Environmental Engineering Reference
In-Depth Information
3.4.10 Human Impact
Humans use plastics/polymers in many ways in their day-to-day life. Most of them
discard them on open beaches and in the sea. The plastics discarded on beaches, also
inally reach the sea, where they can interfere with the safe navigation of marine craft.
It has been estimated that more than a million marine animals are killed every year
either by choking on loating plastic items or by becoming entangled in plastic debris.
Fishing and shipping industries are a major cause of plastic litter. Villages located near
the coast can also directly cause pollution by discarding their plastics inappropriately.
3.4.11 Exposure to Light (especially Ultraviolet) and Sunlight
Polymers exposed to sunlight undergo heat build-ups which helps them to reach
a higher temperature than that of the surrounding air [42]. The main effect of
UV irradiation is to promote photochemical reactions causing oxidation and
which decrease the MW of the polymers. It works by addition of ozone or H
2
O
2
.
This ultimately causes a decrease in mechanical properties, which ultimately increases
biodegradability. On the other hand, a cross reaction may occur which forms networks
which are resistant to biodegradation.
3.4.12 Accumulation of Biomass
The acceptable and indirect indication of biodegradation of polymers is based on
the increase in the biomass in its immediate environment. Microorganisms use the
polymer as a source of carbon as well as for energy. By utilising these materials, the
organism undergoes reproduction. In the degradation of polymers, the percentage
of carbon converted to biomass instead of to carbon dioxide mainly depends on the
type of polymeric material and the metabolic pathway used.
Figure 3.7
and
Figure
3.8
show the effect of several environmental factors on the state
of starch and catalyst blended LDPE, HDPE and PP suspended in surface waters in
the Bay of Bengal (South India). In all the cases, biofouling is severe. Biodeterioration
of the polymers because of wind and ocean currents are also seen within three to four
months of placement (
Figure 3.9
).
