The Evaluation of Contaminated Soil by Petroleum Mulch in Combating Desertification

Document Type: Research Paper

Author

Scientific Member, Research Institute of Petroleum Industry (RIPI), National Iranian Oil Company, Tehran, Iran

Abstract

The most usual type of petroleum mulch, which has been successfully used to combat desertification in large area
in Iran for more than thirty years, is produced by heavy residue petroleum cuts. The petroleum mulch consists of a
wide range of different heavy hydrocarbons such as Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are present at
low level in petroleum mulch, where there is contact with water and soil and the potential for transferring of
compounds into environment. Some of PAHS especially benzo (a) pyrene (BaP) have been recommended for
determining and comparing with standard criteria on causing cancer .Although Iran has a long domestic experience in
sand dune fixation by using petroleum products but so far there is no proper research in probable effects of using
petroleum mulch on environment either in Iran or any other involved countries. In this study it was assumed that
rainfall and temperature would affect mulch disintegration process, then considering these parameters, different
climatic zones in three provinces -Khuzestan, Kerman and Sistan - were selected and samples were prepared from
several sites of any provinces, both in mulch-sprayed sites and non-sprayed sites (observation). In order to estimate
the content of PAHs, several soil samples were taken in different depths from the above-mentioned sites. Quartering
Procedure selected the soil samples beneath mulch layer and the PAHS analysis was performed by solvent extraction
and HPLC method with UV fluorescence detection and results were compared to standard criteria. The results
indicated that the content of PAHs and mostly BaP in petroleum mulch and soil samples beneath mulch layer are less
than the permitted limit in national standards. This component, in the depth of 5 cm, decreased to 1/40 of the initial
even after years. Then, it shows very low penetration. Therefore, the petroleum mulch and contaminated soils can be
considered as safe materials.
The most usual type of petroleum mulch, which has been successfully used to combat desertification in large area
in Iran for more than thirty years, is produced by heavy residue petroleum cuts. The petroleum mulch consists of a
wide range of different heavy hydrocarbons such as Polycyclic Aromatic Hydrocarbons (PAHs). PAHs are present at
low level in petroleum mulch, where there is contact with water and soil and the potential for transferring of
compounds into environment. Some of PAHS especially benzo (a) pyrene (BaP) have been recommended for
determining and comparing with standard criteria on causing cancer .Although Iran has a long domestic experience in
sand dune fixation by using petroleum products but so far there is no proper research in probable effects of using
petroleum mulch on environment either in Iran or any other involved countries. In this study it was assumed that
rainfall and temperature would affect mulch disintegration process, then considering these parameters, different
climatic zones in three provinces -Khuzestan, Kerman and Sistan - were selected and samples were prepared from
several sites of any provinces, both in mulch-sprayed sites and non-sprayed sites (observation). In order to estimate
the content of PAHs, several soil samples were taken in different depths from the above-mentioned sites. Quartering
Procedure selected the soil samples beneath mulch layer and the PAHS analysis was performed by solvent extraction
and HPLC method with UV fluorescence detection and results were compared to standard criteria. The results
indicated that the content of PAHs and mostly BaP in petroleum mulch and soil samples beneath mulch layer are less
than the permitted limit in national standards. This component, in the depth of 5 cm, decreased to 1/40 of the initial
even after years. Then, it shows very low penetration. Therefore, the petroleum mulch and contaminated soils can be
considered as safe materials.

Keywords