Chemistry for Environmental Scientists

Detlev Möller

• Publisher: De Gruyter
• Year: 2015
• ISBN:
  9783110419337
• Edition: 1
• Topic: Physical Sciences
• Subtopic: Environmental Science

Non-chemists in environmental sciences and engineering (e.g. physicists, biologists, ecologists, geographers, soil scientists, hydrologists, meteorologists, economists, engineers) need chemical basic knowledge for understanding chemical processes in the environment. This book focuses on general and fundamental chemistry (including required physics) such as properties and bonding of matter, chemical kinetics and mechanisms, phase and chemical equilibrium, the basic features of air (gases), water (liquids) and soil (solids) and the most important substances and their reactions in the environment. Selected key environmental chemical processes are shortly characterised in the light of multi-component and multiphase chemistry.

This book is also useful for chemists who are beginning work on environmental issues.

1 Introduction

1.1 What do we mean by ‘environment’?

The terms environ (surround, enclose, encircle) and environment (surrounding) come from Old French. Thomas Carlyle (1795–1881) used environment in 1827 to render German ‘Umgebung’ (today environment is rendered in German as ‘Umwelt’). The German biologist Jacob von Uexküll (1864–1944) used ‘Umwelt’ first in 1909 in biology to denote the “surrounding of a living thing, which acts on it and influences its living conditions”, nowadays termed as the biophysical environment. Whereas usually in relation to humanity, the number of biophysical environments is countless, given that it is always possible to consider an additional living organism that has its own environment. The natural environment (synonym for habitat) encompasses all living and non-living things occurring naturally on Earth or some region thereof; an environment that encompasses the interaction of all living species.

Today, the expression ‘the environment’ is often used to refer to the global environment, the Earth system. However, each system to be defined lies in another ‘mother’ system, which is another surrounding or environment, hierarchically structured, where an exchange of energy and material is realised via the interfaces: Cosmic system → Solar System → Earth system → climate system (global environment)→sub-systems (e.g. atmosphere, hydrosphere, pedosphere).

Consequently, there is no fully closed system in our world. In science and engineering, especially in thermodynamics, the environment is also known as the surroundings of a reservoir. It is the remainder of the total system that lies outside the boundaries of the system regarded. Depending on the type of system, it may interact with the environment by exchanging mass, energy, momentum or other conserved properties.

We see that there are different meanings for the term ‘environment’. Following increasing use of this term in the 1950s, and related terms such as environmental pollution, environmental protection and environmental research, we must state that behind ‘environment’ are different natural components:

– ecological units (habitats, ecosystems) that function as natural systems but also under human modification (note: nowadays there is no absolute natural system on Earth without civilised human intervention), including all vegetation, microorganisms, soil, rocks, and atmospheric and natural phenomena that occur within their boundaries,

– natural resources such as air, water, soils and rocks (the climate system),

– built environment, which comprises the areas (settlements, agricultural and forest landscapes) and components (infrastructure) that are strongly influenced by humans belonging to a civilised society.

Furthermore, a geographic environment, the landscape, can be defined. However, all units such as ecosystem, landscape, and habitat can be reduced to air, water, soil and living organisms. Living organisms (vegetation, microorganisms and animals including humans) are an intrinsic part of the environment but also the target of environmental protection. Air pollution control, water treatment and soil decontamination are the primary measures to avoid organism diseases. Harmful impacts on organisms are manyfold: direct through toxicological effects of chemical substances, radiation, noise and land use change; and indirectly through climate change. Naturally, the non-living world (natural resources and built environment) is also subject to the impacts of pollution and mismanagement (e.g. weathering, erosion, corrosion). Hence, the target of environmental protection is to gain a sustainable environment.

Chemistry of the environment means atmospheric chemistry, aquatic chemistry and soil chemistry (note, we exclude biological chemistry because we consider the environment of organisms but knowing that understanding the chemistry of the environment is incomplete without consideration the interaction between organism and the environment). Moreover, it is simply multiphase chemistry in and between the gas phase, the aqueous phase and the solid phase.

There is a simple definition: Soil chemistry is the study of the chemical characteristics of soil. Soil chemistry is affected by mineral composition, organic matter and environmental factors. When you exchange now the word soil for air and water, you know what atmospheric and aquatic chemistry mean.

1.2 What is chemistry?

The definition of chemistry has changed over time, as new discoveries and theories add to the functionality of the science. Chemistry, first established as a scientific discipline around 1650 (called chymistry) by Robert Boyle (1627–1691) had been a non-scientific discipline (alchemy) until then (Boyle 1680). Alchemy never employed a systematic approach and because of its ‘secrets’ no public communication existed that would have been essential for scientific progress. In contrast, physics, established as a scientific discipline even earlier, made progress, especially with regard to mechanics, thanks to the improved manufacturing of instruments in the sixteenth century. Deep respect must be paid to two personalities for initiating the scientific revolution in both the physical and chemical understanding of the environment. First, Isaac Newton (1643–1727), who founded the principles of classical mechanics in his Philosophiæ Naturalis Principia Mathematica (1687), and, one hundred years later, Antoine Laurent de Lavoisier (1743–1794), with his revolutionary treatment of chemistry (1789), which made it possible to develop tools to analyse matter (Lavoisier, 1789). This is why Lavoisier is called “the father of modern chemistry”. We should not forget that the estimation of volume and mass was the sole foundation of the basic understanding of chemical reactions and physical principles after Boyle. While instruments to determine mass (respectively weight) and volume had been known for thousands of years, the first modern analytical instruments were only developed in the late 19^th century (spectrometry) and after 1950 (chromatography).

In the Encyclopaedia Britannica, published in Edinburgh in 1771 (shortly before the discovery of the chemical composition of air) chemistry is defined as: “to separate the different substances that enter into the composition of bodies [analytical chemistry in modern terms]; to examine each of them apart; to discover their properties and relations [physical chemistry in modern terms]; to decompose those very substances, if possible; to compare them together, and combine them with others; to reunite them again into one body, so as to reproduce the original compound with all its properties; or even to produce new compounds that never existed among the works of nature, from mixtures of other matters differently combined [synthetic chemistry in modern terms]”.

This definition further evolved until, in 1947, it came to mean the science of substances: their structure, their properties, and the reactions that change them into other substances. A characterisation accepted by Linus Pauling (1901–1994) in his book General Chemistry (Dover Publications 1947), revolutionised the teaching of chemistry by presenting it in terms of unifying principles instead of as a body of unrelated facts. However, Wilhelm Ostwald (1853–1932) had already used such principles of generalising in his book Prinzipien der Chemie (Leipzig 1907), subdividing chemistry into chapters of states of matter and properties of bodies, phase equilibrium, solutions and ions, chemical processes and reaction rates. The current book will follow that line.

As a short definition, chemistry is the scientific study of matter, its properties, and interactions with other matter and with energy. It follows, inorganic and organic chemistry is the science of matter, physical and theoretical chemistry the science of properties and interactions and analytical chemistry the science that studies the composition and structure of bodies.

Analytical chemistry as a sub-discipline of chemistry and has the broad mission of understanding the composition of all matter. Much of early chemistry was analytical chemistry since the questions of which elements and chemicals are present in the world around us (the environment) and what their fundamental nature is are very much in the realm of analytical chemistry. Before 1800, the German term for analytical chemistry was ‘Scheidekunst’ (‘separation craft’); in Dutch, chemistry is still generally called ‘scheikunde’. Before developing reagents to identify substances by specific reactions, simple knowledge about the features of the chemicals (odour, colour, crystalline structure, etc.) was used to ‘identify’ substances. With Lavoisier’s modern terminology of substances (1789) and his law of the conservation of mass, chemists acquired the basis for chemical analysis (and synthesis). The German chemist Carl Remigius Fresenius (1818–1897) wrote the first textbook on analytical chemistry (1846) which is still generally valid. Today, almost all chemical analyses are based on physical methods using sophisticated instruments (such as gas chromatography – GC, liquid chromatography – LC, mass spectrometry – MS, atomic absorption spectrometry – AAS, inductively coupled plasma – ICP, combinations of them and others) requiring expert knowledge. Whereas sampling in air, water and soil is very specific, and the topic of appropriate handbooks and carried out by the (non-chemist) environmental scientist, sample treatment, and analysis is mostly done by chemists.

However, “to look for definitions, to separate physics and chemistry fundamentally is impossible because they deal with the very same task, the insight into matter,” the German chemist Jean D’Ans (1881–1969) wrote in the preface to his Einführung in die allgemeine und anorganische Chemie (Berlin 1948). Julius Adolf Stöckhardt (1808– 1886) wrote in his textbook, The Principles of Chemistry: “Wherever we look upon our Earth, chemical action [a better translation from the original German is ‘chemical processing’] is seen taking place, on the land, in the air, or in the depths of the sea” (English translation, Cambridge 1850, p. 4). Thus, chemistry is apriori the science of mineral (inorganic), animal and vegetable (organic) matter, the substances making our environment. First Lavoisier found systematically that vegetable matter is composed of C, H and O and that in animal matter N and P are additionally present.

A systematic classification of chemistry into mineral, vegetable and animal according to its origin was carried out by the French chemist Nicolas Lémery (1645– 1715), who wrote Cours de chymie (1675, cited after Kopp 1931). According to Walden (1941), the first use of the term ‘organic chemistry’ is now attributed to the Swedish chemist Jöns Jacob Berzelius (1779–1848) who termed it ‘organisk kemie’ in a book published in 1806. After Lavoisier’s revolutionary book, Traité élémentaire de chimie (1789), Berzelius wrote the first textbook Lärbok i kemien (1817–1830) in six volumes. It was soon published in French (1829) still with the now traditional title, Traité de chimie minerale, vegetale et animale in eight volumes with the subtitle Chimie organique (2ème partie – three volumes). In Germany the first handbook, subtitled Organic compounds, is the third volume of Handbuch der theoretischen Chemie by Leopold Gmelin (1819), later rearranged into separate volumes of inorganic and organic chemistry (from 1848). It was believed at that time that organic matter (also termed ‘organised’) could not be synthesised from its elements and that a special force, the vital force, is needed for its production. However, processes not involving life can produce organic molecules. Friedrich Wöhler (1800–1882) destroyed the theory of vital force by the synthesis of urea in 1828, an event generally seen as the turning point. Justus von Liebig (1803–1873) defined the task of organic chemistry as follows (in Organic chemistry in its application to agriculture and physiology, 1840):

“The object of organic chemistry is to discover the chemical conditions which are essential to the life and perfect development of animals and vegetables, and, generally, to investigate all those processes of organic nature which are due to the operation of chemical laws” (The first phrase in Part I: Of the chemical processes in the nutrition of vegetables).

Gmelin (1848) wrote that carbon is the only element never missing and hence it is the only essential constituent in an organic compound. There has been no change in the definition since that time: the lexical database WordNet (Princeton University) defines organic chemistry as: “...the chemistry of compounds containing carbon (originally defined as the chemistry of substances produced by living organisms but now extended to substances synthesised artificially)”. According to this definition it appears, however, that (for example) carbon dioxide is an organic compound. It has been convenient to distinguish between inorganic and organic carbon compounds to explain the cycles between the biosphere and the atmosphere. On the other hand, when we state that there is a prime chemistry considering a limited number of elements and an unlimited (or at least immense) number of molecules in defined numeric relationship between the elements (including carbon), there is no need to separate chemistry into inorganic and organic chemistry. In contrast to the countless number of ‘organic’ carbon compounds, the number of ‘inorganic’ carbon compounds is rather small (of course, we count here only simple compounds found in nature and not produced in laboratory). Hence, in this book no separation into inorganic and organic chemistry is done – we consider elements and their compounds.

With the focus of many disciplines in science and engineering on our environment, many new sub-disciplines have arisen, such as biometeorology, bioclimatology, environmental chemistry, ecological chemistry, atmospheric environmental research, environmental meteorology, environmental physics, and so on. Basic research is progressing with individuals and in small groups on limited topics and hence growing understanding (learning) and specialisation results in establishing ‘scientific fields’. There is no other way to proceed in fundamental science. However, the complexity of the environment calls for an interdisciplinary approach and we have learnt that, especially at the ‘interfaces’ between biological, physical, chemical and geological systems, crucial and key processes occur in determining the function of the whole system. Therefore, a chemist (or non-chemist) without understanding of the fundamental physical (or chemical) processes in the environment (and vice versa) can only work on discrete research topics and will not be able to describe the environment as a whole.

What we see is that all disciplines overlap. The original focuses of geology as the science of the (solid) Earth, hydrology as the science of liquid water, and meteorology as the science of the atmosphere, are still valid and should not be diffused. However, the modern study of Earth sciences looks at the planet as a large, complex network of physical, chemical, and biologica...

Table of contents

• Cover
• Title
• Copyright
• Preface
• Contents
• List of principal symbols
• 1 Introduction
• 2 Chemistry under environmental conditions
• 3 Fundamentals of physical chemistry
• 4 Chemistry of elements and its compounds in the environment
• 5 Chemical processes in the environment
• A List of acronyms and abbreviations in environmental sciences found in the literature
• Endnotes
• Bibliography
• Author index
• Subject index