The Evaluation of Contaminated Soil by Petroleum Mulch in Combating Desertification

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.