1 Introduction

Wherever we look upon our Earth, chemical action is seen taking place, on the land, in the air, or in the depths of the sea.

Adolph Stöckhardt (1809-1886) "The Principles of Chemistry" (1851, p.?4)

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 the 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 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 'environment' often refers 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 regarded system. 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, including territories (settlements, agricultural and forest landscapes) and components (infrastructure) under strong human influence, 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 and 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 manifold: 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 know that understanding the environment chemistry is incomplete without considering 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 the 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 means.

1.2 What is chemistry?

The definition of chemistry has changed over time, as new discoveries and theories add to the functionality of science. Chemistry, first established as a scientific discipline around 1650 (called chemistry) 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 concerning mechanics, thanks to the improved manufacturing of instruments in the sixteenth century. Deep respect must be given to the two individuals who initiated 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). 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 the mass (respectively weight) and volume had been known for thousands of years, the first modern analytical instruments were only developed in the late nineteenth 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, 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 generalising principles 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 energy. Consequently, inorganic and organic chemistry is the science of matter, physical and theoretical chemistry is the science of properties and interactions, and analytical chemistry is the science that studies the composition and structure of bodies.

As a sub-discipline of chemistry, analytical chemistry has the broad mission of understanding the composition of all matter. Much of early chemistry was analytical chemistry since the questions about what elements and chemicals are present in the world around us (the environment) and what is their fundamental nature are largely within 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...