1 Introduction

It is doubtful if anyone (even though there may be claims to the contrary) who can state with any degree of accuracy (although there is always someone who can make a statement with a high degree of uncertainty) when the Earth was last pristine and unpolluted. Yet, to attempt to return the environment to such a mythical time might have a severe effect on the current indigenous life, perhaps a form of pollution in reverse! However, there is the possibility that through the judicious use of resources and the application of the principles of environmental science, environmental engineering, and environmental analysis (disciplines involved in the study of the environment as well as determining the purity of the environment) (Woodside, 1999; Speight and Lee, 2000; Manahan, 2010), a state can be reached where pollution is minimal and does not pose a threat to the future. Such a program will not only involve well-appointed suites of analytical tests but also subsequent studies that cover the effects of changes in the environmental conditions on the flora and fauna of a region. These studies can include aspects of chemistry, chemical engineering, microbiology, and hydrology as they can be applied to solve environmental problems (Pickering and Owen, 1994; Speight and Lee, 2000; Schwarzenbach et al., 2003; Tinsley, 2004).

The potential for pollution of organic chemicals starts during the production stage. The typical organic chemical synthesis process involves combining one or more feedstocks in a series of unit process operations. Commodity chemicals tend to be synthesized in a continuous reactor, while specialty chemicals usually are produced in batches. Most reactions take place at high temperatures, involve metal catalysts, and include one or two additional reaction components. The yield of the organic chemical will partially determine the kind and quantity of by-products and releases. In fact, many specialty organic chemicals require a series of two or three reaction steps, each involving a different reactor system and each capable of producing by-products. Once the reaction is complete, the desired product must be separated from the by-products by a second unit operation. A number of separation techniques such as settling, distillation, or refrigeration may be used. The final product may be further processed, such as by spray drying or pelletizing, to produce the saleable item. Frequently, by-products are also sold, and their value can influence the economics of the process.

In spite of numerous safety protocols that are in place and the care taken to avoid environmental incidents that are harmful to the environment, every industry suffers accidents that lead to contamination by chemicals. It is therefore often helpful to be aware of the nature (the chemical and physical properties) of the chemical contaminants and the products arising therefrom (when ecosystem parameters interact with the chemicals) in order to understand not only the nature of the chemical contamination but also chemical changes to the contaminants following from which cleanup methods can be chosen.

In the past, the existence and source of such information was unknown and, if known, was not always consulted. When the existence and sources of the relevant information are known, decisions must be made in order for environmental scientists and engineers to make an informed, and often quick, decision on the next steps, even if it is decided at a later time not to use the information for a particular application. However, on the basis that it is better to know than to not know, knowing about the relevant data gives investigators and analysts the ability to assess whether or not a chemical discharge into the environment should be addressed or whether the environment can take care of itself through biodegradation of the chemical. This is especially true for scientists and engineers involved in site cleanup operations, assessment of ecological risk, and assessment of ecological damage. Modern data bases relating to the properties of chemicals, especially organic chemicals (which are the reason for the current text), there can be no reasons (or excuses) for not knowing or understanding the fundamental aspects of the behavior of organic chemicals that pollute the environment.

By way of clarification, an organic pollutant is an organic chemical that is released into an ecosystem and which causes pollution (however temporary or permanent) insofar as the chemical is harmful to or is destructive to the flora and/or the fauns of the ecosystem. Typically, and by virtue of the name, a pollutant is a chemical that is not indigenous to the ecosystem. However, if the discharged chemical is indigenous to the ecosystem (i.e., the organic chemical is a naturally occurring compound), it can be (should be) classed as a pollutant when it is released into the system in amounts that are in excess of the natural concentration of the organic chemical in the ecosystem, and by this increased concentration the chemical can cause harm to (or is destructive to) the flora and/or the fauna of the ecosystem.

Given time, some organic chemicals are removed from the ecosystem by natural events, such as attack by indigenous bacteria (biodegradation) or by increasing the concentration of natural-occurring bacteria to remove the chemical from the ecosystem (bioremediation) (Speight and Arjoon, 2012). However, there are organic chemicals that are known as persistent organic pollutants (POPs) which are compounds that are resistant to environmental degradation through the various chemical and biological processes (Jacob, 2013). POPs, as the name implies, are not easily degraded in the environment due to their stability and low decomposition rates and, thus, have a long life in various ecosystems and often require other forms of removal such as physical or chemical methods of cleanup as well as the addition of nonindigenous microbes for cleanup (Speight and Lee, 2000; Speight and Arjoon, 2012). POPs also have the ability for long-range transport, and environmental contamination by POPs is extensive, even in areas where these chemicals have never been used, and will remain in these environments for a considerable time (even years) and after restrictions implemented due to their resistance to degradation.

POPs, like any organic chemical pollutant, can enter an ecosystem through the gas phase, the liquid phase, or solid phase and which can resist degradation and are mobile over considerable distances (especially in the gas phase or through transportation in river systems) before being redeposited in a location that is remote to the location of their introduction into the ecosystem. Furthermore, POPs can be present as vapors in the atmosphere or bound to (adsorbed on) the surface of soil or mineral particles and also have variable solubility in water.

Many POPs are currently (or were in the past) arose from the extensive use of agrochemicals (agricultural chemicals) such as pesticides, herbicides, and biocides, solvents, pharmaceuticals, and various industrial chemicals (Chapter 3). Although some POPs arise naturally, for example, from various biosynthetic pathways, most are products of human industry and tend to have higher concentrations and are eliminated more slowly. If not removed and because of their properties, POPs will bioaccumulate and have significant impacts on and the flora and fauna of the environment. The most frequently used measure of the potential for bioaccumulations and persistence of an organic compound in the environment are the result of the physicochemical properties (such partition coefficients and reaction rate constants) (Mackay et al., 2001).

Furthermore, the capacity of the environment to absorb the effluents and other impacts of process technologies is not unlimited, as some would have us believe. The environment should be considered to be an extremely limited resource, and discharge of chemicals into it should be subject to severe constraints. Indeed, the declining quality of raw materials dictates that more material must be processed to provide the needed fuels. And the growing magnitude of the products and effluents from industrial processes has moved above the line where the environment has the capability to absorb such process effluents without disruption.

As a result of the increasing concern about pollution (especially pollution by organic chemicals), in May 1995, the United Nations Environment Program Governing Council investigated POPs and placed a global ban on those organic chemicals that were particularly harmful and toxic to the environment among which were many pesticides, herbicides, and fungicides which are historically or commercially important (Appendix: Table A6) (Hites, 2007) and required the participating governments to take measures to eliminate or reduce the release of POPs in the environment. On May 22, 2001, the Stockholm Convention was adopted and put into practice by the United Nations Environment Program. The purpose of the statement of the agreement is to protect the environment from POPs and the members at the recognized the potential for environmental toxicity of POPs which had the potential for long range transport resulting in bioaccumulation and biomagnification (Speight and Lee, 2000; Manahan, 2010; Speight and Arjoon, 2012).

As a commencement to this process of data examination and ingestion, this chapter introduces the terminology of environmental technology as it pertains to the sources and types of organic pollutants. Briefly, a contaminant, which is not usually classified as a pollutant unless it has some detrimental effect, can cause deviation from the normal composition of an environment. A receptor is an object (animal, vegetable, or mineral) or a locale that is affected by the pollutant. A chemical waste is any solid, liquid, or gaseous waste material that, if improperly managed or disposed of, may pose substantial hazards to human health and the environment (Table 4.1). At any stage of the management process, a chemical waste may be designated by law as a hazardous waste. Improper disposal of these waste streams, such as organic solvents (Table 4.2), in the past has created hazards to human health and the need for very expensive cleanup operations (Tedder and Pohland, 1993). Correct handling of these chemicals (NRC, 1981), as well as dispensing with many of the myths related to chemical processing (Kletz, 1990), can mitigate some of the problems that will occur, especially problems related to the flammability of organic liquids (Table 4.3), that will occur when incorrect handling is practiced. Chemical waste is also defined and classified into various subgroups (Table 4.1).

2 Aerosols

An aerosol is a suspension of liquid or solid particles in a gas, with particle diameters in the range of 10^− 9 to 10^− 4 m. In atmospheric science, however, the term aerosol traditionally refers to suspended particles that contain a large proportion of condensed matter other than water, whereas clouds are considered as separate phenomena (Pöschl, 2005). Aerosols give rise to a class of compounds known as volatile organic compounds (VOCs) which can arise from various sources.

In addition to the emissions of VOCs from vegetation, large quantities of organic compounds are emitted into the atmosphere from anthropogenic (man-made) sources, largely from combustion of petroleum products such as gasoline and diesel fuels and from other sources such as solvent use and the use of consumer products. Although the theory is that the combustion of such chemicals (alkanes in particular) should proceed completely to produce quantitative yields of carbon dioxide and water:

This is not always the case, and the reference of heteroatoms (nitrogen, oxygen, and/or sulfur) complicates the process by converting the heteroatoms to the gases oxide (such as nitrogen oxides and sulfur oxides) that are gaseous pollutants. In addition, incomplete combustion (i.e., combustion in a dearth of oxygen) will produce polynuclear aromatic producers that appear in the atmosphere (as particulate matter) or in the soil.

In the atmosphere organic compounds are partitioned between the gaseous and particulate phases, with the chemicals being at least partially in the gas phase for liquid-phase vapor pressures of at least 10^− 6 Torr at atmospheric temperature (1 Torr is a unit of pressure based on an absolute scale and is 1/760 of a standard atmosphere; thus 1 Torr = 1 mmHg pressure). In the atmosphere, these gaseous organic compounds are transformed by photolysis and/or reaction with hydroxyl (OH) radicals, nitrate (NO₃) radicals, and ozone (O₃). Emissions of organic compounds and their subsequent in situ atmospheric transformations lead to a number of adverse effects, including: (1) the formation—in the presence of oxides of nitrogen, NOx—of ozone, a criteria air pollutant; (2) the formation of secondary organic minute particles—aerosols—resulting in loss of visibility and risks to human health; and (3) the in situ atmospheric formation of toxic air contaminants, including, for example, formaldehyde HCHO, peroxy-acetyl nitrate, and nitrated aromatic species.

Atmospheric aerosol particles originate from a wide variety of natural and anthropogenic sources, including biomass. Primary particles are directly emitted as liquids or solids from sources such as biomass burning, incomplete combustion of fossil fuels, volcanic eruptions, and wind-driven or traffic-related suspension of road, soil, and mineral dust, sea salt, and biological materials (such as plant fragments, microorganisms, and pollen) (Oliveira et al., 2011). This also include the commercial conversion of biomass to a variety of chemicals, some of which may not be beneficial when released to the environment (Werpy and Peterson, 2004; Kim and Holtzapple, 2005, 2006a, b; Speight, 2011). Another example of a primary aerosol is the carbonaceous soot formed during incomplete combustion processes—diesel soot is a classic example of this form of primary carbonaceous aerosol. In spite of claims to the contrary, diesel fuel is not a clean fuel—it might be clean insofar as sulfur content is concerned—try following a diesel fuel vehicle under full load and/or up an incline. The emission of black fumes becomes very evident and very uncomfortable.

Another example of primary aerosols (although not organic in nature) is the fly ash from coal combustion systems or the incineration of wastes. This material is typically generated by high-temperature processes that result in the production of condensed inorganic materials formed as small spherical beads, typically high in silicates or iron oxides. Anthropogenic sources of primary aerosol and particulate material include mechanical abrasion that produces construction and industrial dusts, as well as abrasion of tires and pavement materials on roads.

Secondary aerosol particles, on the other hand, are formed by gas-to-particle conversion in the atmosphere (new particle formation by nucleation and condensation of gaseous precursors). The most important aerosol-generating inorganic gases that are released into the atmosphere by human combustion of fossil fuels are the nitrogen oxides (nitric oxide and nitrogen dioxide) and sulfur dioxide. Nitric oxide (NO) is oxidized to nitrogen dioxide (NO₂) and subsequently to nitric acid (HNO₃) by the reaction of hydroxyl radical with nitrogen dioxide. The nitric acid can in turn react with ammonia to form ammonium nitrate, a white solid. The chemical equations are often subject to debate but can be represented simply as:

$\begin{array}{l}\mathrm{NO}+{\mathrm{O}}_2\to {\mathrm{NO}}_2\\ \mathrm{NO}+{\mathrm{O}}_3\to {\mathrm{NO}}_2+{\mathrm{O}}_2\\ {\mathrm{NO}}_2+\mathrm{O}\mathrm{H}\to {\mathrm{H}\mathrm{N}\mathrm{O}}_3\\ {\mathrm{H}\mathrm{N}\mathrm{O}}_3+{\mathrm{N}\mathrm{H}}_3\to {\mathrm{N}\mathrm{H}}_4{\mathrm{NO}}_3\end{array}$

Sulfur dioxide—a common product from the combustion of sulfur-containing organic fuels—in the atmosphere reacts with hydroxyl radical in the gas phase and with hydrogen peroxide and ozone in the aqueous phase to form sulfuric acid (H₂SO₄), which is water soluble and also has a very low vapor pressure, so it rapidly forms aerosol once it is formed. Sulfuric acid can also react with ammonia to form ammonium bisulfate (NH₄HSO₄) and ammonium sulfate [(NH₄)₂SO₄]. These species are all fairly water soluble, and at high relative humidity values they will grow by adding water vapor to their surfaces.

Thus, airborne particles undergo various physical and chemical interactions and transformations (often referred to as atmospheric aging) which involves changes of particle composition, particle size, and particle structure through chemical reaction, gas uptake, and restructuring. Particularly efficient particle aging occurs in clouds, which are formed by condensation of water vapor on preexisting aerosol particles. Most clouds reevaporate, and modified aerosol particles are again released from the evaporating cloud droplets or ice crystals (cloud processing). If, however, the cloud particles cause precipitation which reaches the surface of the Earth, not only the condensation nuclei but also other aerosol particles that are scavenged on the way to the surface are removed from the atmosphere (wet deposition). Particle deposition without precipitation airborne water particles—that is dry deposition—is less important on a global scale but is highly relevant with respect to air quality. Depending on the properties of the aerosol and meteorological conditions, the characteristic residence times (lifetimes) of aerosol particles in the atmosphere can range from hours to weeks (Pöschl, 2005).

Depending on the origin of organic aerosols, the components can be classified as primary or secondary. Primary organic aerosol components are directly emitted in the condensed phase (as liquid particles or as solid particles) or as semivolatile vapors which are condensable under atmospheric conditions. The main sources of primary organic aerosol particles and components are natural and anthropogenic biomass burning (forest fires, slashing and burning, domestic heating), fossil-fuel combustion (domestic heating, industrial operations, traffic density), and wind-driven or the traffic-related suspension of soil and road dust, biological materials (such as plant debris, animal debris, pollen, and spores), sea spray, and spray from other surface waters that contain dissolved organic chemicals.

Secondary organic aerosol components are formed by chemical reaction and gas-to-particle conversion of VOCs in the atmosphere, which may proceed through different chemical and physical pathways, such as: (1) new particle formation; (2) formation of semivolatile organic compounds—SVOCs—by gas-phase reactions and participation of the SVOCs in the nucleation and growth of new aerosol particles; (3) gas-particle partitioning, which results in the formation of SVOCs by gas-phase reactions and uptake through adsorption or by absorption by preexisting aerosol or cloud particles; and (4) heterogeneous or multiphase reactions: formation of low-volatile organic compounds or nonvolatile organic compounds by chemical reaction of VOCs or SVOCs at the surface or in the bulk of aerosol or cloud particles.

Thus, in summary, aerosols caused by either the entry of organic chemicals into the environment or the reactivity of organic chemicals in the environment are of major importance for atmospheric chemistry and physics, the biosphere, and climate. The airborne solid and liquid particles in the nanometer (1 × 10^− 9 m) to micrometer (1 × 10^− 6 m) size range influence the energy balance of the Earth, the hydrological cycle, atmospheric circulation, and the abundance of greenhouse gases and reactive trace gases. Moreover, aerosols play an important role in the reproduction of biological organisms and the primary parameters that determine the environmental effects of aerosol particles are (1) the concentration of the particles, (2) particle size, (3) particle structure, and (4) the chemical composition of the particles. These parameters, however, are spatially and temporally highly variable.

3 Agrochemicals

Agrochemicals (agricultural chemicals, agrichemicals) are the various chemical products that are used in agriculture. In most cases, the term agrochemical refers to the broad range of pesticide chemicals, including insecticide chemicals, herbicide chemicals, fungicide chemicals, and nematicides chemicals (chemicals used to kill round worms). The term may also include synthetic fertilizers, hormones, and other chemical growth agents, as well as concentrated stores of raw animal manure.

Typically, agrochemicals are toxic and when stored in bulk storage systems may pose significant environmental risks, particularly in the event of accidental spills. As a result, in many countries, the use of agrochemicals has become highly regulated and government-issued permits for purchase and use of approved agrichemicals may be required. Significant penalties can result from misuse, including improper storage resulting in chemical leaks, chemical leaching, and chemical spills. Wherever these chemicals are used, proper storage facilities and labeling; emergency cleanup equipment; emergency cleanup procedures; safety equipment; as well as safety procedures for handling, application, and disposal are often subject to mandatory standards and regulations.

While agrochemicals increase plant and animal crop production, they can also damage the environment. Excessive use of fertilizers has led to the contamination of groundwater with nitrate, a chemical compound that in large concentrations is poisonous to humans and animals. In addition, the runoff (or leaching from the soil) of fertilizers into streams, lakes, and other surface waters (the aquasphere) can increase the growth of algae, which can have an adverse effect on the life-cycle of fish and other aquatic animals.

Pesticides that are sprayed on entire fields using equipment mounted on tractors, airplanes, or helicopters often drift away (due to wind or air convection patterns) from the targeted field, settling on nearby plants and animals. Some older pesticides, such as the powerful insecticide DDT (dichlorodiphenyltrichloroethane), remain active in the environment for many years (Table 4.4), contaminating virtually all wildlife, well water, food, and even humans with whom it comes in contact. Although many of these pesticides have been banned (Chapter 1), some newer pesticides still cause severe environmental damage.

There is now an awareness of the health hazards of pesticides and related chemicals due to the pioneering work that commenced in the latter half of the 20th century and has continued into the 21st century (Carson, 1962; Carson and Mumford, 1988, 1995, 2002). These materials are carefully regulated, and the safety requirements for every pesticide product are spelled out in detail. Most fertilizers have been in an opposite category, considered useful, safe, and inert. These and other environmental effects have prompted the search for nonchemical methods of enhancing soil fertility and dealing with crop pests. These alternatives, however, are still emerging and are not yet in widespread use.

4 Chemical Waste

Chemical waste is a general term and covers many types of materials but is generally recognized as a waste that is composed of harmful chemicals. Thus, by this definition, organic chemical waste is composed of harmful chemicals. However, all chemical wastes are not hazardous wastes, and organic chemical waste may or may not be classed as hazardous waste. An organic chemical hazardous waste is a gaseous, liquid, or material that displays either a hazardous characteristic or is specifically listed by name as a hazardous waste (Appendix: Tables A2–A6). There are four characteristics chemical wastes that may have to be considered as hazardous are (1) ignitability, (2) corrosivity, (3) reactivity, and (4) toxicity. This type of hazardous waste must be categorized as to its identity, constituents, and hazards so that it may be safely handled and managed.

The United States Environmental Protection Agency (US EPA) designates more than 450 chemicals or chemical wastes that are specific substances or classes of substances known to be hazardous. Each such chemical or waste is assigned a hazardous waste number in the format of a letter followed by three numerals, where a different letter is assigned to substances from each of the following list: (1) F-type: chemicals or chemical wastes from nonspecific sources (Appendix: Table A2), (2) K-type: chemicals or chemical wastes from specific sources (Appendix: Table A3), (3) P-type: chemicals or chemical wastes that are hazardous and that are mostly specific chemical species such as fluorine (Appendix: Table A4), and (4) U-type: generally hazardous chemicals or chemical wastes that are predominantly specific compounds (Appendix: Table A5).

The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) gives a broader definition of hazardous substances that includes the following: (1) any element, compound, mixture, solution, or substance, the release of which may substantially endanger public health, public welfare, or the environment; (2) any element, compound, mixture, solution, or substance in reportable quantities designated by CERCLA Section 102; (3) certain substances or toxic pollutants designated by the Water Pollution Control Act; (4) any hazardous air pollutant listed under Section 112 of the Clean Air Act; (5) any imminently hazardous chemical substance or mixture that has been the subject of government action under Section 7 of the Toxic Substances Control Act (TSCA); and (6) any hazardous chemical or chemical waste listed or having characteristics identified by the Resource Conservation Recovery Act, with the exception of those suspended by Congress under the Solid Waste Disposal Act.

In terms of quantity by weight, more wastes than all others combined are those from categories designated by hazardous waste numbers preceded by F and K. The F categories are those wastes from nonspecific sources. The K-type hazardous wastes are those from specific sources produced by industries such as, in the context of organic chemicals, the manufacture of organic chemicals, pesticides, explosives, as well as from processes such as wood preservation petroleum refining or wood preservation.

Some refinery wastes that might exhibit a degree of hazard are exempt from the Resource Conservation Recovery Act regulation by legislation and include the following: (1) ash and scrubber sludge from thermal generation or power generation by utilities, (2) oil field and gas field drilling mud, (3) by-product brine from petroleum production, and (4) catalyst dust (Speight, 2005a). Eventual reclassification of these kinds of low-hazard wastes could increase the quantities of regulated wastes several-fold. Thus, as stated earlier, an organic chemical waste is considered hazardous if it exhibits one or more of the following characteristics: ignitability, corrosivity, reactivity, and toxicity. Under the authority of the Resource Conservation and Recovery Act (RCRA) and the United States Environmental Protection Agency (EPA), a hazardous substance has one or more of the earlier characteristics.

Briefly, ignitability is that characteristic of chemicals that are volatile liquids and the vapors are prone to ignition in the presence of an ignition sources. Nonliquids that may catch fire from friction or contact with water and which burn vigorously or are persistently ignitable compressed gases and oxidizers also fall under the mantle of ignitable chemicals. Examples include solvents, friction-sensitive substances, and pyrophoric solids that may include catalysts and metals isolated from various refining processes. Organic solvents are indigenous to the petroleum industry and release to the atmosphere as vapor and can pose a significant inhalation hazard. Improper storage, use, and disposal can result in the contamination of land systems as well as groundwater and drinking water (Barcelona et al., 1990; Speight, 2005a).

Often, the term ignitable chemical (ignitable organic chemical, such as naphtha or gasoline) is used in the same sense as the term flammable organic chemical insofar as it is a chemical that will burn readily but a combustible organic chemical (any higher boiling hydrocarbon product of refining but which can include naphtha or gasoline) often requires relatively more persuasion to burn, that is, the chemical is less flammable. Most petroleum products that are likely to burn accidentally are low-boiling liquids that form vapors that are usually denser than air and thus tend to settle in low spots. The tendency of a liquid to ignite is measured by a test in which the liquid is heated and periodically exposed to a flame until the mixture of vapor and air ignites at the liquid's surface. The temperature at which this occurs is called the flash point (Speight, 2015).

There are several standard tests for determining the flammability of materials. For example, the upper and lower concentration limits for the flammability of chemicals and waste can be determined by standard test methods (ASTM D4982, 2016; ASTM E681, 2016) as can the combustibility and the flash point (ASTM D1310, 2016; ASTM E176, 2016; ASTM E502, 2016). With these definitions in mind it is possible to divide ignitable materials into four subclasses. Thus:

1. A flammable solid is a solid that can ignite from friction or from heat remaining from its manufacture, or which may cause a serious hazard if ignited. Explosive materials are not included in this classification.

2. A flammable liquid is a liquid having a flash point below 37.8°C (100°F) (ASTM D92, 2016; ASTM D1310, 2016). A combustible liquid has a flash point in excess of 37.8°C (100°F), but below 93.3°C (200°F). Gases are substances that exist entirely in the gaseous phase at 0°C (32°F) and 1 atm pressure (14.7 psi) pressure. A flammable compressed gas (such as liquefied petroleum gas, LPG, or any liquefied hydrocarbon gas or petroleum product) meets specified criteria for lower flammability limit, flammability range, and flame projection.

In considering the ignition of vapors, two important concepts are flammability limit and flammability range. Values of the vapor/air ratio below which ignition cannot occur because of insufficient fuel define the lower flammability limit. Similarly values of the vapor/air ratio above which ignition cannot occur because of insufficient air define the upper flammability limit. The difference between upper and lower flammability limits at a specified temperature is the flammability range. In addition, explosions that are not due to the flammability of an organic chemical can also occur. Dust explosions (ASTM E789, 2016) can occur during catalytic reactor shutdown and cleaning are due to production of finely divvied solids through attrition. Many catalyst dusts can burn explosively in air. Thus, control of dust generated by catalyst attrition is essential (Mody and Jakhete, 1988). Organic chemicals that catch fire spontaneously in air without an ignition source are called pyrophoric organic chemicals, all of which may occur on a refinery site. Moisture in air is often a factor in spontaneous ignition.

Corrosivity is that characteristic of chemicals that exhibit extremes of acidity or basicity or a tendency to corrode steel. Such chemicals, as used in various refining (treating) processes, are acidic and are/or capable of corroding metal such as tanks, containers, drums, and barrels. On the other hand, reactivity is a violent chemical change (an explosive substance is an obvious example) that can result to pollution and/or harm to indigenous flora and fauna. Such wastes are unstable under ambient conditions insofar as they can create explosions, toxic fumes, gases, or vapors when mixed with water. Finally, toxicity (defined in terms of a standard extraction procedure followed by chemical analysis for specific substances) is a characteristic of all chemicals be the petroleum or nonpetroleum in origin. Toxic wastes are harmful or fatal when ingested or absorbed and, when such wastes are disposed of on land, the chemicals may drain (leach) from the waste and pollute groundwater. Leaching of such chemicals from contaminated soil may be particularly evident when the area is exposed to acid rain. The acidic nature of the water may impart mobility to the waste by changing the chemical character of the waste or the character of the minerals to which the waste species are adsorbed.

As with flammability, there are many tests that can be used to determine corrosivity (ASTM D1838, 2016; ASTM D2251, 2016). Most corrosive substances belong to at least one of the four following nonorganic chemical classes: (1) strong acids, (2) strong bases, (3) oxidants, or (4) dehydrating agents, which are all are used in the refining industry (Speight, 2005a). For example, sulfuric acid is a prime example of a corrosive substance (ASTM C694, 2016). As well as being a strong acid, concentrated sulfuric acid is also a dehydrating agent and oxidant. The heat generated when water and concentrated sulfuric acid are mixed illustrates the high affinity of sulfuric acid for water. If this is done incorrectly by adding water to the acid, localized boiling and spattering can occur and result in personal injury. The major destructive effect of sulfuric acid on skin tissue is removal of water with accompanying release of heat. Contact of sulfuric acid with tissue results in tissue destruction at the point of contact. Inhalation of sulfuric acid fumes or mists damages tissues in the upper respiratory tract and eyes. Long-term exposure to sulfuric acid fumes or mists has caused erosion of teeth, as well as destruction of other parts of the body!

Reactive chemicals are those that tend to undergo rapid or violent reactions under certain conditions. Such substances include those that react violently or form potentially explosive mixtures with water, such as some of the common oxidizing agents. Explosives (Sudweeks et al., 1983; Austin, 1984) constitute another class of reactive chemicals. For regulatory purposes, those substances are also classified as reactive that react with water, acid, or base to produce toxic fumes, particularly hydrogen sulfide or hydrogen cyanide.

Heat and temperature are usually very important factors in reactivity since many reactions require energy of activation to get them started. The rates of most reactions tend to increase sharply with increasing temperature, and most chemical reactions give off heat. Therefore, once a reaction is started in a reactive mixture lacking an effective means of heat dissipation, the rate will increase exponentially with time (doubling with every 10° rise in temperature), leading to an uncontrollable event. Other factors that may affect the reaction rate include the physical form of reactants, the rate and degree of mixing of reactants, the degree of dilution with a nonreactive medium (e.g., an inert solvent), the presence of a catalyst, and pressure.

Toxicity is of the utmost concern in dealing with chemicals and their disposal. This includes both long-term chronic effects from continual or periodic exposures to low levels of toxic chemicals and acute effects from a single large exposure (Zakrzewski, 1991). Not all toxins are immediately apparent. For example, living organisms require certain metals for physiological processes. These metals when present at concentrations above the level of homeostatic regulation can be toxic (ASTM E1302, 2016). In addition, there are metals that are chemically similar to, but higher in molecular weight than, the essential metals (heavy metals). Metals can exert toxic effects by direct irritant activity, blocking functional groups in enzymes, altering the conformation of biomolecules, or displacing essential metals in a metalloenzyme.

5 Coal and Coal Products

Coal (the term is used generically throughout the book to include all types of coal) is a black or brownish-black organic sedimentary rock of biochemical origin which is combustible and occurs in rock strata (coal beds, coal seams) and is composed primarily of carbon with variable proportions of hydrogen, nitrogen, oxygen, and sulfur. Coal occurs in seams or strata. In terms of coal grade, the grade of a coal establishes its economic value for a specific end use. Grade of coal refers to the amount of mineral matter that is present in the coal and is a measure of coal quality. Sulfur content, ash fusion temperature (i.e., the temperature at which measurement the ash melts and fuses), and quantity of trace elements in coal are also used to grade coal. Although formal classification systems have not been developed around grade of coal, grade is important to the coal user.

Coal is a naturally occurring combustible material with varying composition, and it not surprising that the properties of coal vary considerably from coal type to coal type and even from sample to sample within a specific coal types. This can only be ascertained by application of a series of standard test methods (Zimmerman, 1979; Speight, 2005b).

The constituents of coal can be divided into two groups: (1) the organic fraction, which can be further subdivided into soluble and insoluble fractions as well as microscopically identifiable macerals and (ii) the inorganic fraction, which is commonly identified as ash subsequent to combustion. Because of this complex heterogeneity, it might be expected that the properties of coal can vary considerable, even within a specific rank of coal (Speight, 2005b, 2013).

6 Crude Oil

Petroleum (also known as crude oil) is perhaps the most important substance consumed in modern society. It provides not only raw materials for the ubiquitous plastics and other products but also fuel for energy, industry, heating, and transportation. From a chemical standpoint, petroleum is an extremely complex mixture of hydrocarbon compounds, usually with minor amounts of nitrogen-, oxygen-, and sulfur-containing compounds as well as trace amounts of metal-containing compounds (Speight, 2014, 2015).

Petroleum is a carbon-based resource. Therefore, the geochemical carbon cycle is also of interest to fossil fuel usage in terms of petroleum formation, use, and the buildup of atmospheric carbon dioxide. Thus, the more efficient use of petroleum and is of paramount importance. Petroleum technology, in one form or another, is with us until suitable alternative forms of energy are readily available (Ramage, 1997). For example, the fuels that are derived from petroleum supply more than half of the world's total supply of energy. Gasoline, kerosene, and diesel oil provide fuel for automobiles, tractors, trucks, aircraft, and ships. Fuel oil and natural gas are used to heat homes and commercial buildings, as well as to generate electricity. Petroleum products are the basic materials used for the manufacture of synthetic fibers for clothing and in plastics, paints, fertilizers, insecticides, soaps, and synthetic rubber. The uses of petroleum as a source of raw material in manufacturing are central to the functioning of modern industry.

7 Flame Retardants

Flame retardant chemicals are used in commercial and consumer products (such as furniture and building insulation) to meet flammability standards. Not all flame retardants present concerns, but the following types often do: (1) halogenated flame retardants, also known as organo-halogen flame retardants that contain chlorine or bromine bonded to carbon and (2) organo-phosphorous flame retardants that contain phosphorous bonded to carbon.

Flame retardants inhibit or delay the spread of fire by suppressing the chemical reactions in the flame or by the formation of a protective layer on the surface of a material. They may be mixed with the base material (additive flame retardants) or chemically bonded to it (reactive flame retardants). Mineral flame retardants are typically additive, while organohalogen and organophosphorus compounds can be either reactive or additive.

Many flame retardants, while having measurable or considerable toxicity, degrade into compounds that are also toxic, and in some cases, the degradation products may be the primary toxic agent. For example, halogenated compounds with aromatic rings can degrade into dioxin derivatives, particularly when heated, such as during production, a fire, recycling, or exposure to sun. In addition, polybrominated diphenyl ethers with higher numbers of bromine atoms, such as decabromodiphenyl ether (decaBDE), are less toxic than pentabromodiphenyl ether derivatives with lower numbers of bromine atoms (Table 4.4). However, as the higher-order pentabromodiphenyl ether derivatives degrade biotically or abiotically, bromine atoms are removed, resulting in more toxic pentabromodiphenyl ether derivatives.

In addition, when some of the halogenated flame retardants such as pentabromodiphenyl ether derivatives are metabolized, they form hydroxylated metabolites that can be more toxic than the parent compound. These hydroxylated metabolites, for example, may compete more strongly to bind with transthyretin or other components of the thyroid system, can be more potent estrogen mimics than the parent compound, and can more strongly affect neurotransmitter receptor activity.

When products with flame retardants reach the end of their usable life, they are typically recycled, incinerated, or landfilled. Recycling can contaminate workers and communities near recycling plants, as well as new materials, with halogenated flame retardants and their breakdown products. Electronic waste, vehicles, and other products are often melted to recycle their metal components, and such heating can generate toxic dioxins and furans. Brominated flame retardants may also change the physical properties of plastics, resulting in inferior performance in recycled products. Poor-quality incineration similarly generates and releases high quantities of toxic degradation products. Controlled incineration of materials with halogenated flame retardants, while costly, substantially reduces release of toxic by-products.

Many products containing halogenated flame retardants are sent to landfills. Additive, as opposed to reactive, flame retardants are not chemically bonded to the base material and leach out more easily. Brominated flame retardants, including pentabromodiphenyl ether derivatives, have been observed leaching out of landfills in some countries. Landfill designs must allow for leachate capture, which would need to be treated, but these designs can degrade with time.

8 Industrial Chemicals

Organic chemistry chemicals are some of the important starting materials for a great number of major chemical industries (Chapter 3). The production of organic chemicals as raw materials or reagents for other applications is a major sector of manufacturing polymers, pharmaceuticals, pesticides, paints, artificial fibers, food additives, etc. Organic synthesis on a large scale, compared to the laboratory scale, involves the use of energy, basic chemical ingredients from the petrochemical sector, catalysts and after the end of the reaction, separation, purification, storage, packaging, distribution, etc. During these processes there are many problems of health and safety for workers in addition to the environmental problems caused by their use and disposition as waste.

The industrial organic chemical sector produces organic chemicals used as either chemical intermediates or end-products (Chapter 3) (Sheldon, 2010). This categorization corresponds to Standard Industrial Classification (SIC) code 286 established by the Bureau of Census to track the flow of goods and services within the economy. The 286 category includes gum and wood chemicals (SIC 2861), cyclic organic crudes and intermediates, organic dyes and pigments (SIC 2865), and industrial organic chemicals not elsewhere classified (SIC 2869). By this definition, the industry does not include plastics, drugs, soaps and detergents, agricultural chemicals or paints, and allied products which are typical end-products manufactured from industrial organic chemicals. In 1993, there were 987 establishments in SIC 286 of which the largest 53 firms (by employment) accounted for more than 50% of the industry's value of shipments. The SIC 286 may include a small number of integrated firms that are also engaged in petroleum refining and manufacturing of other types of chemicals at the same site although firms primarily engaged in manufacturing coal tar crudes or petroleum refining are classified elsewhere.

The industrial organic chemical industry uses feedstocks derived from petroleum and natural gas (about 90%) and from recovered coal tar condensates generated by coke production (about 10%) (Chapter 3) (Speight, 2013, 2014). The chemical industry produces raw materials and intermediates, as well as a wide variety of finished products for industry, business, and individual consumers. The important classes of products within SIC code 2861 are hardwood and softwood distillation products, wood and gum naval stores, charcoal, natural dyestuffs, and natural tanning materials.

The chemicals industry is very diverse, comprising basic or commodity chemicals; specialty chemicals derived from basic chemicals (adhesives and sealants, catalysts, coatings, electronic chemicals, plastic additives, etc.); products derived from life sciences (pharmaceuticals, pesticides, and products of modern biotechnology); and consumer care products (soap, detergents, bleaches, hair and skin care products, fragrances, etc.). The global chemicals industry today produces tens of thousands of substances (some in volumes of millions of tons, but most of them in quantities of less than 1000 tons per year). The substances can be mixed by the chemicals industry and sold and used in this form, or they can be mixed by downstream customers of the chemicals industry (e.g., retail stores which sell paint). It is important to note that most of the output from chemical companies is used by other chemical companies or other industries (e.g., metal, glass, electronics), and chemicals produced by the chemicals industry are present in countless products used by consumers (e.g., automobiles, toys, paper, clothing).

The chemical industry involves the use of chemical processes such as chemical reactions and refining methods to produce a wide variety of solid, liquid, and gaseous materials. Most of these products serve to manufacture other items, although a smaller number goes directly to consumers. Solvents, pesticides, lye, washing soda, and Portland cement provide a few examples of product used by consumers. The industry includes manufacturers of and organic-industrial chemicals, petrochemicals, agrochemicals, polymers and rubber (elastomers), oleo-chemicals (oils, fats, and waxes), explosives, fragrances, and flavors (Table 4.6) (Chapter 3).

Chemical processes such as chemical reactions operate in chemical plants to form new substances in various types of reaction vessels. In many cases the reactions take place in special corrosion-resistant equipment at elevated temperatures and pressures with the use of catalysts. The products of these reactions are separated using a variety of techniques including distillation, especially fractional distillation, precipitation, crystallization, adsorption, filtration, sublimation, and drying (Speight, 2002).

The processes and product or products are usually tested during and after manufacture by dedicated instruments and on-site quality control laboratories to ensure safe operation and to assure that the product will meet required specifications. More organizations within the industry are implementing chemical compliance software to maintain quality products and manufacturing standards. The products are packaged and delivered by many methods, including pipelines, tank-cars and tank-trucks (for both solids and liquids), cylinders, drums, bottles, and boxes. Chemical companies often have a research-and-development laboratory for developing and testing products and processes. These facilities may include pilot plants, and such research facilities may be located at a site separate from the production plant(s).

Industrial organic chemical manufacturers use and generate both large numbers and quantities of chemicals (Chapter 3). The types of pollutants a single facility will release depend on the feedstocks, processes, equipment in use, and maintenance practices. These can vary from hour to hour and can also vary with the part of the process that is underway. For example, for batch reactions in a closed vessel, the chemicals are more likely to be emitted at the beginning and end of a reaction step (associated with vessel loading and product transfer operations) than during the reaction.

Industrial organic synthesis, followed a largely stoichiometric line of evolution that can be traced back to the synthesis of mauveine by Perkin, the subsequent development of the dyestuffs industry based on coal tar, and the fine chemicals and pharmaceuticals industries, which can be regarded as spin-offs from the dyestuffs industry. Consequently, fine chemicals and pharmaceuticals manufacture, which is largely the domain of synthetic organic chemists, is rampant with classical stoichiometric processes (Chapter 3).

The desperate need for more catalytic methodologies in industrial organic synthesis is nowhere more apparent than in oxidation chemistry. For example, as any organic chemistry textbook will note that the reagent of choice for the oxidation of secondary alcohols to the corresponding ketones, a pivotal reaction in organic synthesis, is the Jones reagent. The latter consists of chromium trioxide and sulfuric acid and is reminiscent of the phloroglucinol process referred to earlier. The introduction of the storage-stable pyridinium chlorochromate and pyridinium dichromate in the 1970s represented a practical improvement, but the stoichiometric amounts of carcinogenic chromium(VI) remain a serious problem. Obviously there is a definite need in the fine chemical and pharmaceutical industry for catalytic systems that are green and scalable and have broad utility.

9 Natural Gas

As with other fuels, natural gas also affects the environment when it is produced, stored, and transported (Renesme et al., 1992; Speight, 2007, 2014). Because natural gas is made up mostly of methane (another greenhouse gas), small amounts of methane can sometimes leak into the atmosphere from wells, storage tanks, and pipelines. The natural gas industry is working to prevent any methane from escaping. Exploring and drilling for natural gas will always have some impact on land and marine habitats. But new technologies have greatly reduced the number and size of areas disturbed by drilling, sometimes called “footprints.” Satellites, global positioning systems, remote sensing devices, and 3D and 4D seismic technologies make it possible to discover natural gas reserves while drilling fewer wells. Plus, use of horizontal drilling and directional drilling make it possible for a single well to produce gas from much bigger areas.

While the primary constituent of natural gas is methane (CH₄), it may contain smaller amounts of other hydrocarbons, such as ethane (C₂H₆) and various isomers of propane (C₃H₈), butane (C₄H₁₀), and pentane (C₅H₁₂), as well as trace amounts of higher boiling hydrocarbons up to octane (C₈H₁₈). Nonhydrocarbon gases, such as carbon dioxide (CO₂), helium (He), hydrogen sulfide (H₂S), nitrogen (N₂), and water vapor (H₂O), may also be present. At the pressure and temperature conditions of the source reservoir, natural gas may occur as free gas (bubbles) or be dissolved in either crude oil or brine.

The major constituent of natural gas, methane, also directly contributes to the greenhouse effect. Its ability to trap heat in the atmosphere is estimated to be 21 times greater than that of carbon dioxide, so although methane emissions amount to only 0.5% (v/v) of the emissions of carbon dioxide in the United States, they account for approximately 10% (v/v) of the greenhouse effect of these emissions.

There is a great deal of uncertainty about the precise methods and the amounts by which hazardous pollution is being emitted into the air during the development and processing of natural gas. Methane is a potent greenhouse gas, far more warming than carbon dioxide. Methane also adds to ozone levels. Some methane—it is unclear exactly how much—leaks out of natural gas pipelines and fracking equipment. This is unintentional and can happen at many points along the system.

The fracking process (Speight, 2016b) can release VOCs, such as benzene, toluene, and methane, into the air, where they contribute to ozone formation. Ozone is formed when the sun reacts with VOCs and nitrogen oxides (NO_x) in the atmosphere—the presence of these gases play a role in the formation of ozone, which is a powerful oxidant that can irritate the airways, causing a burning sensation, coughing, wheezing, and shortness of breath.

Natural gas is the cleanest of all the fossil fuels. Composed primarily of methane, the main products of the combustion of natural gas are carbon dioxide and water vapor, the same compounds we exhale when we breathe. Coal and oil are composed of much more complex molecules, with a higher carbon ratio and higher nitrogen and sulfur contents. This means that when combusted, coal and oil release higher levels of harmful emissions, including a higher ratio of carbon emissions, nitrogen oxides (NO_x), and sulfur dioxide (SO₂). Coal and fuel oil also release ash particles into the environment, substances that do not burn but instead are carried into the atmosphere and contribute to pollution. The combustion of natural gas, on the other hand, releases very small amounts of sulfur dioxide and nitrogen oxides, virtually no ash or particulate matter, and lower levels of carbon dioxide, carbon monoxide, and other reactive hydrocarbons.

Natural gas, as the cleanest of the fossil fuels, can be used in many ways to help reduce the emissions of pollutants into the atmosphere. Burning natural gas in the place of other fossil fuels emits fewer harmful pollutants, and an increased reliance on natural gas can potentially reduce the emission of many of these most harmful pollutants. Pollutants from the combustion of fossil fuels have led to the development of many pressing environmental problems. Natural gas, emitting fewer harmful chemicals into the atmosphere than other fossil fuels, can help to mitigate some of these environmental issues. These issues include: (1) greenhouse gas emissions and (2) smog, air quality and acid rain.

10 Volatile Organic Compounds

Organic compounds that evaporate easily are collectively referred to as VOCs. Microbial volatile organic compounds are a variety of compounds formed in the metabolism of fungi and bacteria (Korpi et al., 2009). Typically, a VOC is any organic compound that will evaporate at the temperature of use and which, by a photochemical reaction, will cause oxygen in the air to be converted into smog-promoting ozone under favorable climatic conditions.

Thus, VOCs are gases that are emitted into the air from products or processes (Table 4.7). Some are harmful by themselves, including some that cause cancer. In addition, they can react with other gases and form other air pollutants after they are in the air. Many VOCs have been classified as toxic and carcinogenic. They are found in a wide variety of commercial, industrial, and residential products including fuel oils, gasoline, solvents, cleaners and degreasers, paints, inks, dyes, refrigerants, and pesticides. When VOCs are spilled or improperly disposed, they can soak into the soil and eventually end up in groundwater. VOCs are found in almost all natural and synthetic materials and are commonly used in fuels, fuel additives, solvents, perfumes, flavor additives, and deodorants. Potential health hazards and environmental degradation resulting from the widespread use of VOCs have prompted increasing concern among scientists, industry, and the general public (Table 4.8).

Typically, VOCs are organic chemicals that have a high vapor pressure at ordinary room temperature. The high vapor pressure results from a low boiling point, which causes large numbers of molecules to evaporate from the liquid form or sublime from the solid form of the compound and enter the surrounding air. VOCs are numerous, varied, and ubiquitous. They include both human-made and naturally occurring chemical compounds. Many VOCs are dangerous to human health or cause harm to the environment. Anthropogenic VOCs are regulated by law, especially indoors, where concentrations are the highest. Harmful VOCs typically are not acutely toxic but have compounding long-term health effects.

Nonmethane volatile organic compounds (NMVOCs) are a collection of organic compounds that differ widely in their chemical composition but display similar behavior in the atmosphere. NMVOCs are emitted into the atmosphere from a large number of sources including combustion activities, solvent use, and production processes. NMVOCs contribute to the formation of ground level (tropospheric) ozone. In addition, certain NMVOC species or species groups such as benzene and 1,3 butadiene are hazardous to human health. Quantifying the emissions of total NMVOCs provides an indicator of the emission trends of the most hazardous NMVOCs.

11 Wood Smoke

Wood smoke forms when wood is made up of a complex mixture of gases and fine particles (particulate matter, PM). In addition to particle pollution, wood smoke contains several toxic harmful air pollutants including: benzene, formaldehyde, acrolein, and PAHs.

Wood smoke is by far the most compelling argument against wood heating. In cold climates, a frigid, stagnant air mass traps the smoke close to the ground. In the process of wood combustion, wood vaporizes when heated into gases and tar particles. If the temperature is high enough, the tar particles vaporize into chemicals and carbon particles. If the temperature is higher still and there is oxygen present, the gases and particles burn in bright flames.

Chemically, wood is about half carbon, and the rest is mostly made up of oxygen and hydrogen. When a piece of wood is heated, it starts to smoke and turn black at the same time. This is because the other products vaporize under intense heat faster than the carbon burns, so smoking leaves much of the carbon behind until only charcoal, which is just about pure carbon, is left. The smoke that vaporizes out of the wood is a cloud of nasty, gooey little droplets of a tar-like liquid. Chemically, these droplets are actually big, gooey, complicated hydrocarbon molecules that take a number of different forms, mostly bad.

When wood is burned correctly in a bright, hot, turbulent fire, what is observed is the tar droplets rising off the wood into a zone of extreme heat where they revaporize, cracking into their basic, mostly gaseous, constituents, and oxidize. That is to say they burn. This leaves carbon dioxide, some carbon monoxide, and a number of other gases, water vapor and some not quite completely oxidized hydrocarbon products, which are the particulate emissions that US Environmental Protection Agency regulates.

The sentiment that wood smoke, being a natural substance, must be benign to humans is still sometimes heard. It is now well established, however, that wood-burning stoves and fireplaces as well as wildland and agricultural fires emit significant quantities of known health-damaging pollutants, including several carcinogenic compounds (Naeher et al., 2007). Two of the principal gaseous pollutants in wood smoke, carbon monoxide (CO) and the oxides of nitrogen (NOx), add to the atmospheric levels of these regulated gases emitted by other combustion sources. Health impacts of exposures to these gases and some of the other woodsmoke constituents (e.g., benzene) are well characterized in thousands of publications. As these gases are indistinguishable no matter where they come from, there is no urgent need to examine their particular health implications in woodsmoke. With this as the backdrop, this review approaches the issue of why woodsmoke may be a special case requiring separate health evaluation through two questions. The first issue is whether or not woodsmoke should be regulated and/or managed separately, even though some of the individual constituents are already regulated in many jurisdictions. The second issue is whether or not woodsmoke particles pose different levels of risk than other ambient particles of similar size.

Wood smoke interferes with normal lung development in infants and children. It also increases children's risk of lower respiratory infections such as bronchitis and pneumonia. Exposure to wood smoke can depress the immune system and damage the layer of cells in the lungs that protect and cleanse the airways. According to the Environmental Protection Agency (US EPA), toxic air pollutants are components of wood smoke. Wood smoke can cause coughs, headaches, and eye and throat irritation in otherwise healthy people. For vulnerable populations, such as people with asthma and chronic respiratory disease, and those with cardiovascular disease, wood smoke is particularly harmful—even short exposures can prove dangerous.

The particle matter wood smoke is extremely small and therefore is not filtered out by the nose or the upper respiratory system. Instead, these small particles end up deep in the lungs where they remain for months, causing structural damage and chemical changes. Wood smoke's carcinogenic chemicals adhere to these tiny particles, which enter deep into the lungs.

12 Effects on the Environment

To start with an extremely relevant definition, environmental technology is the application of scientific and engineering principles to the study of the environment, with the goal of the improvement of the environment. Furthermore, issues related to the pollution of the environment are relative. Any organism is exposed to an environment, even if the environment is predominantly many members of the same organism. An example is a bacterium in a culture that is exposed to many members of the same species. Thus the environment is all external influences, abiotic (physical factors) and biotic (actions of other organisms), to which an organism is exposed. The environment affects basic life functions, growth, and reproductive success of organisms and determines their local and geographic distribution patterns. A fundamental idea in ecology is that the environment changes in time and space, and living organisms respond to these changes.

Since ecology is that branch of science related to the study of the relationship of organisms to their environment, an ecosystem is an ecological community (or living unit) considered together with the nonliving factors of its environment as a unit. By way of brief definition, abiotic factors include such influences as light radiation (from the sun), ionizing radiation (cosmic rays from outer space), temperature (local and regional variations), water (seasonal and regional distributions), atmospheric gases, wind, soil (texture and composition), and catastrophic disturbances. These latter phenomena are usually unpredictable and infrequent, such as fire, hurricanes, volcanic activity, landslides, major floods, and any disturbance that drastically alters the environment and thus changes the species composition and activity patterns of the inhabitants. On the other hand, biotic factors include natural interactions (e.g., predation and parasitism) and anthropogenic stress (e.g., the effect of human activity on other organisms). Because of the abiotic and biotic factors, the environment to which an organism is subjected can affect the life functions, growth, and reproductive success of the organism and can determine the local and geographic distribution patterns of an organism.

Living organisms respond to changes in the environment by either adapting or becoming extinct. The basic principles of the concept that living organisms respond to changes in the environment were put forth by Darwin and Lamarck. The former noted the slower adaptation (evolutionary trends) of living organisms, while the latter noted the more immediate adaptation of living organisms to the environment. Both essentially espoused the concept of the survival of the fittest, alluding to the ability of an organism to live in harmony with its environment. This was assumed to indicate that the organism that competed successfully with environmental forces would survive. However, there is the alternate thought that the organism that can live in a harmonious symbiotic relationship with its environment has an equally favorable chance of survival. The influence of the environment on organisms can be viewed on a large scale (i.e., the relationship between regional climate and geographic distribution of organisms) or on a smaller scale (i.e., some highly localized conditions determine the precise location and activity of individual organisms).

Organisms may respond differently to the frequency and duration of a given environmental change. For example, if some individual organisms in a population have adaptations that allow them to survive and to reproduce under new environmental conditions, the population will continue but the genetic composition will have changed (Darwinism). On the other hand, some organisms have the ability to adapt to the environment (i.e., to adjust their physiology or morphology in response to the immediate environment) so that the new environmental conditions are less (certainly no more) stressful than the previous conditions. Such changes may not be genetic (Lamarckism).

In terms of anthropogenic stress (the effect of human activity on other organisms), there is the need for the identification and evaluation of the potential impacts of proposed projects, plans, programs, policies, or legislative actions upon the physical-chemical, biological, cultural, and socioeconomic components of the environment. This activity is also known as environmental impact assessment and refers to the interpretation of the significance of anticipated changes related to a proposed project. The activity encourages consideration of the environment and arriving at actions that are environmentally compatible.

Identifying and evaluating the potential impact of human activities on the environment require the identification of mitigation measures. Mitigation is the sequential consideration of the following measures: (1) avoiding the impact by not taking a certain action or partial action; (2) minimizing the impact by limiting the degree or magnitude of the action and its implementation; (3) rectifying the impact by repairing, rehabilitating, or restoring the affected environment; (4) reducing or eliminating the impact over time by preservation and maintenance operations during the life of the action; and (5) compensating for the impact by replacing or providing substitute resources or environments.

Nowhere is the effect of anthropogenic stress felt more than in the development of natural resources of the earth. Natural resources are varied in nature and often require definition. For example, in relation to mineral resources, for which there is also descriptive nomenclature, the terms related to the available quantities of the resource must be defined. In this instance, the term resource refers to the total amount of the mineral that has been estimated to be ultimately available. Reserves are well-identified resources that can be profitably extracted and utilized by means of existing technology. In many countries, fossil fuel resources are often classified as a subgroup of the total mineral resources.

In some cases, environmental pollution is a clear—cut phenomenon, whereas in others it remains a question of degree. The ejection of various materials into the environment is often cited as pollution, but there is the ejection of the so-called beneficial chemicals that can assist the air, water, and land to perform their functions. However, it must be emphasized that the ejection of chemicals into the environment, even though they are indigenous to the environment, in quantities above the naturally occurring limits can be extremely harmful. In fact, the timing and the place of a chemical release are influential in determining whether a chemical is beneficial, benign, or harmful! Thus, what may be regarded as a pollutant in one instance can be a beneficial chemical in another instance. The phosphates in fertilizers are examples of useful (beneficial) chemicals, while phosphates generated as by-products in the metallurgical and mining industries may, depending upon the specific industry, be considered pollutants (Chenier, 1992). In this case, the means by which such pollution can be prevented must be recognized (Boyle Breen and Dellarco, 1992). Thus, increased use of the earth's resources as well as the use of a variety of chemicals that are nonindigenous to the earth have put a burden on the ability of the environment to tolerate such materials.

Finally, some recognition must be made of the term carcinogen since many of the environmental effects referenced in this text can lead to cancer. Carcinogens are cancer—causing substances and there is a growing awareness of the presence of carcinogenic materials in the environment. A classification scheme is provided for such materials (Table 4.9) (Zakrzewski, 1991; Milman and Weisburger, 1994). The number of substances with which a person comes in contact is in the tens of thousands, and there is not a full understanding of the long-term effects of these substances in their possible propensity to cause genetic errors that ultimately lead to carcinogenesis. Teratogens are those substances that tend to cause developmental malformations.

Pollution is the introduction of indigenous (beyond the natural abundance) and nonindigenous (artificial) gaseous, liquid, and solid contaminants into an ecosystem. The atmosphere and water and land systems have the ability to cleanse themselves of many pollutants within hours or days especially when the effects of the pollutant are minimized by the natural constituents of the ecosystem. For example, the atmosphere might be considered to be self-cleaning as a result of rain. However, removal of some pollutants from the atmosphere (e.g., sulfates and nitrates) by rainfall results in the formation of acid rain that can cause serious environmental damage to ecosystems within the water and land systems (Pickering and Owen, 1994).

Briefly, lakes in some areas of the world are now registering a low pH (acidic) reading because of excess acidity in rain. This was first noticed in Scandinavia and is now prevalent in eastern Canada and the northeastern United States. Normal rainfall has a pH of 5.6 and the slight acidity (neutral water has a pH equal to 7.0) because of carbon dioxide (CO₂) in the air that, with water, forms carbonic acid (H₂CO₃):

${\mathrm{C}\mathrm{O}}_2+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_2{\mathrm{C}\mathrm{O}}_3$

The increased use of hydrocarbon fuels in the last five decades is slowly increasing the concentration of carbon dioxide in the atmosphere, which produces more carbonic acid leading to an imbalance in the natural carbon dioxide content of the atmosphere that, in turn, leads to more acidity in the rain. In addition, there is a so-called greenhouse effect, and the average temperature of the earth may be increasing.

In addition, excessive use of fuels with high sulfur and nitrogen content cause sulfuric and nitric acids in the atmosphere from the sulfur dioxide and nitrogen oxide products of combustion that can be represented simply as:

$\begin{array}{l}{\mathrm{SO}}_2+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_2{\mathrm{SO}}_3\left(\mathrm{sulfurous}\mathrm{acid}\right)\\ 2{\mathrm{SO}}_2+{\mathrm{O}}_2\to 2{\mathrm{SO}}_3\\ {\mathrm{SO}}_3+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}}_2{\mathrm{SO}}_4\left(\mathrm{sulfuric}\mathrm{acid}\right)\\ \mathrm{NO}+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}\mathrm{N}\mathrm{O}}_2\left(\mathrm{nitrous}\mathrm{acid}\right)\\ 2\mathrm{NO}+{\mathrm{O}}_2\to {\mathrm{NO}}_2\\ {\mathrm{NO}}_2+{\mathrm{H}}_2\mathrm{O}\to {\mathrm{H}\mathrm{N}\mathrm{O}}_3\left(\mathrm{nitric}\mathrm{acid}\right)\end{array}$

A pollutant is a substance (for simplicity most are referred to as chemicals) present in a particular location when it is not indigenous to the location or is in a greater-than-natural concentration. The substance is often the product of human activity. The pollutant, by virtue of its name, has a detrimental effect on the environment, in part or in toto. Pollutants can also be subdivided into two classes: (1) primary and (2) secondary.

$\mathrm{Source}\to \mathrm{Primary}\mathrm{pollutant}\to \mathrm{Secondary}\mathrm{pollutant}$

Primary pollutants are those pollutants emitted directly from the source. In terms of atmospheric pollutants by crude oil constituents, examples are hydrogen sulfide, carbon oxides, sulfur dioxide, and nitrogen oxides from refining operations (see earlier text).

The question of classifying nitrogen dioxide and sulfur trioxide as primary pollutants often arises, as does the origin of the nitrogen. In the former case, these higher oxides can be formed in the upper levels of the combustors. The nitrogen, from which the nitrogen oxides are formed, does not originate solely from the fuel but may also originate from the air used for the combustion.

Secondary pollutants are produced by interaction of primary pollutants with another chemical or by dissociation of a primary pollutant, or other effects within a particular ecosystem. Again, using the atmosphere as an example, the formation of the constituents of acid rain is an example of the formation of secondary pollutants (see earlier text).