Environmental Chemistry
Objectives
Introduces the topic of environmental chemistry
Defines the meaning of the word pollutant
Discusses selected topics under the headings air, water and land pollution
Introduction
Environmental chemistry is the study of the behaviour of chemical species within
the earth’s environment. This unit contains a brief introduction to some of the top-
ics of concern to the environmental chemist: air, water and land pollution.
Pollutants
A substance becomes a pollutantwhen it is present in a concentration that is high
enough for it to have a harmful effect on the natural environment.
Often, only highly toxic substances are thought of as pollutants, but even sub-
stances that are normally considered harmless may pollute if they are present in high
enough concentrations and in the wrong placeat the wrong time. For example, nitrate
is added to soil in order to increase plant growth, but an excessive concentration of
nitrate present in drinking water can be toxic, especially to young children.
Pollution originates from a source. The pollutant is then transportedby air, water
or dumped on land by man. Some of the pollutant may be absorbed (assimilated) or
chemically changedby the environment; the rest builds up to a concentration that
enables it to damage organisms or buildings, or to upset the balance of environ-
mental processes (Fig. 22.1).
22.1
Contents
22.1Introduction 41122.2Atmospheric
pollution 41222.3Water pollution 41522.4Land pollution 41922.7Revision questions 421Fig. 22.1An environmental
pollution model.
22
UNIT