Petroleum hydrocarbons

2. 
 Petroleum hydrocarbons (PHs) are composed of
short-chain hydrocarbons such as paraffin, alicyclic,
and aromatic compounds, and non hydrocarbon
compounds such as naphthenic acid, phenol, thiol,
metalloporphyrin, asphaltene, and heterocyclic
nitrogen, sulfur compounds
 . PHs are extensively used worldwide as the major
energy source for industry and daily life. With the
increasing population and modernization,
petrochemical products are in heavy demand.
Introduction

3. 
Classes of petroleum hydrocarbons

4. 
 The interactions between petroleum hydrocarbons
and soil, are extremely complex. Petroleum
hydrocarbons are made up of complex of mixtures of
hundreds of compounds ranging from light, volatile,
short chained organic compounds to heavy, long
chained, branched compounds.
 The major hydrocarbon fractions have different
environmental fates and the degradability of simple
hydrocarbons and petroleum fuels decreases as
molecular weight and degree of branching increases
Fate of petroleum hydrocarbons in soil

5. 

6. 
 Once the oil is spilled into the environment, thousands of
compounds are formed, mainly hydrocarbons and a small
proportion of nitrogen, sulfur, and oxygen, in their right
proportion are produced.
 Once the PHCs is released into the soil, depending on their
chemical properties the complex PHCs mixture then
separate into individual compounds. Compounds with
lower molecular weight e.g. BTEX compounds (Benzene,
Toluene, Ethylbenzene, and the Xylenes) are naturally
occurring constituents of gasoline and diesel although also
present in kerosene and fuel oils.

7. 
 BTEX compounds are highly mobile in environments and
more volatile and easily leach to the groundwater than PHCs
of higher molecular weight.
 Generally, hydrocarbons with straight chain and few chains
can degrade more readily than those with complex chains .
Compounds with longer chains, such as PAHs and aromatics
tend to bind strongly to soil particles and soil organic matter
plays a vital role in the degradation of contaminants

8. 
Polyaromatic
hydrocarbons

9. 
 They tend to remain in surface soils and do not
migrate in groundwaters significantly.
 However, the smallest member of this group,
naphthalene, is fairly water-soluble and frequently is
found as a groundwater contaminant. In general,
PAHs are assumed to be primarily soil, rather than
water, contaminants. However, they can concentrate
in the sediments of rivers, lakes, and streams
Fate of polyaromatic hydrocarbons

10. 
 PAHs can easily be absorbed from the gastrointestinal tract
of a mammal because they are highly lipid soluble with a
devastating effect in bone marrow cells, e.g., non-Hodgkin
lymphoma, leukemia, and multiple myeloma.
 Naphthalene is among the PAHs that causes skin irritants,
whereas anthracene and benzo[α]pyrene causes allergy to
the skin in both animal and human
Health hazards of PAH

11. 
 Pseudomonas sp capable of degrading napthelene
 Starts with hydroxylation of one of the aromatic
rings to produce 1,2-dihydroxynaphthalene. 1,2-
digydroxynaphtalene later undergo further reaction
to metabolized to salicylic acid, and further
metabolized through catechol cleaved either meta- or
ortho-rings.
 1,2-dihydroxynaphthalene is regarded as a toxic
organic solvent with aromatic and alicyclic ring that
shares two carbon atoms
Degradation of Napthalene

12. 
Naphthalene degradation with
bacteria nah gene is arranged in two
operons in plasmid pNAH7, where
one operon codes for enzymes and
can covert naphthalene to salicylate

13. 
Pathway of napthalene degradation

14. 
Naphthalene is degraded via metabolic diversities by
 Mycobacterium sp
 Pseudomonas putida
 Rhodococcus opacus
 Bacillus pumilus
 Nocardia sp
Microbes degrading napthelene

15. 
 Another PAH anthracene, once enters the body, it
appears to target the skin, stomach, intestines and
the lymphatic system. It may even cause burning,
itching and edema.
 Anthracene is sparingly soluble in water, highly
resistant to nucleophilic attack and hence,
recalcitrant to biodegradation and accumulate easily
in the ecosystem.
Degradation of anthracene

16. 

17. 
Degradation of xylene