Pollution and Pollution Control - Environmental Biotechnology: Theory and Application - page 67

concentrated in their tissues over time. This tendency of some chemicals to be
taken up and then concentrated by living organisms is a major consideration,
since even relatively low background levels of contamination may accumulate
up the food chain.
Chemistry
Pollution effects are not always entirely defined by the initial nature of the con-
tamination, since the reaction or breakdown products of a given pollutant can
sometimes be more dangerous than the original substance. This is of particular
relevance to the present discussion, since the principle underlying much of prac-
tical bioremediation in general involves the break down of pollutants to form
less harmful products.
This is further complicated in that while the chemistry of the pollutant itself is
clearly important, other substances present and the geology of the site may also
influence the outcome. Accordingly, both synergism and antagonism are possible.
In the former, two or more substances occurring together produce a combined
pollution outcome which is greater than simply the sum of their individual effects;
in the latter, the combined pollution outcome is smaller than the sum of each
acting alone.
The Pollution Environment
There is sometimes a tendency for contamination to be considered somewhat
simplistically, in isolation from its context. It is important to remember that
pollution cannot properly be assessed without a linked examination of the envi-
ronment in which it occurs. The nature of the soil or water which harbours the
pollution can have a major effect on the actual expressed end-result. In the case
of soil particularly, many properties may form factors in the modification of the
contamination effect. Hence, the depth of soil, its texture, type, porosity, humus
content, moisture, microbial complement and biological activity can all have a
bearing on the eventual pollution outcome. Moreover, recent work on the transla-
tory flow of water in soil has shown that under certain circumstances, particularly
after prolonged dry spells, the soil matrix can hold novel precipitation so tightly
that it almost never mixes with other water (Brooks et al ., 2010). Inevitably, the
combination of all these factors can make accurate prediction difficult, though
a consideration of system stability can often give a good indication of the most
likely pollution state of a given environment.
The more stable and robust the environmental system affected, the less damage
a given pollution event will inflict and clearly, fragile ecosystems or sensitive
habitats are most at risk. It should be obvious that, in general terms, the post-
pollution survival of a given environment depends on the maintenance of its
natural cycles. Equally obviously, artificial substances which mimic biological
molecules can often be major pollutants since they can modify or interrupt these
processes and pollution conversion can spread or alter the effect.