Precious water
Our’s is an aqueous world. Over 71% of the Earth is
covered in oceans or seas, while streams and rivers criss-cross the land
masses. All plants and animals rely on water, and will die without it. While
some are incredibly well adapted to a lack of water, their biochemistry still
requires it
for life. Welwitschia mirabilis (see Figure 1), which lives in Namibia, is an example
of such a plant. Its adaptions to a desert environment mean that it needs only a
few millilitres of water every couple of years, and is reputed to have lived
without water for over 5 years. But, without water, eventually even Welwitschia mirabilis will die.
Figure 1 A mature Welwitschia
mirabilis.
Older specimens such as this one in Namibia can measure over 3 m across and 1 m
high. © Rosemary Walden.
An ordinary human being can go without any water
for only about a day before feeling ill effects, and death will occur within
about 3 to 4 days. The European Food Safety Authority recommends that women
should drink about 1.6 litres of fluid and men should drink about 2.0 litres of
it per day. That's about eight 200 ml glasses for a woman and 10 for a man.
We are extremely lucky in the UK and most of
northern Europe; water is so plentiful that it is largely taken for granted.
One might complain about the size of the next water utilities bill, but to
think that water might not be available would not cross our minds. Yet there
are many places in the world where water is considered precious precisely
because it is a fragile resource. Historically, wars have been fought over the
provision of sufficient water. The supply of water has driven wars in the
Jordan and Tigris-Euphrates basins since biblical times. Pi-Ramesses Aa-nakhtu, the ancient
Egyptian capital of Rameses II was actually moved to ensure that it was
positioned on one of the flowing distributaries of the Nile delta when the one
it was on dried up, such was the need to have water available. Thousands of
stones and statues, some weighing a thousand tonnes were dragged 30 km to a new
site. The Middle East now contains 5% of the world’s population, yet has access
to only 1% of the globe’s water. It seems likely that the availability of water
will be one of the major factors in any new conflict there.
Sufficient water is not enough; it must be fresh
and unpolluted too. Water is an incredibly good solvent, taking into its liquid
structure a wide range of materials, some of which provide us with nutrition,
such as sugars, while others can act as poisons. Many materials, such as plain
table salt (NaCl) are readily soluble in water, with about 350 g dissolving in
every litre of water, while others dissolve to a much smaller extent. For
example,
calcium carbonate (calcite) dissolves to an extent of only 0.006 g in every
litre. Even so, the components that are present in small amounts can often be
significant over long timescales. It
is the constant drip of waters containing dissolved calcium carbonate that
build giant stalactites and stalagmites over tens of thousands of years, and
which take hundreds of years to turn artefacts to stone at Lourdes in The
Pyrenees, or at Mother Shipton’s cave in Knaresborough, Yorkshire. Recently the
bones of a young girl were found in a cave in The Yucatan peninsula of Mexico.
They were dated at between 12,000 and 13,000 years old by measuring the
thickness of the calcite that had grown on parts of their surface; growth at a
rate between 0.005 and 0.1 mm per year.
We all know that the one thing that water will not
mix with is oil. Nevertheless oil may be present in water in the form of tiny
globules. Normally such globules will join together resulting in a layer of oil
floating on the surface of water because most oil is less dense than water.
Everyone knows that colourful patters are formed when a small amount of oil is
spilt onto a wet road. This is due to an extremely thin layer of oil that sits
on top of the moist surface. Sunlight reflecting off both the oil surface and
the water surface just below it combine in such a way to separate it into its
component colours. Slightly different thicknesses of oil give different colours,
and the colours swirl and move as the oil thickness changes. Since there are
large changes in colour for very small changes in oil thickness, this property
has been used to make extremely fine measurements such as those required to
grind telescope lenses to an accurate shape.
French Dressing with Surfactant
1 tbsp vinegar
(sherry, wine, or even spiced vinegar left over from pickling)
Salt
and pepper to taste
3 tbsp olive
oil
1 tbsp mustard
(smooth or grainy to taste)
1 finely
chopped garlic or shallot
·
Take a jam jar
with a tight-fitting lid.
·
Add vinegar,
salt and pepper, and shake vigorously.
·
Add mustard and
shake again.
·
Add oil and
garlic/shallot and shake again vigorously.
The dressing may be kept in a fridge, shaking it
thoroughly before use.
|
An oil and vinegar salad dressing is another
example. Here we shake the oil and vinegar together to obtain a fine suspension
of oil globules in the watery vinegar. The resulting mixture is technically
called an emulsion. However, after a short time the oil and vinegar separate
again. The time this takes can be lengthened by adding a pinch of sugar or a
spoonful of made mustard (see box). The sugar or
mustard act as natural surfactants; a material which stabilises the oil
globules so that they remain suspended in the water for longer.
While natural surfactants are present in the
environment, we also make great use of artificial surfactants. Soap is one.
Perhaps our greatest use of surfactants domestically is the powder and liquids
used in washing clothes. These all contain surfactants, and their job is to
allow the oily marks on clothes to be ‘dissolved’ by the water in the washing
machine. An incredibly large volume of surfactant-rich fluids are flushed into
the waste water systems of the world’s developed nations every day. It is
estimated that the UK alone disposes of 1.9 thousand million litres (1.9
million m3) of surfactant containing water per year from
personal, clothes and kitchen washing. The water is highly dilute, but
represents over
5 million litres of pure
surfactant nonetheless. Later in this chapter, when we consider the amount of
various fluids required for a mature shale gas industry, we will see that the
amount of surfactant laden water used and disposed of domestically in the UK is
350 times the total
volume of fracking fluids required to drill the 100 wells and 400 laterals a year that
reasonable shale gas development would require. It is odd, perhaps, that so
many people are motivated to express their justified concerns over fracking
fluids, while contributing to a much more serious problem every day without
thinking about it.
But is it a problem to dispose of surfactant-rich
fluids in our environment? After all, we do not seem to be suffering for it. Well
the scientific jury is out on that. It is true that all common surfactants are
biodegradable, and that most waste waters are processed in waste water
treatment plants. However, together with pesticides, fertilisers, drugs and
artificial hormones, the chemicals found in domestic and industrial cleaning
products are beginning to be thought of as a potential health time bomb. It has
been suggested that a widespread but largely unrecognised health problem is
gestating, in much the same way as tetraethyl lead in leaded petrol seems to
have caused violence and immoral behaviour in the 70s, 80s and 90s, but this
time for human and animal fertility. When flushing anything into the waste
water at home it should be remembered that the final destination of all the
processed waste waters and solid waste is the surface environment, its rivers,
seas and surface soils, and this is where they can do most damage. It is a sobering thought that ultimately
whatever we discard in the household and industrial waste waters will
eventually end up in the water we drink and the food we eat.
Since water is such a ready solvent for many chemicals,
it also represents an extremely efficient route into our bodies. Anything that
dissolves in water, even to a small extent, can enter the body of any plant,
animal or human by ingestion, adsorption through the skin, or even by inhalation.
Water gives us life, but it is also a threat. Consequently, the provision of
plentiful fresh and clean water is perhaps the most precious resource we have
on Earth.
This chapter is dedicated to the idea that shale
gas exploitation could cause damage to our water resources, and hence put all
the plants, animals and people that live on or near the surface of the earth at
risk. The risks that are foreseen can be classified into two broad categories;
water use and water pollution.
For water use, the questions that we must ask are
whether water is actually needed for shale gas development, and if it is
needed, how much of it, as well as where it will come from and where will the
waste water eventually be disposed. But first, it is important to consider what
the UK’s water resources are.
From the point of view of water pollution, we need
to ask questions concerning what possible routes of contamination there are,
whether the risk of pollution via any
of these routes is significant, and whether any pollution has been recorded so
far. There is a polarisation of views between those supporting the exploitation
of shale gas and those opposed to it. This seies of articles will, I hope, leave the
reader with a greater capacity to examine the evidence presented to her or him
in a dispassionate way in order that the reader may give his or her fully
informed consent to, or rejection of, shale gas.
Part 2 will be posted in a few days.
