**1. Introduction**

The oil refinery industry is involved in the global processes of exploration, extraction, transporting (often with oil tankers and pipelines), and marketing petroleum products. The products of largest volume of the industry are oil and gasoline [1, 2]. Crude oil and petroleum are also the raw materials for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics. Oil and its derivatives (such as polycyclic aromatic hydrocarbons, PAHs) are among very significant and dangerous sources of ecosystem contaminants. Oil derivatives that contaminate soil are a threat to human health as well as a hazard to all living beings [2].

Polycyclic aromatic hydrocarbons (PAHs) are a large group of carcinogenic compounds emitted into the atmosphere by incomplete combustion of fossil fuel or biomass. As semi‐ volatile chemicals, PAHs can be transported over long distances in the atmosphere. In general, 3‐4‐5 ringed PAHs are largely predominant in air wherever the sampling was established, whether in rural, suburban, or urban areas. PAHs can pass from air to water, soil, and vege‐ tation, through dry gaseous, dry particle‐bound, and wet depositions [3]. They are persistent in various environmental media and can subsequently enter the food chains. Nowadays, it is well known that human exposure mainly occurs by ingestion of contaminated agricultural and natural food [4, 5]. Using plant in bioremediations is more popular and common. Plants are capable of accumulating PAHs from the soil, water, and air. In the ryzosphere of plants, we have a very higher activity of microorganism capable of using PAHs as the only source of carbon and energy [2, 5, 6].

The main source of hydrocarbons (PAHs) is incomplete combustion of organic different material. Polycyclic aromatic hydrocarbons are colorless, white, or yellow solids. They present low solubility in water and also low vapor pressure [7]. They arise mainly from anthropogenic sources (forest fires, oil seeps, and volcanic eruptions). Other sources of PAHs are burning of fossil fuel, coal tar, wood, oil derivatives, petroleum spills, and discharge. These substances are very toxic, mutagenic, and carcinogenic [8]. The remediation and bioremediation of PAHs are very longer and technically hard. Their persistence in soil increases with increase in molecular weight of PAHs. It is estimated that more than 90% of the total burden of oil derivatives such as PAHs reside in the surface layer of soils where they accumulate the most. Recent determinations of PAHs in agricultural soils in Poland indicate that the content of these contaminants in the majority of the soils is low but in long‐term contaminated soils, this content is very higher [9, 10].

Several techniques of remediation of PAHs are known: volatilization, photooxidation, chemi‐ cal oxidation, adsorption on soil particles, and microbial biodegradation. The main popular techniques are expensive and very time‐consuming. Otherwise, the effect of that remediation in many cases transfers the pollutant from one phase (soil, water, or air) to another [2, 4].

Bioremediation process is much less dangerous, and the results (products) of this process are safe for the environment such as inorganic minerals, H2O, CO2 (aerobic), or CH4 (anaerobic) [1, 11].

Microbes are known for their catabolic activity in bioremediation, but changes in microbial communities are still unpredictable [1, 11]. The most popular PAH‐degrading microorganisms are bacteria and fungi. The bioremediation of PAHs very often depends on the environmental conditions (climates, number and type of the microorganisms, soil structure, plants). The extent of biodegradation process depends on many biotic and abiotic factors, including pH, temperature, oxygen, microbial population, degree of acclimation, accessibility of nutrients, chemical structure of the compound, cellular transport properties, and chemical partitioning in growth medium [2, 4, 12].

**1. Introduction**

86 Soil Contamination - Current Consequences and Further Solutions

hazard to all living beings [2].

carbon and energy [2, 5, 6].

is very higher [9, 10].

[1, 11].

The oil refinery industry is involved in the global processes of exploration, extraction, transporting (often with oil tankers and pipelines), and marketing petroleum products. The products of largest volume of the industry are oil and gasoline [1, 2]. Crude oil and petroleum are also the raw materials for many chemical products, including pharmaceuticals, solvents, fertilizers, pesticides, and plastics. Oil and its derivatives (such as polycyclic aromatic hydrocarbons, PAHs) are among very significant and dangerous sources of ecosystem contaminants. Oil derivatives that contaminate soil are a threat to human health as well as a

Polycyclic aromatic hydrocarbons (PAHs) are a large group of carcinogenic compounds emitted into the atmosphere by incomplete combustion of fossil fuel or biomass. As semi‐ volatile chemicals, PAHs can be transported over long distances in the atmosphere. In general, 3‐4‐5 ringed PAHs are largely predominant in air wherever the sampling was established, whether in rural, suburban, or urban areas. PAHs can pass from air to water, soil, and vege‐ tation, through dry gaseous, dry particle‐bound, and wet depositions [3]. They are persistent in various environmental media and can subsequently enter the food chains. Nowadays, it is well known that human exposure mainly occurs by ingestion of contaminated agricultural and natural food [4, 5]. Using plant in bioremediations is more popular and common. Plants are capable of accumulating PAHs from the soil, water, and air. In the ryzosphere of plants, we have a very higher activity of microorganism capable of using PAHs as the only source of

The main source of hydrocarbons (PAHs) is incomplete combustion of organic different material. Polycyclic aromatic hydrocarbons are colorless, white, or yellow solids. They present low solubility in water and also low vapor pressure [7]. They arise mainly from anthropogenic sources (forest fires, oil seeps, and volcanic eruptions). Other sources of PAHs are burning of fossil fuel, coal tar, wood, oil derivatives, petroleum spills, and discharge. These substances are very toxic, mutagenic, and carcinogenic [8]. The remediation and bioremediation of PAHs are very longer and technically hard. Their persistence in soil increases with increase in molecular weight of PAHs. It is estimated that more than 90% of the total burden of oil derivatives such as PAHs reside in the surface layer of soils where they accumulate the most. Recent determinations of PAHs in agricultural soils in Poland indicate that the content of these contaminants in the majority of the soils is low but in long‐term contaminated soils, this content

Several techniques of remediation of PAHs are known: volatilization, photooxidation, chemi‐ cal oxidation, adsorption on soil particles, and microbial biodegradation. The main popular techniques are expensive and very time‐consuming. Otherwise, the effect of that remediation in many cases transfers the pollutant from one phase (soil, water, or air) to another [2, 4].

Bioremediation process is much less dangerous, and the results (products) of this process are safe for the environment such as inorganic minerals, H2O, CO2 (aerobic), or CH4 (anaerobic) Overall, PAHs are immobile and persistent in soil and also more difficult to extract. PAHs are less accessible to living organisms (microorganism) when they come in contact with the aggregate soil structure [2]. There are many methods used to clean up PAH and oil derivatives in contaminated soils, but bioremediation using bacteria and fungi consortium is most popular [1, 2, 8].

However, molecular methods have been used to study soil bacterial communities in conta‐ minated soil with PAHs and oil derivatives. While many anthropogenic activities, such as city development, agriculture, and use of pollution, can potentially affect soil microbial di‐ versity, it is unknown how changes in microbial diversity can influence below‐ground and above‐ground ecosystems. The study of bacterial diversity in soil contaminated with PAHs has some problems. The problems arise not only from the methodological limitations, but also from a lack of taxonomic knowledge. This studies focuses on whole groups of microor‐ ganism (bacteria and fungi) and its function in in the contaminated sites.
