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