Environmental Engineering Reference
In-Depth Information
combined with a falling price for gas, these developments were postponed until the next
century. However, the environmental damage which has already occurred in Siberia is
enormous, and it is to be hoped that North America does not repeat it.
ARCTIC POLLUTION
Although polar regions are still widely regarded as remote and pristine environments, in
reality they have been subject to pollution from distant sources in Europe, North America
and Eurasia. Indeed, in the 1950s the discovery of DDT residues in Antarctic penguins
was one of the first indicators that pollution is a global problem. Although the
concentrations of contaminants are generally lower than in temperate regions, their
presence is serious because of their persistence, due to slow turnover rates in polar
ecosystems. Cold temperatures slow down degradation processes and tend to condense
volatile organic pollutants. The cold slows evaporation rates also, and this may lead to a
continuous transfer of organic chemicals from warmer parts of the world. Mammals and
birds in polar regions are long-lived organisms, at the top of long food chains (e.g.
whales, seals and polar bears) and they have high levels of body fat, which stores
contaminants in the body. Many native Arctic peoples eat large amounts of wild game or
'country food'; fat, liver, kidneys and heart (often regarded as the 'choicest' parts) are
organs where the pollutants are most liable to accumulate. Because of their great
chemical persistence, stability in biological systems and solubility in fat, polychlorinated
biphenyls (PCBs) illustrate how pollution levels can be biomagnified by each link in the
food chain, so that levels in the blubber of seals and whales are about 400 million times
those in the Arctic Ocean, and magnified about 3200 million times in polar bears and
humans (Figure 24.9). Table 24.2 lists the main contaminants from urban and industrial
areas which have been detected in polar regions. Owing to proximity, the levels are
higher in the Arctic than in the Antarctic. Chlorinated organics have been in widespread
use in agriculture since the first insecticide, dichlorodiphenyltrichloroethane (DDT), was
introduced in the 1940s. Polychlorinated biphenyls have been used in paints, plastics and
electrical and mechanical equipment since the early 1930s. The commonest pollutant of
this group detected in the Arctic is hexachlorocyclohexane (HCH) in terrestrial
ecosystems, and toxaphene, chlordane and PCBs in marine ecosystems. The effects on
wildlife can be very serious, with reproductive failure in mammals, eggshell thinning in
birds, and reduced egg hatching in fish, in addition to increased cancers in animals.
Heavy metal concentrations are more difficult to interpret, as there is a background
concentration from local rock sources. However, there are more data on mercury and
lead, whose levels are extremely high in the kidney and liver of marine mammals.
