Human Intake of Cadmium

Cd2+ is rather soluble in water, unless sulfide ions are also present to precipitate the metal as CdS. Thus humans usually ingest only a small proportion of their cadmium directly from drinking water or from air, except for individuals who live near mines and smelters, particularly those that process zinc. The maximum containment level (MCL) for cadmium in drinking water is 5 ppb in the United States and Canada (Table 15-2). Smokers are also exposed to cadmium rhat is absorbed from soil and...

I

100,00010,000 1,000 100 10 1 101 102 10 3 10 1,000,000 (1 mm) (1 nm) Particle diameter in micrometers (jam) FIGURE 3-14 Sizes of common airborne fine and coarse particulates. Source Adapted from J. C. Henry and G. W. Heinke, Environmental Science and Engineering (Upper Saddle River, Nj Prentice Hall, 1989). concentration of water droplets. An aerosol is a collection of particulates, whether solid particles or liquid droplets, dispersed in air. A true aerosol (as opposed to, say, the fairly...

Catalytic Processes of Ozone Destruction

In the early 1960s it was realized that there are mechanisms for ozone destruction in the stratosphere in addition to the processes described in the Chapman mechanism. These additional processes all involve catalysts present in air. In the material that follows, we investigate two general reaction mechanisms by which stratospheric ozone is catalytically destroyed, paying particular attention to the role of chlorine and bromine. There exist a number of atomic and molecular species, designated in...

Further Readings

Maczka et al., Evaluating Impacts of Hormonally Active Agents in the Environment, Environmental Science and Technology ( 1 March 2000) 136A G. M. Solomon and T. Schletter, Environment and Health 6. Endocrine Disruption and Potential Human Health Implications, Canadian Medical Association Journal 163 (2000) 1471 S. H. Safe, Endocrine Disruptors and Human Health Is There a Problem Environmental Health Perspectives 108 (2000) 487. 2. P. H. Jongbloet et al., Where the Boys Aren't Dioxin and the...

O

Phthalate esters (R ethyl, n-butyl, n-hexyl, n-octyl, isononyl, isodecyl, benzyl butyl, 2-ethylhexyl) resemblance to estrogen itself. However, most such compounds bind to the receptor with only a small fraction of the strength of estrogen itself. Estrogen itself binds to its main receptor by hydrogen bonding from its two OH groups and by attractive van der Waals forces from its ring system to amino acid side chains. A second estrogen receptor has recently been discovered. In addition to the...

Commercial Uses of PCBs

All PCBs are practically insoluble in water but are soluble in hydrophobic media, such as fatty or oily substances. Commercially, they were attractive because they are chemically inert liquids and are difficult to burn, are inexpensive to produce, and are excellent electrical insulators. As a result of these properties, they were used extensively as the coolant fluids in power transformers and capacitors. Later, they were also employed as plasticizers, i.e., agents used to make plastic...

The Recycling ofTires

Another consumer commodity that presents a waste-management headache is vehicle tires. In North America, about one 10-kg rubber tire per person per year on average is discarded thus about one-third of a billion tires are added to the supply of approximately 3 billion tires presently stored in mountainous piles, awaiting ultimate disposal Because the tires are made primarly from oil and consequently are flammable, tire fires in these huge piles are not uncommon and produce tremendous amounts of...

Groundwater Contamination by Organic Chemicals

The contamination of groundwater by organic chemicals is a major concern. Many organic substances decay rapidly or are immobilized in the soil, so the number of compounds that are sufficiently persistent and mobile to travel to the water table and to contaminate poundwater there is relatively small. The compounds that are most often detected in groundwater-based U.S. community public water supplies, including those near hazardous waste sites, are summarized in Table 14-1. Municipal landfills as...

Sewage Treatment

In the primary (or mechanical) treatment stage of wastewater (sec the schematic diagram in Figure 14-8), the larger particles including sand and silt are removed by allowing the water to flow across screens and slowly along a lagoon or settling basin. A sludge of insoluble particles forms at the bottom of the lagoon, while liquid grease (a term which here includes not only fat, oils, and waxes but also the products formed by the reaction of soap with calcium and magnesium ions) forms a...

The Interaction of Light with Particles

All solids and liquids including atmospheric particles have some ability to reflect light. Atmospheric particles can reflect incoming sunlight, with the consequence that some of it is directed back into space and so is unavailable later for absorption at the surface (see Figure 6-18). The particles can also reflect outgoing infrared light, with the consequence that some of it is redirected back toward the Earth's surface rather than escaping from the atmosphere. The redirection of light by a...

The Climate Modifying Effects of Aerosols

In Chapter 2, we saw that the initial neglect by scientists of the effects of atmospheric aerosol particles, specifically ice crystals in the stratosphere, led to a large underestimation of the amount of ozone that would be destroyed by chlorine. Similarly, neglect of aerosols led to misleading predictions about the extent of global warming to be expected. It is now realized that aerosols offset and thereby mask a significant fraction of the atmospheric temperature increase that would have...

Allocation of Warming to Natural and Anthropogenic Factors

The best estimates of global warming or cooling in 2005 arising from the various factors is summarized by the bar graphs in Figure 6-21 the effect of each factor is expressed as a percentage of the total anthropogenic effect. The order of the greenhouse gases in terms of the amount of extra warming they have produced is C02 > CH4 > O3 > CFCs > NzO The value in Figure 6-21 for CFCs includes the cooling of the stratosphere induced by their destruction of ozone, and that for methane...

Review Questions

On what factors does the magnitude of its use in a country depend 2. What is the equation relating exponential growth to the annual increase in a quantity 3. Define the term carbon intensity. Describe how the carbon intensity has changed over the last few decades (a) globally, (b) for the United States, and (c) for China. 4. How does the rate of C02 emissions by a country depend on its population, its carbon intensity, and its GDP 5. Explain why the...

Environmental Sources of Cadmium

Most cadmium is produced as a by-product of zinc smelting, since the two metals usually occur together. Some environmental contamination by cadmium often occurs in the areas surrounding zinc, lead, and copper smelters. As is the case for the other heavy metals, burning coal introduces cadmium into the environment. The disposal by incineration of waste materials that contain cadmium is also an important source of the metal to the environment. A major use of cadmium is as an electrode in...

The Numbering Systems for PCBs

The numbering scheme used for individual PCB congeners begins with the carbon that is joined to a carbon in the other ring it is given the number 1, and the other carbons around the ring are numbered sequentially. As illustrated below, the positions in the second ring are also numbered 1 through 6, starting with the ring-joining carbon, but are distinguished by primes. By convention, the 2' position in the second ring lies on the same side of the C C bond joining the rings as does the 2...

Hydrogen Fuel of the Future

Hydrogen gas can be used as a fuel in the same way as carbon-containing compounds some futurists believe that the world will eventually have a hydrogen-based economy. Hydrogen gas combines with oxygen gas to produce water, and in the process it releases a substantial quantity of energy H,(g) + 1 2 02(g) H20(g) AH -242 kj mol The idea that hydrogen would be the ultimate fuel of the future goes back at least as far as 1874, when it was mentioned by a character in the novel Mysterious Island by...

Background Organic Chemistry

In Chapters 10-12, the most important environmental problems caused by toxic organic chemicals are discussed in detail. In this appendix, we provide some necessary background in organic chemistry for those students whose previous education has not included this subject. The organic compounds of interest environmentally are mostly electrically neutral molecules containing covalent bonds. Stable compounds of this type inevitably involve the formation of four bonds by carbon in carbon-centered...

Toxaphene

During the 1970s, after DDT had been banned, the insecticide that replaced it in many agricultural applications, such as the growing of cotton and soybeans, was toxaphene. It is a mixture of hundreds of similar substances, all of which are produced when the hydrocarbon camphene, produced from chemicals extracted from pine trees, is partially chlorinated. Toxaphene became the most heavily used insecticide (1966-1976) in the United States before restrictions were placed on its use in 1982 and a...

Indoor Air Pollution

The levels of some common air pollutants often are greater indoors than outdoors, although pollutant concentrations do vary significantly from one building to another. Since most people spend more time indoors than outdoors, exposure to indoor air pollutants is an important environmental problem and may cause more problems to human health than does outdoor air. Indeed, the inadequate ventilation practices encountered in developing countries that burn coal, wood, crop residues, and other...

O2

The rate of a given chemical reaction is affected by a number of parameters, most notably the magnitude of the activation energy required before the reaction can occur. Thus reactions with appreciable activation energies are inherently very slow processes and can often be ignored compared to alternative, faster processes for the chemicals involved. In gasphase reactions involving simple free radicals as reactants, the activation energy exceeds that imposed by their endothermicity by only a...

Green Chemistry Questions

See the discussion of focus areas and the principles of green chemistry in the Introduction before attempting these questions. 1. The replacement of lead with yttrium in electro-deposition coatings won PPG a Presidential Green Chemistry Challenge Award. (a) Into which of the three focus areas does this award best fit (b) List one of the twelve principles that is addressed by the green chemistry developed by PPG. 2. What environmental advantages does the use of yttrium oxide bave over the use of...

Bioaccumulation of Heavy Metals

Recall from Chapter 10 that some substances display the phenomenon of biomagnification Their concentrations increase progressively along an ecological food chain. The only one of the five heavy metals under consideration that is indisputably capable of doing this is mercury. Many aquatic organisms do, however, bioconcentrate (but do not biomagnify) heavy metals. For example, oysters and mussels can contain levels of mercury and cadmium that are 100,000 times greater than those in the water in...

Methane Emission Sources

About 70 of current methane emissions are anthropogenic in origin. The manner in which total methane emissions rose over the last century is illustrated by the black line in Figure 6-15. As in the case of carbon dioxide, post-World War II rates increased annually much more quickly than had been the case before. In the last 20 years, however, the emission rate for methane has leveled off (Figure 6-15). Most of the methane produced from plant decay results from the process of anaerobic...

The Chemistry Of Groundlevel Air Pollution

In this chapter, the following introductory chemistry Equilibrium concept, including redox reactions and their balancing Acid-base theory, including pH and weak acid calculations Background from Chapter 1 used in this chapter o'er hanging firmament, this mages tic roof appears no other thing to me than a foul and pestilent congregation of vapours One of the most important features of the Earth's atmosphere is that it is an oxidizing environment, a phenomenon due to the large concentration of...

Additional Problems

The threshold NOEL level found for a particular chemical from animal studies is 0.004 mg kg body weight per day. The only source for the chemical is freshwater fish, where it occurs at an average level of 0.2 ppm. What is the maximum average daily consumption of such fish that would keep exposure level below the ADI or RfD for the compound 2. An approximate mathematical fit to the form of the dose-response curve of Figure 10-5a is where R is the fractional response and d is the dose, (a) Plot R...

Info

Scientists believe that both the acidity itself and the high concentrations of aluminum together are responsible for the devastating decreases in fish populations that have been observed in many acidified water systems. Different types of fish and aquatic plants vary in their tolerances for aluminum and acid, so the biological composition of a lake varies as it gradually becomes increasingly acidic. Generally speaking, fish reproduction is severely diminished even at low levels of acidity that...

Air Quality Indices and Size Characteristics for Particulate Matter

As we shall see in subsequent sections, the effect of particles suspended in air upon human health depends significantly upon the size of the particles involved. In the material that follows, we investigate the pollution indices used by governmental agencies to characterize the level of particulate air pollution present in an air sample as well as the effect of particle size on visibility through air masses. When air quality is monitored, the most common measure of the concentration of...

Aerosols and Global Warming

The cooling effect of the sulfate aerosol is concentrated almost entirely in the Northern Hemisphere because most industrial activity takes place in that half of the globe, so it is there that most emissions occur. The relatively short lifetime of such sulfate aerosols precludes their spreading to the Southern Hemisphere consequently, the concentration of sulfate particulates is much higher over the Northern Hemisphere. The short lifetime of the sulfate particles can be understood by...

Systematics of Stratospheric Chemistry

There are many similarities between the chemical reactions discussed in Chapters 1 and 2 for the stratosphere and those outlined above for the troposphere. For example, a characteristic process in both regions of the atmosphere is hydrogen atom abstraction. The stratosphere and troposphere differ, however, in which reactions are dominant. In the stratosphere OH', O , CI', and Br are all important in abstracting a hydrogen atom from stable molecules such as methane, whereas only the hydroxyl and...

Stages in the Decomposition of Garbage in a Landfill

There are three stages of decomposition in a municipal landfill. Operating landfills still receiving garbage undergo all three stages simultaneously in different regions or depths. In practice, only food and yard waste biodegrade. Rubber, plastics, and much of the paper content of garbage are very slow to degrade. In the first, short, aerobic stage, oxygen is available to the waste it oxidizes organic materials to C02 and water with the release of heat. The internal temperature can rise to...

The Greenhouse Effect

In this chapter, the following introductory chemistry topics are used Molecular shape, bond angles and distances Background from previous chapters used in this chapter Sunlight wavelength regions (UV, visible, IR) (Chapter 1) ppm ppb concentration scale for gases (Chapter 1) CFCs and their replacements (Chapter 2) Tropospheric ozone nitrous oxide (Chapter 3) Aerosols sulfur dioxide (Chapter 3) Everyone has heard the prediction that the greenhouse effect will significantly affect climates around...

Health Problems of Organophosphates and Carbamates

The organophosphates and carbamates solved the problem of environmental persistence and accumulation associated with organochlorine insecticides, but sometimes at the expense of dramatically increased acute toxicity to the humans and animals who encounter them while the chemicals are still in the active form. These less persistent insecticides together with the pyrethroids mentioned below largely replaced organochlorines in residential uses. Organophosphates and carbamates are a particular...

Determining the Emissions of Old Carbon Sources of Methane

The relative abundances of carbon isotopes in atmospheric carbon dioxide can be used to help deduce its origin by the following logic. The carbon in all living matter contains a small, constant fraction of a radioactive isotope, carbon-14 (14C), taken in via the carbon cycle when photosynthesis captures atmospheric C02 and when animals in turn feed off plant matter. This fact underlies the radiocarbon dating methods used by archaeologists and anthropologists When an organism dies, its 14C...

The Treatment of Cyanides in Wastewater

The cyanide ion, CN , binds strongly to many metals, especially those of the transition series, and is often used to extract them from mixtures. Consequently, cyanide is widely used in mining, refining, and electroplating metals such as gold, cadmium, and nickel. Unfortunately, cyanide ion is very poisonous to animal life since it binds strongly to metal ions in living matter, e.g., to the iron in proteins that are necessary for molecular oxygen to be utilized by cells. Cyanide is a very stable...

DDT A Symbol Gone Awry

In the 1950s a worldwide campaign to eradicate malaria had as its centerpiece the spraying of houses with DDT (dichlorodiphenyltrichloroethane). In less than two decades, the pesticide enabled many countries to control the disease. In India, for example, deaths from malaria plummeted from 800,000 annually to almost zero for a time. Then, in 1972, the U.S. government banned DDT for spraying crops although public health and a few other minor uses were excepted. Rachel Carson's eloquent book...

Websites of Interest

Log on to www.whfreeman.com envchem4e and click on Chapter 5. Instrumental Determination of NOx via Chemiluminescence Environmental Instrumental Analysis I In the preceding chapters, we have seen that nitrogen oxides play a leading role in atmospheric chemistry, both in the stratosphere and at ground level. In this box, we see how the concentration of NO arid NQ2 gases in environmental air samples can be determined using a sophisticated, modern method of analysis. When chemicals react to...

Detecting Dioxins in Food and Water

As a consequence of their widespread occurrence in the environment and their tendency to dissolve in fatty matter, dioxins bioaccumulate in the food chain. More than 90 of human exposure to dioxins is attributable to the food we eat, particularly meat, fish, and dairy products. Typically, dioxins and furans (a group of compounds resembling the dioxins in structure, which we'll discuss later) are present in fish and meat at levels of tens or hundreds of picograms (pg, or 10 12 gram) per gram of...

Deep Underground Storage of C02

There have been suggestions that the C02 output from power plants could be pumped deep underground into cracks and pores in common alkaline rocks such as calcium aluminosilicates there, the rocks could react with the gas, in microorganism-catalyzed processes, to produce calcium carbonate and thereby store the CO,. Such carbonate minerals are known to be present in deep caves in Hawaii and elsewhere, so the process could well be feasible if the reactions occur quickly enough. Recently, Norway...

The Degradation of Pesticides

Although some pesticides such as DDT are very long-lived in the environment, most undergo chemical or biochemical reactions within a few days or months, producing other compounds. Based upon their typical half-lives in the environment, the U.S. EPA classifies pesticides as being nonpersistent, if they last less than 30 days moderately persistent for those lasting 30-100 days and persistent for lifetimes greater than 100 days. Like most organic compounds, pesticides in the environment whether...

CIO no2 ciono2

However, under normal circumstances, more chlorine exists at steady state as C10N02 than as CIO. (Processes similar to the reaction above occur for several other constituents of the stratosphere as we shall see at the end of Chapter 5, the reactions are easily systematized, thereby greatly reducing the number of processes that have to be learned.) The other catalytically inactive form of chlorine, HCl, is formed when atomic chlorine abstracts a hydrogen atom from a molecule of stratospheric...

ClOOct o2

Activation of chlorine on particle surfaces HjO(aq) + Cl0N02(g)- HOCl(aq) + HN03(aq) Cl (aq) + HOCl(aq)-> Cl2(g) + OlT(aq) FIGURE 2-7 A summary of the main ozone destruction reaction cycles operating in the Antarctic ozone hole. there is some sunshine at that time) and in the summer as well as the spring, and, indeed, there is now some persistence of the depletion from one year to the next, The vertical region over which almost total ozone depletion occurs, 12-22 km, has not increased since...

Biodiesel

Another biofuel that has found some application, especially in the United States and Europe, is the mixture of fatty acid methyl esters, R COOCH3, called biodiesel. This material usually corresponds to an oil usually derived from a plant source such as soybeans or rapeseed (canola) that has been esterified and can be used in diesel engines. The rapid rise in annual global biodiesel production began in the late 1990s, as illustrated by the dark green curve in Figure 8-9 note the difference by a...

Common Functional Groups

In addition to being replaced by simple single-atom substituents like CI and F, the hydrogen atoms in alkanes and alkenes can be replaced by more complex attachments called functional groups these are typically headed by oxygen or nitrogen atoms. The common functional groups are listed in Table 2. The simplest such polyatomic group is O H, usually simply shown as OH it is called the hydroxyl group. Compounds that correspond to alkanes or alkenes with the hydrogen of one C H bond replaced by an...

No No4 2 CIO ciooci sunllght 2 cr o2

CIO* + NOi > ClONO, CIO' + BrO' - CI + Br' + 02 The Y O O Y molecules have little thermal stability, and even at moderate temperatures they may dissociate back to their Y O components before light absorption and photolysis have time to occur. Which of the following species do(es) not contain a loose oxygen (a) HOO' (b) OH' (c) NO' ' (d) 02 (e) CIO (a) does NO' abstract an oxygen atom (b) does atomic oxygen abstract an oxygen atom (c) does sunlight in the stratosphere detach an oxygen atom (d)...

Methanol

Methanol, CH3OH, is a colorless liquid that, like ethanol, is somewhat less dense than water. Although methanol was produced in the past from the destructive distillation of wood, giving rise to its historical name wood alcohol, it is now produced mainly from a fossil fuel. Methanol can be blended with gasoline to produce a fuel that bums more cleanly than gasoline. In a labeling scheme analogous to that used for ethanol-gasoline m lxturc s, blends of methanol are designated by an M rating thus...

Organotin Compounds

Although inorganic compounds of tin (Sn) are relatively nontoxic, the bonding of one or more carbon chains to the metal results in substances that are toxic. Such organotin compounds have some common uses, such as additives to stabilize PVC plastics and fungicides to preserve wood, and therefore are of environmental concern. Tin forms a series of compounds of general formula R3SnX, which are molecular substances though often shown in formulas as if they were ionic, e.g., (R3Sn+) (X ), where R a...

CFCs and Their Replacements

Gaseous compounds consisting of molecules with carbon atoms bonded exclusively to fluorine and or chlorine atoms have perhaps the greatest potential among trace gases to induce global warming, since they are both very persistent and absorb strongly in the 8- to 13- m atmospheric window region. Absorption due to the C F bond stretch is centered at 9 xro. The C CI bond stretch and various bond-angle-bending vibrations involving carbon atoms bonded to halogens also occur at frequencies that lie...

Ion Chromatography of Environmentally Significant Anions

The quantitative determination of levels of environ' mentally important ions, such as those discussed in the preceding chapters, can he accomplished using chromatographic methods described in this box. The need to determine the prevalence of common anions like phosphate (P043), nitrate (N03 ), or fluoride (F ) isn't immediately clear. The biospheric significance of these ubiquitous ions is not as obvious as is, for example, the presence of PCBs, pesticides, or toxic metals like lead, mercury,...

[h2so3

The concentrations in such expressions are equilibrium values. Since the equilibrium molarity of H2S03 is determined in the FIGURE 3-13 Dissolution of atmospheric gases S02 03, and H202 raindrop by its interchange with S02 in into a water droplet and their subsequent reactions. air, we can substitute that known value into the Ka expression Rearranging the equation to solve for the ion concentrations, which from stoichiometry are equal in value, we obtain HS03 z 1.7 x 102 M x 1.0 x 10 7 M Thus...

The Structure of PCB Molecules

Biphenyl molecules consist of two benzene rings linked by a single bond formed between two carbons that have each lost their hydrogen atom Like benzene, if biphenyl reacts with CI, in the presence of a ferric chloride (FeCl j) catalyst, some of its hydrogen atoms are replaced by chlorine atoms. The more chlorine initially present and the longer the reaction is allowed to proceed, the greater the extent (on average) of chlorination of the biphenyl molecule. The products are polychlorinated...

1

In this chapter, the following introductory chemistry Elementary organic chemistry (as in the Appendix in this book) Concepts of vapor pressure solubility half-life chemical versus physical change enzymes acids'and bases Background from previous chapters used in this chapter Photochemical reactions (Chapters 1, 3, 5) The term synthetic chemical is used to describe substances that generally do not occur in nature but have been synthesized by chemists from simpler substances, The great majority...

Cr y ct H0v a cr v v ci

OCDD is the most prevalent dioxin congener found in human fat and in many environmental samples. Indeed, pentachlorophenols are one of die largest chemical sources of dioxins to the environment however, the main dioxin they contain, OCDD, is not particularly toxic, as discussed in a later section. Commercial supplies of chlorinated phenols themselves are contaminated with various dioxins. In naming OCDD and pentachlorophenol, no numbers are used to specify the positions of the chlorine...

Er voh er

If it is assumed that the oxygen atom at the top of the dioxin congener originates with the chlorophenol congener on the left side of the dioxin molecule, then the bottom oxygen must come from the chlorophenol on the right side of the dioxin molecule with this set of assumptions, the original reactants must have been 2,4,5- and 2,3,4-trichlorophenol. (Notice in the diagram above that the chlorine atoms eliminated must have arisen from positions adjacent to the oxygen atoms.) The alternative...

Energy Reserves and Usage

Ever since the Industrial Revolution, the worldwide use of commercial energy that sold to users and usually derived on a large scale from fossil-fuel combustion, hydroelectricity, and nuclear power, as opposed to the biomass collected and used by individual families has risen almost every year the current annual global growth rate is about 2 . The period of the most rapid increase began after World War II, when global commercial energy consumption was only about one-tenth the current level....

Brominated Fire Retardants

Highly brominated organic compounds are common commercial fire retardants. Large amounts of these fire retardants are used worldwide, and because of their persistence, they now are accumulating in the environment and have even been detected in the Arctic, to which they presumably migrated by the LRTAP mechanism discussed above. Based upon animal studies, they may have potential for liver toxicity, thyroid hormone-level disruption, and reproduction and development effects. Many brominated...

Speciation and the Toxicity of Heavy Metals

Although mercury vapor is highly toxic, the heavy metals Hg, Pb, Cd, Cr, and As are not particularly toxic as the condensed free elements. However, all are dangerous in the form of their cations and most are also highly toxic when bonded to short chains of carbon atoms. Biochemically, the mechanism of the toxic action usually arises from the strong affinity of the cations for sulfur. Thus, sulfhydryl groups, SH, which occur commonly in the enzymes that control the speed of critical metabolic...

Molecules

Collins and Chip Walter Chemists have invented a new class of catalysts that can destroy some of the worst pollutants before they get into the environment The fish that live in the Anacostia River, which flows through the heart of Washington, D.C., are not enjoying its waters very much. The Anacostia is contaminated with the molecular remnants of dyes, plastics, asphalt and pesticides. Recent tests have shown that up to 68 percent of the river's brown bullhead catfish suffer from...

R np

If the X attached to every second carbon atom in each chain is chlorine, then the clear (or blue-tinted) polymer polyvinyl chloride (PVC) (recycling number 3) is obtained. If the substituent X is a methyl group, we have polypropylene (recycling number 5), and if it is a benzene ring we have polystyrene (recycling number 6). The plastics formed from all these polymers are used extensively in packag ing> as indicated by the original uses listed in Table 16-1. The other plastic that is commonly...

Alkanes

The simplest hydrocarbons are those that contain strings of carbon atoms, each one singly bonded to its closest neighboring carbon atom(s) and to several hydrogen atoms. Such hydrocarbons are called alkanes, of which the simplest are methane, CH4 ethane, C2H6 and propane, C3H8. Commercial supplies of all three are readily available from natural gas wells. Structural formulas for these three alkanes are _C> _u n__f _tjr u_< -> _( > _r> _14 L. rl n U rl rt Lv tl For convenience,...

Oh no2hno3

Consequently, lowering the NOx concentration actually produces more ozone, not less, since more OH is available to react with the VOCs, although production of other smog reaction products such as nitric acid is thereby reduced. Thus, for example, when the VOC concentration is about 0.5 ppm, lowering the NOx concentration from 0.21 ppm corresponding to point B on Figure 3-6 even by two-thirds of this amount is predicted to increase the ozone level slightly beyond 160 ppb further reductions do...

Types of Direct Solar Energy

The direct absorption of energy from sunlight and its subsequent conversion to more useful forms of energy such as electricity can occur by two mechanisms Thermal conversion Sunlight (especially its infrared component, which accounts for half its energy content) is captured as heat energy by some absorbing material. (An everday example of such a material is a shiny metal surface, which becomes very hot when left in sunlight.) Solar energy is an excellent source of heat at temperatures near or...

The Destruction of Volatile Organic Compounds

The major stationary sources in North America of VOCs (Chapter 3) are the evaporation of organic solvents, the manufacture of chemicals, and the petroleum industry and its storage activities. Wastewater effluent that is contaminated with VOCs, e.g., the water emanating from chemical or petrochemical plants, is commonly treated by a two-step process 1. The VOCs are removed from the wastewater by air stripping. In this process, air is passed upward into a downward stream of the water, and the...

Time Dependence of Concentrations in the Two Step Oxidation of Ammonia

The bacteria-catalyzed oxidation of ammonia (or of other reduced organic nitrogen compounds) to nitrate is a reaction with two main steps, with nitrite ion, N02 , an intermediate If sufficient oxygen is available, the rate of each reaction is first-order only in the concentration of the nitrogen reactant, so the sequence can be represented as where A stands for ammonia, B for nitrite ion, and C for nitrate ion, and kt and k2 are the pseudo-first-order rate constants. Since the rate of step 1...

Co2 h2 CO h2o

Since running the reaction in the direction shown consumes H2 and produces CO, and the opposite result is obtained by running the reaction in reverse, the initial 3 1 or 1 1 ratio of H2 to CO can be altered to 2 1 by the partial conversion of the excess material, whether it is H2 or CO, into the other, deficient material. For example, consider the adjustment of the 3 1 ratio produced by the reaction of methane with steam to the required 2 1 ratio. Call the initial molar...

The Long Range Transport of Atmospheric Pollutants

At first glance, it seems amazing to discover that relatively nonvolatile organochlorines and PAHs can eventually travel thousands of kilometers by air from their point of release and end up contaminating relatively pristine areas of the world such as the Arctic. Some quantitative understanding of this long-range transport of atmospheric pollutants (LRTAP) has been made using principles of physical chemistry. By a global fractionation (or distillation) process, pollutants travel at different...

Tapping rcury

OT-SPOT UNKNOWNS COMPLICATE MERCURY REGULATIONS BY REBECCA RENNER In issuing the Clean Air Mercury Rule this past March, the Bush administration hoped to ease health concerns about mercury from coal-fired power plants. The White House enacted ET II Distinct environmental conditions help to amplify local ncentrations of methyl mercury, leading to health warnings such as this one in the rida Everglades. ET II Distinct environmental conditions help to amplify local ncentrations of methyl mercury,...

Fossil Fuels Coal

The main fossil-fuel reserve is coal, which is available in abundance in many regions of the world, including developing countries, and which is cheap to mine and transport. Five countries the United States, Russia, China, India, and Australia have 75 of the world's coal reserves. At today's rate of consumption, coal reserves are estimated to last another 200 years, much longer than oil or gas (see below). Indeed, some observers believe the world will return to a greater reliance on coal as the...

Wave and Tidal Power

Wave power and tidal power can be obtained in many coastal regions of the world and is competitive economically in niche markets. It is estimated that about 20 E of power is potentially recoverable from waves and tides. The source of the energy of tides is the gravitational influence of the Sun and Moon on the water's mass. In some locations, coastal currents generated by tides can be exploited to turn submerged turbines mounted on pipes that fit into holes drilled in the seafloor. Because...

Chloroacetamides and the Occurrence of Pesticides in Groundwater

In some regions where soybeans and corn are grown intensively, atrazine has yielded its status as the herbicide of choice to one of the chloroacetamides, which are derivatives of chloroacetic acid, ClCH2COOH, in which the OH group is replaced by an amino group NR . The most prominent herbicides of this type are alachlor, metolachlor, and acetochlor. These three compounds differ only in minor variations in the complicated organic groups R and R2 attached to the amino nitrogen. Alachlor is a...

Arsenic in Organic and Other Molecular Forms

The common environmental organic forms of arsenic are not simple methyl derivatives, as with mercury and lead. Rather, they are water-soluble oxyacid derivatives that can be excreted by the body and thus are less toxic than some FIGURE 15-8 Steady-state model mass-balance diagram for arsenic in Lake Ontario. Source Adapted from S. Thompson et al., A Modeling Strategy for Planning the Virtual Elimination of Persistent Toxic Chemicals irom the Creat Lakes, journal of Great Lakes Research 25...

No

Some progress has been reported recently in the use of less valuable metals, such as copper and chromium, instead of the expensive platinum-group metals as catalysts in catalytic converters. Although the metals are recycled from old converters, a portion is inevitably lost in the process. Recently, scientists have become concerned about the environmental problem of widely broadcasting the tiny particles of platinum, palladium, and rhodium that are lost from the converters themselves during...

Benzene

One of the most common and most stable organic structural units is the benzene ring, which is a planar hexagon of six carbon atoms. In the parent hydrocarbon, it also contains six hydrogen atoms, one bonded to each carbon and lying in the C6 plane Each carbon in C Hg is bonded to two carbons and to one hydrogen, so in order to form four bonds, it must be doubly bonded to one of its neighboring carbons. The two ways of achieving this result are shown in the so-called Kekul structures (A and B at...

The Recycling of Household and Commercial Waste

In the past few decades, there has been mounting pressure in developed countries to reduce the amount of material discarded as waste after a single use. The incentives here are to conserve the natural resources, including energy, from which the materials are produced and to reduce the volume of material that must be buried as garbage, incinerated, etc. The four Rs of such waste management philosophies are Reduce the amount of materials used (sometimes called source reduction). Reuse materials...

The Detailed Chemistry Of The Atmosphere

In this chapter, the following introductory chemistry topics are used Lewis structures (for nonradicals) Activation energy reaction mechanisms Basic organic chemistry (see Appendix to this book) Background from previous chapters used in this chapter Concept of free radicals (Chapter 1) Atmospheric structure (Chapter 1) Photochemical reactions (Chapters 1 and 3) Stratospheric chemistry (Chapters 1 and 2) Photochemical air pollution, smog, NOx (Chapter 3) In Chapters 1 through 4, we have...

Rings of Carbon Atoms

Networks of carbon atoms exist as rings in many organic molecules. The most common rings are those that contain five, six, or seven carbon atoms. Molecules containing rings are named by placing the prefix cycb in front of the usual name for the carbon chain of that length. Thus, a ring of six carbons, all joined by single C-C bonds, is called cyclohexane. The molecule shown at the right below is called methylcyclopentane. Write out both simple and symbolic bond diagrams for the following...

[0 WW [Ml

Thus the concentration of atomic oxygen is predicted to increase with altitude as M declines as in our previous analysis for the upper atmosphere and as k and Jc3 increase, since UV light intensity increases with increasing altitude. Indeed, atomic oxygen dominates over ozone at high altitudes, whereas below about 50 km, ozone is always dominant. The production of ozone through reaction (2) is critically dependent upon the supply of free oxygen atoms in reaction (1). The rate of oxygen atom...

Hazardous Wastes

In this section, we consider the nature of various types of hazardous wastes and discuss how individual samples of such wastes can be destroyed as an alternative to simply dumping them and thereby deferring the problem to a later date. Currently there are more than 50,000 hazardous waste sites and perhaps 300,000 leaking underground storage tanks in the United States alone. The Superfund program of the U.S. EPA was created to remediate waste sites its eventual cost is estimated to be 31 billion...

So21h2so4 nox1hno3

Consequently, acid rain is a pollution problem that does not respect state or national boundaries because the atmospheric pollutants often undergo longrange transport. For example, most acid rain that falls in Norway, Sweden, and the Netherlands originates as sulfur and nitrogen oxides emitted in other countries in Europe. Indeed, the modern recognition of acid rain as a problem stems from observations made in Sweden in the 1950s and 1960s, which were due to emissions from outside its borders....

Dr Darrin Lew Solutions Manual For Environmental Chemistry Questions

Senior Acquisitions Editor Jessica Fiorillo Marketing Manager Anthony Palmiotto Media and Supplements Editor Samantha Calamari Cover and Text Designer Blake Logan Senior Illustration Coordinator Bill Page Production Coordinator Paul W. Rohloff Library of Congress 'reassigned Control Number 2007939344 ISBN-13 978-1-4292-0146-0 ISBN-10 1-4292-0146-0 2008 by W. H. Freeman and Company. All rights reserved Printed in the United States of America W. H. Freeman and Company 41 Madison Avenue New York,...

Lead Salts as Glazes and Pigments

One form of the oxide PbO is a yellow solid that has been used at least as far back in history as ancient Egypt to glaze pottery. In glazing, the material is fused as a thin film to the surface of the pottery in order to make it waterproof and to give it a brilliant high gloss. The oxide becomes a hazard if applied incorrectly Some of it will dissolve over a period of hours and days if acidic foods and acidic liquids, such as cider, are stored in pottery containers, giving dissolved Pb2+, up to...

Less Persistent Analogs of DDT

A number of compounds having the same general molecular structure as DDT are found to display similar insecticidal properties. This similarity arises from the mechanism of DDT action, which is due more to its molecular shape than to its chemical interactions. The shape of a DDT molecule is determined by the two tetrahedral carbons in the ethane unit and by the two flat benzene rings. In insects, DDT and other molecules with the same general size and 3-D shape become wedged in the nerve channel...

The Chemicals That Cause Ozone Destruction

The increase in levels of stratospheric chlorine and bromine that occurred in the last half of the twentieth century was due primarily to the release into the atmosphere of organic compounds containing chlorine and bromine that are anthropogenic, that is to say, they are man-made. These anthropogenic contributions to stratospheric halogen levels completely overshadowed the natural input. In this section, we investigate why the levels of chlorine and bromine increased due to the release into the...

Rich World Poor World

To keep global emissions constant, both developed nations (defined here as members of the Organization for Economic Cooperation and Development, or OECD) and developing nations will need to cut their emissions relative to what they would have been arrows in graphs below) .The projections shown represent only one path the world could take others are also plausible. To keep global emissions constant, both developed nations (defined here as members of the Organization for Economic Cooperation and...

Sediments AND waste disposal

Chapter 15 Toxic Heavy Metals Chapter 16 Wastes, Soils, and Sediments Environmental Instrumental Analysis VI Inductively Coupled Plasma Determination of Lead Scientific American Feature Article Mapping Mercury In this chapter, the following introductory chemistry topics are used Solubility product and acid-base equilibrium constant calculations, including manipulations for multiple equilibria Background from previous chapters used in this chapter Steady state UV and visible light wavelengths...

Natural and Green Insecticides and Integrated Pest Management Pesticides from Natural Sources

As pointed out earlier, many plants themselves manufacture certain molecules for their own self-protection that either kill or disable insects. Chemists have isolated some of these compounds so that they can be used to control insects in other contexts. Examples are nicotine, rotenone, the pheromones, and juvenile hormones. One group of natural pesticides that has been used by humans for centuries is the pyrethrins. The original compounds, the general structure for which is illustrated on the...

HOO 8b NO

Subsequently undergo photochemical decomposition and, by a further series of steps, be oxidized to carbon dioxide. Add these steps to the net reaction. Also add the reactions by which HOO* oxidizes NO'. What is the final net reaction obtained by adding all these processes together Repeat Problem 5-8, but this time assume that the alkyl group R in the aldehyde RHCO produced by photochemical smog is a simple methyl group, CH3, and that, when the aldehyde undergoes photochemical decomposition by...

Hsor ir so

Given that Ka for HS03 is 1.2 X 10 calculate the concentration of S032-that is present in the raindrops of pH 4.4 discussed above. Hint The concentrations of bisulfite and hydrogen ion will be very close to their previously established values. Calculate the pH of rainwater in equilibrium with S02 in a polluted air mass for which the sulfur dioxide concentration is 1.0 ppm, Hint Recall the relationship between partial pressure and ppm concentration discussed earlier in the chapter. Calculate the...

The Pollution And Purification Of Water

In this chapter, the following introductory chemistry Acid-base and equilibrium concepts and calculations pH Basic structural organic chemistry (as in the Appendix) Oxidation numbers redox half-reactions Background from previous chapters used in this chapter Maximum contaminant levels (Chapter 10) Photochemical reactions UV light (Chapters 1-5) BTX hydrocarbons (Chapter 7) ppm concentration scale in water (Chapter 10) No effects level, NOEL (Chapter 11) The pollution of natural waters by both...

Dioxin Production in the Preparation of 245T

Traditionally, the industrial synthesis of the herbicide called 2,4,5-T (discussed in Chapter 10) started with 2,4,5-trichlorophenol, which itself was produced by reacting NaOH with the appropriate tetrachlorobenzem. The OH group replaces one chlorine atom in the process. Unfortunately, during this synthesis there occurs an additional reaction that converts a very small portion of the trichlorophenol product into dioxin. In this side reaction, two trichbrophenoxy anions react with each other,...

Basic Soil Chemistry

Natalie Darrin

Soils are composed roughly equally of solid particles, about 90 of which are inorganic in nature and the rest organic matter, and of pore space, about half of which is air and half water. The inorganic particles are residues of weathered rock chemically they are mainly silicate minerals. At the atomic level, these minerals consist of polymeric inorganic structures in which the fundamental unit is a silicon atom surrounded tetrahedrally by four oxygen atoms. Since these oxygen atoms are in turn...

The Human Health Effects of Outdoor Air Pollutants

It is now well established that breathing polluted air can have a dramatic influence on human health. In this section, the most important effects of outdoor air pollutants are described, and the variation in concentration of the dominant air pollutants in different countries is discussed. The effect that pollutants have on human health cannot be deduced from general laws of biology or physiology they must be established by experimentation. One can imagine experiments involving animals or human...

Protection Against Low Levels of Cadmium

Cadmium is acutely toxic The lethal dose is about 1 g. Humans are protected against chronic exposure to low levels of cadmium by the presence of the sulfur-rich protein metallothionein, the usual function of which is the regulation of zinc metabolism. Because it has many sulfhydryl groups, metallothionein can complex almost all ingested Cd2+ the complex is subsequently eliminated in the urine. If the amount of cadmium absorbed by the body exceeds the capacity of metallothionein to complex it,...

Sequestration of C02

In the future, C02 might be removed chemically from the exhaust gases of major point sources that would otherwise release it into the atmosphere, such as power plants that burn fossil fuels and that collectively are responsible for one-quarter to one-third of total emissions. The carbon dioxide gas so recovered would then be sequestered i.e., deposited in an underground or ocean location that would prevent its release into the air. For example, the C02 could be sequestered by burial in the deep...

Fossil Fuels Petroleum

Petroleum, or crude oil, is a complex mixture of thousands of compounds, most of which are hydrocarbons the proportions of the compounds vary from one oil field to another. The most abundant type of hydrocarbon usually is the alkane series, which can be generically designated by the formula CnH2n+2- In petroleum, the alkane molecules vary greatly, from the simple methane, CH4 (i.e., n 1), to molecules having almost 100 carbons. Most of the alkane molecules in crude oil are of two structural...

PCB Contamination by Furans

Strong heating of PCBs in the presence of a source of oxygen can result in the production of small amounts of furans. These compounds are structurally similar to dioxins they differ only in that the molecules are missing one oxygen atom in the central ring. The furan ring contains five atoms, one of which is oxygen and the other four of which are carbon atoms that participate in double bonds The dibenzofurans (DFs) have a benzene ring fused to opposite sides of the furan ring As with dioxins,...

PCBs Cycling Among Air Water and Sediments

Food Chain Pcbs

If released into the environment, PCBs persist for many years because they are so resistant to breakdown by chemical or biological agents. Although their solubility in water is very slight indeed they are more likely to be adsorbed onto suspended particles in the water than dissolved in it the tiny amounts of PCBs in surface waters are constantly being volatilized and subsequently redeposited on land or in water after traveling in air for a few days. By such mechanisms, PCBs have been...

The Ozone Layer

In this chapter, the following introductory chemistry topics are used Moles concentration units including mole fraction Ideal gas law partial pressures Thermochemistry AH, AHf Hess' law Kinetics rate laws reaction mechanisms, activation energy, catalysis The ozone layer is a region of the atmosphere that is called Earth's natural sunscreen because it filters out harmful ultraviolet (UV) rays from sunlight before they can reach the surface of our planet and cause damage to humans and other life...

Dioxin Numbering System

The nomenclature and numbering system used for ring systems like the dioxins is a little unusual. Since the central dioxin ring is connected on either side to benzene rings, the three-ring unit is properly known as dibenzo-f)-dioxin. The chlorine substitution on the outer rings also should be recognized, so the dioxin shown below is a tetrachlorodibenzo-p-dioxin, or TCDDt The numbering scheme for the ring carbons in dioxins takes into account the fact that the carbons shared between two rings...

No2 Ono o2

Not all XO molecules such as NOz survive long enough to react with oxygen atoms some are photochemically decomposed to X and atomic oxygen, which then reacts with 02 to re-form ozone. Write out the three steps (including one for ozone destruction) for this process and add them together to deduce the net reaction. Does this sequence destroy ozone overall, or is it a null cycle, which is defined as one that involves a sequence of steps with no chemical change overall Another important X catalyst...

Principles of Toxicology

Toxicology is the study of the harmful effects on living organisms of substances that are foreign to them. The substances of interest include both synthetic chemicals and those that exist naturally in the environment. In toxicology, the effects are normally determined by injecting or feeding animals with the substance of interest and observing how the health of the animal is affected. By contrast, in epidemiology, scientists do not run experiments in a lab but instead determine the health...