Pollution and Pollution Control - Environmental Biotechnology: Theory and Application - page 68

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. Inevitably, this 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.
Pollution Control Strategies
Dilution and dispersal
The concept of 'dilute and disperse' was briefly mentioned earlier in this dis-
cussion. In principle, it involves the attenuation of pollutants by permitting
them to become physically spread out, thereby reducing their effective point
concentration. The dispersal and the consequent dilution of a given substance