N2o5
The uptake and hydrolysis of N2Os on pure liquid water appears to be about the same as for sulfuric acid-water mixtures, ranging from about 0.01 to 0.06 over the temperature range from 262 to 293 K (e.g., Van Doren et al., 1990 Kirchner et al., 1990 George et al., 1994). It is also noteworthy that similar reactions of N2Os occur with anionic and cationic water clusters (Wincel et al., 1994, 1995). Dentener and Crutzen (1993) have modeled the impact on a global scale of the uptake and hydrolysis...
Photochemistry of Important Atmospheric Species
Absorption of sunlight induces photochemistry and generates a variety of free radicals that drive the chemistry of the troposphere as well as the stratosphere. This chapter focuses on the absorption spectra and photochemistry of important atmospheric species. These data can be used in conjunction with the actinic fluxes described in the preceding chapter to estimate rates of photolysis of various molecules as well as the rate of generation of photolysis products, including free radicals, from...
Problems
Construct a mechanism that shows why methyl tert-butyl ether (MTBE), a common gasoline additive, oxidizes in air to give formaldehyde as well as acetone, ierf-butyl formate (HC(0)0C(CH3)3), and methyl acetate (CH3C(0)0CH3). 2. High levels of acetaldehyde and PAN have been observed in Brazil, where ethanol is used extensively as a fuel. Show why this is expected. 3. Calculate the lifetime of HCHO with respect to reaction with OH at a concentration of 1 x fO6 radicals cm3, N03 at 50 ppt, and CI...
Info
FIGURE 10.5 UV absorption spectrum of naphthalene ( 8 X 10 6 M in cyclo-hexane) (spectrum taken by Alisa Ezell, 1998). et al. (1993), Turpin et al. (1993), Gundel et al. (1995a), Kamens and Coe (1997), and Feilberg et al. (1999a). Compared to PAHs, much less has been published about the gas-particle distributions of PACs in ambient air. Table 10.11 gives average gas- and particle-phase concentrations, and their percentage in the particle phase, of several O-PAC and a widely distributed S-PAC,...
Laboratory Techniques For Studying Heterogeneous Reactions
Heterogeneous reactions in the context of atmospheric chemistry are defined as those between gases and either solids or liquids. Heterogeneous reactions have been suggested for decades as being important in the atmosphere. However, historically, forays into this area by a variety of scientists usually concluded in a rapid retreat, due to highly variable results that were (and, unfortunately, continue to be) common. The recognition of the importance of condensed phases in the oxidation of S02 to...
N
Natural lifetime, see Lifetime Nebulizers, in aerosol generation, 633-634 Nephelometer extinction coefficients measured using, 368 in humidograph technique, 390 schematic diagram, 368 in ice cores, 808 photochemistry of, 317 trends in, 808, 915 Nitrate radical absorption spectrum and cross sections, 100-101 aldehyde reactions, 213-214 alkane reactions, 8, 184 alkene reactions, 201-205 alkyperoxy radical reactions, 187 aqueous phase reactions, 277-279 aromatic hydrocarbon reactions, 212 biogenic...
Kup
Small drops (4 < D < 23 im) 1500 _ Na+ NH4+ Mg2+ Ca2+ Cf N03 S042 H+ FIGURE 8.19 Concentrations of major anions and cations in coastal stratus clouds at La Jolla Peak, California, on July 6, 1993 (adapted from Collett et ai, 1994). centrations, e.g., by 02 and 03, these variations in composition with particle size can be important. Thus oxidation of S(IV) by 02 and 03 would be expected to be inhibited in the more acidic droplets. In the vast majority of studies, the chemical composition of...
References
Meleti, I. C. Ziomas, and K. Tourpali, Spectral Measurements of Solar UVB Radiation and Its Relations to Total Ozone, S02, and Clouds, J. Geophys. Res., 98, 5199-5204 (1993). Ball, J. C., and T. J. Wallington, Formation of Trifluoroacetic Acid from the Atmospheric Degradation of Hydrofluorocarbon 134a A Human Health Concern Air Waste, 43,, 1260-1262 (1993). Barone, S. B., A. A. Turnipseed, and A. R. Ravishankara, Kinetics of the Reactions of the CF30 Radical with...
HONO and HN03
As discussed in Chapter 7.C.1, HONO is formed by the reaction of N02 with water on surfaces. The reac- Plastic storm windows Galvanized metal duct Vinyl floor tile Asphalt floor tile Polyethylene sheet Formica counter top Used furnace heat exchanger Window glass Waxed asphalt tiles Walltex covering Spider plants (with soil covered) Cotton terrycloth Wool (80 ) polyester (20 ) fabric Ceramic tile Furnace filters (used) Particle board Vinyl-coated wallpaper Oak paneling Dehumidlfier Furnace...
Vem
Ice core data, 778, 780, 808, 825-828 Impactors, in particle size measurement, 610-611 Index of refraction of typical atmospheric compounds, 366-367 Indoor air pollution chemistry, 860-861 carbon monoxide, 849-850 dinitrogen pentoxide, 860 nitrate radical, 860 nitric acid, 847-848, 860 nitrous acid, 847-849 ozone, 859-861 PAH, 863 particles, concentrations and sources, 861-865 pesticides, 851-852, 858 radon, 844-846 sulfur dioxide, 849-850 volatile organic compounds aldehydes, 856-857, 860, 861...
B o3
Detection techniques for surface-based measurements of ozone include (f) UV absorption at 254 nm (2) chemiluminescence on reaction with NO (or ethene) (3) DOAS (4) TDLS and (5) wet chemical methods, mainly those involving the oxidation of r to 12 and measurement of the I2 colori-metrically or coulometrically. The wet chemical method and the principles behind DOAS and TDLS were discussed earlier and are not treated further here. UV absorption relies on the strong peak...
Reactions In Solution
The rate of diffusion, J dn dt (in molecules s1), is given, according to Fick's first law, by where dn is the amount of A crossing the area E (cm2) in time dt, D is the diffusion coefficient (in units of cm2 s1), and < 5 _ VA Sx is the gradient (in units of molecules cm4) of the concentration of A in the x direction. Starting with Fick's first law, one can calculate for a solution of two reactants A and B the frequency of A-B encounters, which is in effect the...
Tncta rrxn rS1
As already discussed, yncl is a net probability normalized to the number of gas-surface collisions and is the parameter actually measured in experiments (and hence also often referred to as ymcas). In Eq. (QQ), each conductance represents one of the processes involved i.e., Tg involves the conductance for gas-phase diffusion, rran that for reaction in the aqueous phase, and rsol that for solubility and diffusion into the bulk. Each of the terms has been normalized and made unitless by dividing...
Tropospheric Ozone And Associated Photochemical Oxidants 871
Preparation of Reactants, Including Clean Air 876 d. Typical Time - Concentration Profiles of Irradiated VOC - NOx - Air Mixtures 878 e. Advantages and Limitations of Environmental Chambers 880 2. Isopleths for Ozone and Other Photochemically Derived Species 882 c. Simple Mathematical Models 892 d. Grid Models Urban to Regional Scales 893 e. Models Incorporating Particles 907 1. Typical Reactivity Scales 907 2. Application to Control of Mobile Source Emissions 909 C. FIELD OBSERVATIONS OF...
Hc8p
Butadiene and other anthropogenic dienes Isoprene a-Pinene and other cyclic terpenes with one double bond d-Limonene and other cyclic diene terpenes Toluene and less reactive aromatics Cresol and other hydroxy-substituted aromatics Xylene and more reactive aromatics Methylglyoxal and other a-carbonyl aldehydes Unsaturated dicarbonyls Methacrolein and other unsaturated monoaldehydes Unsaturated dihydroxy dicarbonyl Hydroxy ketone Peroxyacetyl nitrate and higher saturated PANs Unsaturated PANs...
Homogeneous and Heterogeneous Chemistry in the Stratosphere
Although widespread interest in the chemistry of the stratosphere followed that of the troposphere, there has been an explosion of research in this area over the past three decades. This was prompted by the recognition that oxides of nitrogen (Crutzen, 1971) emitted directly into the stratosphere by the proposed fleet of supersonic transports, SSTs (Johnston, 1971 Crutzen, 1972, 1974 McElroy et al., 1974), and chlorine (Stolar-ski and Cicerone, 1974) from chlorofluorocarbons (CFCs) emitted at...
Analytical Methods and Typical Atmospheric Concentrations for Gases and Particles
Optical Spectroscopic Techniques 548 c. Infrared Spectroscopy (IR) 549 d. DOAS (UV- Visible Absorption Spectroscopy) 556 3. Filters, Denuders, Transition Flow Reactors, Mist Chambers, and Scrubbers 567 c. Transition Flow Reactors (TFRs) 568 d. Mist Chambers and Scrubbers 568 4- Methods for, and Tropospheric Levels of, Specific Gases 569 f. Aldehydes, Ketones, Alcohols, and Carboxylic Acids 589 g. PAN, Other Peroxynitrates, and Alhyl Nitrates 594 h. H202 and Organic Peroxides 595 5. Generation...
Editing filenameinp AND meccm777 FILES
The input tile for Example 1, exl.inp, has associated with it the RADM mechanism, called meccm.rad and a set of actinic fluxes as a function of solar zenith angles stored as zen.rad. A copy of the RADM chemical species list is found in Table 16.1. The input file for Example 8 is ex8.inp and has the associated mechanism meccm.cb4, actinic fluxes as zen.cb4 and reac.cb4. CB4 (or CBIV) stands for carbon bond mechanism, version 4. A species list is found in Table 16.2. To run OZIPR, you need to do...
Global Absorption and Emission of Radiation
In Chapter 3 we examined the interaction of incoming solar radiation in the UV and visible regions of the spectrum with atmospheric gases, which drives atmospheric photochemistry. This incoming solar radiation also determines the temperature of the earth's surface through its absorption and reradiation. Although, as chemists, we tend to think of the absorption and emission of radiation in molecular terms, the greenhouse effect is best thought of in terms of the energy balance of the...
Nd
For cancer potency equivalence factors and human cell mutagenicities, see Table 10.13. See text for more information on sampling times and dates collected. h From Atkinson et al. (1988a). Highest and lowest 12-h concentrations measured in 1986-1987 at six sites in California with different emissions (see Fig. 10.21). The only measurable concentrations at the clean air site, Point Arguello, were benz a anthracene, 0.007 chrysene + triphenylene, 0.050 and benzo e pyrene, 0.007 ng m 3. Highest...
Laboratory Techniques For Determining Relative Rate Constants For Gasphase Reactions
Many of the rate constants for gas-phase reactions of atmospheric interest reported in the literature were actually determined not as absolute values but rather as a ratio of rate constants. Thus if the absolute value for one of the rate constants has been determined independently, the second one can then be calculated from the experimentally determined ratio. In the simplest case, determining relative rate constants for a reactive species A is based on a competition between two reactions X,...
Chemistry and Toxicological Implications
NOMENCLATURE AND SELECTED PHYSICAL AND SPECTROSCOPIC PROPERTIES OF POLYCYCLIC AROMATIC HYDROCARBONS (PAHs) AND POLYCYCLIC AROMATIC COMPOUNDS (PACs) 440 1. Combustion-Generated PAHs and PACs 440 2. Structures and IUPAC Rules for Nomenclature 440 3. Solubilities and Vapor Pressures 451 4- Gas - Particle Partitioning, Sampling Techniques, and Ambient Levels of Selected PAHs and PACs 453 5. Absorption and Emission Spectra of Selected PAHs and PACs 461 B. BIOLOGICAL PROPERTIES OF PAHs AND PACs. I...
Lifetimes Of Typical Organics In The Troposphere
To pare the list of VOC oxidations down to the most important processes, we can calculate the effective lifetimes of organics with respect to reactions with each of the oxidants listed in the previous section. Since these natural lifetimes are defined as r l cp X , we also need to assume an average concentration for the oxidant, X , We can therefore take a typical organic from each of the major classes (alkane, alkene, aromatic, etc.) and compare the individual lifetimes for reaction with OH,...
M
Respectively, what are the minimum wavelengths needed to break these bonds Comment on the relevance with respect to why (1) organoiodine compounds have such short lifetimes in the troposphere and (2) the lifetimes of organoiodine compounds are shorter than those of the analogous organobromine compounds. 2. CH3Br reacts with OH with a room temperature rate constant of 2.9 X 1014 cm3 molecule1 s1. (a) What is the lifetime of methyl bromide with respect to reaction with OH at a global mean...
Rates and Mechanisms of Gas Phase Reactions in Irradiated Organic NOx Air Mixtures
The myriad organics found in the troposphere, in combination with a variety of potential oxidizing species, can easily conjure up a nightmare in terms of the chemistry and kinetics needed to fully understand the gas-phase chemistry of organic-NOx mixtures in the lower atmosphere. Fortunately, through studies over the past three decades, a great deal has been learned regarding which oxidants are important for each class of organics. One can use this information to examine the most important...
Tropospheric Ozone And Associated Photochemical Oxidants
Since Haagen-Smit and co-workers established in the late 1950s that the key ingredients in the formation of tropospheric ozone are organics, NOx, and sunlight, there has been a great deal of research devoted to developing and applying effective control strategies for ozone and associated photochemical oxidants. Their chemistry is very complex, sufficiently so that accurately predicting the impacts of controlling the precursor VOC and NOx on ozone and other photochemically derived species at a...
Chemistry Of The Unperturbed Stratosphere
Figure 12.1 shows typical average vertical ozone profiles measured at Edmonton, Alberta, Canada, in the January-April period in 1980-1982 and in 1993, respectively. The high concentrations of ozone in the stratosphere are evident, demonstrating why this region is often referred to colloquially as the ozone layer. (The significant decrease in stratospheric ozone from the period 1980-f982 to 1993 will be discussed below. While a small decrease in tropospheric ozone is seen in these particular...
Ho2 h 1 k2[H k2k3[H2 B
Equations (A) and (B) allow one to calculate at a given pH the value of H*u and hence the total concentration of the dissolved forms of C02 for a given gas-phase concentration. Alternatively, one can estimate the pH of the water for given gas- and aqueous-phase concentrations. It should be noted that Henry's law describes the equilibrium situation and can only be applied when this is the case. The presence of surfactants on the surface, for example, has been shown in laboratory studies to...
Q Co
1960 1980 2000 2020 2040 2060 2080 2100 Year FIGURE 13.1 Estimated equivalent effective stratospheric chlorine for a continued 3 growth per year, for controls contained in the Montreal Protocol, and for those in the Copenhagen amendments (adapted from World Meteorological Organization, 1995). surface reach the stratosphere, in addition, the effectiveness of compounds in destroying stratospheric ozone depends on how readily they dissociate to form chlorine or bromine. As discussed in Chapter...
Types Nomenclature and Uses
Chlorofluorocarbons, that is, compounds containing chlorine, fluorine, carbon, and possibly hydrogen, have been used extensively in the industrialized nations in the past decades primarily as propellants in aerosol spray cans, as refrigerants, and as blowing agents, for example, for producing polyurethane foam. Their chemical characteristics have made them ideally suited for such uses in that they are generally nontoxic and chemically inert. Thus, they can be used around open flames, and leaks...
Sources and Sinks of Brominated Organics
Brominated organics are emitted into the atmosphere by a variety of natural and anthropogenic sources. Methyl bromide, CH3Br, is the most abundant organobromine compound emitted into the atmosphere, although others such as dibromomethane and chlorobromomethane may also contribute to a significant extent (e.g., see Kourtidis et al., 1996). Halons, especially CF2ClBr (Halon-1211) and CF3 Br (Halon-1301), are used as fire suppressants in situations where the use of water is not appropriate (e.g.,...
The
FIGURE 16.19 Schematic diagram showing basic elements of a simple box model (adapted from Schere and Demerjian, 1978). FIGURE 16.19 Schematic diagram showing basic elements of a simple box model (adapted from Schere and Demerjian, 1978). correspondingly crude, especially in terms of spatial and temporal resolution. A well-known box model that was developed initially for regulatory purposes is the EKMA model (.Empirical kinetic Modeling Approach) (Dodge, 1977a, 1977b Dimitriades and Dodge,...
O
< D(D< D(D< D(D(D (D(D(D ccccccccccccc < D(D< D(D< D(D(D (D(D(D ccccccccccccc FIGURE 10.3 Average mass percent contributions (gas + particle phase) of 13 PAHs collected in urban Chicago air during 15 sampling events in February March 1995. Open bars, approximate percentage in gas phase solid bars, approximate percentage in particle phase. 2-Ring PAHs not determined. Average percent of total mass in the particle phase was 4.4 and 42.9 for 3- and 4-ring PAHs, respectively. Averages...
Formation of HONO
As already discussed, a major source of HONO is believed to be heterogeneous reactions of NOz, includ FIGURE 7.8 Calculated rates of formation of OH radical from photolysis of HONO, 03, and HCHO at Long Beach, California, on December fO, 1987 (adapted from Winer and Biermann, f994). ing that with water adsorbed on various surfaces and with reactive sites on the surface of soot. During the day, it can also be formed by the reaction of OH with NO This termolecular reaction is in the falloff...
Reactions of N03
Because of the rapid photolysis of N03 during the day (see Chapter 4.G), competing reactions of N03 are important primarily at night. Some of the most important dark reactions are discussed in the following sections. For detailed treatments of nitrate radical chemistry, the reader should consult the extensive reviews by Wayne et al. (1991) and Atkinson (1991). One of the most important reactions of N03 is that with N02 to form N2Os, discussed earlier. This is the only known source of N205 in...
Esca
Col, AA, NA, ASV, ES, XRF, PIXE, MS, ICP Source Adapted from LBL (1979) and Chow (1995). XRF X-ray fluorescence analysis. 6 PIXE particle-induced X-ray emission. ' Col colorimetry. '' AA atomic absorption spectrometry. '' NA neutron activation analysis. ' ASV anodic stripping voltammetry. MS mass spectrometry. h ES emission spectrometry. ' ESCA electron spectroscopy for chemical analysis also known as XPS X-ray photoelectron spectroscopy. ' ICP inductively coupled plasma spectroscopy. Source...
Sources Of Oxidants In The Troposphere Oh 03 N03 H02 And Ci
The major recognized oxidants for organics in the troposphere are OH and 03, with a contribution from N03 at night. The hydroperoxyl free radical, H02, as we shall see, also reacts readily with aldehydes but does not significantly impact tropospheric chemistry due to a rapid reverse reaction, ft is, of course, responsible for converting NO to N02, ultimately leading to the production of 03, as well as a whole host of compounds included under the umbrella of NOr The H02 + NO reaction also...
Removal From The Atmosphere Wet And Dry Deposition
While the central thrust of this book involves the chemical transformations occurring in air, it is clear FIGURE 2.20 Schematic of mixing processes in atmosphere close to the earth's surface as a function of time of day. (Adapted, with kind permission from Kluwer Academic Publishers, from R. B. Stull, 1988, An Introduction to Boundary Layer Meteorology, Fig. 1.7. 1988 by Kluwer Academic Publishers.) FIGURE 2.20 Schematic of mixing processes in atmosphere close to the earth's surface as a...
Ch3coch3 O
Adapted from Atkinson (1997a). 6 Hakola et al. (1994). ' Hakola et al. (1993). '' Hatakeyama et al. (1991) yields may be too high due to contribution from other products to IR absorption. ' Grosjean et al. (1993a). ' Aschmann et al. (1998). s Alvarado et al. (1998b). noon, likely reflecting their simultaneous removal by reaction with OH and or photolysis. The atmospheric oxidation of biogenic hydrocarbons appears to be a significant source of CO on a global level, accounting for 10-20 of the...
Solubility Of Gases In Rain Fogs And Clouds Henrys Law And Aqueousphase Equilibria
The distribution of a species between the gas and the aquated forms due simply to physical solubility of the gas is described by the Henry's law constant, hx (Fig. 8.1). The Henry's law constant (hx) for a particular species X is, in effect, the equilibrium constant for the reaction Table 8.1 shows the values of these constants for some species of tropospheric interest. The most soluble gases have Henry's law constants of approximately 105 M atm ', whereas the least soluble have values about...
Absorption Of Light
Light has both wave-like and particle-like properties. As a wave, it is a combination of oscillating electric and magnetic fields perpendicular to each other and to the direction of propagation (Fig. 3.f0). The distance between consecutive peaks is the wavelength, A, and the number of complete cycles passing a fixed point in 1 s is the frequency, v. They are inversely proportional through the relationship where c is the speed of light in a vacuum, 2.9979 X 10 m s_l. Considered as a particle,...
1
Adapted from Nielsen (1984). h Water-methanol-dioxane, 40 36 24. ' HN01 alldcd 0.16 M, NaN02 addcd 0.016 M, plus trace of N204 25 C. '' Relative reactivity of anthanthrene set at 100,000. ' See text and Table 10.30. Adapted from Nielsen (1984). h Water-methanol-dioxane, 40 36 24. ' HN01 alldcd 0.16 M, NaN02 addcd 0.016 M, plus trace of N204 25 C. '' Relative reactivity of anthanthrene set at 100,000. ' See text and Table 10.30. TABLE 10.30 Reactivity Scaleb for the Electrophilic Reactions of...
A Oxidation Of No To Noz And The Leighton Relationship
In the early 1950s, the major ingredients in photochemical air pollution had been identified by Haagen-Smit and co-workers as VOC and NOx, and the photolysis of N02 had been identified by Blacet as the source of the high ozone levels (see Chapter 1.B.3). Initially, the atmospheric conversion of emitted NO to N02 was thought to be due to its reaction with 02 FIGURE 7.2 Ratio of final concentrations of PAN to HNO, (PAN HN03) versus initial VOC NOt in a series of smog chamber experiments. The HN03...
Between Absorption And Vapor Pressure Of
Following the approach of Goss and Schwarzenbach (1998), for equilibrium between a species, i, in the gas phase at pressure Pt and dissolved in a liquid organic material at a mole fraction Xt om, the chemical potentials ( ) in the two phases must be equal, i.e., The chemical potential in the gas phase is given by where P is a standard-state pressure and , is the associated chemical potential of the standard state. Taking the standard state as the pure liquid, P is the saturation vapor pressure...
O 75 O 70 65 60 55 50
FIGURE 11.36 Zonal average concentrations of CO in (a) the Northern Hemisphere and (b) the Southern Hemisphere (adapted from Novelli et al., 1998b). Southern Hemisphere. The seasonal trends observed in both hemispheres reflect an anticorrelation with OH that removes CO from the atmosphere. CO in the NH, for example, peaks in March April and is a minimum in July. Detection techniques. As shown in Table 11.1, common techniques for measuring SOz include UV fluorescence, DOAS, and a wet chemical...
A A
Solute ions (B) is then given by Eq. (DD) ifflB MWB Using Eq. (CC), the vapor pressure lowering due to mB grams of dissolved salt that forms i ions per dissolved molecule is therefore given by Thus, if a nonvolatile solute is dissolved in water, the vapor pressure of water is lowered by an amount proportional to the mole fraction of dissolved solute, taking into account any dissociation that occurs (vide infra). It should be noted that this assumes ideal solution behavior. As we have seen in...
Global Tropospheric Chemistry and Climate Change
Over the past several decades, there has been increasing recognition in a number of areas of the environmental impacts, both realized and potential, of human activities not only on local and regional scales but also globally. This is particularly true of changes to the composition and chemistry of the atmosphere caused by such anthropogenic activities. One example, for which there is irrefutable evidence, is stratospheric ozone depletion by chlorofluorocarbons, discussed in detail in Chapters...
Ionic Strength Vs Rate Constant
The rate of the reaction is given by k X * , where X * is the concentration of the activated complex in the transition state. The concentration of the activated complexes can be obtained from the equilibrium assumed between the reactants and the transition state where the reaction rate constant is given by Using the Debye-Hiickel limiting law for the relationship between the activity coefficients y and the ionic strength of the solution, one finds log k log k ) + log yA + log yu - log yx * ,...
Electric Vehicles
Electric passenger vehicles powered by batteries have been reintroduced in the United States. Although there are no tailpipe emissions associated with electric vehicles, charging the batteries requires power with which there are associated emissions. However, emissions from large sources are relatively easier to control than from millions of individual automobiles. In addition, the emissions of VOCs and CO from power plants are generally low, while those of NO,, S02, and particles depend on the...
Field Studies
Combustion of fossil fuels containing sulfur produces S02. Because virtually all of the sulfur is emitted in the form of S02, with only small amounts in other forms such as H2S04, sulfates, and S03, one can readily calculate S02 emissions from the sulfur content of the fuel. Once emitted, the gaseous S02 is oxidized in the plume itself or, after dilution with the surrounding air, to form H2S04 and sulfates. It is these oxidation reactions that are the major focus of this chapter. Numerous field...
Laboratory Techniques For Determining Absolute Rate Constants For Gasphase Reactions
In this section we discuss the major experimental methods used to determine absolute rate constants for gas-phase reactions relevant to atmospheric chemistry. These include fast-flow systems (FFS), flash photolysis (FP), static reaction systems, and pulse radiolysis. The determination of relative rate constants is discussed in Section C. In general, we use simple bimolecular reactions of the type as illustrations. However, the techniques can be modified to study termolecular reactions, as...
Calculation Of Solar Zenith Angle
The solar zenith angle can be calculated in the following manner for any particular location (i.e., latitude and longitude), day of the year (dn), and time of day as described by Spencer (1971) and Madronich (1993). First, one needs to calculate what is known as the local hour angle (ih), which is defined as the angle (in radians) between the meridian of the observer and that of the sun where GMT is Greenwich mean time converted from the local time, longitudes (in degrees) west of the Greenwich...
Control Of Particles
As discussed in Chapter 2, epidemiological studies have suggested that small particles may cause significant health effects, including increased mortality rates. Depending on location and time, such particles may be either primary in nature, i.e., directly emitted, or secondary, i.e., formed from reactions of gases in air. Diesel engines are significant sources of particles, indeed the major source in some urban cores, and their use in many regions of the world is increasing (e.g., see Walsh...
Overview of the Chemistry of Polluted and Remote Atmospheres
Atmospheric chemistry is an exciting, relatively new field. It encompasses the chemistry of the globe, from polluted to clean, remote regions and from the region closest to the earth's surface, the troposphere (< 10-15 km), through the tropopause ( 10-15 km) into the upper atmosphere which, for the purposes of this book, we restrict to the stratosphere ( 10-50 km). Chemical and physical processes occurring at the earth's surface emissions, transport, lifetimes, and fates of certain...
Running the Ozipr Model
The EPA's OZIPR model (Ozone Isopleth Plotting Program, Research Version) was designed to be used primarily for calculating emissions reductions needed to reach the NAAQS for 03. Both DOS-based and Windows versions are available and can be downloaded from the Web site http www.academicpress.com pecs download OZIPR contains two comprehensive chemical mechanisms that use two different approaches to lumping organics. The two mechanisms used in these models, the RADM (Regional cid Deposition Model)...
Units of Concentrations and Conversions
A number of different units are used in expressing the concentrations of various species in the atmosphere we shall review these here. For a review of IUPAC recommendations, see Schwartz and Warneck (1995). a. Parts per Million, Parts per Hundred Million, Parts per Billion, and Parts per Trillion For gas-phase species, the most commonly used units are parts per million (ppm), parts per hundred million (pphm), parts per billion (ppb), and parts per trillion (ppt). These units express the number...
Oh
The major source of OH in remote areas is the photolysis of 03 to electronically excited O('D), followed by its reaction with water vapor 03 + MA < 336 nm) -> O('D) + 02, (1) O('D) + HzO - 20H, (2a) ft should be noted that only a portion of the O('D) formed generates OH via reaction (2a) the remainder is deactivated to ground-state 0(3P), reaction (2b), which then re-forms 03. For example, at 50 RH and 300 K at the earth's surface, about 10 of the O('D) formed generates OH. As a result, as...
From Kinetics
The expressions for half-lives and lifetimes in Table 5.2 can be readily derived from the rate laws. For a first-order reaction of a pollutant species A, the rate law for the reaction Integrating from time t 0 when the initial concentration of A is A to time t when the concentration is A , one obtains After one half-life i.e., at t 2 by definition A 0.5 A 0. Substituting into the integrated rate expression, one obtains For second- and third-order reactions, if one assumes the concentrations of...
Nc Nc
H A sign means an increase of 20 or more in concentration. NC means less than 20 change. ' Texanol isomers of 2,4,4-trimethyl-l,3-pentanediol monoisobutyrate. Wolkoff, 1998 Haghighat and de Bellis, 1998 . Table 15.7, for example, shows the effects of temperature and relative humidity on the emissions of particular compounds associated with carpet, PVC flooring, sealants, varnish, and wall paint Wolkoff, 1998 . Interestingly, exposure of these samples to N2 rather than air also increased the...
