Environmental Chemistry

Review Questions

In the micrograms per cubic meter concentration scale, to what substances do micrograms and cubic meters refer 2. In general terms, what is meant by photochemical smog What are the initial reactants in the process Why is sunlight required 3. What is meant by a primary pollutant and by a secondary pollutant Give examples. 4. What is the chemical reaction by which thermal NO is produced From which two sources does most urban NO arise What is meant by the term NOxl 5. Describe the strategies by...

Green Chemistry Questions

See the discussion of focus areas and the principles of green chemistry in the Introduction before attempting these questions. 1. PERC replaced gasoline and kerosene in the dry-cleaning process. (a) Describe any environmental problems or worker hazards that would be associated with these solvents. (b) Would these same environmental problems or worker hazards be eliminated by the use of PERC (c) By the use of carbon dioxide 2. The development of surfactants for carbon dioxide by Joseph DeSimone...

Aerosols and Global Warming

So2 Free Radical

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...

Organophosphate and Carbamate Insecticides

Organochlorine insecticides have now largely been replaced by those that are less persistent and less subject to bioaccumulation. The most important classes of these newer insecticides are organophosphates and carbamates, both of which are discussed below. Structurally, all organophosphate (OP) pesticide molecules can be considered as derivatives of phosphoric acid, 0 P(0H)3, and consist of a central, pentavalent phosphorus atom to which are connected an oxygen or sulfur atom doubly bonded to...

How To Homemade Iron Can Be Converted To Dichromate Ion And Vice Versa

Solubility Iron Carbonate

Solving for the carbonate concentration, we obtain Thus, as expected by application of Le ChStelier's principle to the reactions, the solubility of calcium carbonate decreases as the fixed hydroxide concentration increases, the limit at high levels of OH being Ksp 2, the value we obtained assuming no reaction of carbonate ion with water. In contrast, for water that is neutral or acidic and therefore low in hydroxide ion, the CaC03 solubility is much larger than this value, as illustrated in...

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...

The Chemistry Of Natural Waters

Pressure Enthalpy Diagram R22 Dupont

In this chapter, the following introductory chemistry topics are used Concepts of oxidation and reduction as electron loss gain half-reactions redox reactions oxidizing and reducing agents electrode potentials Solubility product and weak acid weak base calculations water constant Kw Oxidation numbers and the balancing of redox reactions reviewed in Box 13-1 Background from previous chapters used in this chapter Equlibria involving gases dissolved in water Henry's law Chapter 3 All life forms on...

Ch2o o2 co2 h2o

Co2 H2o Ch2o Moleculas

Some organic matter is partially oxidized to aldehydes, ketones, and alcohols, which give fresh waste its characteristic sweet smell. In the second, anaerobic acid phase, the process of acidic fermentation occurs, generating ammonia, hydrogen, and carbon dioxide gases and large quantities of partially degraded organic compounds, especially organic acids. The pH of the leachate in this phase, 5.5-6.5, is chemically aggressive. Other organic and inorganic substances dissolve in this leachate due...

Toxic Organic Compounds

Lanthionization Reaction

The Accumulation of Organochlorines in Biological Systems Other Organochlorine Insecticides Box 10-1 The Controversial Insecticide Endosulfan Principles of Toxicology Organophosphate and Carbamate Insecticides Natural and Green Insecticides, and Integrated Pest Management Green Chemistry Insecticides That Target Only Certain Insects Green Chemistry A New Method for Controlling Termites Herbicides Box 10-2 Genetically Engineered Plants Summary Box 10-3 The Environmental Distribution of...

Sequestration of C02

Sequestration Carbon Chemical Structure

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...

The Mechanism of the Greenhouse Effect The Earths Energy Source

Darrin Marchus

The Earth's surface and atmosphere are kept warm almost exclusively by energy from the Sun, which radiates energy as light of many types. In its radiating characteristics, the Sun behaves much like a blackbody, i.e., an object that is 100 efficient in emitting and in absorbing light. The wavelength, Apeak, in micrometers, at which the maximum emission of energy occurs by a radiating blackbody decreases inversely with increasing Kelvin temperature, T, according to the relationship Since for the...

Alternative Fuels Alcohols Ethers and Esters

For environmental and supply reasons, attention is turning to the development of cleaner-burning alternatives to hydrocarbon fuels, especially to power vehicles. Some of these alternatives are, at least in principle, renewable in the sense that their production could be sustained indefinitely into the future without resulting in the accumulation of additional carbon dioxide. In the material that follows, we discuss the nature and properties of the major contenders for alternative fuels. In a...

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...

Electric Cars Powered by Batteries

An alternative to vehicles that use fuel cells are those powered by batteries. Some electric cars have already been produced, and most use a number of the same sort of lead-acid batteries that gasoline-powered vehicles have traditionally employed singly to operate the starter motor. In the future, electric cars will probably use nickel-cadmium, nickel-metal hydride, and lithium-based batteries. The practical difficulties that discourage widespread adoption of such vehicles are their high cost,...

The Health Effects of Dioxins Furans and PCBs

Pcbs Effect Human Health

Over a billion dollars has been spent on research to determine the extent to which dioxins, furans, and PCBs cause toxic reactions in humans. Nevertheless, conclusions about this issue are still tentative and controversial. Evidence about toxicity is derived from two sources toxicological experiments on animals that have been deliberately exposed to the chemicals and epidemiological studies of humans who have been accidentally exposed. It is generally agreed that most PCBs are not acutely toxic...

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...

Mercury Mercury Vapor

Environment Conversion Low Drowning

Elemental mercury was employed in hundreds of applications, many of which e.g., electrical switches took advantage of the unusual property that it is a liquid that conducts electricity well. In automobiles built before 2000, electrical switches that operate convenience and trunk lighting contained mercury, as did instrument panels and antilock brakes all of this mercury is lost to the environment when the cars are recycled for their steel unless the element is specifically collected, as is...

Environmental Lead from Leaded Gasoline

When these additives are used in gasoline, the atoms of lead that are liberated by the combustion of the tetraalkyl compounds must be removed before they form metallic deposits and damage the vehicle's engine. In order to convert FIGURE 15-4 The historical consumption of load in gasoline in the United States. Source C. E. Dunlop et al., Past Leaded Gasoline Emissions as a Nonpoint Source Tracer in Riparian Systems, Environmental Science and Technology 34 2000 1211. the combustion products into...

The Chemicals That Cause Ozone Destruction

Methyl Bromide Dupont

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...

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...

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...

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 Interaction of Light with Particles

Albedo Light Reflection Types Grass

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...

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...

Groundwater Contamination by Organic Chemicals

Ground Water Chemistry

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...

PCB Contamination by Furans

Worksheets Connect The Dots

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,...

Oh O H2ccch3

FIGURE 8-12 Preparation of propylene glycol and acetol from glycerin. In the absence of H2 acetol can be isolated as the major product by distillation as it is formed. Propylene glycol has many desirable properties, including its low toxicity, which allow it to be used in a number of different products. Propylene glycol is the only glycol approved by the U.S. Food and Drug Administration for use in products meant for human consumption. It can be found in alcoholic beverages, confections and...

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...

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...

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...

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...

Tuf HyhrnnFN FfONOMY

In this chapter, the following introductory chemistry topics are used Thermochemistry calculations Electronic structure of atoms Electrochemistry oxidation numbers redox half-reactions batteries electrolysis M Crystalline versus amorphous solids Basic organic chemistry structures alcohols, ethers, carboxylic acids, esters, sugars, carbohydrates Background from previous chapters used in this chapter Greenhouse gases (carbon dioxide, methane, nitrous oxide) (Chapter 6) Anaerobic decomposition...

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...

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...

So21h2so4 nox1hno3

New Jersey Acid Rain

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....

Answers to Selected Odd Numbered Problems

1-1 a 427 kj mol junction of UV-B with UV-C b 299 kj mol junction of UV with visible region c 160 kj mol junction of visible and infrared regions d 29.9 kj mol beginning of thermal IR region Box 1-1, Problem 1 O kt 02 k7 M Each O reacts as O 02 - O 2.5 X 10 12 g cm3 y 1 9. 1.5 X 10 6 3. No, not if the carbon dioxide is a waste by-product from another process. 5. Harpin is applied to the plant, which elicits the plant's own natural defenses. Additional Problems 1. b 4 X 10l5g 3. a 140 b 10 7....

Describe The Chemical Processes That Are Predominant In The Stratosphere

In Chapter 1, the gas-phase chemistry of the unpolluted stratosphere was explored. Since the late 1970s, however, the normal functioning of the stratosphere's ozone screen and the protection it provides us has been periodically upset by anthropogenic chlorine-containing chemicals in the atmosphere. Most famously, these substances now cause an ozone hole to open each spring season above the South Pole. Ozone levels in the stratosphere over the North Pole as well, and to some extent even that...

The Most Predominant Fate In Air For Most Simple Radicals Is Reaction With

Peroxy Radicals Reaction Produce

(Here and elsewhere in this book we write Lewis structures that assume that d otbitals in atoms such as sulfur and phosphorus allow these elements to form double bonds.) Hydroxyl radical does not add to carbon dioxide, O C 0, since the molecule contains only very strong C 0 bonds. However, OH' addition does occur to the carbon atom in carbon monoxide, CO, since the triple bond is thereby converted to the very stable double bond and a new single bond is also formed This process is exothermic...

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...

Nitrate Contamination of Groundwater

The inorganic contaminant of greatest concern in groundwater is the nitrate ion, NO3-, which commonly occurs in both rural and suburban aquifers. Although uncontaminated groundwater generally has nitrate nitrogen levels of 4-9 ppm, about 9 of shallow aquifers from which water is often extracted via privately owned wells in the United States now have nitrate levels that exceed the 10-ppm nitrogen MCL value. Indeed, elevated levels of about 100 ppm can result from agricultural activity. The...

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...

Number Of Ozone Molecules Per Cm3

Now 40.7 mol X 6.02 X 1023 molecules mol 2.45 X 1025 molecules, or 2.45 X I016 billion molecules of air. 3.01 X 1018 molecules of SP2 2.45 X 1016 billion molecules of air 123 ppb Note that the conversion of moles to molecules was not strictly necessary, as Avogadro's number cancels from numerator and denominator. As stated previously, ppb refers to the ratio of the number of moles as well as to the ratio of the number of molecules. It is vital in all interconversions to distinguish between...

Universidad De Antioquia Riri lOTFfiA Central

Is devoted to exploring this problem and its possible solutions, as well as to the nature and properties of fossil fuels, namely coal, petroleum, and natural gas. Carbon dioxide is produced when any carbon-containing substance undergoes complete combustion As we saw in Chapter 6, C02 is an important greenhouse gas, and the increase in its atmospheric concentration is responsible for the largest fraction of global warming of any anthropogenic factor. Developed countries have accounted for about...

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...

Additional Problems

Using a ruler and calculator, estimate from Figure 7-1 the fraction of COz emissions in 2004 compared to 1990 a from the United States and b collectively from China, India, and other developing countries. Did the fraction of emissions from EU countries increase or decrease over that period 2. List several reasons that you think proponents of carbon dioxide allocations based strictly on a country's population would advance in support of their position. What objections can be raised to their...

Websites of Interest

Log on to www.whfreeman.com envchem4 and click on Chapter 16. Environmental Instrumental Analysis VI Inductively Coupled Plasma Determination of Lead The analysis of heavy metals in environmental samples is now routinely accomplished by the spectroscopic method discussed in this box. As discussed in the text, anthropogenic lead contamination in the environment in North America and Europe has been decreasing since tetraethyllead and tetra-methyllead were phased out of gasolines in the 1970s and...

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,...

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...

Health Hazards of Nitrates in Drinking Water

Perchlorate Colorado River

Excess nitrate ion in drinking water is a potential health hazard since it can result in methemoglobinemia in newborn infants as well as in adults with a specific enzyme deficiency. The pathological process, in brief, runs as follows. Bacteria, e.g., in unsterilized milk-feeding bottles or in the baby's stomach, reduce some of the nitrate to nitrite ion, N02 N03 2 H 2 e- gt NO, H20 The nitrite combines with and oxidizes the iron ions in the hemoglobin in blood from Fe2 to Fe3 and thereby...

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 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 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...

The Disposal of Sewage Sludge

The sludge from both the primary and secondary treatment stages of sewage is principally water and organic matter. It can be digested anaerobically, in a process that takes several weeks to complete. Bacteria levels in the sludge are not thereby completely eliminated, but the levels are reduced about a thousandfold. The sludge that remains after this further organic decomposition has occurred and after the supernatant water is removed is sometimes then incinerated or simply dumped into a...

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...

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...

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...

Disinfection by Chemical Methods Ozone and Chlorine Dioxide

To rid drinking water of harmful bacteria and viruses, especially those arising from human and animal fecal matter, by use of a chemical agent requires an oxidizing agent more powerful than 02. In some localities, particularly in France and other parts of western Europe but also in some North American cities Montreal and Los Angeles are examples ozone is used for this purpose. Since O3 cannot be stored or shipped because of its very short lifetime, it must be generated on-site by a relatively...

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...

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...

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,...

Anthropogenic Sources of Arsenic to the Environment

Anthropogenic environmental sources of arsenic stem from the continuing use of its compounds as pesticides its unintended release during the mining and smelting of gold, lead, copper, and nickel, in whose ores it commonly occurs (the leachate from abandoned gold mines of previous decades and centuries can still be a significant source of arsenic pollution in water systems) the production of iron and steel the combustion of coal, of which it is a contaminant and arsenic-contaminated water...

Ion Chromatography of Environmentally Significant Anions

Dentist Equipment

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,...

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...

Environmental Chemistry 5 Reactions That Produce And Consume Ozone Naturally

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...

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...

Conclusions About Solar Energy

In these discussions, some general features concerning the use of solar energy, as opposed to fossil-fuel and nuclear energy, have emerged, and others have also been reached by energy analysts. Many of these conclusions apply to all forms of renewable energy. The advantages of solar energy appear to be that it is free and fantastically abundant has low environmental impact does not require imported oil or large, centralized suppliers and expensive distribution networks and has high public...

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...

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,...

Urban Ozone The Photochemical Smog Process The Origin and Occurrence of Smog

Mechanism For Photochemical Smog

Many urban centers in the world undergo episodes of air pollution during which relatively high levels of ground-level ozone an undesirable constituent of air if present in appreciable concentrations at low altitudes in the air that we breathe are produced as a result of the light-induced chemical reaction of pollutants. This phenomenon is called photochemical smog and is sometimes characterized as an ozone layer in the wrong place, to contrast it with the beneficial stratospheric ozone...

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...

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,...

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...

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...

Dose Response Relationships

Most of the quantitative information concerning the toxicity of substances is obtained from experiments performed by administering doses of the substances to small animals, although recently tests on certain bacteria have been used to determine whether a substance is likely to be a carcinogen or not. Owing to practical considerations including cost and time, most experiments involve acute rather than chronic toxicity, even though it is the latter that usually is of primary interest in...

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...

Onh22 h2o 2 nh3 co2

The neutralization of acidity by ammonia gas released into the air from livestock and from the use of fertilizers, and by carbonate ion suspended in air from the dust raised by farming activities, is the main reason why precipitation over the central United States is not particularly acidic, and similarly for regions of China. However, some acidification results from the ionization of the ammonium ion, NH4+, a weak acid, that is produced by ammonia neutralization Although the nitrate and...

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...

Symbolic Representations of Carbon Networks

Organic molecules often contain extensive networks of carbon atoms. Chemists find it convenient to construct shorthand visual representations of such molecules using a symbolic system of lines that indicate only the position of the bonds (not including bonds to hydrogen atoms), rather than writing out a structure in which the C and H atoms are shown explicitly. To indicate the presence of a carbon atom, a kink is shown in the chain's representation. For example, the molecule n-butane can be...

Aikenes and Their Chlorinated Derivatives

In some organic molecules, one or more pairs of the carbon atoms are joined by double bonds since each carbon atom forms a total of four bonds, there are only two additional bonds formed by such carbon atoms. The simplest hydrocarbon of this type is a colorless gas called ethem, usually known by its older name ethylene Notice that the actual planar geometry of this molecule, with bond angles of about 120 around each carbon, can be shown in the structural formula. Condensed formulas normally...

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...

Tetravalent Organic Lead Compounds as Gasoline Additives

Whereas the compounds of Pb(Il) are ionic, most Pb(IV) compounds are covalent molecules rather than ionic compounds of Pb4+. In this respect, tetravalent lead is similar to the corresponding form of the other elements (C, Si, Ge, Sn) in its group of the periodic table. Commercially and environmentally, the most important covalent compounds of lead (IV) are tetraalkyl compounds, PbR4, especially those formed with the methyl group, CH3, and the ethyl group, CH2CH3 namely tetra-methyllead,...

Ay h2oco3 oh

Because these reactions reduce the concentrations of the original anions produced by dissolution of the salt PbS or PbC03, the position of equilibrium in the original reactions shifts to the right side, thereby dissolving more of the salt, in analogy with the process involving CaC03 that we analyzed in Chapter 13. Thus the solubilities of PbS and PbC03 in water are substantially increased by the reaction of the anion with water. If highly acidic water comes into contact with minerals such as...

Other Advanced Oxidation Methods

A process called direct chemical oxidation has been proposed for the destruction of solid and liquid organic wastes in the aqueous phase, particularly in environments such as those under buildings, where the light required for UV processes cannot conveniently be supplied. It uses one or another of the strongest known chemical oxidants e.g., acidified peroxydisulfate anion, S2082-, under ambient pressure and moderate temperatures to oxidize the wastes. Such a process needs no catalysts and...

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...

Decontamination of Groundwater In Situ Remediation

Scientists have developed a promising in situ technique for treating groundwater contaminated by volatile (mainly C5 and Cz) chlorinated organics. They construct an underground permeable wall of material (mostly coarse sand) along the path of the water. The water is cleansed as a result of its passage through the wall and never has to be pumped out of the ground (see Figure 14-7). The ingredient that is placed within the sand bed and that chemically cleans the water is metallic iron, Fe , in...

Decontamination of Groundwater Bioremediation and Natural Attenuation

Bioremediation is the term applied to the decontamination of water or soil using biochemical rather than chemical or physical processes. Recently there has been interesting progress reported in using bioremediation to cleanse water of chlorinated ethene solvent contamination. The biod gradation of chloroethenes by aerobic bacteria becomes less and less efficient as the extent of chlorination increases, so it is ineffective for perchloroethene. However, under anaerobic conditions, the reductive...

Cicr 2 cr o2

Hypochlorous acid can also be generated by the reaction with water of the chlorine-containing compound isocyanuric acid, C3N303H3 Either the trichloro derivative, in which each hydrogen is replaced by CI to give C3N3O jCl3, or the sodium dichloro derivative, C3N303Cl2Na, is used. In either case, the OH group from water combines with the chlorine to produce HOC1 and the hydrogen of H,0 becomes bonded to the nitrogen, giving isocyanuric acid, C3N303H3 C3N303C13 + 3 H,0 C3N303H3 + 3 HOC1 Since...

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...

Biblioteca Central

That the solution is alkaline is not surprising, given that the carbonate ion, as weak bases go, is a moderately strong one. Repeat the calculation of the solubility of calcium carbonate by the approximate single equilibrium method using a realistic wintertime water temperature of 5 C at that temperature, ksp 8.1 X 1CT9 for CaC03, ka 2.8 X 1CT11 for HC03and kw 0.2 X lu14. By comparing the result with that in the foregoing text for 25 C, decide whether the solubility of calcium carbonate...

K2 [co32 ih[hco3t

From the second and third equations, respectively, we can express both H2C03 and C032 in terms of HC03 and h j, and substitute these relationships solutions into the mass balance equation H2co3 HCO3 H+ Kx CO32 k2 HC03 H+ ( HC031 H+J Kj) + ( HC03D + (K2 HCO3I H+D C Solving this equation for bicarbonate and substituting the solution into the preceding pair of equations yields the expressions given in the main text for the fraction of each species present at any pH. Although this salt is almost...

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...

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...

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...

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...

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...

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...

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...

Risk Assessment

Once toxicological and or epidemiological information concerning a chemical is available, a risk assessment analysis can be performed. This analysis tries to answer quantitatively the questions What are the likely types of toxicity expected for the human population exposed to a chemical and What is the probability of each effect occurring in the population Where necessary, risk assessment also tries to determine permissible exposures to the substance in question. In order to perform a risk...

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...

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...