Geology Reference
In-Depth Information
between wet and dry weight concentrations, in other words, whether the
kilogram of vegetation or soil is determined before or after drying. Since
the moisture content of vegetation can easily exceed 50%, the data can
be very sensitive to this correction.
In aquatic systems, concentrations can also be expressed as mass per
unit mass and in the oceans some trace constituents are present at
concentrations of ng kg
1
or mgkg
1
. More often, however, sample sizes
are measured by volume and concentrations expressed as ng L
1
or mg
L
1
. In the case of freshwaters, especially, concentrations expressed as
mass per litre will be almost identical to those expressed as mass per
kilogram. As a kind of shorthand, however, water chemists sometimes
refer to concentrations as if they were ratios by weight, thus, mg L
1
are
expressed as ppm, mgL
1
as ppb and ng L
1
as ppt. This is unfortunate
as it leads to confusion with the same units used in atmospheric
chemistry with a quite different meaning.
1.5 THE ENVIRONMENT AS A WHOLE
A facet of the chemically centred study of the environment is a greater
integration of the treatment of environmental media. Traditional bound-
aries between atmosphere and waters, for example, are not a deterrent to
the transfer of chemicals (in either direction), and indeed many important
and interesting processes occur at these phase boundaries.
In this topic, the treatment first follows traditional compartments
(Chapters 2, 3, 4, and 5) although some exchanges with other compart-
ments are considered. Fundamental aspects of the science of atmosphere,
waters, and soils are described, together with current environmental
questions, exemplified by case studies. Subsequently, the organic chem-
istry of the environment is considered in Chapter 6, and quantitative
aspects of transfer across phase boundaries are described in Chapter 7,
where examples are given of biogeochemical cycles.
REFERENCES
1. For readers requiring knowledge of basic chemical principles R.M.
Harrison and S.J. de Mora, Introductory Chemistry for the Environmen-
tal Sciences, 2nd edn, Cambridge University Press, Cambridge, 1996.
2. For more detailed information upon pollution phenomena Pollution:
Causes, Effects and Control, 4th edn, R.M. Harrison (ed), RSC,
Cambridge, 2001 or R.M. Harrison (ed), Introduction to Pollution
Science, RSC, Cambridge, 2006.
