Draft of RRL for Defense

Section: Graviton Rating:

Summary of Output: Draft of RRL for Defense

Review of Related Literature

I. Biodegradation

Biodegradation is nature's way of recycling wastes, or breaking down organic matter into nutrients that can be used by other organisms (Environmental Inquiry, 2009). It hastens the degradation of organic pollutants.

A.1. Crude oil

Crude oil contains polycyclic aromatic hydrocarbons (PAH) which are harmful to the environment. Crude oil is normally described as sweet (low sulphur) or sour (high sulphur) and light or heavy (depending on its density). Heavier oils may also be described as medium and bitumen. A light crude oil is generally one with an API (American Petroleum Institute) gravity of less than about 40. Brent crude, an important benchmark crude, has an API gravity of 38 to 39. Heavy crudes will typically have an API gravity of 20 or less - the higher the API gravity, the lower the density. Sweet crude oil has a sulphur content less than 0.5%, anything more is sour. Heavy crude is harder to handle and is refined in a higher cost to produce petroleum products such as petrol, diesel and aviation fuel (Pietersz, 2006-2009). Crude oil is classified in three groups based on the type of hydrocarbons they contain. Parrafin-based crude oil contain high molecular weight parrafins which are solid at room temperature, bit little or no asphaltic (bituminous) matter producing high-lubricating oils. Asphaltic-base crude oil contain large portions of asphaltic matter, and little or no paraffin and sensitive to temperature changes than paraffin-base crude oil. Mixed-base crude oil is the gray area between the paraffin-base crude oil and asphaltic-base crude oil. Both paraffins and napthenes are present ...

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...al degradation of hydrocarbons in the aquatic environment. Nitrogen and phosphorus limits biodegradation in soi. It is observed that no increase in biodegradation rates or an increase only after a delay of several months to a year when fertilizers are used. Rates of hydrocarbons metabolism decreased with increasing salinity in the range 3.3 to 28.4% (Leahy and Colwell,1990).

E.2. Utilization of PAH by bacteria

Mycobacterium vanbaalenii initiates degradation at three different sites: the K region (9,10-position), the Bay region (1,2-,3,4-position), the non K or non Bay region. It utilizes different enzymes which are the ring hydroxylating dioxygenases and monooxygenases. The initial ring cleavage is performed by NidAB dioxygenase, large and small subunits which are encoded by nidA and nidB genes respectively. Dioxygenase activity is stereo- and region- specific.