Fluoranthene, benzo(a)pyrene (five rings)
The four- and five-ringed molecules are considered as high molecular
weight polyaromatic hydrocarbons.
3. Resins
Resins (pyridines, quinolines, carbazoles, sulfoxides, and amides) (Leahy and
Colwell 1990) are aromatic compounds with long alkyl chains and are rich in
polar functional groups (N, S, O as well as trace metals Ni, V, and Fe). They form
an amorphous solid which is soluble in linear alkanes such as n-heptane and npentane.
4. Asphaltenes
These are high molecular weight compounds having polycyclic clusters,
substituted with varied alkyl groups. These are also rich in polar functional
groups and are dispersed in saturates and aromatics as colloid. They are soluble
in light aromatic hydrocarbons such as benzene and toluene. Phenols, fatty acids,
ketones, esters, and porphyrins fall into this category (Leahy and Colwell 1990).
11.3 Petroleum Hydrocarbons as an Environmental
Pollutant: Biological Effects of Contamination
Petroleum hydrocarbons are persistent pollutants that cause extensive damage to the
ecosystem. Due to their widespread use and accidental release into open systems
such as oceans and waterways, they are considered a global environmental hazard.
Pollution of the terrestrial environment, namely soil, occurs during oil drilling
and accidental damage to overland pipelines. Transport of petroleum oil is generally
through the aquatic medium; oceans, seas, and bays, by either ship or underwater
pipelines. Accidental spillage of oil during transport through water conduits occur
due to technical failures. Although sporadic, they are increasing in frequency with
the increase in global utilization. The impact of such spillage is significant, due to the
open mobile nature of the systems. The oil disperses on the water surface and due to
its viscosity, forms a slick on the surface causing great damage to aquatic life. It cuts
off the exchange of gasses at the air-water surface and depending on the thickness
and viscosity, may affect penetration of sunlight into the water (Freitas et al. 2016).
This would impede photosynthesis and respiration, with disastrous consequences on
the food chain.
The effect of petroleum hydrocarbon contamination, either aquatic or terrestrial,
is alteration of the natural dynamic balance of the ecosystem. While some species
may be lethally affected, it may also result in enrichment of species with capacity for
utilizing hydrocarbons. Either way, efficient mechanisms for restoration of the
ecological balance is therefore crucial.
The damage to the ecosystem may be direct, due to toxicity of some petroleum
fractions. The BTEX and PAH compounds are known carcinogens and may be
teratogenic (Pérez-Cadahía et al. 2007; Costa et al. 2012). Also, they may
11 Microbial Bioremediation of Petroleum Hydrocarbons
267
The four- and five-ringed molecules are considered as high molecular
weight polyaromatic hydrocarbons.
3. Resins
Resins (pyridines, quinolines, carbazoles, sulfoxides, and amides) (Leahy and
Colwell 1990) are aromatic compounds with long alkyl chains and are rich in
polar functional groups (N, S, O as well as trace metals Ni, V, and Fe). They form
an amorphous solid which is soluble in linear alkanes such as n-heptane and npentane.
4. Asphaltenes
These are high molecular weight compounds having polycyclic clusters,
substituted with varied alkyl groups. These are also rich in polar functional
groups and are dispersed in saturates and aromatics as colloid. They are soluble
in light aromatic hydrocarbons such as benzene and toluene. Phenols, fatty acids,
ketones, esters, and porphyrins fall into this category (Leahy and Colwell 1990).
11.3 Petroleum Hydrocarbons as an Environmental
Pollutant: Biological Effects of Contamination
Petroleum hydrocarbons are persistent pollutants that cause extensive damage to the
ecosystem. Due to their widespread use and accidental release into open systems
such as oceans and waterways, they are considered a global environmental hazard.
Pollution of the terrestrial environment, namely soil, occurs during oil drilling
and accidental damage to overland pipelines. Transport of petroleum oil is generally
through the aquatic medium; oceans, seas, and bays, by either ship or underwater
pipelines. Accidental spillage of oil during transport through water conduits occur
due to technical failures. Although sporadic, they are increasing in frequency with
the increase in global utilization. The impact of such spillage is significant, due to the
open mobile nature of the systems. The oil disperses on the water surface and due to
its viscosity, forms a slick on the surface causing great damage to aquatic life. It cuts
off the exchange of gasses at the air-water surface and depending on the thickness
and viscosity, may affect penetration of sunlight into the water (Freitas et al. 2016).
This would impede photosynthesis and respiration, with disastrous consequences on
the food chain.
The effect of petroleum hydrocarbon contamination, either aquatic or terrestrial,
is alteration of the natural dynamic balance of the ecosystem. While some species
may be lethally affected, it may also result in enrichment of species with capacity for
utilizing hydrocarbons. Either way, efficient mechanisms for restoration of the
ecological balance is therefore crucial.
The damage to the ecosystem may be direct, due to toxicity of some petroleum
fractions. The BTEX and PAH compounds are known carcinogens and may be
teratogenic (Pérez-Cadahía et al. 2007; Costa et al. 2012). Also, they may
11 Microbial Bioremediation of Petroleum Hydrocarbons
267