Environmental degradation of petroleum hydrocarbons

Abstract

Petroleum hydrocarbons are causing widespread pollution in both the aquatic and the terrestrial environment. Petroleum consist of alkanes, cycloalkanes, aromatics, polyaromatics (PAHs) and other compounds. All of these hydrocarbons groups are toxic for the environment, but especially the PAHs and their degradation products are known for their carcinogenic properties.

The partitioning of hydrocarbons in the environments depends on volatility and hydrophobicity, influencing the partitioning between soil, water and sediment. The risk and degradation rates of hydrocarbons are besides this partitioning strongly dependent on bioavailability. Presence of other reactive or absorbing substances and environmental conditions have shown to influence the fate and degradation rates of hydrocarbons in the environment. Sediments, and more specific the carbon compounds in sediment, are the most important absorbing substances.

The most important degradation pathways in the environments are performed by light and organisms, bacteria, fungi and algae. Where bacterial degradation results in total degradation of nearly all hydrocarbons light is only able to make some photochemical modifications in the hydrocarbons. The degradation mechanisms have shown enormous influence not only on degradation but also on physical and chemical properties of hydrocarbons, resulting in change of partitioning in the various compartments in the environment. Environmental condition influencing degradation are pH, temperature, oxygen, nitrogen compounds, humic acids and salinity.

Due to the widespread use of hydrocarbons and subsequent pollution several methods for soil and water remediation have been developed. These methods include physical based methods as evaporation of hydrocarbons and biodegradation methods by stimulation of bacteria able to degrade hydrocarbons. For water treatment absorption and biodegradation are the most used methods.

The concequences of soil and sediment remediation for society in the Netherlands are enormous, which is illustrated by two examples; PAH pollution in the river delta in the Netherlands and soil pollution of former gas factories in the area of Utrecht.