The Evaluation of Contaminated Soil by Petroleum Mulch in Combating Desertification

Abstract

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