This chapter examines the acidity of natural water, which depends on the nature of material dissolved in it and its interaction with other materials such as the rocks, the organisms living in it, and added pollutants. Rivers and lakes in granite areas, for example, are unable to neutralize any added acidity and are therefore highly susceptible to the effects of acid rain. Significant increases in the acidity of these water bodies produces an environment which is not well suited to life for a number of reasons. Firstly, most organisms are not well adapted to acidic conditions or changes in acidity. In addition, acidification leads to the dissolution of a number of toxic elements which can poison flora and fauna. In limestone areas, however, the water can neutralize moderate quantities of added acid. The chapter then considers the chemical nature of water, before studying polyprotic acids and the solubility of gases.
The acidity of water
The aquatic environment
This chapter discusses the aquatic environment. Water is the most important liquid on the Earth and has a major impact on the chemical, physical, and biological processes which take place. There are many ways by which natural waters can be classified and it must be recognized that the movement of water through the environment does not limit it to any single category. It is often convenient however to consider the Earth's surface as a suitable cut-off point. Groundwater is the water below the Earth's surface. Meanwhile, surface waters can be divided into two broad categories: freshwater and seawater. The chapter then looks at the hydrologic cycle, before considering the dissolved inorganic compounds and organic material in natural waters.
Alan G. Howard
Aquatic Environmental Chemistry covers the composition and underlying properties of both freshwater and marine systems and, within this framework, explains the effects of acidity, complexation, oxidation and reduction processes, and sedimentation. Equilibrium inorganic chemistry underlies the composition and properties of the aquatic environment and provides a sound basis for understanding both natural geochemical processes and the behaviour of inorganic pollutants in the environment. The format adopted for the book consists of two parallel columns. The inner column is the main body of the book and can be read on its own. The outer column is a source of useful secondary material where comments on the main text, explanations of unusual terms, and guidance through mathematical steps are to be found. A wide range of examples to explain the behaviour of inorganic species in freshwater and marine systems are used throughout.
This chapter concentrates on understanding the role played by atmospheric aerosols in the global environmental chemistry context. It explains the nature of aerosols and their environmental significance and identifies their sources, both natural and anthropogenic. It then goes on to investigate the condensation chemistry processes for the formation of aerosols before considering their concentrations, lifetimes, and other properties. It also examines control technologies that are used to minimize industrial emissions of particulates. The chapter defines an aerosol as a suspension of particles in a gas and explains that an atmospheric aerosol consists of particles that remain aloft in the air. It distinguishes particles in an aerosol from smaller gas molecules or molecular clusters by their ability to cause incoherent scattering of visible light and interfere with light transmission.
The chemistry of global climate
This chapter examines the ways in which global climate is influenced by the composition and chemistry of the atmosphere. It discusses the composition of the atmosphere and investigates the energy balance of incoming solar radiation and outgoing infrared or black-body radiation from the Earth. It also identifies greenhouse gases and their infrared radiation absorption properties and examines the radiative influence of aerosols. The chapter introduces the concepts of radiative forcing (RF) and the global warming potential (GWP) index for measuring the present and long-term impact of greenhouse gases. It provides an overview of energy resources, the relationships between carbon-based fuels and carbon dioxide emissions, and mitigation strategies.
The chemistry of solid wastes
This chapter discusses the chemistry of solid wastes. It looks at how best to make use of them in creative ways that cause little adverse impact on the natural environment. It looks at the various types of bulk solid wastes and their potential to be useful resources, as well as at the chemical issues related to managing wastes from mining and metal production. It outlines the uses of organic wastes, especially as compost and as an energy source, and the processes that can be used to manage mixed urban wastes and the related environmental considerations. The chapter mentions bulk solid wastes, which are produced as a by-product of the normal and fundamental activities of living. These include food scraps, ash from fires, and excreta from humans and animals. It refers to the circular economy, which turns goods at the end of their service life into resources for others.
Chemistry of urban and indoor atmospheres
This chapter focuses on the air in surroundings where everyone lives and breathes and the concerns that should be considered as we continue to work and engage in recreational activities. It describes the principal atmospheric pollutants in the urban environments where most people spend the majority of their time. It also reviews the fundamental factors that affect indoor air quality and discusses some common indoor air contaminants. The chapter investigates the air quality in major urban areas around the world, revealing serious problems in some cities that are a direct consequence of the use of energy in all its traditional and modern applications. It highlights the combustion of fossil fuels in motor vehicles, in space heating and cooling, in power generation and industrial processes, and the incineration of waste materials as major contributors to atmospheric pollution.
Dissolution and deposition processes
This chapter assesses dissolution and deposition processes. Some of the solid matter which is suspended in a natural water, or deposited to make up the top layers of the bottom sediments, is material which has been recently deposited from solution. This may arise from a purely chemical process such as precipitation or colloidal aggregation, or may result from the production of solid biomass, such as that which results from the photosynthetic activity of algae. Some of this solid material will be rapidly returned to the dissolved phase by changes in solution chemistry or bacterially-assisted decomposition; the remainder will eventually be incorporated into the sediments. The chapter then considers chemical weathering, looking at hydrolysis and oxidation.
Distribution of species in aquatic systems
This chapter deals with the distribution of species in aquatic systems, including how to calculate and diagrammatically represent their distribution based on empirically determined constants. It illustrates the methodology for generating a single variable species distribution diagram and introduces two variable species distribution diagrams that are relevant to natural aquatic environments. It also covers redox chemistry in water and the concept of electron activity before introducing pE/pH diagrams, with a detailed example of the sulfur system. The chapter notes that the species distribution or speciation for an element or compound depends on the nature of the chemical and the particular environmental conditions in which it is found. It elaborates on the calculation or prediction of the forms that will be present in aquatic ecosystems, assuming that one has access to the appropriate analytical data and the required thermodynamic constants.
The Earth and biogeochemical cycling
This chapter begins by describing the structure of the Earth. Current understanding of the composition of material at the centre of the Earth is restricted to that which can be inferred from indirect physical measurements. The outermost layer of the solid Earth—its crust—is the most familiar to man and is the part of the Earth most intimately associated with the aquatic environment. Below the crust is the mantle, and at the centre of the Earth is its core. In describing the chemistry of the aquatic environment, it will be necessary to draw upon terms originating from fields such as biology, geology, and hydrology. The chapter lists some of the most commonly encountered terms. It then looks at the geochemical cycles.
The Earth’s atmosphere
This chapter focuses on the fundamental concepts needed to understand chemical processes that occur in the atmosphere. It describes the physical nature of the atmosphere, its structure and composition, and the important role played by solar radiation in defining these features. The chapter also outlines basic concepts to describe important chemical processes related to ozone, smog, acid precipitation chemistry, atmospheric aerosols, urban and indoor air, and global climate. The chapter reviews fundamental physical chemistry properties of gases. It introduces gas-phase reactions along with related thermodynamic and kinetic calculations, including photochemical reactions as the extremely important category of free radical reactions.
This chapter defines the universe as consisting of a system and its surroundings, where the system is the portion of the universe that is under direct investigation while the surroundings comprise everything beyond the system. To illustrate, it applies this concept of the universe in considering an industrial chemical process, such as the production of the wood preservative pentachlorophenol (PCP). In this context, what happens in the factory is the system whereas the impact of the industrial process outside the factory would concern the surroundings. The chapter also examines mechanisms by which chemicals, such as dioxins, enter a living organism, the biochemical transformations they undergo, their molecular mode of action, and their elimination. The chapter explains that what goes on in the surroundings outside a system is the subject matter of environmental chemistry. It provides the chemical basis for understanding the surroundings, or the global environment.
Gary W. VanLoon and Stephen J. Duffy
Environmental Chemistry describes the chemical principles which underpin the natural processes occurring within and between the air, water, and soil, and explores how they are impacted by humans. It is subdivided into three parts that focus on the chemical composition of the three key environmental systems. Part A looks at the Earth's atmosphere and consists of a number of chapters which consider stratospheric chemistry (ozone), tropospheric chemistry (smog and precipitation), atmospheric aerosols, the chemistry of urban and indoor atmospheres, and the chemistry of the global climate. Part B focuses on the hydrosphere and includes examinations of gases in water, organic matter in water, metals and semi-metals in the hydrosphere, microbiological processes, and water pollution. The final part looks at the terrestrial environment and covers soil properties, solid wastes, toxic organic chemicals, and the future Earth.
Environmental chemistry of colloids and surfaces
This chapter deals with the chemistry of colloids and surfaces and considers the crucial role that the interface between the solid and aqueous environments plays in the dispersion of species in aquatic systems. It reviews the size and surface properties of solid particles and introduces two adsorption isotherm relations, Langmuir and Freundlich. It also analyses aqueous phosphate chemistry and its environmental consequences and outlines the distribution constants Kd , KOM , and KOW , their environmental relevance, and the terms relating to bioconcentration. The chapter investigates the types of colloidal material in the natural environment, emphasizing clay minerals. This category of minerals consists of aluminosilicate minerals that are produced by physicochemical weathering of primary minerals of terrestrial origin and have been carried to the hydrosphere as eroded material.
The future Earth
This chapter reviews environmental chemistry by summarizing the beginning and early stages of the Earth's natural history. It highlights the interactions and cycles of the inorganic and living components of the Earth which have been acting together to make the planet what it is. It also emphasizes that environmental chemistry begins with a knowledge of the natural processes that have taken place and are ongoing now. The chapter highlights the processes within the atmosphere, the hydrosphere, the geosphere, and the biosphere, as well as the processes that move across boundaries, linking all parts of the environment together. It emphasizes that while the impact that modern humans exert on the environment through industry and agriculture is massive, the nature of the environmental footprint of humans varies across geographies.
Gases in water
This chapter explores how gases distribute themselves between air and water and how the properties of water change accordingly. It cites Henry's law for simple gases, such as oxygen or nitrogen, that do not react with water and considers the specific case of carbon dioxide, which is a gas that reacts with water and creates a more complex equilibrium system. It also demonstrates how to define alkalinity and acid neutralization capacity and their relation to environmental issues. The chapter refers to gases and other volatile compounds whose vapours may be present at low concentration in the atmosphere. It provides a quantitative description of the distribution of gases between air and water, which depends on the substance's vapour pressure, solubility, and ability to react with water and other components in the hydrosphere.
This chapter introduces the hydrosphere, emphasizing the critical importance of water and its unique properties. It discusses the distribution of water throughout the Earth, the physical and chemical properties of water, and the methods of expressing concentration of solutes in water. It highlights that water is one of the essentials that support all forms of plant and animal life, noting that the quality of the environment is defined by the quality of water. The chapter points out that unsafe drinking water, turbid lakes and rivers, or ponds green with algae are obvious signs of a degraded water environment. Water covers 73% of the Earth's surface, almost three times as much as the continents, but it is also a crucial component of the atmosphere and the terrestrial environment.
Metal complexes in solution
This chapter investigates metal complexes in solution. With modern technology, it is possible to find almost every element of the periodic table in a sample of natural water. Which metals are present in significant quantities will, in the case of groundwaters, streams, rivers, and lakes, reflect the geology of the catchment area and the past history of the water. Some of the major factors influencing the concentrations of trace metals in oceanic waters, away from coastal influences, are inputs from bottom sediments and hydrothermal activity; deposition of material from the atmosphere together with removal by chemical adsorption onto surfaces; and precipitation and accumulation by marine organisms. The chapter then describes some of the chemistry underlying the formation of metal complexes and outlines some of the techniques which can be employed to provide an insight into the chemical species which might be present in natural and polluted waters.
Metals and semi-metals in the hydrosphere
This chapter describes the nature, occurrence, and behaviour of dissolved metals and semi-metals found in various aquatic systems and their influence within the environment. It discusses the types of metals and semi-metals that occur in water and explains how various classification schemes are used to explain the complexation behaviour of metals, including an environmental classification. It also examines how chemical speciation influences the bioavailability of metals and semi-metals. The chapter discusses the elements calcium, copper, and mercury as examples for understanding the environmental chemical behaviour of different classes of metals. It mentions the arsenic contamination of surface and groundwater that occurs in many other countries.
This chapter highlights the role that microorganisms play in facilitating environmental processes. It considers their role in organic matter degradation processes in terms of their energy relationships. It discusses the important environmental cycles of carbon, nitrogen, and sulfur and looks at the classification systems and properties of microorganisms. It also clarifies that abiotic reactions occur through purely physical or chemical means that can take place in a completely sterile environment while biotic reactions have a biological component. The chapter points out that the biological component of biotic reactions typically involves microorganisms. Biota classified as microorganisms are often very small, with dimensions frequently in the micrometre size range. The chapter highlights that microorganisms, despite their small size, play an essential role in facilitating many chemical reactions that occur in the natural environment, such as the process through which ammonium ion is converted to nitrate in water or soil.