 

Most of the research to date has focused on aerosols and PSCs containing inorganic species such as nitric and sulfuric acids. While CH4 is the only hydrocarbon that is sufficiently unreactive in the troposphere to reach the stratosphere, it is oxidized to compounds such as HCHO that can be taken up into sulfuric acid particles (Tolbert et al., 1993). The effects of such uptake and subsequent chemistry are not well established. 

Air Pollution Control Strategies and Risk Assessments for Tropospheric Ozone and Associated Photochemical Oxidants, Acids, Particles, and Hazardous Air Pollutants... 

Understanding the chemical and physical processes discussed throughout this book is key to the development of cost-effective and health-protective air pollution control strategies. Application of atmospheric chemistry to reducing stratospheric ozone depletion was discussed in Chapter 13. Here we focus on its key role in strategies for controlling tropospheric pollutants, including ozone, acids, particles, and hazardous air pollutants. 

Hales extended these considerations to make the sulphurous acid particles the active agent in holding the particles of air fixed in solid bodies. Many of his experiments showed that after air had been produced by strong heating, the air was reabsorbed when it was allowed to cool and stand for some time in contact with the solid residue. This was owing, said Hales, to the strong attraction the acid sulphurous particles had for air, both of which then somehow recombined with the solid. 

Inflammable bodies contain not only sulphurous acid particles, equivalent to the traditional sulphur of the Chymists, but they also contain air. As Hales expressed it, fire and especially flame, consist of... 

Acids were thought to have sharp, pointed particles, which accounted for their sour taste and ability to attack or corrode substances, whereas alkalis were thought to have porous particles. Neutralization and salt formation consisted in the points of the acid particles becoming mechanically wedged in the pores of the alkali particles, thus blrmting or neutralizing their properties (Figure 1). 

Silicon is an alloy in the Cu cladding being stripped and, hence, Si concentration is proportional to Cu concentration. The gelatinous silicic acid tended to coat the solid oxalic acid particles and inhibit the rate of dissolution of the crystals at higher Cu/Si concentrations. 

These sulfuric acid particles become less concentrated as the temperature decreases or the water vapour increases. Under very cold stratospheric conditions, these liquid aerosols may take up water and HNO, forming ternary solutions H,S0/HN0,/H,0, which eventually freeze [19,24,26], Below 192 K, HNO, becomes the dominant condensed acid, and H,S04 drops to below 3 wt %. The thermodynamics and freezing nucleation of ice and H,S04 or HNO, hydrates from such solutions are however not well understood [27,28]. Other types of solid particles, such as the less stable nitric acid dihydrate (NAD, HN0,.2H,0) [29], sulfriric acid tetrahydrate (SAT, H S04.4H,0) [18,30], sulphuric acid hemihexahydrate (SAH, H2S04.6.5H20) [18], nitric acid penta-hydrate (NAP, HN03.5H,0) [31] and more complex sulfuric acid/nitric acid mixed hydrates [32] may also be a key to understanding Type IPSC nucleation and evolution [28],... 

Lovejoy, E.R., and Hanson, D.R. (1995) Measurement of the kinetics of reactive uptake by subrmcron sulfuric acid particles, J. Phys. Chem 99,2080-2087. 

Traditionally, fractionation of the lipid extract was accomplished using open glass columns containing rather coarse and irregular silicic acid particles (9). Neutral lipids were eluted by chloroform, glycolipids were recovered using acetone, and methanol was used to obtain the phospholipids. Thus, Mounts et al. isolated PL from 5 g of oil on a 10-g column of silica gel (60-200 mesh) by sequential elution with 200 ml of chloroform, 100 ml of acetone, 100 ml of methanol, and 100 ml of 0.1% phosphoric acid in methanol (28). The last two fractions were combined to recover the phospholipid fraction. 

The surface area has been increased by powdering the limestone (Figure 7.6). The acid particles now have an increased amount of surface of limestone with which to collide. The products of a reaction are formed when collisions occur between reactant particles. 

Lu, Y., and Pignateho, J. J. (2004). Sorption of apolar aromatic compounds to soil humic acid particles affected by aluminum (III) ion cross-linking. J. Environ. Qual. 33,1314-1321. 

Limbeck, A., Kulmala, M., and Puxbaum, H. (2003). Secondary organic aerosol formation in the atmosphere via heterogeneous reaction of gaseous isoprene on acidic particles. Geophys. Res. Letters 30,1996, doi 10.1029/2003GL017738. 

The capture of acid particles, or acid droplets, by forests is considered an important cause of acidification of soils and water courses in mountain regions (Lovett, 1984 Lovett Reiners, 1986). Field experiments on the required scale are hardly feasible. Several authors have made calculations of the wind profile within the forest, and the capture efficiency of model leaves and twigs in the canopy. Figure 6.12 shows the results of calculations by Belot (1975), Slinn (1982), and Lovett (1984). When expressed in terms of the normalised velocity of deposition v., there is little difference in Fig. 6.9 between the calculated... 

---