Hydrocarbons and Other Emissions from Automobiles

The automobile is a major nonnatural source of hydrocarbons in the atmosphere. The photochemical reactions of its gasoline and exhaust gases is an important source of an array of atmospheric oxidants that cause eye irritation and other problems for animals and plants (Section 5.3). Automotive air pollution is caused by the evaporation of gasoline or by tailpipe emissions. Gasoline evaporation occurs during the filling of the gas tank, and by the heating and cooling the automobile, as a result...

[Pb2[HCO4 Ksp 74 x10414

K H3O+ Ka2 4.8 x 10411 (9-32) 5The equations necessary for an exact calculation of the solubility of carbonates have been discussed by M. Bader and by S. Roo, L. Vermeire, and C. Gorller-Walrand, J. Chem Educ., 74, At a pH of, say, 5, and in the absence of other sources of bicarbonate, the solubility of Pb2+ is now 1.2 x 10 4M. In natural waters, this would be further modified by other bicarbonate sources.

Chronic Toxicity of DDT and Related Compounds

The large-scale use of DDT as an insecticide entailed the release of large amounts into the environment, where it and its degradation products persist for decades. These compounds are so volatile that, like PCBs, they were spread worldwide in small amounts by the global winds. Yet while the use of DDT was increasing, it was noted that there was a decrease in many species, especially those at the end of food chains, on earth. These included especially eagles, hawks, and falcons, birds that feed...

Nuclear Fuel Requirements

A fission rate of 3.1 x 1010 fissions per second will provide 1W of power (thermal). For a power plant with a thermal output of 3000 MWt as heat or an electrical output of about 1000 MWe of electricity the number of 235U nuclei that must be fissioned per second is 9.3 x 1019.30 This corresponds to the fissioning of 3.1 kg of 235U per day. Uranium in spent fuel contains about 0.8 w 235U. 29Zircaloys are alloys of zirconium and tin with minor constituents. 30MWe indicates the rate at which...

Nitrogen Oxides N0X in the Absence of Volatile Organic Compounds VOCs

As pointed out in Section 6.7, the main anthropogenic sources of nitrogen oxides in a polluted atmosphere are mobile and stationary petroleum and coal combustion chambers, where inside temperatures and pressures are high enough for the fixation of nitrogen to occur, (NO* represents a mixture of oxides of nitrogen mainly NO and NO2) and where quenching to low temperatures outside the chambers is rapid enough to prevent the thermodynamically favored back-reaction (dissociation) from occurring....

Kinetics Of Photochemical Processes

The second principle of photochemistry, that absorption is a one-photon process, taken together with quantum theory, requires that each quantum that is absorbed bring about a change (excitation) in that one molecule. In essence, this may be considered to be a bimolecular process involving interaction of one photon and one molecule. What happens to the excitation energy, however, depends on the amount of energy absorbed and the nature of the excited molecule. For example, the excited molecule...

Complex Stability and Lability

The formation of a complex ML n+ in solution is part of an equilibrium process that can be represented by a series of steps, each described by its own equilibrium constant (often called formation constant) M(H20)6 n+ + L M(H2 )5L n+ + H2O (9-53) M(H20)5L n+ + L M(H20)4L2 n+ + H2O (9-55) 2 M(H2O)5L + L 1 (The ligand L has been written as a neutral species for simplicity it may equally well be an anion.) The overall process is M(H2O)6f + + 6L ML6 b+ + 6H2O (9-57) and the overall equilibrium...

Reactions In The Upper Atmosphere 521 Nitrogen

We have seen that molecular nitrogen is the most prevalent species in the atmosphere. The reason that nitrogen is not so important photochemically is its large bond energy (7.373 eV, corresponding to a photon of wavelength X 169 nm), which limits its photodissociation chemistry to areas above the ozone layer. Molecular nitrogen absorbs only weakly between 169 and 200 nm, absorption in this region leading to a spin-forbidden excitation from ground-state N2 to the (3X+) excited state 1The...

Alkaline Earth Metals Beryllium Magnesium Calcium Strontium and Barium

Magnesium and calcium ions are extremely common in natural water systems, with calcium carbonate (limestone) and dolomite CaMg(CO3)2 being two widespread natural sources. Solubility in water is influenced by pH and CO2 content. The two ions are responsible for the hardness of water, which manifests itself by precipitation with soaps, the calcium carbonate deposits that form when water is heated (boiler scale), and so on. For many purposes (washing, waters for certain heat exchange processes),...

Hormones

Insect hormones regulate growth and maturation from the larva to the adult. The juvenile hormone controls the development of the immature larva through successive growth stages. If, however, it remains present during the metamorphosis of the larva to the adult, a deformed larva results or the adult that is formed soon dies. The molting hormone, ecdysone, is required for the differentiation to the adult. If the immature larva is treated with the molting hormone, it passes through its life cycle...

Sources Used in Nuclear Medicine

In nuclear medicine, a radiopharmaceutical, also called an imaging agent or a tracer and containing a particular radionuclide in a specific chemical form, is administered orally or intravenously to a patient. Diagnostic imaging is the usual purpose but, less frequently, radiation therapy is performed.23 The radiation that is measured to obtain an image of an organ originates within the body rather than in an external source of x or y rays. Radionuclides suitable for diagnostic imaging decay by...

Temperature Inversions

When pollutants are trapped for a long time over a city, it is usually because of a temperature inversion above the city. This may result in accumulations that can reach lethal proportions, at least for the sick and elderly. Temperature inversions occur when air at some elevation in the troposphere ceases to decrease smoothly in temperature with increasing altitude as is normal near the surface of the earth (see later Figure 3-20). At a temperature inversion, the air temperature increases with...

Complexing in Natural Systems

Most natural water systems contain an excess of Ca(II) compared with the available strong ligands. Consequently, although calcium complexes are rather weak, the amount of ligand left over to complex with trace metals is often small, perhaps often negligible. In some situations, however, complex formation is believed to be important in natural waters for example, when the concentration of dissolved metal ions is higher than expected in the solubiliza-tion of metal ions for transport in soils and...

Absorption of Light

The rather simple example just presented can be used to point out one of the basic principles of photochemistry (the Grotthus-Draper law, first formulated early in the nineteenth century) for light to be effective in producing photochemical transformations, not only must the photon possess sufficient energy to initiate the reaction, it must also be absorbed. Thus, even though we see from equation (4-5) that a 243-nm photon possesses enough energy to break the oxygen bond, in fact oxygen is not...

Coal Formation and Structure

Coal was probably the first of the fossil fuels to be used for energy. It was recognized as an energy source by the Chinese around 1100 b.c., while the ancient Greeks were probably the first of the western cultures to be aware of coal. The Romans reported that the flammable earth was being mined in Gaul when they captured that section of Europe. The first known coal mines in North America were operated by the Hopi Indians of Arizona some 200 years before Columbus. Coal occurs mainly in the...

Phosphorus Fertilizers And Eutrophication

In solution, the mono- and dihydrogen phosphate ions, HPO4 and H2PO4 are the predominant forms of phosphate at the usual pH values (since H3PO4 is a strong acid), and it is in these forms that phosphate is taken up by organisms. The orthophosphate ion PO3 will exist in significant concentration in solution only at very high pH values. Polyphosphates can be formed from the heat-induced condensation polymerization of simple orthophosphate units, for example, which occurs readily with pure...

Biochemical Methods Of Insect Control

The development of insect resistance has been an important factor prompting the search for methods of insect control that are not totally dependent on the use of pesticides. These methods are outlined briefly because their adoption by farmers will help both to minimize the amounts of synthetic pesticides in the environment and to slow the development of resistant strains of insects. It should be noted that the majority of U.S. farmers use synthetic pesticides, but the amounts used per acre have...

Metal Ligand Preferences

The various metals show differing complexation tendencies and preferences for donor atoms. Ions of the alkali metals (Li, Na, K, Rb, Cs) have little electron pair acceptor tendency, although in aqueous solution they are hydrated by predominantly ion-dipole interactions. This tendency is greater for the smaller ions, which also have the lowest energy orbitals and greatest covalency in their interactions. Complexing is weak for this family. The alkaline earth ions, especially Mg(II) and Ca(II),...

General Circulation Of The Atmosphere

Only very general patterns of atmospheric movement are within the scope of this chapter, where they are pertinent because we are interested in discussing general movements of pollutants and other constituents of the atmosphere. Atmospheric circulation will thus be considered in an extremely simplified manner. Books on meteorology, such as the ones given in the Additional Reading at the end of this chapter, may be consulted for further details. There are two major reasons for the existence of a...

Net N

Thus, for the reversible Carnot cycle operating with no frictional or other losses (i.e., operating under maximum efficiency conditions), it can be shown5 that where T1 and T2 must be in kelvin. It turns out, in fact, that nmax is the maximum efficiency for any heat engine operating between two temperatures. Thus, the maximum efficiency depends on the difference between the two temperatures, T2 T1, at which the engine operates it becomes more efficient as the temperatures T1 and Ti move farther...

Colloidal Material

Although we have been discussing concentrations of dissolved substances, a good deal of material may be present in water as suspended particles. If the particles are small enough, they may pass through filters and travel in aqueous systems very much like material in true solution. Such suspensions of small particles are called colloids. Typically, colloids are particles in the size range of 1-10 m, although some suspended material in natural water systems may be larger than this. Mineral...

Ch2ch3

FIGURE 7-5 The structure of the phthalic acid plasticizer di(2-ethylhexyl)phthalate. DEHP might affect development of their offspring. The concern arose from rodent studies in which juvenile rats that ingested DEHP had lower testicular weight, testicle degeneration, and reduced sperm counts in comparison to controls. From these results, the possibility was raised that DEHP might be leached from vinyl surgical tubing by fluid running through it to infants with serious medical problems. In...

Incoming Radiation from the

The discussion on the general circulation of the atmosphere in Chapter 2 presupposed that most of the heating of the earth's surface comes from solar radiation. The total solar energy reaching the surface of the earth each year is about 2 x 1021 kj (5 x 1020 kcal). Heat generated by radioactive processes in the earth and conduction from the core contribute 8 x 1017 kj (2 x 1017 kcal), and human activities contribute about 4 x 1017 kj (1017 kcal) per year. This means that less than 0.1 of the...

Properties And Reactions Of Atomic Nuclei Radioactivity And Ionizing Radiation

The physical properties, chemical reactions, toxicity, carcinogenicity, and other properties of an element or compound present in the environment and discussed in the preceding chapters are determined by the electronic configuration of the atom, ion, or molecule of interest. Except for the fact that the number of electrons in an atom is determined by the number of protons in its nucleus, there is generally no need to give further consideration to the nucleus when dealing with the basic...

Other Factors

The mean temperature of the earth's surface is certainly affected by the magnitude of the greenhouse effect, but it is also affected by the percentage of incoming solar radiation that is reflected back out to space, that is, by the earth's albedo. It has already been stated that approximately 30 of the incoming radiation is immediately reflected. This is an average value Table 3-1 shows the albedo of various major features on earth. Major changes in cloud cover, snow and ice, field and forest,...

Oxidationreduction Processes

Pourbaix Diagram For Sulfur

The oxidation state of an atom in a molecule is a concept helpful in keeping account of electrons. In many cases it is an indication of the number of electrons involved in bonding, but this is not always true and the oxidation state (or oxidation number) need not have any physical meaning. The oxidation state is equivalent to the charge on a positive or negative ion in an ionic substance, while for a covalent compound it is arrived at arbitrarily by assigning the electrons in a bond to the most...

Arsenic

Arsenic is a member of the same family as phosphorus. Although a classical poison, it is also an essential element. It occurs in the same phosphate rocks from which phosphorus chemicals are obtained, and in many industrial phosphates, arsenic remains as an impurity, and thus is found in small amounts in phosphate fertilizers and also among combustion products, mine tailings, and by-products from the metallurgical processing of copper and other metals. It is also used in pesticides for example,...

Solid Waste Disposal And Recycling

Recycling Oil Plant Syosset

Safe disposal of solid wastes is a serious problem. With our culture, which generates ever larger amounts of disposable materials and an increasing population density, we can no longer simply throw things away. If we discard them on land, they must be buried for aesthetic, safety, and health reasons. Even this is not enough, because toxic materials can be dissolved and enter the groundwater. Consequently, disposal site construction that minimizes leaching and includes elaborate leachate...

Structure and Properties of Water

Chemical interactions in aqueous systems make up an important area of environmental chemistry, and the properties of water determine the behavior observed in solution. The water molecule is angular and, owing to the large difference in electronegativity of oxygen and hydrogen, quite polar. Consequently, water molecules will have strong electrostatic interactions with one another, and with dissolved ionic materials or other highly polar molecules. Because the electronegativity of oxygen is large...

Uncatalyzed Ozone Destruction

5.2.3.1 Ozone in a Clean Stratosphere Below 100 km into the midmesosphere region, the three-body recombination of O atoms, reaction (5-21), becomes potentially important because of the increasing total third-body pressure. However, the O2 concentration is also increasing as we go to lower altitudes, increasingly leading to absorption of the solar radiation below 243 nm. Photodissociation of O2 is decreased, lowering the O atom concentration. Since the rate of reaction (5-21) varies as the...

Designation of Spectroscopic States

The recipes briefly summarized here are used in arriving at atomic and molecular state (energy) descriptions. The reader is referred to standard textbooks of quantum mechanics and spectroscopy, some of which are given in the Additional Reading, for the mathematical formulations of these principles. The state of the electron in the hydrogen atom or hydrogen-like ion (e.g., He+ and Li2+, each containing only one electron) is specified by the three quantum numbers n, i, and mi. The principal...

Climate History Of The Earth

Before trying to decide whether humans are actually succeeding in changing the earth's climate at present, we must consider what sorts of climate change occurred before humans evolved, and what climate changes occurred before the major industrialization of the twentieth century. It is, unfortunately, beyond the scope of this chapter to discuss the various methods of calculating average temperatures at different times in the past these methods are discussed in some of the references at the end...

Carbonic Acid

The most important environmental acid is carbonic acid, which is produced in natural waters by the dissolution of CO2 gas. The dissolution of gaseous CO2 is comparatively slow the average lifetime of a CO2 molecule in the atmosphere is about seven years. The air-solution transfer process may be catalyzed by the enzyme carbonic anhydrase in waters containing biological materials. When CO2 enters solution, two steps are actually involved CO2(aq) + H2O H2CO3(aq) (9-18) The species CO2(aq)...

Kinetics Of Thermal Processes

Most chemical reactions are kjnetjeally complex. That is, they take place by means of a series of two or more consecutive steps rather than by means of a single encounter of the reacting species. Nevertheless, the overall reaction between, say, two reactants A and B can be represented by the generalized equation aA + bB cC + dD + (4-15) where the stoichiometry of the reaction is given by the coefficients a, b, c, d, The rate, v, is then given by the differential equation _ _idnA _ _idnB 1dnc...

Coordination Number and Geometry

The number of donor atoms linked to a metal ion is the coordination number of the complex. The most common coordination number is 6, with the donor atoms lying at the corners of a regular or distorted octahedron as illustrated in Figure 9-16. A 4-coordinate, tetrahedral structure also is common, and a variety of other structures are found in specific examples. The coordination geometry (i.e., the arrangement of the donor atoms around the central metal ion), favored by a given element may vary...

Catastrophic Oil Spills

Oil Tanker Ship Spill

FIGURE 6-5 The midsize oil tanker Ventiza, built in 1986. It is 247m (811 ft, or 2.7 U.S. football fields) long and 41.6 m (136 ft) wide. In 2000 the largest tanker in the world was the Jahre Viking, which is 458m (1504ft, or 5 U.S. football fields) long and 69m (266ft, or 0.89 U.S. football field) wide. From http www.rigos.com ventiza.html. Also see color insert. FIGURE 6-5 The midsize oil tanker Ventiza, built in 1986. It is 247m (811 ft, or 2.7 U.S. football fields) long and 41.6 m (136 ft)...

Wastewater Treatment

Clean water is a vital commodity, and usage is now so extensive that waste-waters must be repurified to avoid destruction of aquatic ecosystems and because, often, the water will be reused. Industrial wastewater may require specialized treatment that depends on the contaminants, while treatment of domestic waste (sewage) involves more general procedures. A great deal of water is used for cooling purposes. Such water, if discharged back to freshwater systems, could lead to so-called thermal...

Soaps Synthetic Surfactants And Polymers

Soaps, surfactants and polymers are discussed together, following the discussion of petroleum, because most of the polymers and the surfactants in detergents are made mainly from chemicals derived from petroleum. Natural fats and oils are also used in the manufacture of surfactants (Figure 7-1). Soaps and surfactants contain segments of linear or lightly branched hydrocarbon chains that are, in the main, broken down to acetate up on metabolism by microorganisms in the environment. The...

The Catalytic Converter

Catalytic Converters With Zeolite

2HC + CO + 2NO* + (3x02) 3C02 + H20 + N2 2HC + CO + 3O2 3CO2 + H2O FIGURE 6-14 Cutaway view of an automotive catalytic converter. The honeycomb (enlarged, bottom left) contains 300-4000 square channels per square inch on which the metal catalysts are coated. Emissions pass through these channels and react on the catalyst surface. Provided by R. J. Farrauto, Engelhard Corp., NJ. FIGURE 6-14 Cutaway view of an automotive catalytic converter. The honeycomb (enlarged, bottom left) contains 300-4000...

The General Nature of Smog

In polluted lower regions of the troposphere, particularly in urban environments (see Section 3.4), copious quantities of chemical compounds are released into the atmosphere, leading to a number of complex photochemical reactions producing a variety of eye and throat irritants, aerosols and reduced visibility, and other irritating or destructive species manifesting themselves in the general category of photochemical smog. Unlike the notorious smogs (smoke plus fog) that were a part of London...

Rcoch2

The sodium salt of stearic acid, CH3(CH2)16C02H, is the major product released upon hydrolysis of animal fat, while the sodium salt of oleic acid, CH3(CH2)7CH CH(CH2)7C02H, is the main product from the hydrolysis of olive oil. Hydrolysis of palm oil yields approximately equal amounts of the salts of oleic acid and palmitic acid, CH3(CH2)14C02H. These naturally occurring fatty acids contain linear hydrocarbon chains, which are synthesized biochemically from the acetate ion (CH3C0 ). They are...

Zinc Cadmium and Mercury

Zinc, cadmium, and mercury make up one family of the periodic table. These three elements are representative metals possessing two valence electrons. Their position in the periodic classification immediately follows the transition series, and in keeping with the usual periodic trends, they have comparatively high electronegativity values for metallic elements and form bonds with non-metals of significant covalent character. The covalent properties are emphasized on going down the family from...

Effluents from Nuclear Power Plants

A nuclear power plant is obviously not a source of greenhouse gases. If a 1000-MWe nuclear power plant is substituted for a coal-fired plant of the same size, the annual production of such gases is reduced by approximately the following amounts, depending on the composition of the coal and the type of pollution control equipment installed about 7 million tons of C02, about 100,000 tons of S02, about 25,000 tons of N0*, and about 1500 tons of particulates. In addition, there would be about 1...

Summary of Photochemical Smog

Only a very small portion of the hundreds of reactions possible in polluted atmospheres have been presented, but these are representative of the types of mechanism being considered to account for photoinitiation, oxidation of NO and VOCs, and formation of noxious products associated with photochemical smog. Figure 5-12 shows a computer integration of the differential kinetic rate 45The oxidation of HOSO2. to H2SO4 in the troposphere is not simply the addition of another .OH radical. Rather, it...

Sulfur And The Sulfur Cycle

Sulfur Cycle

Sulfur is an important, relatively abundant, essential element. As is true of many elements, it takes part in a biogeochemical cycle discussed shortly. It is a major component of air pollution, particularly in industrialized areas, although natural sources of sulfur also contribute. Several oxidation states are encountered in environmental systems the most stable under aerobic conditions is S(VI) as in SO3 and sulfates. The reduced form S(-II) is encountered in organic sulfides, including some...

Fish

Laboratory studies have shown that dissolved hydrocarbons destroy the membranes in gills, which results in a diminished ability to absorb oxygen from the water. This loss of gill efficiency results in an enlarged heart. There is also less efficient utilization of food, an effect that may be related to diminished adsorption of food through the intestinal walls. The proposed decrease in food adsorption may also be due to damage to the lipid layers in the intestines. The diminished populations of...

Haloorganics And Pesticides

Haloorganic compounds have many uses, such as pharmaceutical agents, fibers, building materials, agricultural chemicals, solvents, and cleaning agents. Many of these compounds are inexpensive to manufacture and are used in large quantities. Many were manufactured and deliberately distributed in the environment as pesticides to control plant and insect pests. Some were allowed to be released in the environment because their long-term toxicity and environmental hazards were not understood. Yet...

Pressurized Water Reactor Power Plants

Pressurized Water Reactor Eccs

First developed for the propulsion of submarines and other naval vessels, PWRs are much more compact than the graphite-moderated reactors used in the nuclear weapons program during World War II.31 The PWR type of reactor was also a logical choice for central power stations because its compactness made possible the use of relatively small containment buildings and because the electric utilities were experienced in the use of liquid water and steam in their fossil-fueled power stations.32 In...

Mechanism of Action of DDT and DDT Analogues as Pesticides

Insects sprayed with DDT exhibit hyperactivity and convulsions consistent with the disruption of the nervous system by DDT. Many theories have been suggested for the toxic effect of DDT, and the exact mechanism is not known. A theory that appears to be plausible and has some experimental basis suggests that the DDT molecules are of the correct size to be trapped in the pores of the nerve membranes, which are thus distorted, allowing sodium ions to leak through and depolarize the nerve cell so...

Tin and Lead

Anorexia Organ Damage

Tin and lead are the last two members of the carbon family but, in keeping with the general tendency for metallic character to increase with atomic number in a family, they show typical metallic properties. However, they have comparatively weak electropositive characteristics and strong electron acceptor properties. Bonds to nonmetals such as carbon have considerable covalent character and make up an important aspect of their chemistry. Both tin and lead form compounds in which they have the...

High Level Dose

There is no single value for absorbed dose that marks a sharp cutoff between a high-level and a low-level dose of ionizing radiation.69 For each harmful health 69Sometimes an absorbed dose above about 1 Gy is referred to as a high-level dose. The U.S. Nuclear Regulatory Commission refers to a High Radiation Area as one in which an individual effect, there is a range of values of dose within which the severity or the number of occurrences of the effect correlates with the dose in a statistically...

Ci

Thus the ground states of the vinyl and aryl halides are more stable than the corresponding ground states of aliphatic halides. This results in a greater energy of activation Ea for carbocation formation and a slower rate of reaction. This is shown qualitatively in Figure 8-1. The reactivity of aryl halides is enhanced by electron-withdrawing groups. For example, a nitro substituent greatly accelerates the rate of displacement of aryl-bound halogens This is due to the formation of an...

J

Energy is in MeV. nuclide. For positron emission to be energetically possible, the Q value must be at least 1.022 MeV refer again to footnote 25 Emax for positrons for a given transition is equal to the total transition energy minus 1.022 MeV. In the decay scheme for a positron emitter, the 1.022 MeV is indicated by the vertical section of the line for the p transition to the decay product, as shown for 22Na in Figure 13-14. When N Z for a radionuclide is...

Iron

Pourbaix Diagram Magnetite

Iron is a common and important element environmentally. It forms two oxidation states in nature, Fe II and Fe III . The latter is of greater importance. In water solution, Fe III forms a strongly hydrated ion in which the water molecules are bonded to the iron by coordinate, largely covalent bonds to give the species Fe H20 6 3 . The shift of electron density to the iron and out of the 0H bonds of the coordinated water molecules makes their protons acidic and results in dissociation equilibria...

Thorium and Actinium Series

Symbol used in the early studies of naturally occurring radioactivity is given in parentheses MsThj , mesothorium I RdTh , radiothorium Tn , thoron. 7 indicates low intensity 1-5 7 rays with intensity below 1 are not included. Where both a and are given, branched decay occurs. 90 Th 232 89 Ac 88 Ra 228' 87 Fr 86 Rn 85 At 84 Po 83 Bi 82 Pb 81 Tl FIGURE B-1 Thorium 4k series. The main sequence is indicated by arrows and a dash. Symbol used in the early studies of naturally occurring...

Symbols and Abbreviations

Note Some of these symbols have other meanings when used in specific contexts other symbols that are used only in specific contexts may not be Earth's albedo reflectivity also Beer-Lambert proportionality constant also Extinction coefficient also efficiency of a fuel cell Wavelength also nuclear decay constant Orbital angular momentum quantum number along internuclear axis Frequency also kinetic rate also symbol for electron neutrino Absorption cross section, also nuclear reaction cross section...